Homebrew Hvid


Part 2

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Click on the picture for the high definition version.


The next order of business is to design the governor assembly.  I've decided to use 3/8" pitch roller chain for the timing and governor drive.  Although gears would be more authentic looking, I'm having trouble finding a set that will fit in the center-to-center range I need.  Also, cost is a factor.



The governor will run off of a semi-idler sprocket that will also be the chain tensioner.


24 December 2008:

Been busy on the Cad, working on the timing chain details and the governor.  I think I've got a governor that should work fine.  It is driven at crankshaft speed off of the timing chain.  The linkage to the fuel needle will be a bit on the "monkey motion" side but the governor should have enough mass to be able to work it fine.  here's the CAD image.

To give you some idea of the size, the bearing (green) is a little under 1/2" thick and the pushrod (cut off out of the left side of the governor) is 1/4" in diameter. The section of the engine frame that the bearing fits into is 1/2".



I've designed it to use a compression spring for speed adjustment.  Speed will not be changeable without stopping the engine unless I make a change in the method of adjusting the spring force.


26 December 2008:

Governor weights are done.

Governor weights.

I don't know why I showed a fillet on the governor weights in the CAD drawing.  I chamfered the weights because, to do a fillet like that is beyond my capabilities.


29 December 2008:

Except for boring out the sprocket to fit the shaft of the governor, it is done.

Governor parts.

I learned a few things in working on this assembly.  One is that you have to be extremely careful when centering the slots on the turnings.  I was off about 0.005" on the slot in the piece that the governor weights engage in and that caused me to have to spend about an hour diddling around with it to get it to not bind and work correctly.  I ended up filing on the cam part of the weight that was binding to remove the interference.  The spring I selected is a starting point, my best guess.  Once I have it together enough to motor it, I can see how far off it is.



Note that the speed is adjustable by squeezing the spring more or less.  More squeeze will give higher speed and vice-versa.


Assembled governor.

I'll probably start on the camshaft and the cams next.  The "Plan" is to make the cams separate and use setscrews to hold them to the shaft once the timing is set.  



Presently, I have the exhaust cam designed to give 210 degrees of opening.  I'll start the valve at 150 degrees after TDC on the power stroke and have it close at TDC on the power stroke.  Due to the very small headspace of this engine, I plan to have no overlap and set the intake to be 180 degrees, starting at TDC on the intake stroke and closing at BDC on the intake stroke.



If anyone has any insight into valve durations and timing on a Hvid engine, PLEASE contact me.



I can always change valve timing and durations if need be to get the engine to run right (OR at all!) but it would be nice to get it right from the get-go.  That will make fewer "Aw Shoots" during the debugging.


5 January 2009:

My friend Frank took the time to carefully time the valves on his Thermoil and he made an Excel spreadsheet  with durations of both intake and exhaust of about 220 degrees with the intake starting 10 degrees BTDC and ending at about 210 degrees.  The exhast starts at about 135 degrees ATDC and ends at 5 degrees BTDC.



That puts the valves in overlap at 5 degrees BTDC with the intake valve substantially open at TDC.  This may be an anomoly with that particular engine as I think the overlap should occur right at TDC.



In any case, I re-drew the cams to be identical with 220 degrees of duration.



Click HERE to see the spreadsheet.  You must have Microsoft Excel to view it.



Camshaft and cam blanks.                                                       Cam profiling fixture.

Since I don't have any fancy CAM machinery to translate the CAD drawings into finished hardware, I use the method of plotting the cam profile at full size, cutting out the profile and gluing it onto the cam blank.



My cam profiling fixture is made of some scraps.  The block is bored for a snug fit of the shaft (right hand picture above).  The cams are mounted on the top of the shaft and the setscrews are tightened.  The block is then mounted in the mill vise and the shaft inserted into it.


Machining the cams.

This process is not without "aw-shoots".  Holding the cam against the milling cutter is very tricky, especially when feeding the tool into the stock.  The tool tries to pull itself into the larger diameter so a very slow feed rate is necessary.  Once, when I wasn't holding on tight enough, the tool was sucked into the workpiece (or vice-versa), causing me to have to modify the cam profile to clean up the boogers.  Fortunately, nothing was broken.



I may have to get a dividing head if I'm going to make more cams.  That would securely hold the workpiece and keep it from getting "sucked" into the mill.

The finished cams.

In spite of the limitations of my fixture, the cams are useable, although the duration is a little bit short due to the nature of manually tracing the profile.  Here's the CAD with the "as Designed" and "As Made" drawings.


9 January 2009:

I have the sprockets mounted on both the governor and the camshaft plus have started on the lifters.

