Homebrew Hvid


Part 4

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Click on the picture for the high definition version.


22 May 2009:

While waiting for the flywheels, I decided to fix the wobbly cam followers.  

Cam follower guides.

What I did was to mill 0.125" wide by 0.125" deep slots in the followers.  Then I drilled and tapped the follower guides for 8-32 brass screws.  I put the screws into the lathe and turned the end 1/8" of them to 0.125" diameters so the cylindrical ends of the screws would run in the slots, thus keeping the followers from rotating.  


The engine was motored for a couple more hours today.


23 May 2009:

Now, I'm getting down to the stuff that could be trouble.  Today, I made the "Momentum  Accumulation Device".


The "Momentum Accumulation Device", otherwise known as a crank.

I spent the day fiddling around making the starting crank.  You will notice a couple of odd things about it.  First, it has a short throw, only making about an 8" circle.  This is so I can spin it fast..Since the compression is so high, there's not much chance I can keep it turning long after the compression is turned on.  Also, you will note that the handle is quite long.  This is so I can have plenty of room for my hand.  I hate cranks that have short handles!



Another brainstorm occured while filing on the crank.  I think that I really should add to the governor weights.  Right now, I have to have such a light spring on it that it doesn't return properly.  If I add some weight, I can use a heavier spring which will make it return with more force.


25 May 2009:

The governor works much better now.

Added weight to governor.

After I put the governor back on and adjusted, I found that I can use a much stronger compression spring and that makes it more forceful both in cutting the fuel back and turning it back on.


I motored it for a while and tried turning on the compression slightly to put some pressure on the rings.  I'm glad I did that because I found that the fuel valve (the poppet valve going to the explosion cup) wasn't seating very well.  I guess I now have another lapping session in store.


27 May 2009:

Hoo-RAY!!  Frank got the first flywheel shipped yesterday so I should have it and have it on the engine by the weekend.


             Grinding the O.D.                                                    The finished flywheel.

We're not sure what alloy of steel I got (freebie!) but it must have been hardenable because it was tough to machine, especially around the O.D. where it had been plasma cut.  The O.D. was so tough that he chipped a few carbide tools before going to the 'ol "bench-grinder-on-the-table" trick.  Also, since the steel "rang" when being milled, it left some pretty heavy marks.  I may sand them off.........Then, again, I might not.   


After discussing the machining problems with Frank today, I looked in McMaster-Carr and found that they sell 12" diameter gray cast iron rod cut to 2" lengths.  I ordered one and had it drop shipped to him so the second wheel will be a lot easier to make.  He's now got a nice 12" diameter by 2" thick hunk of some kind of hot rolled steel to play with.


Even though the wheels will be the same shape, they will look different...but, at this point, if it really bugs me, I'll just paint 'em.


Today, I re-lapped the fuel valve which got it to seal and motored it some more.  I put some kerosene (parrafin) in the tank and tried to make it fire but, without the flywheel, it won't go over compression the first time (from 500 RPM!) with the compression full-on.  I did get some white "hot oil" smoke when I opened the fuel valve with partial compression though, so I might be pretty close to the right compression.  We'll find out in a few days!


2 June 2009:

The flywheel arrived last Thursday but I had to go out of town over the weekend so I didn't get anything done 'til today.

First flywheel installed and undergoing fueling tests.

With the flywheel mounted, I spun it up and turned on the compression.  The motor can keep it going long enough to go over compression about a half-dozen times before bogging down.


When I turned on the fuel and threw in the compression, nothing happened.  That was about what I expected.  I took a rag and soaked it in naphtha and held it near the intake and threw the compression in again.  It started hitting and sounding like a true Hvid engine - in other words, it clanked like it was going to come unglued.  As long as I kept the rag close to the intake, it continued to run on it's own.  I did see a little black smoke but every time I removed the rag, it quit firing.


I spent the afternoon fiddling with the hole in the explosion cup.  The original hole was 0.028" and it would smoke a little when naphtha was present so I thought the hole may have been too small so I drilled it to 0.035" then to 0.040" and finally to 0.0465".  The only thing I accomplished was to stop the black exhaust smoke.  Right now, I think the original hole was close.


In the meantime, I made some shims (2 each 0.021" and one 0.060") to raise the compression.  All increasing compression did was to make the engine slow when naphtha fumes were introduced.  This indicates that the vapor was firing too early (too high compression).


I re-worked the fuel needle with no improvement.  It acts like it's not getting any fuel.  I would think that if fuel were being delivered in any appreciable quantity, it would at least smoke white if the compression was too low and would smoke black when naphtha fumes were used to initiate combustion.  I've gotta think over the fuel block.  Something's not kosher there!


3 June 2009:

I have found one reason the engine won't run on kerosene.  The fuel delivery valve in the fuel block is not seating properly.  This causes compression pressure to force the fuel back toward the tank before it gets to the explosion cup.  In any case, if you're just itching to see it run on naphtha vapors, click on the line below:


After making the video, I rigged a hose to the air bleed port on the fuel block and immersed it in a cup of kerosene (parrafin).  If I held it high enough above the fuel block, the gas bubbles would be sort of bypassed and some fuel got into the cup.  It actually made a little power and smoked black some.


I'll take the fuel block off once more (about the dozenth time) and again lap on the fuel valve.  The face and seat look good but for some reason, it leaks.


4 June 2009:

After relapping the fuel valve with the lightest compound I have, it finally seats but only after tweaking the torque of the fuel block mounting bolts.  I figure that the block is being distorted when the bolts are too tight.


Anyway, after fiddling with compression ratio and fuel feed, it will "sorta" run on it's own without introducing the naphtha vapors.  One of the things I find is that the fuel tank needs to be elevated at least a couple of feet above the fuel block for the engine to fire regularly.  Not sure what that's all about but I will think on it while getting the Diesel fumes outta my lungs!


After it ran for a while, the exhaust valve stuck solid.  I did get it worked loose but hope that's not a preview of future troubles.  I did consider making brass valve guides but decided not to spend the effort.


Anyway, I've uploaded another YouTube video of it as it ran today:



5 June 2009:

Today, going with a suggestion from Kirk Taylor on Harry Matthews' SMOKSTAK, I lapped the fuel valve again but only put compound on the smaller diameter of the valve face.  This caused metal to be removed only from the area within the smaller diameter where metal is removed more slowly than at the outer diameter.  Thanks, Kirk!


I also tried reducing the size of the explosion cup hole.  I did this by partially tapping the existing hole (0.0465" or 1.18mm) with a 0-80 tap and jamming a screw into the threaded hole.  Then I cut the screw off flush with the cup, filed it smooth and drilled it back to the original 0.028" or 0.071mm size.  


About the time I got to testing the smaller explosion cup hole, the exhaust valve began sticking again so there was nothing for it but to pull the head and make a guide.

New exhaust valve guide on the left.

While I was at it, I followed the suggestion of Ad Langelaar of The Netherlands who was kind enough point out that I should enlarge the hole that communicates between the explosion cup and the combustion chamber.  The hole was originally 0.250" or 6.35mm.  I enlarged it to the next larger end mill size I have, 0.375" or 9.525mm.  Since the outside of the original hole was in line with the cylinder, I offset the new hole toward the center of the head, making a step in the bores.


Also, since the exhaust valve was too proud (sticks into the combustion chamber too far) and there's the serious worry that it could hit the piston, I put the valve in the lathe and removed about 0.020" or 0.5mm from the head.


Tomorrow, I'll put the head back on and again attempt to make mass quantities of noxious smoke and loud mechanical sounds.


Enlarged transfer hole between the explosion cup and the cylinder.


7 June 2009:

Yesterday, I put the head back on and couldn't get the engine to run worth a hoot even after I increased the compression by lengthening the rod by another 0.040" or 1.02mm.  Then, on a hunch, I took off the flex exhaust pipe that runs outdoors and spun the engine.  The exhaust valve wasn't seating completely!  Nothing for it but "off with it's head!".  


I found that, after I'd put in the exhaust guide and re-cut the seat, the tool was about 0.001" or 0.025mm off center so, even though I lapped the heck out of it, there was still a small area that wasn't seating.  I again recut the seat (VERY carefully!) and lapped the valve again.  This time, the valve seats fine.


After sticking the whole works back together, it wouldn't run because the compression ratio was now too high.  I removed 0.020" or 0.51mm and it would start on naphtha vapor and, when it had warmed up a bit, ignition of the Diesel fuel occured but it still doesn't make enough power to knock over a feather.


I may try increasing the explosion cup spray hole back to 0.0465" or 1.18mm and see if that makes any difference.


Now, I know I'm getting ignition in the cup like I'm supposed to.  If I weren't getting cup explosions, it wouldn't run at all on Diesel fuel.  I did notice that the exhaust never has smoked as heavily as I would expect except on the odd occasion when I've intentionally turned off the compression without turning off the fuel and then, after several revolutions, turned the compression back on.  When I do this, I get heavy detonations and more smoke but only for a couple of revolutions until the excess fuel burns off.  This phenomenon could be something having to do with the passages in the fuel block being too small.  If nothing else, I can increase the size of the passages and see what happens.  Another clue pointing to the passages is that the engine will only continue run at all if I hook up an external fuel tank and elevate it about three feet.


