Homebrew Hvid

Engine, Part One

Click here for Part Two.

Click here for Part Three.

Part Four - Getting It Running and Further Experiments and Development.

Part Five - Switching It Over to Naphtha and Spark Ignition.  (It was eventually switched back.  See Part Four).




Click on the picture to view in high resolution.


A Brief Tutorial About The Brons Patent and Hvid Engines


In the Netherlands about 1902, a man named Jan Brons invented a compression ignition engine that did not use any external form of high pressure for injecting fuel into the combustion chamber of a four cycle oil engine.  His first European patent for this design appears to have been awarded in 1907.

An American named Rasmus Martin Hvid (pronounced "veed") was granted a United States patent for an "oil injection device" in 1915.  Hvid also patented a "Hydrocarbon Engine Governor".  At this time, I'm not sure if Hvid used the Brons patent under license or his design differed enough from the Brons design to allow him to obtain a stand alone patent for it. 

The first Hvid patent engines were manufactured by the Hercules Engine Company of Evansville, Indiana, USA in late 1915 and sold under the Sears-Roebuck brand, "Thermoil". 

In any case, Hvid then licensed several companies to manufacture the Brons-type engines, as seen below in the database compiled by Denis Basson. 

This kind of engine is also called an "explosion cup" engine, because the fuel first detonates in a small cup shaped sub-chamber in the combustion chamber.  Because of the way the fuel is introduced and how combustion takes place, this type of engine is limited to low-speeds, the maximum RPM being around 500 RPM.

About the smallest production Brons Patent engines were in the 1-1/2 HP range.  They ranged up to over 100 HP.

Early Brons Patent combustion chamber details.


In the above drawing, you can see the "injector" and the explosion cup just below it.  The "injector" has a fuel valve and a metering rod in it.  The fuel valve is operated by the main air intake valve.  The fuel metering rod is controlled by the speed control and the governor.  During the intake stroke, the fuel valve opens.  Since the outlet port of the metering rod shares the seat with the fuel valve, when the fuel valve opens, it allows the fuel metering rod to admit fuel into the cup.

On the intake stroke, a small amount of fuel is drawn into the explosion cup where it stays until late in the compression stroke (the compression ratio being around 16:1, depending on the fuel used) when the highly heated compressed air blows into the explosion cup through small holes drilled just off the bottom.  This hot air blows across the fuel and causes the vapors to combust.  The resulting sharp rise in pressure then blows the remaining fuel out of the cup through the holes where it is burned in the combustion chamber.

A variation on the Brons Patent, similar to most Hvid designs.


In order for these engines to run successfully with different fuels, the compression ratio is adjustable via shims at the big end of the connecting rod.  Different types of fuel including crude oil, Diesel fuel, kerosene and other heavier fractions are successfully used in these engines.

Because their operation is similar to air and solid injection Diesel engines, they require a speed governor because compression ignition engines have a tendency to "run away" or overspeed, especially at light loads.

These engines are built with heavy crankshafts and rods in order to stand up to the high compression loading which occurs when the fuel detonates.


Here's a link to a nice Hvid webpage with full discussion of the operation of the Hvid engines.


11 March 2010:

Denis Basson of Australia has created an Adobe Acrobat listing that compiles a somewhat complete listing of Brons and Hvid engine manufacturers and brand names. 

The listing has been relocated to the Home Page. 

If you have any confirmed additions to fill-in the blanks, please contact me or Denis and it will be added.

The list was last updated in January 2013

Denis: [email protected]

Elden: [email protected]

Thanks, Denis!



The design and construction of

The Homebrew Hvid

The Engine Whose Design Is Based Upon The Engine Originally Built By Jan Brons of The Netherlands

I've long wanted a Cummins Hvid engine but since they are relatively large, heavy, rare and expensive to buy, I will have to try to make my own version.

8 October 2008:

I got started today by sketching out a crankshaft. Then I started a new CAD drawing and worked in some dimensions.

The bore is to be 2 inches and the stroke is to be 4 inches.  I'll use a cast iron liner and piston this time because of the pressures involved.