Finished camshaft and governor.

The sprocket mounting for the governor was designed to match the 1/2" bore of the sprocket, which will drive it at crankshaft speed.  I had to make a hub for the cam sprocket that setscrews to the camshaft.  The camshaft is 0.625" in diameter and the cam sprocket bore is 0.625.



I'll have to bore out the crankshaft timing sprocket to 1.500 and make a hub for it to be setscrewed to the crankshaft.



The two follower bodies are 0.650" in diameter and will be slotted for small sealed ball bearings to be used as the cam followers.  The follower bodies are going to be made of Leadloy steel and will run in low carbon steel guides in the engine frame.  In order for the followers to stay perpendicular to the cams (not turn or cock) as they run, I've designed the centerlines of the followers to be 0.031" below the centerline of the cam.


10 January 2009:

Today, I finished the cam followers and made the collar for the crankshaft timing sprocket.


               Cam followers.                                                      Crankshaft timing sprocket.     


Since the crankshaft journal diameter will be 1.500", there wasn't a whole lot left of the sprocket once it was bored out.  For reference, the thickness of the collar is about 0.25".  I made it out of the only 2" material I had, which was some of the cast iron rod that I will be making the piston out of.



I'm starting to run out of steel to make parts.  The rocker tower and compression release are on hold as well as materials to make the entire engine frame, crankshaft and hopper.


15 January 2009:

The cam follower guides are done and the piston is coming along.

Finished cam followers and guides.

The piston is made from cast iron bar stock.  After cutting it to length, facing off both ends and turning it to a rough dimension, I drilled then bored the piston from the back.



         Boring the back of the piston.                                                  Starting on the wrist pin bore.

The piston is 4 inches long so it will have a very long thrust face for the high compression.  It will have four 1.8" wide rings above the wrist pin and none below.



After laying the rod and piston together, I find that it looks really wierd with that very big connecting rod hooked to the little piston.  I suppose you could say it will probably be robust.


17 January 2009:

Well - I screwed-up bigtime!  After ordering the rings and getting advice on fitting them from Dave Reed of Otto Gas Engine Works, I was getting ready to chuck the piston in the lathe and cut the ring grooves.  



Just for funzies, I checked the wrist pin for squareness to the piston length.


(Please note the colorful language)

As you can see in the photos below:


      One end of the wrist pin bore.                                           The other end of the wrist pin bore.

The difference is 0.0055" which means that the pin is out of square big time!  THEN, it dawned on me what had happened.



I hadn't checked the square of the mill quill with the table for a while and found that it was out about a degree!  This made it cock the wrist pin hole.  Now, it wouldn't have been too bad if I had bored the hole with the vise turned 90 degrees so the piston was diagonal to the table.  Then, all that would have happened was that the pin wouldn't be quite centered on the diameter of the piston.  It would have, though, been square with the length.

The result of not thinking ahead and checking EVERYTHING!

Luckily, I had bought a foot of the cast iron bar so I had enough to make another piston, which I started on today.  This time, I've indicated the quill on the mill and have it as close as it can get. 



ALSO, I've rotated the vise so any error will only cause the pin to be offset from the center of the diameter a shade.  I can't goof-up again because there's not enough of the bar to make a third!


22 January 2009:

Well, the dangnabbits happened again.  A couple of days ago, I bored the wrist pin hole in the new piston and doggone it if I didn't get the bore 0.001" oversize!  Since that won't do at all, I bored the pin diameter out to 0.875" and made a bushing that I again bored -this time to size-.



Back side of piston with material hogged-out.                                             Finished piston.                            

I had to work blind to get the excess material hogged-out of the backside of the piston so the route of the end mill was a little "wobbly".  As in the other homebrew engine, I drilled a 1/8" hole directly over the oil hole in the little end of the rod and then milled a 1" long 1/8" slot about 0.030" deep to help the oil get to the hole and to the wrist pin ("gudgeon" pin to our friends across the pond).



The last thing I have to do with the piston is to make a couple of brass buttons to go at the ends of the wrist pin so, if the pin drifts out of it's tight press fit in the piston, it won't score the cylinder wall.


Piston and rod assembled.

With it all assembled, the rod and piston have a kind of ridiculous look.  That huge big end and that little bitty piston.  Well, 'ya can't say the bottom end's gonna be overloaded!


29 January 2009:

There has been a bit of a pause in the project.  A friend from Kentucky was coming down for a visit and he volunteered to haul some gift steel parts to me from another friend.  I think he now knows to think carefully before doing me a favor, heh heh!  The steel weighed the better part of 300 lbs!



Anyhoo, I have the steel to make the frame and cylinder assemblies.