I also modified a DeLaval oiler by adding a check valve and installed it.  The previous oiler wouldn't do but a drop a minute, even wide-open.  It oils fine now.


9 June 2009:

Made some mods to the fuel block including opening up the fuel hole in the fuel valve seat and changed the fuel needle and seat.  In so doing, I have more or less messed-up the fuel valve and will most likely have to re-design it and make another one.  When I enlarged the fuel hole in the seat, I got it too close to the inside edge of the seat and it leaks a little.  In any case, the engine does run better in spite of it dripping fuel out of the fuel block.  Since I've had problems seating the fuel valve in the steel block, I think I'll make the new one out of cast iron.  It'll be easier to drill those small, deep holes, too.


Having said all of that, the engine runs a bit better and is almost to the point of running on it's own.  I've made another movie and posted it to YouTube:


10 June 2009:

Today was another one of those good news/bad news days.  


I drilled out the spray hole in the explosion cup to 0.064" or 1.626mm and just touched up the fuel valve to try to minimize the fuel leak.


The fuel leak is now almost gone and the increased spray hole diameter helped in the running.   Since the shop got so stinky yesterday (even with the exhaust going outside), I turned off the A/C and opened up as soon as I was ready to test.  I even had a box fan in one window to get some cross draft (I still stunk-up the shop AND made it really hot and humid in there).  


I made a discovery when motoring it with the window open so I could hear the exhaust.  The good news is that I've gotten a handle on the engine sounds.  I was getting a nice ignition ping all along but, when motoring, it would only give a good exhaust thump once in a while.  I reasoned that I was getting a regular cup ignition but a very irregular  combustion chamber ignition.  With the windows closed, I couldn't hear the exhaust bark and just assumed that it was normal.


To try to get regular combustion chamber ignition, I added compression shims until I had 0.140" 3.6mm in the rod.   At this point, with the engine cold, I got a more or less regular exhaust thump.  As the engine warmed up, the exhaust thump got very regular and the engine acted like it was -almost- ready to run on it's own.


I switched the fuel over to kerosene just to see if it would do better on the lighter fuel and immediately found out that I had to lower the compression by removing compression shims until I had 0.080" or 2mm in the rod.  It still didn't run well enough to pull itself so I theorized that my cam angles were not right.  As you recall, when I made the cams, they turned out a bit short on duration and ended up being only about 185 degrees.  By carefully charting the valve action on Frank's Thermoil, we came up with an angle of 220 degrees with a slight overlap.


Trying to get the most duration on the exhaust cam, I started reducing the exhaust valve clearance and, true to my prediction, the engine ran slightly better as I closed up the gap.  Well, folks, I went too far and, before long, the engine started faltering and finally quit firing.  Bad news time!  Problem......burned exhaust valve!  Dagnabbit!  Those suckers sure burn fast on a compression ignition engine.


Oh, well.  At least now, I'm really getting a handle on the peculiarities of Mr Brons' engine.


I'll spend the next few days making a couple of new cams, grinding the exhaust valve, washing all the black goo off the engine parts and cleaning some of the black oil spots off the walls of my shop.  Whoever said that a shop had to have nice white walls??!!  By that time, the second flywheel should be here, then it's back to testing and I think it's going to come to life.


13 June 2009:

Yesterday, I reworked the exhaust valve.  I wasn't happy with the fit of the brass guide I'd made so I made another one.  This time, though, I carefully aligned the head in the mill with the bore of the valve port.  Using a boring head, I bored the valve port larger so as to have a narrower valve seat.  I then reamed the guide hole so it was exactly concentric. Without disturbing anything, I used my very old valve seat cutter in the mill to touch off the seat just 'til it cleaned up all around.


The new guide was made.  Since the valve stem is metric and I have no metric reamers, I drilled it to the nearest smaller decimal size (-0.002" or 0.51mm).  It took the rest of the afternoon to lap the guide to a nice close fit to the valve stem.  After pressing the guide into place, lapping-in the valve was a breeze.


Today, I made new cam lobes per a new design.  I can call this version the "Big Cam" engine.

Old cams above - Big Cams below.

Both of the cams were made identical in angle for 220 degree duration and with slightly higher lift.   Then, not shown, I re-milled the duration of the intake cam back for 190 degree duration.  I believe the engine should "come to life" with these cams.  I'll find out tomorrow.


14 June 2009:

Well, it tried.  Then the exhaust valve started sticking.  Tomorrow, I'll pull the head again and lap the guide a little looser.  I guess that carbon built up on the stem, sticking it.


I also noticed that it was pinging with cup ignition but smoking grey, indicating incomplete combustion.  While I have the head off, I may take a die grinder to the communication hole and build a lip toward the center of the cylinder to try to direct the spray that way.


15 June 2009:

Hurrah!  Today, it ran under it's own power for a few minutes!!!

And, it pulled the motor and belt drive........barely.


I pulled the head and lapped the exhaust valve guide a bit looser then lapped the valve seat.  It wasn't burned, just carboned-up from running with too little clearance.  Then, I decided to pull the piston because it seemed to have a bit of blowby yesterday.


Carboned-up piston with stuck rings......ICK!

The top three rings were stuck solid due to carbon buildup.  It was heaviest on the top of the piston, inline with the communication hole in the head between the explosion cup and the combustion chamber.  I figure the blast from the hole was cramming partially burnt fuel down between the piston and the bore and generally trashing everything.  


I soaked the piston in solvent, made witness marks for reassembly and gently worked the rings loose.  Then I took them off the piston and cleaned up the piston.  When I turned the ring grooves, I made them a bit on the snug side so I put the piston back up in the lathe and used a parting tool to remove the carbon from the grooves and put about another 0.001" or 0.025mm clearance in them.


After reassembling the rings on the cleaned up piston, I lined up the witness marks for the grooves, hoping they'd be close enough to rotate into their broken-in positions then put it back in and let it motor to reseat the rings while I revisited the head.


Modified explosion cup communication hole.

To keep the burning fuel spray from getting into the clearance between the piston and the bore, I used a flat-ended mill to make a 0.125" or 3.175mm deep hole the same diameter as the communication hole and slightly above it's centerline.  I then turned a steel rod to a tight press fit in the new hole and cut it off slightly longer than 0.125".  After pressing the "button" into the hole, I used a file to dress it flush with the head surface.  


Then, with a Dremel and a carbide burr, I made a lip on the valve facing side of the hole and made a roughly matching lip on the inside of the button.  This is supposed to divert the gases away from the gap between the piston and the bore.  It also probably introduces some turbulence.


After putting it back together, I motored it with fuel and after a little coaxing with naphtha, it began to try to run.  This time, though the smoke was mostly dark black, indicating combustion but too much fuel.


I removed the fuel block and again plugged the explosion cup hole and re-drilled it to 0.035" or 0.89mm. 


I suppose because the engine was still warm from the previous run, it began pinging almost as soon as I turned on the fuel and compression and picked up RPM like it was really in the mood to run.  Still, though, it wouldn't quite pull itself with the motor.  I figured the rings needed some time to reseat so I turned the fuel needle down to just where it could just keep up with the motor and sat back and let it run.  After about ten minutes, it started speeding up until the governor started holding it back.  I slowly decreased the speed of the motor and the engine began carrying itself.  For a few minutes it ran with the motor turned off.


Because it was getting HOT and stinky in my shop, I quit for the day.



- Until decent combustion can be obtained, carbon deposits will be heavy.

- Explosion cup spray hole size appears to be slightly critical and I have to go back through the different size holes to find the optimum diameter.

- Fuel blast past rings is to be avoided.

- Clearances should be a bit larger for Hvid engines than for gasoline engines because of the carbon issue.


Tomorrow, I will run it some more and tinker with fuel settings.  Once I've used up the kerosene I've been testing it with, I'll change over to #2 Diesel and add compression shims appropriately.  I've also got to figure out why it will not feed fuel from lower than 18 inches above the fuel block.  If I try to use the tank I built onto the engine, it hardly fires.  If I get the temporary tank too high, it drips out the fuel valve.


18 June 2009:

Yesterday, I tried running the Hvid again and had disappointing results.  Today, I pulled the head again and modified the transfer hole again.


Old insert (above) and new insert below.                                          New chamfer.                  

Thinking I was onto something with the deflector insert, I made another one that blocked more of the hole, especially right at the O.D. of the cylinder.  The new insert is sort of hourglass shaped.  It doesn;t fit perfectly but, for being filed out by hand, it will do.  I took the Dremel and enlarged the chamfer toward the valves then put a reverse chamfer underneath the insert to help deflect the fuel spray downward.


Because the exhaust valve had some carbon on the seat (the valve hasn't stuck again), I made a 0.100" or 2.54mm shim to go under the exhaust valve spring to increase the closing pressure.