At first, I thought I'd just use a piece of an auto crankshaft but ended up drawing one made from scratch.  The rod journal will be 1.4 inch in diameter and 1 inch long.  The main journals will be 1.15 inch in diameter and 1.25 inch long.  The cheeks of the crank will be made from 1 inch thick rounds and the counterweights will be integral instead of bolted on as in the spark ignition Homebrew Engine.

Like the spark ignition Homebrew Engine, it will be tank cooled.  The camshaft will be mounted in the crankcase a'la Thermoil.

I can only go so far with this until I get measurements off of a Thermoil that a friend owns.  He has generously allowed me to take it apart to make measurements for scaling.

Stay tuned.


12 October 2008:

Been piddling with the CAD drawings in lieu of having real dimensions.  I'm tempted to build it like I think it should be and see if it will run.



In the drawings, I show the piston at the middle of the stroke as well as both ends.  I've got the compression ratio drawn-in at 16:1.  These dimensions will be with no shims in the rod.  If I need higher compression, I will add shims between the bearing block of the rod and the rod itself a'la Thermoil, Cummins, etc.

The valve lift will be 0.250" (minus lash of, say, 0.010").  They will be proud of the head by 0.070" and the headspace including the headgasket will be 0.258".  That means that the valves will interfere with the piston by 0.052 at the lowest compression ratio.  This shouldn't be a problem except when (and if) I design-in any overlap, which I doubt I'll do.

I'm using the valves, springs and keepers out of a Honda lawnmower engine and they will work as-is.  My only potential problem is that the valve stem diameters are not the same and they are metric.  I may bite the bullet and get a couple of reamers or I might just ream them as close as I can get them with my 0.0156 increment set.


I still have to work out the fuel valve linkage from the intake valve rocker and it looks like a bellcrank may be needed to get the motion in the right direction.

Facing the exhaust side                                  Facing the head    


The "injector" is shown above.  On the lefthand view (facing the head), the fuel needle is on the left (nearest) and the fuel valve is on the right (behind).  One of the tricky parts is going to be coming up with the fuel metering needle which is 0.062" in diameter, kinda small to do in the lathe.  I may be looking for some straight music wire.

The fuel needle is controlled by both a screw to set the speed and the governor to keep the speed constant.  That and the governor have to be worked out.

I still haven't made up my mind which valve to apply the compression release to.  It will likely be the exhaust unless someone has the real story.  It'll probably be an eccentric on the rocker shaft with about an eighth of an inch of travel.


15 October 2008:

Today, I worked on the head.  The O.D. was turned and it was faced square.  Then I drilled the 1/2" head stud holes and flycut the flats for the rocker arm pedestal and the injector.

The head, first operations

I've laid-out and punchmarked the air inlet holes but will not drill them until I've got the valve guides, ports and valve seats done.  All of these operations except for the injector body and the exhaust port (which are located on the circumfrence of the head) will be done with the combustion side up.  

On this engine, I'm not going to machine separate valve guides.  I'll just let them run in the head.  If I have a problem with that arrangement, I can always put guides in later.

I may not flycut the flat for the exhaust flange.  In thinking about it, it may be better to just turn the O.D. of a piece of galvanized pipe to a press fit into the port.  That way, I don't have to make the flycut or drill and tap a couple of holes.  My rationale is that the less I take off of the head, the stronger and more stable it will be.

I haven't done any drawings of the water passages in the head.  I may not be able to do any coolant passages because of the complexity of it.  At least, I can drill some holes in the combustion face of the head that will match corresponding holes in the water jacket.  There will be no circulation but I think it will be better than nothing.  I'll see how it comes out before deciding.


16 October 2008:

The head is almost done


Plunge milling the intake valve port.                                    Machining the intake valve seat.   

Since my drill press can only go to 1/4" and the mill doesn't have enough "depth" to be able to drill larger holes, I had to do a tool changing game.  I started with the chuck and drilled the guide hole then reamed it close to size.  Without changing anything, I then plunge milled the hole, followed with the boring bar to get it to size.  The last thing before moving to the intake side was to cut the exhaust seat.