Sawing off the excess on the frame side plates.

Since the frame parts (1/2" thick hot rolled steel) were sheared from the sheet, I specified that they be cut 1" larger overall so I could trim off the bent area where the shear did it's cutting.  What a job!

Squaring and trimming the frame side plates.

I laid the side plates together and milled both together so the dimensions would be the same for both pieces.  I think I will get a carbide 3/4" roughing mill the next time I place a tooling order.  It took all afternoon to remove the pile of steel you see below the cutter.  There was a lot more where that came from!



To make the job even more interesting, I found that my mill lacks about 5" of table length of being able to do the whole length of the side plates without stopping, shifting, re-squaring and continuing the cut.  What a pain!

Boring the cam bearing bores.

I re-clamped the side plates onto the mill table and squared them up.  Then I found the two reference sides.  One of them is at the left, clamped and the other is next to the red chip shield.  I will step-off all the dimensions from this reference corner.  


Since the cam bearing bores will be stepped to locate the camshaft, I will have to counterbore for the bearing O.D.'s.  Here, I am finishing the smaller 'thrust' bore.  The bearings will go in from the outsides of the side plates and rest against the steps which will be on the insides.  This means that I will have to make the counterbore for this side (opposite cranking side) from this setup then remove the top plate here and flip the one that's on the bottom (cranking side) then clamp and re square it to bore for the cam bearing, the governor bearing bore and counter bore and the slot for the chain tensioner.


I'm not sure exactly how to proceed to make the main bearing block slots but I think I will clamp the plates in the vise and see if I have enough depth in the mill to be able to use a milling cutter to remove the material.  Otherwise, there'll be a LOT of sawing going on.


The story on the flywheels is that I told the shop what diameter I wanted the wheels to be and they did a nice job of cutting them out with a CNC plasma cutter.  Then, I discovered (Doh!) that I have nothing in my shop that is large enough to grab onto the blanks and machine them.  Unless I can think up a special machine using a big gearmotor I've got to turn the wheels, I'm gonna have a couple of good boat anchors.


I then thought that if I couldn't make the wheels, I could probably cut the crankshaft cheeks out of them.  Another "Drat" happened when I realized that I'd designed the crankshaft with 1.25" thick cheeks and that my flywheels were 2" thick steel.


Based on that, I'm gonna have to go to the local steel supply house and have 'em burn out a couple of crankshaft cheek blanks.   Since they are on a 7" circle, I can just fit them into the mill for boring and finishing.


My friend in KY also gave me a hunk of 1-1/2" shafting so I have the journal material for the crankshaft.

It looks like I will have to break-down and buy a couple of rough-cast flywheels.  Geez, Marie!  This project is getting to be kinda 'spensive! 


2 February 2009:

I think I'm about finished with the frame sides.


                   Test fit of cam bearing.                             Drilling break-away holes for main bearing saddles.

The cam bearings go in from the outsides of the frame sides and seat against a shoulder on the inside.  These bearings are a nice slip fit on both the shaft and the sides.


Then, I moved the frame sides so I could finish the main bearing saddles.  Again, both sides were clamped together so the main bearing saddles would be in alignment.  Since I didn't want to make a career of sawing the material out, I drilled a bunch of 1/4" holes 1/4" apart inside the "finish" lines, kind of like perforated paper.



Breaking along "dotted line".                                                     Milling to size.             

The frame sides were then individually grabbed in the vise and the steel was torn along the "dotted line".  Worked pretty well.  Then both sides were again lined-up in the mill and the opening was milled to size.


The finished side plates, burrs and all.

The plate on the top is the cranking side, showing the outside face.  You can see the two cam bearing bores and the single bore for the governor bearing with the 1/4" hole in the opposite side for the governor pushrod to exit.  The 1/2" slot is for the chain tensioner adjustment.


Prior to welding, the frame parts will be bolted together and aligned.  I hope this will minimize distortion from the heat.


11 February 2009:

It's going kind of slow but I am making some progress.


I got the end plate made and, looking at that scabrous scale on the steel, I decided to do a little cleaning up.  THAT ended-up taking a couple of hours.  First, I used a grinding disc on them then I used a coarse sanding disc.  There are a few goobers left but I think it looks a lot nicer.  


My work on the scale may be all in vain because, in the end, I might just opt to paint the whole thing.

Frame sides with cam, governor, tensioner and bearing blocks being test fitted.


Here's the inside of the frame.

The bolts holding the end plate on (and the rest of it together) are not for strength, they are there just to hold everything in position when the welding takes place.