(As I write this at 5:15pm, United Parcel Service just delivered the second flywheel!)


After putting it all back together, I had a little trouble with the fuel valve but, once I got that sorted out and spun it up, turned on the fuel and turned on the compression, the Homebrew Hvid took off like it really wanted to run!  I figured I'd quit while I was ahead so here I am.


Maybe tomorrow, I can have it doing well enough to start off the crank and I can then make another movie.


18 June 2009:

Well, today, the little engine ran on it's own.  I did some work on the fuel valve and reset the cam timing to what seems to be it's sweet spot.

Fuel valve as modified.

It was suggested by a Hvid expert on Harry's SMOKSTAK.COM that running would be improved if a couple of changes were made to the fuel valve.  They are shown in the photo above.  One of the changes is to make three flats in the valve stem so there's more clearance in the guide for airflow, which is necessary for proper fueling.  Since the valve stem is made of drill rod, the only way I could do this was to grind the flats.  


The second suggested change was to cut a groove in the valve seat around the fuel port to allow fuel to collect between fuel valve openings.  Since I didn't have a way to do this to the seat, I chucked the valve in the lathe and turned a small groove in the face of the valve where the fuel port is located.  I could have made a bigger groove but thought this would be a good start on it.


After reinstalling the fuel block, the engine took right off so I took it outside and made a movie of it running.  There are still some more tweaks that need to be done but the project is basically finished.  I will post any significant work here.



4 July 2009:

I've been making small improvements to get it running better and have been successful in getting it to start on it's own without using naphtha.  It's still very wimpy 'til it's warmed up, though.


One of the things I changed was to enlarge and reshape the communication hole between the explosion cup and the combustion chamber.  I also reworked the explosion cup hole and aimed it roughly toward the center of the piston.


    Former communication hole.                                    New, reshaped communication hole.

The fuel block was re-made twice after breaking a #50 drill bit deep inside the new block and being unable to get it to come out.  The bad news is that the block was almost finished when that happened.


The third fuel block turned out okay with revised passage sizes for better fueling.  The mods work.


The governor's still wonky.  It's way too insensitive and it's gonna get a going over - mostly changing the length of the arms to make the fuel needle move faster.  I'll also make the angle of the fuel needle point much steeper so it takes less movement to shut down fuel flow.


There is a Delco lawnmower starter/generator on the way that I will use in the show version of the engine.  I'm still undecided whether to make a hybrid butt-buggy with it or just make a nice roll around stand and show it as simply an engine.


5 July 2009:

I revised some of the governor parts to make it more sensitive and reworked the fuel needle so it closes faster.


New drive point for momentum charging device.

Also, I decided that I'd never be able to hand-crank the engine by the crankshaft fast enough to get it to start so I made a hub for the cam sprocket that will accept the crank.  Now I can spin it twice as fast.


THEN, when I went out to see if it would start with the crank and how it ran after modifying the fuel block, the furschlugginer compression release packed-in.  The eccentric insert in the lever worked loose from the lever and pinched the detent spring, locking everything up.  Once I got the pieces of the spring fished out, I used the sparks-and-smoke connection maker (welder) to make sure the insert didn't wander again.  Then, I made a simple ball-end plunger to replace the ball that I wasn't happy with.


Time ran out so I'll test it tomorrow, if'n it don't rain all day.


7 July 2009:

Yesterday, I ran the engine and, although the governor is still a bit on the insensitive side, once the engine warmed up, it wanted to run.  Using the "shop towel on the flywheel" version of a Prony brake, the little engine acted like it really wanted to make some power.  Especially if I held the fuel metering valve open.


About the time I was starting to have fun, the exhaust valve started sticking so I packed it in for the day.


Today, I removed the rod and piston to check the rings and they're okay.  When I first put the piston in after giving the ring grooves some more clearance to stop the rings from sticking, I put witness marks for each ring so if I had to remove the piston, I could get them back to close to where they'd seated.


I changed the angle of the fuel metering valve to one that was less of a point.  This was to make the fuel cutoff sharper.  I also took the governor off and checked it for wear and found it okay.


Then, when running it today, it just didn't seem to do well.  About the time I sorta had a handle on the governor setting it started slowly hunting.  When I looked to see what it was, the pushrod from the governor to the balcrank on the side of the engine had broken off and was just rubbing on the broken end.  I think I'll make a new one of a slightly different design so minor misalignments won't stress it.


12 July 2009:

After making a muffler, I have decided that, except for a few minor tweaks and possibly a revised governor (more sensitive), The Homebrew Hvid engine is about done.  Below is a synopsis of the modifications I made to the engine since I first started motoring it for fueling tests.

Starting on 2 June and to date here are the steps in the revision process to get the engine running well enough to pull a modest load.


- Tests Using Kerosene (parrafin) -


Original #1: The spray hole in the cup was 0.028" (#70 drill) or 0.7112 mm.  There was no ignition at all, even with naphtha vapor at inlet.


Modification #2: Changed spray hole to 0.035" (#65 drill) or 0.889 mm.  No ignition except with naphtha vapor at the inlet valve.  Heavy smoke but no power.


Modification #3: Changed spray hole to 0.040: (#60 drill) or 1.016 mm.  Ignition with naphtha vapor but no smoke.  No power.


Modification #4: As above, raise compression with 0.021" or 0.5334 mm shim.  Ignition with naphtha vapor.  Smoke. No power.


Modification #5: As above, raise compression with 0.042" or 1.0668 mm shims.  Ignition with naphtha vapor.  Smoke. No power.


Modification #6: Increase spray hole diameter to 0.0465" (#56 drill) or 1.1811 mm .  Same shims as #5.  No improvement.


Modification #7: As above, raise compression with 0.102" or 2.5908 mm shims.  Will ignite kerosene after warming up with naphtha.  No power.  Increase compression shim pack to 0.123" or 3.1242 mm, then to 0.144" or 3.6576 mm with no improvement.


Modification #8: As above but bore cup as shown in "Revised" so bottom is 0.250" or 6.35 mm in diameter.  (NOTE: Spray is still straight out from cup and isn't changed to angled spray until Modification #18)  No improvement.  


Modification #9: As above but change compression shims to 0.123" or 3.1242 mm.  No improvement.


Modification #10: As above but change compression shims to 0.081" or 2.0574 mm.  


- End of Kerosene (parrafin) Tests -

- Start of #2 Diesel (fuel oil) Tests -


Modification #11: Bush and re-drill cup spray hole to 0.028" (#70 drill) or 0.7112 mm.  Add compression shims up to maximum of about 0.150" or 3.81 mm.  At maximum compression, getting ignition and small combustion, giving exhaust note with smoke.  No power.


Modification #12: Drill spray hole to 0.035" (#65 drill) or 0.889 mm.  No improvement.


Modification #13: Drill spray hole to 0.040" (#60 drill) or 1.016 mm.  Increase transfer hole in head (between explosion cup and combustion chamber) to 0.375" diameter or 9.525 mm.  Compression shims 0.120" or 3.048 mm.  Some improvement.


Modification #14: Drill spray hole to 0.0465 (#56 drill) or 1.1811 mm.  Compression shims 0.100" or 2.54 mm.  Regular combustion when warm.  Very minimal power.


Modification #15:  Drill spray hole to 0.055" (#54 drill) 1.397 mm.  Re-aim transfer hole in head.  Block passage at edge of cylinder diameter and use rotary file to make hole oval shape toward center of cylinder.  Regular combustion when warm, some governor action but still has to run with motor assistance.


Modification #16: Drill spray hole to 0.064 (#52 drill) or 1.6256 mm.  Increase compression shim to 0.120" or 3.048 mm.  Runs better but still requires motor.  Heavy smoke.


Modification #17: Bush and drill spray hole to 0.035" (#65 drill) or 0.889 mm.  No improvement.


Modification #18:  Bush and drill spray hole to 0.028" (#70 drill) or 0.7112 mm and aim spray toward center of cylinder per Revised Explosion Cup drawing.  Poor combustion, irregular firing.  On motor.


Modification #19: Drill spray hole at same angle and to 0.035" (#65 drill) or 0.889 mm.  Regular ignition and combustion.  Makes some power and will run without motor when warm.


Modification #20:  Drill spray hole at same angle and to 0.040 (#60 drill) or 1.016 mm.  Re-design fuel block with larger passages and with steeper angle on fuel metering rod point.  Compression shims 0.120" or 3.048mm.  Revise governor-to-first balcrank pushrod for less binding.  Shorten fuel needle valve arm and lengthen opposing balcrank to get more governing stroke at fuel needle valve.


When I get the starter/generator and have it belted up, I will be able to roughly determine relative power output (generator amps) at a fixed load.  This will enable me to more accurately tweak the design for best power.


While running the engine today, when the water temperature in the top of the tank reached 160 degrees Farenheit or 71 degrees Centigrade.  At the water jacket outlet, the temperature was about 190 degrees F or 88 degrees C.  Since the head is "dry" or has no water cooling passages, cooling of this part is strictly via conduction through the copper head gasket to the front of the cylinder and thence to the water.  As a result, the head is running significantly hotter.