Note the fancy valve seat tool.  I found that little gem, rusty in a box of junk at the dump when I was a kid a LONG time ago.  It works like a champ!


         Plunge milling the injector bore.                                                The head nearly complete.

After doing the intake port, I turned the head and set-up to do the injector bore.  Again, I drilled a 1/4 hole to the depth needed, followed by a 1/2" mill, plunged to intersect the 1/4" hole for the fuel to spray into the combustion chamber.  Then, I changed to a 3/4" mill and plunged it to where the injector seats.

To finish up the head, I need to set it in the mill and drill and plunge mill the exhaust port to the outside of the head, drill the intake holes around the intake valve guide and drill and tap the holes for mounting the rocker stand.


19 October 2008:

Unless I figure to try to machine some cooling passages in the head, I should be done with it.  I'm a little reluctant to try for cooling passages because one slip and the head will be scrap.

The 1/4-20 bolt holes for the rocker tower and the injector were drilled and tapped.


                 The top side of the head.                             The combustion chamber side of the head.

Today was another one of those days where a seemingly trivial operation ended up nearly taking all day.  What took the time was the exhaust valve guide bore.

The valves, out of a Honda one-lunger, are metric.  All I've got is a cheap 1/64" increment Chinese reamer set.  The inlet valve stem has a diameter of 0.248" and, since it could be a bit on the loose side, I took the easy way and reamed it to 0.250".

The exhaust valve stem, on the other hand, has a diameter of 0.246" and this would be too loose in a 0.250" guide.  Since I'm cheap and don't want to buy a metric reamer (whatever size THAT is!), I decided it would be easy to drill the guide bore to 0.234" (25/64") and lap it to size.  Using lapping compound and several pieces of 1/4" all thread turned to successively larger diameters and reaming the guide over and over, I now have a nice snug about 0.0005" fit.  Knowing my luck, the valve will probably try to stick for a while until the lapping marks wear down but, what the heck,.........that's what Marvel Mystery Oil is for, ain't it?

The last thing I did was to turn down an end of a piece of 1/2" galvanized pipe and press it into the exhaust port.  The angle of the port is real close to 45 degrees so with a 45 degree elbow, the exhaust will be directed to the horizontal.


4 November 2008:

Took a trip last week back to Kaintuck.  While there, I pulled a chunk of steel out of Frank's scrap pile.  It's kinda gnarly with rust pits, etc. but I figured that since it was 1-1/2" thick, it would make nice stock for the bearing blocks.

Raw material for the bearing blocks.

This was one of two garden tractor weights that were made from the "holes" that were torch cut from what must have been a humongous hunk of steel.  This piece is about 12" in diameter.

Starting the cuts.

Finishing the first cut

To get the blanks cut out, I had to kind of finesse the little band saw.  The piece was too tall to fit in the saw until I'd cut about 3" into the big piece.  Then, while tilting the piece the blade was started into the cut.  At that point, the piece could be stood up vertical and the cut could be finished.  Needless to say, this took all afternoon and I wore out a blade in the process.

The blank for the bearing blocks.

I cut the blank a bit oversize so I could clean it up in the mill.  The plan is to flycut the sawn edges so the blank will fit tightly in the mill vise.  Then, since it is badly pitted, I will clean up the thickness by taking 1/8" off each side, giving me a finished thickness of 1.25".

After that, I will saw out the two main bearing blocks and the rod bearing block.

I got lucky (I think).  When I was in Kaintuck, I called a former neighbor who is the manager of a plant that uses a lot of steel.  He agreed to cut the steel for this project in his shop.  Since they have a CAM plasma cutter, I'm getting the flywheels cut from 2" thick hot rolled steel and the crankshaft cheeks cut from 1-1/4" HRS.  


                   Image from which flywheel is to be cut.                Image from which crankshaft cheeks are to be made.