The order of attack as far as the welding is concerned is to build the cylinder liner, headers and water jacket assembly.  After welding and once these parts are trued-up, the main bearing blocks are to be welded to the frame side rails.  After that, the rest of the engine will be bolted together and checked for alignment then welded.


The problem with the above is that I had planned to have the crankshaft finished before welding the bearing blocks onto the side plates.  That way, when I had the crank finished and trued-up, I would know what to bore the mains to and could put the blocks together in the mill and do that little chore.  THEN, I could have the bearing blocks welded to the side plates (tacked with the crankshaft in place) followed by finishing the welding job on the rest of the engine.


Since I don't know how long it will take me to get the material for the crankshaft cheeks, things will be somewhat in the air.  I do still have some parts to make, though.


12 February 2009:

The bed plate is now done.  I reassembled the cam, governor, tensioner and a temporary crankshaft to test the fit of the timing chain.

Bed plate in place and timing chain being test-fit.


14 February 2009:

The head-end header, cylinder liner and water jacket are about done.  I'll need to get more steel to make the crankshaft end header for the jug.


                                Head-end header.                                                             Cylinder liner.

In order to be sure to have a good weld bond, I've chamfered both the header and the liner.  You will note the step in the liner diameter.  At first this would appear to be just a bit of extra work but, due to the head stud circle, I had to give some room so the head studs didn't run into the outside diameter of the liner.


                           Head-end header set on liner.                   Jug set together with spacers simulating                   

                                                                          crankshaft-end header.

I will drill the cylinder oiler holes in the liner and water jacket after welding


15 February 2009:

I worked on the compression release today.  After a false start on the eccentric which resulted in a couple of hours of work that ended up in the scrap bin, I have the hard part done.


Start and near finish of compression release.

The compression release consists of an eccentric that rides on the 0.750" rocker shaft which is shown in the right hand photo.  The eccentric is 0.022" offset and the exhaust rocker works on the 0.885" diameter eccentric part.  When the handle is turned a quarter turn counterclockwise (as seen in the print), the valve lash is reduced about 0.011".  I think I will end up with a valve lash of around 0.008", so when the lever is flipped up, the valve will stay open about 0.003", releasing compression.


There is a detent on the compression release.  On the left-hand end of the rocker shaft there is a 90 degree slot with a deeper hole in each end.  A ball and spring are in the horizontal hole in the eccentric.  This ball drops into the hole at either end of the slot in the rocker shaft, making the eccentric hold in either position.  When the position of the eccentric is changed, the ball cams out of the hole and rides in the bottom of the slot before dropping into the hole at the other end of the slot.


I made what looks like a one-piece assembly out of two pieces of steel.  To do it out of a single piece would have required a blank 1" thick and 1.75" on a side.  Since I only had 1/2" HRS, I pressed the shaft part into the flat part.  I did have to do a little freehand grinding and filing to get the outside shape close but you're not going to tell anyone, are you?


16 February 2009:

The rocker stand is done.

Rocker stand with rocker shaft and compression release.

The next session will be to make the rocker arms.


Drawing and material for the rocker arms.

Where you see the uglyish squared-off edges will end up being ground and filed.  The bushings are out of some long-dead machine and will be modified and pressed into the rocker arms.


17 February 2009:

The rocker arms are coming along.

Rocker arms in process.

I haven't quite figured out just how I'm going to hog out the surplus metal on the rockers.  If there was some way to glue them together so I could hog both of them on the bandsaw, I think I'd do that.  I could also stick 'em in the mill and spend an entertaining day.  What I might do is to hog the one I've got laid-out on the bandsaw then transfer the cut lines to the other one and hog it on the saw.  Then put 'em together in the mill and finish the shapes there.


17 February 2009:

Rockers are finished.


Excess sawed off and removed.                                                        Removing excess.    

I elected to use the saw, drill and bash method of getting rid of the excess metal before milling.  Rather than do multiple cuts with the bandsaw to get the diagonal cuts, I elected to drill a series of holes for a sort of "break along the dotted line" deal.



Cleaning up and contouring corners.                                            Contouring and corners done.

I laid the rockers together and milled all of the surfaces to clean them up from the saw.  The radiuses were made with a 1/2" end mill.



   Edges filed and adjustment bolts made.                           The finished valve rocker assembly and head.

Then, the sharp edges were filed, the rockers were deburred and the oil holes were drilled.  I made the high crown adjustment bolts out of easy machining 7/16" hex lead-alloyed steel bar stock.  The ball ends were free hand filed on the lathe.


I'll have to figure out the linkage from the intake valve rocker to the fuel inlet rocker.  It will probably be a simple turnbuckle link between a joint on the intake valve rocker arm to the fuel inlet rocker.


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