When this temperature is reached, the governor starts hunting and I believe it is because fuel in the fuel block is beginning to boil.  If I let the engine cool about 10 degrees F and re-start it, it runs fine until it again gets to the higher temperature.


I may try vegetable oil as fuel to see if it's higher boiling point will cure this problem.  Also, with veggie oil, the exhaust will smell a lot nicer.  I hope it doesn't smell so nice I'm irrestibly drawn to a McDonald's restaurant for a super sized order of french fries ("chips" to our friends across the pond).  That could be a problem because I'm trying to shed about 20 pounds!


13 July 2009:

This morning, I stole a little Wesson oil from my wife.  Of course, I told her (but after the fact) but she got me!  I thought Wesson was corn oil.  It was canola oil but I figured it would work the same.  I mixed a little kerosene/coal oil/number one fuel oil/parrafin with it and let it sit awhile to make sure it would mix.  It did, so I drained the number two fuel oil/Diesel fuel from the tank and dumped the veggie/kero mix in.


Hauled it out in the driveway and spun it.  It wouldn't even make smoke so I added another shim and then it would make smoke and barely ran.  I let it motor along until it warmed up some but it still was very weak.  The exhaust smelled like I remembered when I used to go to the dirt track races and the guys ran castor oil.  I was hoping for french fries!  The only thing is that it doesn't smell as bad as Diesel smoke.


To make it run, I dumped my remaining Diesel fuel and some kerosene into the tank, making the mixture about 25% canola oil, 25% Diesel and 50% kerosene.  After I got the stuff mixed up well and motored it for a few minutes, it ran pretty well and I could remove the added shim.


After that, I ran the engine for about an hour and a half and it didn't hunt like it did yesterday so I suppose it could be that the canola oil raises the boiling point of the fuel brew enough that the hot head doesn't make it vaporize.


Tomorrow, If I remember it, I'll go to the store and get a quart of cheap corn oil and try that.


18 July 2009:

I've been doing some stuff and fooling with fuels.


Muffler and exhaust pipe.                                                     Splatter shield.                

The muffler is made from a piece of black pipe with four big washers stuffed into it at 1" intervals with another washer at each end.  This makes a sort-of Maxim silencer.  With the addition of the conduit elbow, it gives a nice deep tone.


I finally made a "splatter shield" or "crank guard" because I was getting tired of being sprayed with blobs of gooey black stuff when the engine was running.  I've got to slick it up some adn paint it yet.


Also, today, it got a good solid two hour run.  The fuel mix was what was left of the Canola, #2 fuel oil and #1 fuel oil (kerosene or paraffin) brew with a big dollop of corn oil and some more kerosene.  After it warmed up some, I could hand crank it started but the detonation knock was really loud.  I removed an 0.020" or 0.508 mm shim from the rod and this lowered the compression enough to sorta quiet the knocking down.  Next time I run it, I'll see if it will start and run cold with this ratio.


I think that the fuel formula I'm going to end up with will consist of about 75% corn oil and 25% #2 fuel oil.  With 100% veggie oil (lower cetane rating than fuel oil), the power is down and it is hard to start and get to run until it warms up.  I find that it takes a significant percentage of either #1 or #2 fuel oil mixed with the veggie oil in order to get the engine to run at all when it's cold.  This is probably due to the vaporization point and higher igniton point of veggie.  


With kerosene or #2 Diesel fuel, added, the exhaust doesn't smell very appetizing but it's a lot better smelling than the fuel oil by itself.


During the run today, I hooked two 100 Watt light bulbs up to the motor and the engine could power them.  The power's not impressive but I think I'm doing okay with the size of the engine and the relatively slow speed I have to run it.  If I could get the revs up to a couple of thousand, it might make significant power.  With the Hvid fuel system, though, this kind of speed would probably be difficult to achieve.


More testing shows that the governor could use more work as it is not very sensitive, having a droop of around 11% between no load (796 RPM) and 200 Watts of load (710 RPM).  In order to not get too burned out on the engine, I will leave the governor redesign for another time (if ever).


23 July 2009:

Been fiddling with different fuels.  Today, I tested a 50/50 mix of #2 Diesel and corn oil.  Not too good.  I think I may need to either use kerosene as a mix or go heavier on the #2 Diesel.  The veggie oil must have a high flash point.  In a true solid injection Diesel, it works fine because the compression ratio has no effect on the timing.  That means that the ratio can be high enough to develop substantially more heat than is needed for combustion.


With the Hvid design, compression ratio determines timing.  Get it too high and ignition occurs too early, resulting in the engine either kicking back or knocking really loud and not making power.  I've tried straight corn oil and couldn't get ignition even with all the compression shims in place.  When I run a mix of mineral and veggie, I can lower the compression ratio some but I do get knocking.


Here is a video on YouTube of the testing done today:



25 July 2009:

Yesterday, I tried to start the engine by hand with the 50/50 Diesel and Corn oil fuel but it just didn't want to run.  When I finally gave up on the crank and motored it, it started reluctantly.  After warming up, it still ran badly so I drained the Diesel/Corn mix and refilled the tank with 100% #2 Diesel.  It still acted like it didn't want to run.  I kept it running until it started getting really sorry.  It was smoking a lot and slowing down.  No matter what I did, it wouldn't get up on the governor.  Finally, it slowed and stopped.


At first, I thought something was binding and loading the engine-up.  As soon as it stopped, I turned the flywheels and they turned easily so friction wasn't the problem.


Today, I pulled the head and found out why it wasn't running well.


    Explosion cup totally clogged with coke.                           Explosion cup stuck in bore of fuel block.



    Explosion cup after prying it out of bore.                                Note slight coking of exhaust valve.    

No wonder it wouldn't run!  The explosion cup was totally stuck in the fuel block and I had to force it out by prying from the combustion chamber side.  The exhaust valve was also coked up almost to the point of closing off the exhaust port completely.  It took a while to get all the sooty coke off everything and get the head reassembled and back on the engine.


Since it was raining when it came time to test it, I decided to wait 'til tomorrow but I'm sure it will run fine.  My theory is that the vegetable oil is the culprit.  I heard somewhere that veggie oil has glycerin in it and it's that stuff that clogs everything up.  Whatever the cause, I think I'll just run it on #2 Diesel fuel for the foreseeable future.


Next, I started on the radiator.  The core is the evaporator coil from a defunct RV air conditioner.  The fins are aluminum but the tubes are copper so I can solder it.  I used my trusty bandsaw to cut the  top and bottom ends of the tubes off of the evaporator, getting rid of all the "U" fittings.  Then, using one of the aluminum mounting plates that the tubes went through as a template, I drilled a couple of pieces of copper sheet and soldered the tubes to it.


I'll have to make top and bottom tanks, some side panels and mountings.  I think I'll have enough copper to do it.  I'd like to emboss "H-C" on the top tank but, unless I can come up with a way to make it look professional, I may have to pass on that little feature.


Radiator with top and bottom header plates in place.


26 July 2009:

More done on the radiator.  It isn't going to be the prettiest radiator around but I'm getting a little more used to bending and soldering copper.

Bottom tank done and soldered-in.  Top tank sitting on header awaiting neck and inlet.

I'm planning on making copper side rails to neaten it up a little.  It's going to be interesting to see how badly it leaks.  If there are only a few seepers, I may just load it up with stop leak and be done with it.


29 July 2009:

Yesterday, I finished the radiator (except for the cap, which is 'optional') and put the engine under test for the new spray hole angle and to see how much better it runs after de-coking.


Under test with radiator and loaded with lamps and motor.

Again, I tried to start it without using the motor.  It -almost- took off on it's own.  It started firing after a couple of times over compression but wouldn't quite pull itself well enough to go, even with a little help from naphtha vapor.  My 'cranking battery' ran down and I had to resort to the motor.  It didn't take much on the motor before it had built up enough heat to run on it's own.  (Tomorrow, I'm going to add another 0.020" or 0.51 mm to the compression shim pack and see if it will cold-start easier.)


After it warmed up, it ran MUCH better than ever.  I think the major thing that made it run was the change of explosion cup spray hole angle more toward the center of the piston.  It ran a bit quieter and smoked much less than before, running almost smokeless when unloaded.


Because the motor is one of those 90 Volt DC "variable speed" types with a permanent magnet field, it can be used as a generator.  I hooked up a couple of lamp sockets to the motor, cranked it up and screwed in a couple of 120 volt bulbs (one 100W and one 50W).  The engine took the load fine and barely let me know it was working.


After watching the lightbulbs for a while, it got boring so I went into my shop and got another (different brand) 90 Volt, 1/4 H.P. motor off of another variable speed drive.  I hooked it up with the light bulbs, cranked up the engine and connected the load to the generator-motor.  The motor-motor started right up and the engine was now barking a little and sending light smoke signals to let me know it was working.