I've been told that the cutter can take the CAD drawings and directly cut the parts.  There will be some roughness from the cutting that I will have to remove but doing them that way will definitely be easier than by hand.  I'm having the shaft bores burned undersize.


6 November 2008:

A little more got done on the bearing blocks today.


                                              More cutting.                                        Flycutting the rust & pits from the faces.

The raw material surface wasn't as bad as I first thought.  When I got the rust off of the faces of the piece, I found that the thickness was just slightly under 1.500" so I modified the design so the bearing blocks are 1.400" instead of 1.250".  I've got the bearing journals designed for 1.500" width so there will be 0.050" of bearing sticking out of each side of the bearing blocks instead of 0.125".  


            Cleaned-up.                                                                Marked for the next sawing operation.

I used the brazed carbide flycutter that came with the mill to do the cleanup.  No point in dulling the good flycutter with the rust.  Although there are fairly heavy flycutting marks on the piece, they're only appearance points.  

Now, I've got to cut out the individual bearing blocks, split them and flycut them to size before boring them out for the bearings.  I'm thinking of using the main bearings I took out of the Jack of All Trades engine that I restored a couple of years ago.  They're a little oversize but once they're split, I can squeeze them a bit so they will bore out to the shaft size.  Note that I've laid out the parts taking into account saw kerf and cleanup.  I'm also accounting for the block split kerf.  The mill is getting a workout on this.

I won't know the exact shaft size until I've got the crankshaft finished.  If it warps from the welding, I will have to take it to a shop and have the journals ground true.  At that point, I'll be able to do the bearings.


14 November 2008:

Got a little more done today.  

The semi-finished main bearing blocks and the rod bearing block in progress.

I've now got the bearing blocks cut out of the big chunk.   Since the main bearing blocks came out of the big chunk about 0.250" wider than needed and instead of hogging off all that metal, I decided to just leave it and change the design to accomodate it.  They will be a bit stronger that way.


21 November 2008:

It's been a week since I've been able to do anything on the project but, today, I got the bearing blocks cut in two and flycut to size.

The main bearing blocks are on the left and the rod is on the right.

What I have done is machine the blocks so it will require a 0.100" shim pack to get them to design height.  I will make up some thick (about 0.080") shims that will be used to keep the bearing shells from turning and then add another 0.020" of shims to take up for wear.

I'm going to make the bearings put of the bronze bushings I replaced in the 1897 Fairbanks-Morse Jack of All Trades engine.  They will be cut and sized to fit into the bearing blocks then bored to size.

I may be taking my time finishing the Homebrew Hvid because I've just made up the McMaster-Carr order for the materials to make the piston, cylinder liner, water jacket, wrist pin and bushing and the timing belt and sprockets.  It's gonna cost me what I'd pay for a nice engine and I have to dole out the funds to get the job done.

Yes - I know.........A timing belt is just not in keeping with the "old" look but, because of the length of the rod and distance from the crankshaft line to the back of the cylinder, I can't use gears.  The ones I could find don't come such that the center distance is nearly long enough.  Thus, a timing belt.  Anyhoo - I'll be working at it as materials come to hand.  When the steel for the frame and the flywheel blanks get here, I will be very busy.


22 November 2008:

Not shown, but I've got the bolt holes drilled and tapped in all the bearing blocks.  I also milled a 45 degree  chamfer along the rod block down close to where the connecting rod bolts on.  This is to remove some un-needed metal and weight.  The plate that the rod itself is attached to will remain square.

Connecting rod block.

Note the lovely bolts I've used.  One is a chunk of 7/16-20 all-thread that is the size of the bolts that will go in when I get them.  The other is a slightly used 3/8" carriage bolt.

The rod is arranged so the bolts go in with their heads on the left or outside of the rod.  They screw into the cylinder half of the block then will pass through clearance holes in the rod plate with nuts on the cylinder end.  This way, I can change compression shims without disturbing the rod bearing fit because it will stay tight when removing the rod plate.


28 November 2008:

Remind me to try to design around having to extend the thread of 7/16-20 grade 8 bolts.   They are tough and hard on the die!  Anyway, I got it done.