Curious, I went in and got out a DMM and Ammeter and hooked 'em up.  The Ammeter (which reads a bit low) showed about 1 Amp and the Voltmeter showed about 90 Volts, giving an actual electrical load of about 90 Watts.  Taking a wild guess as to how efficient the generator and the belt drive are, I figured a good guess was about 40% (flywheel to electrical load) so the actual output of the engine could have been in the ballpark of 130 Watts or 0.172 H.P. (130 W divided by 756 W/H.P.)

The metering setup.

After letting it run for a while, I went back into my shop and got my prony brake out of the scrap lumber box.  Laying a piece of 2X4 against the hub of the sprocket on the motor, I loaded it up until the engine was starting to fall on it's face, then backed-off until it was steady.  The readings I got were 75 Volts and 2.2 Amps or 165 Watts.  Taking the 40% guessed efficiency factor into account, the actual engine output could have been about 412 Watts.  Again, doing the H.P. calculation, the horsepower could have been about 0.54 H.P.  (130 W divided by 756 W/H.P.)


[I think if I increase the RPM to around 900, I should be able to get an honest 3/4 H.P., possibly more, out of it]


While I let the engine run (for a total of about three hours), I cogitated on a butt-buggy run by that combination of motor-generator and motor-motor with a home designed and built PWM controller.  The tranny would be the spare Interstate gearbox/axle from a Sears Suburban tractor.  


The Interstate tranny's got a 2-speed transfer, giving six speeds.  The reason I swapped another tranny for it in the Hoyt-Clagwell 54/75 was because it wouldn't stay in reverse.  If I use it with the DC motor, I won't have to worry about reverse.  I'll simply swap polarity on the motor and it will run backwards.


Now all I've got to do is dope out the overall gear ratio of the tranny and see if I can direct couple the 1/4 H.P. motor to it and get enough torque to move it over the ground.  My initial thought is that it ought to pull okay in low/low gear.


More thinkin' is in order.


17 August 2009:

I got the Delco starter/generator and cleaned it up.  The other day I mounted it on the engine skid and fired it up.  As a starter motor, it is fine but as a generator it ain't much.  Either there is a problem in the generator field or they are just a poor compromise between a strong motor and a strong generator, favoring the motor a LOT!


              Delco starter/generator setup.                                    Note the belt, an inside-out tooth belt


I turned a flat belt pulley with a 2 degree crown on it.  The diameter of the pulley ended up being 2.160" in diameter.  driven by a flywheel of 12.4375" diameter, at about 660 RPM, the generator turns about 3,800 RPM.  This was not enough to even make 13 Volts at the armature with the field grounded.  In other words, it wouldn't charge the battery, which needs to be at around 13.9 volts to be fully charged.


I sped the engine up by holding the fuel needle open and, when it got to around the same speed as it ran unloaded (800 RPM - yes, it does have a droopy governor), the generator was turning 4600 RPM and would charge the battery just a little.  


I turned the pulley on the starter/generator down to 2.0" and tried again.  This time, of course, it didn't crank as fast but did try to charge when the governor was tightened up to run the engine at 800 RPM under a moderate load (the motor/generator was turning about 4,975 RPM).  As it was, the field current was higher than the armature charging current.


I took the pulley off again and turned it to 1.75".


At 1.75" diameter on the motor/generator pulley, it was turning almost 5,700 RPM but it was still only putting out about 2 amps at 13.5 volts and still required about 1.4 amps to make that 2 amps.  Not very efficient!


I've either got a motor/generator with a bad generator field or the design is just too inefficient for me to use.  I will need about 5-10 amps to run a small drive motor unless I want to sit around charging the battery almost all the time.


I suppose I could make up a friction drive (a small tire on the motor shaft that runs on a flywheel rim) for the motor/generator, abandoning the generator part.  Then I could get a small alternator from something like a Kubota tractor to charge the battery.  I'm sure it would be a better charger than the Delco unit.


Anyhoo - that's how it stands as of today.  I'm gonna research the Delco units more to see if I may have to replace a field coil as that's the only thing I can think of that could be wrong with it.  That is, if it isn't simply a crummy generator.


10 September 2009:

I've decided to ditch the Delco unit.  I think it's got a shorted turn in the armature and it just isn't worth fixing.  A friend has given me the alternator from a small tractor which I'll use to charge a battery.


I've also decided to design and build the 2009 Hoyt-Clagwell butt-buggy using this engine, alternator, battery and an electric motor to power it.  I've started a new page in which I will detail the design and construction of this new GREEN machine.


22 October 2009:

Since the engine has been plagued by the exhaust valve sticking from carbon build-up, I finally got disgusted with it and reamed the exhaust valve guide out so it now has about 0.010" clearance.  It is a sloppy fit but I don't think it will stick again.


Then, since I bent the camshaft while cranking it at it's first show (it was cold and the engine didn't want to start but finally did), A new camshaft was in order.


                           The original shaft above.                               The new camshaft with lobes and sprocket mounted.

The original cam shaft was 0.625" and it bent slightly from pulling on the crank.  I used a piece of 1.000" bar stock to make the new shaft.  The end bearing opposite the sprocket was retained but, since I didn't want to re-bore the engine frame, I had to make a brass bushing for the sprocket end.

The new camshaft in place ready for test run.

With the new camshaft and hogged-out valve guide done, I test ran the engine.  First results are good, although, for some reason, there is now some drag in the governor linkage that I'll have to fix.


29 October 2009:

In the last few days, I got the governor linkage sorted out and it's working pretty well. 


Since the Homebrew Hvid engine is now on the new Hoyt-Clagwell, I guess it's time for me to turn this thread over to the pages for the 2009 Algore Edition Green Hybrid Hoyt-Clagwell with the exclusive "Plough By Wire" Gee-Haw steering.  That's where this saga will continue.


22 December 2009:

After experimenting with the engine 'til I believe I've gotten about all the power out of it I can, I've decided to abandon the Hvid.  The smoke and low output make it sub-marginal for driving The 2009 Algore Edition Green Hybrid Hoyt-Clagwell so it gets changed into a naphtha burning spark ignition engine.


You can see the conversion here:

Go To Converting to Naphtha 




Converting Back to Hvid

1 July 2010:

Well, since I converted the engine to spark ignition burning gasoline (naphtha), I've had a change of heart.  As a throttle governed gas engine it was really sweet running but it still didn't produce the power I expected.  In addition, I'd designed the rod, crankshaft, etc. for strength to withstand the 20:1 compression ratio of the Hvid system.  To get right down to it, I still like the Hvid idea so there's nothing for it but to convert it back to Hvid.


The conversion was a matter of just replacing the head and other Hvid parts.  While I was at it, I replaced the piston rings that were worn out; probably from back when they stuck on the piston from the coking.  I think the coke in the bottoms of the grooves forced them to really rub the cylinder wall hard and that was what did the deed.


I've made a cart (trolley to my Brit and Aussie friends) and am in the process of building a radiator for it.



    Raw material from air conditioner                                                          Stripping fins to expose tube ends.

For my core, I am using some of the condenser coil from the junked RV air conditioner I salvaged.  First, I used the bandsaw to cut off a piece of the coil.  Then, I bandsawed the 180 degree elbows off of one end of the coil so I would have a bunch of parallel tubes.  Enough fins were removed from the coil to expose the ends of the tubes.


Using a header as a drill guide for the top and bottom flanges.                                          Cutting the holes for the tubes.                    

Since I had to remove one of the headers from the coil, I used it as a drill guide for making the holes in the new copper headers for the radiator.  A flat ended milling cutter was used to make the holes which were slightly smaller than the tubes.


                  Bending the headers.                                                  Header with tubes swaged into place before soldering.

I allowed for a 1/4" flange on the headers so the tanks could be soldered to them.  Using a long punch, I hogged-\out the holes in the header for a snug fit over the tubes.  After securing the header, the tube ends were peined enough to lock them into the header.


      Tubes soldered to header.                                                                               Blank for top tank.       

I used my big 150 Watt soldering iron to sweat the tubes to the header. 


Then, after drawing it out, I cut the one piece that would make up the top, sides and ends of the top tank.  After bending the tank together, it was soldered, using 14 gauge copper wire on the insides of the joints for reinforcement.


Delving into the junk box got me the filler and inlet pieces which were soldered in place.

The radiator, done except for the bottom tank.

The bottom tank will be easier to make because it won't have the fancy curves.  As you can see from the photo, the radiator looks lopsided.  I didn't notice it 'til I'd finished soldering on the tanks that the core sticks out farther from the tube on one side.  I suppose I'll have to figure a way to hide this "feature".


Tomorrow if the creek don't rise, I'll finish the radiator and get it mounted and plumbed.


3 July 2010:

Well, I think its ready to show.

The Homebrew Hvid with radiator and cart.

With the new rings, I wore myself out trying to get it to run when cranking.  I just couldn't get up enough speed even when using the naphtha soaked rag as a starting aid.  It would smoke and knock but couldn't reach critical speed because the compression was low.   I jury-rigged a motor to spin it up fast enough to keep going and, as the rings seated, I could wean it off of the naphtha and it ran stronger as the run progressed.


Notice the gloves under the rear feet of the cart?  They are needed because without them, the cart slowly scoots around.  You can see the paint tracks in the concrete.  The gloves do the trick.


In all, I ran it for about an hour and a half which should have allowed the rings to seat.  After about an hour, I stopped to tweak-in the governor and it cranked right back up.


In the photo, the black thing in front of the cart is my moving handle.  The "U" channel fits up into the bottom of the rear 2 X 6 cross member.  It's long enough that I don't have to stoop to lift the end so it will roll on the wheels.


The radiator worked out all right, although it looks kinda thin.  In 90 degree (F) heat, unloaded, the water temperature at the top tank of the radiator was about 160 degrees.  After loading it up for five minutes or so, the temperature slowly rose to 185 degrees then, after removing the load, it slowly went back to about 160 degrees.  Since I'm not going to work the engine, this will be fine.


I hope to take it to some Florida shows during the next season.  See 'ya there!


1 August 2010:

Ignition Knock Experiments

I've been doing some work and experimentation on the Hvid to see if I can make it a better showpiece.  For one thing, I made a muffler to change the "bark" into more of a "woof".  That works fine.

Showing the new muffler.

Today, while sitting outside running the engine in the 105F (40.5C) heat index and listening to the hard detonation knocking, I think I've figured out why it knocks hard at times then fades into relative quietude at other times.  This is all at the same no-load and RPM condition.  I believe that the effective diameter of the fuel spray hole in the explosion cup changes slightly while running due to carbon build-up and loss.   


This morning, I started out running it at a little over 600 RPM.  After it warmed up, it was knocking irritatingly loud and almost constantly, making a little smoke.  When I increased the speed to about 750 RPM, it didn't seem to knock quite as loud, smoked less and had longer periods of relative quiet.  I also noticed that, when a load was applied, the knock lessened, probably due to the slower burning of the heavier fuel spray.  Also, after removing the load, the knock was loud for a minute or so, then faded a bit, especially at the higher speed.  I think that was caused by the spray hole being cleared of carbon during the heavy fueling, taking some time to build-up again after the load was removed.


Sitting on my upturned drywall bucket in the driveway, sweating a puddle onto the concrete, I came up with a theory.  In a Hvid, it is my understanding that the detonation of the fuel in the cup is controlled to a major extent by compression ratio.  The spray hole has less influence upon the timing of the cup explosion than the actual compression pressure.  It would appear that lowering the compression would lessen the detonation knock but, in the case of the Hvid engine, lowering compression has little effect until it is too low for reliable explosion cup combustion and even then, when combustion takes place, some knock is present.


That brings me to the conclusion that compression ratio should only be high enough to ensure reliable cup detonation.  Any higher than that simply places more stress on the engine and makes it harder to crank.


I also believe that, after the compression ratio is set for reliable cup ignition, the major factor determining timing is the diameter of the spray hole in the cup.  The larger the spray hole, the faster the fuel is sprayed after the cup explosion occurs and, if the hole is too large, the fuel charge will be blown into the combustion area too suddenly and heavy detonation knocking will result.


I also think that the running speed of the engine will determine how advanced the timing should be and because I now believe main combustion timing (not cup detonation) is dependent upon the diameter of the spray hole, this must be reduced in order to lessen the detonation knock.  With everything optimized, if the speed is decreased, the spray hole must be made smaller to slow the spraying of the fuel charge into the combustion space, thus retarding the main combustion timing.


I know that there will always be some combustion knock, but the quieter, the better.


It all boils down to me taking the fuel block off and making the spray hole smaller.  Somewhere in my files is the present diameter of the hole but, when I have the cup off, I'll measure it then (probably) pein the opening down and then drill it to about 0.005" (0.127mm), about ten percent, smaller than it was.  A test run will tell if this is the right approach.


If anyone out there has any more insight on this, I'd be happy to hear it.  I will post the results of the test here in the next day or so.


2 August 2010:

Yesterday afternoon, I took the fuel block off and here's what I found.

Clagged-up explosion cup.

The bottom of the cup and the head of the fuel valve were covered with carbon build-up.  At this time, I'm not precisely sure that the carbon is the cause of the knocking.  The wet fuel is from the disassembly process where what fuel is left in the passage between the metering valve and the fuel valve gets drained into the cup when the valve is disturbed.


After cleaning the explosion cup, I measured the diameter of the spray hole and found it to be the size of a #60 drill or 0.040" (1.016mm).

0-80 screw threaded into spray hole.                  Screw broken off.                          Screw filed and center punched.

Spray hole re-drilled to #65.

Since I was going to reduce the size of the hole and peining didn't seem to be the best way to do it, I drilled and tapped the hole to fit a 0-80 steel screw.  I only ran the tap in about three turns so the screw would jam into the hole.  The screw was tightened until it twisted off, the face was filed flat and a center punch mark was made.


The fuel block was mounted in the drill press vise and set to a 45 degree angle to vertical, then the cup was positioned on it.  A #65 or 0.035" (0.889 mm) hole was then drilled.  After deburring and cleaning, the whole works was reassembled on the engine.

This morning, I had another two hour sweat session outside with the Hvid. 

At the start of the run, the RPM was set at about 780 but, as the run continued, I lowered it to the 725 range.  After it warmed-up, there was hardly any visible smoke and throughout the first hour and a half of the run, the heavy knock was absent, even at the lower RPM. During the last half hour, there would occasionally be a couple of heavy knocks with attendant smoke then it would settle down for a while.

My theory on this is that carbon is again building up in the cup, causing erratic ignitions due to fuel soaking into the deposit. Before tomorrow's run, I will try adding a proper amount of Diesel injector cleaner to the fuel and see if the problem persists or fueling improves.

There's also the matter of the slight inconsistencies in the exhaust note. My present theory is that, since this disappears when a very slight load is imposed on the engine, the cause is a combination of the very tiny amount of fuel that is metered for each combustion and a possible slight over-sensitivity in the governor. Like the small Diesel engines I'm familiar with (Perkins, Mercedes, etc.) which, at idle, sometimes have an unsteady gate which sounds almost like one cylinder misfiring, the amount of fuel at idle is so small, it is hard to control effectively and usually isn't worth the trouble to attempt to correct.

Tomorrow, I will again run the engine for a couple of hours and see if the injector cleaner improves things.  I may also fiddle with the governor sensitivity a bit to see if the engine can be made to hit more evenly.

On another note, I measured the fuel tank and figured the capacity to get some idea of the fuel consumption at show speed and no load.  The tank is 2-7/8" (73.025 mm) in diameter and 6-3/8" (161.925 mm) long, giving a volume of 41.39 cubic inches (678.2606 cc) or about 0.1791775 gallon (U.S.).

Since the engine used about a half a tank of fuel for the combination of running both days, or about three hours, I figure one tank of fuel will run the engine well in excess of six hours, giving a fuel consumption of approximately 0.03 gallons (113.5624 cc) per hour.  Since one hour of running was with the larger spray hole and smoky exhaust, further testing will see if this is a nearly correct figure.


3 August 2010:

I ran the engine again today for a couple of hours.  This time, I added the recommended amount of Lucas fuel system cleaner to the tank and topped it off with #2 Diesel fuel.


After the engine had run for a little over an hour at about 700 RPM, the knocking was about the same as yesterday so I added another amount of the cleaner (to about double the maintenance amount I'd added earlier).  By the end of the run, it seemed not to have changed - the knocking maybe even got a little worse.


Since I have the compression set to just a point high enough for me to be able to hand-crank start the engine when it's cold (using just a little naphtha vapor in the intake to lower the combustion temperature of the fuel).  It is possible to lower the compression even more but starting is difficult and it needs a longer period of naphtha vapor to keep running.  I've tried higher compression but it only makes the engine harder to crank and doesn't seem to improve running.


If I can get ahold of some #1 Diesel fuel or Jet-A, I'll try it.  I tried some hardware store kerosene (paraffin) early-on but the engine didn't run real well on it and I'm not sure it was even engine fuel grade kerosene.  The engine seemed to be a little harder to start on it which is reverse of what I'd thought would be the case.  Maybe that particular gallon jug wasn't really the same as motor fuel grade #1 Diesel.


I'd really like to get it to run without the heavy knocking but I could be barking up a tree because of the smallness of the engine.  Suggestions?


4 August 2010:

This morning, while preparing the Hvid for another run, I discovered that the off-side flywheel was beginning to walk off of the crankshaft!  The gib key was fully seated but it was only tight in the flywheel so the key and wheel were sliding on the crankshaft keyway.  I removed the wheel, thoroughly cleaned all surfaces and reassembled it using Loktite and a new key.  So far, so good.  The new key is only about half seated so I will remove it and dress it to fit all around when tight.


The good news is that part of the knocking was from the loose flywheel.  There is still some periodic knock and smoke but I'm almost convinced it's about as good as it can get.  If I can obtain some #1 motor fuel, I'll clean the cup and run it some more to see if it carbons-up less and runs quieter.