AND, I got the rod big end nearly finished.  


    Boring the big end                                                              Finished bore            

Boring out the rod bearing block was slow going.  Note the temporary 0.100 steel shim I made to hold the spacing.  I bored it until I hit the bolts as seen in the right-hand photo above.  That's as big as it can be without ruining the bolts and having to extend the thread of another couple of bolts.  I don't think my poor 'ol die would make it through another two.

The old bearing I was to machine for the rod big end was already worn about 0.010" so I bored the big end about 0.025" smaller than the O.D. of the bearing so as to force the I.D. down enough to clean up at around 1.500(-)" to fit the pin.


Bushing made from old bearing                                               Rod big end nearly finished    

On the right in the above left photo is one of the worn Jack of All Trades main bearings from which I turned  the rod bushing, shown on the left.  The original oil hole ended up close enough to the middle of the bearing to use to get the grease into the bearing.

After sawing the bushing in half, the halves were witness marked then inserted into the bearing halves and clamped into place.  A file was used to make the parting lines flush with the bearing block halves.  Then the rod bearing was assembled with the permanent shims and torqued down.

It was returned to the mill and bored to a rough starting dimension for fitting once the crankshaft is finished.


29 November 2008:

Started on the "injector" body today.

Here's what the injector will be made of.


Beginning the first diameter.                                                    First diameter finished.

There's a lot of "whittling" to one of these engines!  Also a lot of smoke!

There are going to be some pretty deep holes in the injector body but, when drilling deep holes like in the bearing blocks, I've had the hole drift by the time it broke out at the bottom end.  Even after carefully sharpening the bits they drift.  I'm going to have to call him again 'cause I can't remember what they are called.  CRS Syndrome strikes again!


1 December 2008:

I'm getting better at drilling deep holes without too much drift.  What I did today was to drill, redrill, redrill again and ream the injector valve bore and turn the 45 degree seat.  It looks like the drill drifted about 0.005" in about 1-3/4" and I can tolerate that.  It's gonna be trickier when I go to drill and ream the injector metering rod bore because the holes will be a lot smaller and I have to hit (see the 12 October CAD drawing of the injector).

I've also made some minor changes to make the parts easier to machine.  The injector valve stem is straight (no steps in the diameter).  The metering rod also does not have a step and I will shrink the spring retainer onto it.

Anyway, I got some 0.120" diameter polished drill rod for the injector valve and a piece of 0.062" polished drill rod for the metering rod.  I made the injector valve head out of some mild steel and pressed the drill rod onto it and then brazed the two parts together.  It's a bit distorted from the heat so I will be spending some quality time with lapping compound and elbow grease.  I won't finish lapping until I have the metering rod bore done and the passages from there to the injector valve seat drilled.

Injector valve in place.

After the metering rod boring is done, I still have to drill the mounting holes and the ports from fuel inlet and outlet to the tank and drill the air hole to the injector valve.


4 December 2008:

Almost finished with the "injector".  Today, I made the cover plate, finished the metering needle, lapped both the valve and the needle and drilled and tapped the fuel line ports.

Main injector valve assembly.

The valve stem is so hard that I had to use the Dremel with a grinding disc to neck the keeper groove.  The spring is out of a ball point pen that bit the dust.  I also changed from a pin-through-the-hole in the valve stem because I didn't want to put any of my remaining small solid carbide bits to risk.  I'm saving them for drilling fiberglass printed circuit boards.

I lapped it to fit the seat using a hand drill.  I won't really know if it's tight until I get it on the engine and under compression.  It -seems- like it will be okay.  The injector valve is normally closed and is actuated by the intake valve rocker so it opens during the air intake stroke.

The Injector metering needle.

I chucked the metering needle in the drill press and at high speed, used the Dremel disc to grind the point on the end.  Then I put it in the injector body and tapped it a few times with a small hammer to form a rough seat to the angle of the point.  After that, I lapped it until it was a good seal.  

There is an internal spring on the needle that works between the stepped hole in the housing and the "bushing" on the needle.  The needle is normally fully open and is closed by the governor.  There is also a mechanical override (a knob on a threaded shaft) that is used to limit the maximum fueling rate and to shut off the fuel to stop the engine.  Note also that the needle is just barely long enough to clear the top of the housing cap by about 1/8".  The thick rubber gasket is also an interference fit with the stem of the metering needle so fuel does not leak from it.

The semi-finished injector.

The fuel supply (on the right) and the fuel return (on the left, to give air in the system a way to get out of the "injector") are plumbed with some 1/16" steel pipe.  I've found that if I tap shallowly the holes in the body to 10-24 and almost completely run a die over the end of the pipes, I can get what looks like a nice pipe thread.

The untapped hole in the injector body is the breather hole for the injector valve.  I think this is needed so a little air can be drawn past the clearance between the valve stem and the body (0.005") to help deposit the fuel into the cup.

I may have to revisit the rubber "gasket" as I'm concerned that the squishiness of the rubber is going to cause the cover plate to move.  Also, it will limit the amount of pressure I can put on the seal at the bottom of the injector port in the head.  I'll probably simply plunge an end mill into the top of the metering valve bore and make a rubber donut that can be compressed just a little when the cover plate is flat against the top of the body.  Since there's nothing that needs to be sealed other than the metering needle shaft, I can simply leave out a gasket altogether.

I've also added a couple of 6-32 flathead screws to hold the cover plate on until it is bolted to the head.  This will keep everything in alignment.

The reason I say "semi-finished" in the caption is that I've got to figure out how to actuate the valve and needle.  I'll probably do that tomorrow.  Note that the valve keeper is crooked.  I ran out of time fitting it and will have to file about 0.002 off of one side of the keeper washer so it doesn't interfere with the side of the cup.

You will note that I am modifying the design as I go along.  Some of this is because I didn't visualize the sizes of some of the parts and my intuition said that they had to change.  This ain't a pre-production prototype so it doesn't matter if the actual engine does not exactly match the prints.


8 December 2008:

The explosion cup is finished.  It didn't turn out as "pretty" as I hoped but, since I will most likely re-designing it when testing the engine, I figure it'll do.  In any case, it won't be anywhere it can be seen.


The explosion cup showing the spray hole.                               The inside of the explosion cup.        

On Frank's Thermoil, the explosion cup had two 0.040"(#60) spray holes.  Since this engine is considerably smaller, I decided to start with one 0.028" (#70) spray hole and see how it works.

To finish the "well" of the cup, I first drilled the blow hole then put a 1/8" end mill in the drill press and carefully made a flat bottom hole deep enough so the spray hole is a few thousandths above the bottom.  The buggered area around the milled hole is where I fumbled the drill press and the mill made a chatter mark.  I can't see how this imperfection can affect the operation of the cup so I'll just let it be hidden.  Don't tell anybody!


          Explosion cup mounted on injector.                         Screw which allows the cup to be withdrawn.

You will note on the left-hand photo that the steel I used to make the injector was a little rusty.  I learned that it is not good to flycut rusty metal.  It is very hard on the tool bits.  In any case, the pitted area will not be seen becauseit will be hidden by the hopper.

I will lap the cup to the injector body and then lap the cup to the head.  I'm hoping I won't need a gasket here.  If I do, I will have to make a couple of washers out of annealed copper.


12 December 2008:

Here's my version of the fuel control arm and shutoff screw.

Fuel control.

The knurled-handled screw is to enable turning down the fuel needle to limit or shut off the fuel to the engine.  This is the usual way the engine is stopped.

The arm goes to a pushrod socket.  This will go down to an arm that is turned by the governor.  Pushing up on the rod will turn down the fuel.

Note that I've made a "running design change" in that I've eliminated the fuel return pipe.  In it's place, I've got a gasketed screw that can be loosened to bleed out air in the fuel passages.  I had to do this because the return line interfered with the fuel control arm.

Next on the agenda is to make the rocker arm that operates the fuel valve.