Today's run was supposed to be for two and a half hours but about ten minutes into the third hour, it clouded up and I got the engine shut-down and inside just before it poured.


During the test, I measured the temperature in the top tank of the radiator right at the inlet.  Ambient outside was about 90F (32.2C).  

At the start, it was 84F (28.8C).

At 30 minutes, the temperature was up to 143F (61.6C).

At 60 minutes, temperature was at 158F (70C).  

At 90 minutes, it was still 158F.  

At this point, the engine was in the sun and the air temperature was about 92F (33.3C).  

At 120 minutes, it had risen to 166F (74.4C).

At 130 minutes, when the test run was concluded, it had risen to 168F (75.5C).


All in all, I don't think the engine is running too hot and, although I haven't measured the head temperature, it shouldn't have been over about 220F (104.4C).


I may do more tests but I think the engine is ready for prime time.


10 October 2010:

Well, last weekend I took the Homebrew Hvid to a show.  When I cranked it up, the fuel valve started leaking probably because the engine had been sitting around for a while.  I used a pair of pliers to rotate the fuel valve to work out whatever was fouling the seat.  SNAP!!!  The drill rod valve stem broke where I ground a groove in it for the spring keeper.

Broken fuel valve stem.

Since I don't have any more drill rod to make a new valve with, I figured out a way to repair the existing valve.


New fuel valve stem cap and spring keeper.

What I did was to take a 0.5" length of 0.25 diameter steel rod.  I drilled a slip-fit hole 0.200" deep in it to accept the fuel valve stem then turned the upper part of the valve extension so it would clear the governor valve stem.  I then ground a flat on the fuel valve into which a #4-40 setscrew seats.

Repaired fuel valve in place.

The repair cap/spring keeper was calculated to return the total length of the fuel valve stem to what it had originally been so the rocker and pushrod would still work.


I ran the engine for about an hour this afternoon and all's well again.  Maybe the next show I take it to, I can manage to not break anything so I can run it.


10 February 2011:

Well - I finally got to a general aviation airport and bought some Jet-A fuel.  It's supposed to be about as close to old fashioned kerosene "coal oil" as you can get, only with some anti-jelling additives for high altitudes.  


I drained all the #2 Diesel from the tank and flushed the lines with Jet-A.  I figured that I would have to remove a compression shim and I did.  That didn't work out.  It was hard to wean off of the naphtha, was really sluggish and smoked a lot.  When I put the shim back in, it ran a lot better and I think it knocks less and is a little more responsive to the governor.  I have no way of telling what the power output is on jet fuel but using my "rag-on-the-flywheel" dynamometer, it seems to be making close to the same power as on Diesel.


The engine ran about an hour (about six ounces of fuel) before it started getting dark and I quit.  All in all, it may be worth it even though Jet-A costs about $1.75 more a gallon than Diesel.


12 October 2011:

Denis Basson, who lives in Adelade Australia has been doing some research on Bronz and Hvid engines.  One of the things he's noticed is that there are a couple of variations of the later explosion cup.  One of them has a tapered bottom and the other one has a flat bottom.  That got my interest up.


Cup, carboned, as removed.                                                                               Cup cleaned-up    

The cup that I removed was one that had been run in the engine for about 20 hours.  You can see it is pretty well carboned-up.  On the right is the same cup with the carbon removed, showing the tapered bottom. 


Old tapered bottom cup, Left.  New flat bottomed cup Right.

I made a new cup with a flat bottom.  Note where the spray hole impinges with the flat bottom of the new cup.  The spray hole is the same as the old cup, #65 or 0.035" (0.889mm).


I installed the cup and had a devil of a time getting the engine to run on it's own.  The fuel was Jet-A (kerosene or paraffin).  After increasing the compression ratio, it would run but was very sluggish.  I changed the fuel to Diesel #2 with only slightly better results.  My theory is that, since it is difficult to position the spray hole accurately, the spray is not aimed at the center of the communication port and is hitting a wall of the hole, making combustion poor.


Tomorrow, I'll remove the head and make a drill jig that fits into the communication port to accurately position the spray hole.  This will most likely necessitate making a bushing for the present hole and re-drilling it.


13 October 2011:

I pulled the head and checked the aim of the fuel spray and found that it was aimed at the wall of the communication port, just missing the combustion chamber.  I think this was what made the engine run so poorly yesterday.


I removed the spray cup and welded-up the spray hole then put it in the lathe and turned it clean.  The cup was then put back on the injector body and bolted to the head.  Taking a center punch, I carefully eyeballed the center of the rim of the cup and made a punch mark.  The head was then put in a vise and, in the drill press, the #65 drill bit was aligned to run along the center of the communication port.  The hole was drilled.

Alignment of spray hole.

The photo above shows the drill inserted in the hole in the cup and the aim is about perfect.


The exhaust valve was touched-up and the whole works was assembled and mounted on the engine.


Using #2 Diesel fuel and with the compression shims all in place as they were for yesterday's tests, I started the engine.  It started much easier but knocked very loudly and smoked white.  After it warmed up, I proceeded to remove shims from the rod to lower the compression with the following results:


- All shims (0.318 or 8.0772 mm) in place.  Heavy knocking, white smoke, slow acceleration.


- One thin (0.022" or 0.5588 mm) shim removed.  Total pack = 0.296" or 7.5184 mm thick.  Knocking not so heavy but still some white smoke.  Acceleration slightly better.


- Second thin shim removed.  Total pack = 0.274" or 6.9596 mm thick.  Less knocking, still white smoke.  Little improvement overall.


- First thick (0.137" or 3.4798 mm) removed.  Total pack = 0.137" or 3.4798 mm thick.  Slight hard knock, less white smoke.  Better acceleration.


- Second thick shim removed.  Total pack = 0.  No knock.  Much black smoke.  Engine labored and misfired.


- One thin shim replaced.  Total pack = 0.022" or 0.5588 mm.  No knock.  Some black smoke and slight misfiring.


- Second thin shim replaced.  Total pack = 0.044" or 1.1176 mm.  Occasional knock.  Slight smoke, no misfiring, picked up well under load.


Then, I changed the fuel from #2 Diesel fuel to Jet-A (kerosene or paraffin) and ran the engine with the same shims as in the last Diesel fuel test.  The engine ran very well.  No knocking.  Only the occasional puff of smoke*.  Picked up well under load.  It is noted that, as of this afternoon, the engine runs better than it ever has.  I believe that this is the result of making a flat-bottomed cup and carefully aiming the fuel spray.


*: Throughout the testing at the lower compressions, I noticed a slight variance in the note of the exhaust.  I now believe that this (and the occasional change in smoke) is caused by a slight hunting of the governor or, because of the small amount of fuel being metered, slight differences in fuel delivered.


Tomorrow, after it has cooled off, I will see how hard it is to start with the present settings.


14 October 2011:

This morning, I hauled the engine out into the driveway to see how it started cold.  With no naphtha to help, it wouldn't even make white smoke.  When a rag, slightly dampened with naphtha, was draped over the head, the engine started readily, smoking and knocking as it had done in the past, before the latest modifications.  When the rag was removed, the engine quit firing so I left it draped over the head until all the naphtha had dried out.


Sometime during the evaporation process, the engine was able to sustain itself and ran unevenly, smoking.   After a few minutes, when it warmed up sufficiently, the black smoke faded and the beat steadied-out.  The water temperature stabilized at about 140F (60C) and the engine ran very nicely at a constant 700 RPM.


One other thing I noticed today is that, unless you knew it was a Hvid and only heard it running, you'd think it was a well behaved throttle governed spark ignition engine.  There was no noticeable ignition knock!


I'd like to thank Denis Basson of Adelaide, Australia for coming up with the information that allowed me to design and adjust the improved explosion cup.


14 October 2011:

I made an additional compression shim out of what I had on hand, some 0.026" (0.66mm) aluminum sheet.  After installing it, I started the engine, this time without aid of naphtha.  It ran rather rough and smoked black for a while but once it warmed up, it was almost as quiet as yesterday and there was no smoke at no load.


Here's a video of it, taken today.

No cracks about my having cut my head off in the video!


22 October 2011:

Yesterday, while running the engine to see if it would carbon (clag) up, the engine suddenly began running really oddly.  Investigation of the cause found that the return spring for the fuel valve (operated via the intake valve) had broken.  This allowed the fuel valve to be sucked open at the beginning of the intake stroke and blown shut at the beginning of the compression stroke.  The engine would hit a few licks until enough air had been blown back into the fuel line, then it would quit firing and coast until fuel again was present.


This is when I had a major (if you'll kindly pardon the expression) BRAIN FART.  You may want to brace yourself for this by having an adult beverage or the like while I 'splain my idea to you.


First, remove all the intake linkage (intake pushrod, rocker, fuel valve pushrod and fuel valve rocker).  Substitute a weak spring for the fuel valve spring (only strong enough to lift the valve to it's seat).  Consider it now to be "automatic".