13 December 2008:

The "injector" is about done.  I got the fuel valve rocker stand and rocker finished.  I haven't finished the end of the rocker opposite the valve because I have to see how the valve rocker arms work out.  It shouldn't be a big deal to make the fuel valve work with the intake valve.


Injector with fuel valve rocker arm and stand.


15 December 2008:

Back to the connecting rod the last couple of days.

Rod parts before machining.

The rod itself is made from 1/2" galvanized pipe.  I turned the zinc off of the surface and polished it.

Then I turned the bearing mount for the little end with the I.D. rough and cut it to length.  I milled the "little" end of the rod itself to fit the bearing mount.

The rod was then reversed in the mill and the "big end" end was trimmed square and to length + 0.100".  The big end plate was bored to the diameter of the rod and 0.100" deep.

Rod on mill table for aligning prior to welding.

Both the big end plate and the little end bearing mount were drilled to 1/4" so a threaded rod could be used to hold the whole works together for welding.

The whole works was then laid on the mill bed and checked for straightness by clamping it and measuring the gap between the little end and the mill bed then flipping it over and repeating the measurement.  It was within 0.015", which will be fine.  

After welding, I will again put it on the mill bed and check to make sure the alignment is close.  It will be shimmed off of the bed and the little end will be trimmed to width and bored for the bushing.  This should assure that the crankpin and the wrist pin will be parallel.


18 December 2008:

Well, I now have a rod.  All that needs to be done is to lap the big end bearing to the crankshaft whenever I get the materials to make it.

 Truing the big end plate of the rod.

I got the ends TIG welded to the rod tube today.  It was then shimmed it in place on the mill table with the rod tube square to the mill.  I used feeler gauges to hold the big end plate so it wouldn't try to turn.  The heat of the welding caused the plate to be about 0.005" out of square.

Boring the little end for the wrist pin bushing.

I then turned the rod around on the mill table and re-squared it, again shimming the big end plate so the rod couldn't turn and faced and turned the end for the wrist pin bushing.  After doing this, I removed the rod from the mill and pressed the bushing in.

The rod was again mounted and squared-up and the bushing was bored to a snug fit with the wrist pin.

The finished rod.

I've left the rod bearing a bit on the small side (I hope!) so, when the crankshaft is trued, there will be enough "meat" in the bearing so I can lap it to the crankpin.

I'll have to order some more materials to continue.  I need the cylinder blank (2" I.D. Sked 80 pipe) and a piece of cast iron bar stock that is a little over 2" in diameter to make the piston out of.

To keep the wrist pin from damaging the cylinder wall if it drifts to one side or the other, I will make brass buttons to fit into the piston.


19 December 2008:

I'm getting a lot of practice with the boring head in the mill!  The crankshaft is going to have four more of these bores in it.  By the time it is finished, I think I can truly say it was a boring job (ecccch!). 

The main bearing blocks are now done and all I have left to do is fit the bearings to the blocks.  When I get the crankshaft done and know for sure what the journal diameters will be, I can bore the bearing I.D.'s to slightly smaller than the crankpins for lapping to fit.


     0.100" spacer plate.                                                                Spacer plate in place.

The spacer plate serves two purposes.  One is that it simulates the spacing that the shim packs give and the second is that it keeps the boring bar from constantly having to do an interrupted cut where the space for the shim is.


Drilling starter boring hole.                                                                  Boring the block.    

I started with a 1/4" drill then enlarged the hole with successively larger bits until I had drilled the hole to 3/4", the largest bit I have.  Then the boring head was used to bring out the diameter to 1.840".

Finished bearing block.

Not pictured above is the 0.500" milled slot on the sides and bottom of the lower block.  This slot will allow the main bearing lower halves to be solidly positioned in the frame side rails before welding.  I also have the 1/8"NPT grease cup holes to drill and tap in both the rod and the mains.


20 December 2008:

Bushings fitted to bearing blocks, awaiting finish bore to fit crankshaft;


Click here for Part Two


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

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Visits since 8 February 2010