Then, remove the intake valve spring and substitute a much weaker one so it will act as an "automatic" intake valve.

Atmospheric set-up                                                        Test spring for the atmospheric intake valve  

Atmospheric fuel valve


Parts removed from the engine in the conversion.

Several things were quickly learned.  As long as the fuel valve spring is just strong enough to hold it closed, it works fine. 


Intake valve spring strength greatly affects the fueling.  To weak an intake valve spring does not allow enough suction to be developed (it doesn't have to be much) for the engine to get enough fuel and it runs erratically.  Increasing the strength of the intake valve spring makes the engine more easily draw fuel.  If the spring is too strong, the engine will overfuel badly on heavy loading.  This causes it to bog-down and smoke excessively.


Now, I know that a few Hvid engine manufacturers used an automatic (atmospheric) intake valve but, so far, I haven't heard of any that used an automatic fuel valve.


Testing of the engine shows that, with the modifications and proper spring strengths, the engine runs smokeless at no load and fuels better at full load than with the mechanical arrangement of intake and fuel valves.


In conclusion I can only speculate on the question of how well these modifications would work on a full-sized Hvid engine.  If someone feels like doing an experiment, I'd be really happy to know how a full-size engine runs with the mods.  


If, in the past, no one thought of this, why didn't they?  If they had thought of it and had developed a successful engine and had put such a Hvid engine into production, would they have made the engines simple enough and inexpensive enough to survive in the market longer?  Interesting questions.


YouTube Video of the "automatic" version of The Homebrew Hvid engine.


23 October 2011:

Today, I rigged up one of my permanent magnet DC motors to the engine and used light bulbs for a load.


    With 140 Watt load, cold.                                           With 140 Watt load, warmed-up.

As you will note above, when the engine was just warm to the touch (cold), it smoked a little with the 140 (corrected) Watt electrical load applied.  (Note below how I corrected for voltage)  After about 30 minutes, the water temperature arriving at the top tank of the radiator was in the range of 170F (77C) and the engine was just making the barest amount of smoke.


Later, I found a larger bulb and increased the load to about 200 (corrected) Watts.  The engine took the load very well with no noticeable increase in smoke and only a very slight knock.  After one hour at this load, the water temperature at the top tank of the radiator was 180F (82C).  At the engine, between the fuel block and the deck of the cylinder block is a space just large enough to insert a thermocouple and the temperature at that point was 212F (100C).  


In all of the running with the atmospheric setup, there was no sign of fuel valve leakage.  With the original setup and a stronger return spring on the fuel valve, occasionally, the fuel valve would leak for a few strokes, shoving the fuel back into the tank.  This usually caused the engine to stop.  


NOTE:  I figured the loads by correcting the wattage.  The way the motor (generator) was belted to the engine made about 75 Volts with a total of 220 Watts of light bulbs connected.  Since the light bulbs are rated at 120 Volts, I decreased the wattage to 137.5 Watts, rounding it to 140.  Later, with the larger bulb in the string, the total was 330 Watts, corrected to 206.25 Watts at 75 Volts.


Making a really rough guess as to the horsepower, I'd say that at 200 Watts, the engine was making, maybe about 1/2 horsepower.  Not too shabby because it wasn't even breathin' hard.


For the past three days, the fuel I've been using is Jet-A (kerosene/paraffin).  Yesterday's long unloaded run (about five hours) consumed less than a half tank of fuel (I haven't yet figured the capacity but it's probably a bit less than a quart (maybe 3/4 Liter).  Today, I ran the engine for about 3-1/2 hours, mostly with the 200 W load and the engine consumed about 3/4 quart (0.7 L) of fuel.


So far, the engine runs very steadily at load and there's no sign of any excess carbon buildup.  All in all, I'm extremely pleased with the atmospheric Homebrew Hvid.


I suppose one of these days, I'm going to have to come up with some kind of prony brake so I can actually tell what I'm doing.


25 October 2011:

Just for funzies, today I did a fuel efficiency test.  These are very unscientific tests.  The horsepower I calculated was an estimated guess.


                             Engine being tested with 140 Watt load.                                             Engine maxed-out at 182 W and bogging down.

To see which side of the power curve I was on, I first set the governor to give an engine speed of 700 RPM unloaded.  Adding 150 Watt light bulbs to the load, I got the fourth one in the load bank before the engine began to smoke badly and bog-down.  With the load applied, the RPM dropped to around 550 then, when the engine almost immediately began bogging-down, the RPM fell quickly until the load was removed.


I then adjusted the governor to give a 600 RPM no load speed and began adding lamps.  As before, when the fourth lamp was turned on, the engine bogged-down.  I then removed the load and, after the engine had recovered, I applied a three lamp load.  The engine took this load initially, the RPM falling to 545 RPM with fairly heavy smoke.  After about 5 minutes, the engine RPM slowly fell and smoking increased so the test was ended.  I can assume the maximum intermittent load is about 65 Volts and 2.8 Amps or 182 Watts.  Since one horsepower is around 746 Watts, doing the division gives 0.244 HP at 100% efficiency.  I'd guess that with belt and generating losses, I could easily double the horsepower to 0.487 HP when efficiency is taken into account.


I'd hazard a guess that the most efficient speed for the engine as it is now configured is somewhere slightly above 600 RPM.


To get some idea of fuel efficiency, what I did was to use a load of two of the 150 Watt light bulbs.  Idle speed of the engine was 600 RPM.  Under a two lamp load, the RPM fell to 571 RPM and remained constant.  Measuring the voltage of the generator (70V) and the current through the bulbs (2.0A), gives 140 Watts or 0.188 HP at 100% efficiency or about 0.375 HP when losses are guessed-into the calculation.  It could be more, but who knows.


Now that I had some semblance of a power reading, I topped-off the fuel tank then ran the engine for exactly 30 minutes with this load.  Fuel use was about 125cc or 0.033 gallon of fuel.  Since kerosene weighs about 6.5 lb. per gallon, the fuel weight was 0.2145 lb.


Since I ran the engine for a half hour, I multiply the amount of fuel (0.2145 lb.) by two and get 0.429 lb. per hour of running.


Now, scaling fuel use up from 0.375 HP to 1 HP, I get a fuel consumption of 1.144 lb. per horsepower-hour.  That figure doesn't sound like something I'd brag about but, if I ever make a prony brake so I can accurately measure horsepower, it could get better.


Interestingly, at the beginning of the 30 minute test, the coolant temperature at the inlet to the top tank of the radiator was 178F (81C) and at the end, the temperature was 203F (95C) and more or less stable, varying a few degrees either way.  All throughout the 30-minute test, the engine smoked lightly and ran steadily.


29 August 2012:

Today, I thought it would be nice to run the engine.  After getting set-up with my lawn chair and starting it, I relaxed and watched.  After a while, I thought I could possibly get rid of some of the unbalance shake so I got our several C-clamps and took my life in my hands.

Stand BACK!!!!
After several tries, I got enough clamps on the flywheels to cancel out most of the shaking.  Actually, I added one two many and the shaking went from barely noticeable to noticeable, meaning I'd gone past the optimum counterweight point.  I found that the engine, despite the big counterweights on the crankshaft, is underbalanced.  That means that I needed to add weight to the counterweight side of the crankshaft.  After the run, I borrowed my wife's little digital scale and found that the total weight of all the clamps was precisely 0.99 lb.

Now, here's where the guesswork comes in.  In order to figure out added weights inside the rims of the flywheels, I have to guess that the effective center of the 1lb of weight was most likely located at about the outside diameter of the wheels.  This means that, in order to have the same effect at a smaller diameter, I'd have to have heavier weights.

Giving me some extra weight so I could trim if it was overbalanced, I came up with a couple of 1/2" thick steel plates cut to fit inside the outsides of the flywheel rims.  They will be bolted to the spokes using hard 10-32 socket head machine screws.  Once the weight is correct, I will remove the weights and reinstall, using Loktite to secure the screws.  

I drew the weights in CAD, then plotted them 1:1.  The drawings were then cut-out and glued to the steel for cutting.  The mounting holes were also located in CAD and the centers were center punched for drilling.

One of the roughed-out weights
For reference, the weights will be about 6-1/4" across the chord.  As noted on the paper, it weighs 0.74 lb.  This will make the total added weight about 1.4lb after trimming.


30 August 2012:

I got the counterweights finished today and on the engine.

The weights, trimmed to fit.

On the running engine.

After the weights were trimmed to fit, the weight had fallen to 0.66 lb and 0.67 lb, making the total 1.33 lb.  After mounting them on the flywheels, I ran the engine and it has virtually no shake.

Note that before the weights were added, when the engine ran, it would "scoot" over a foot an hour downhill (about a one degree slope) on the part of the driveway I use for testing.  After the weights were added, I ran the engine for about two hours and it didn't move a bit.  Another successful engineering triumph here at Hoyt-Clagwell & Company.


BOY!  This is fun!

If you have any questions or comments, please email me at:

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