The Homebrew Engine

Part Five

Making The Governor, Sideshaft And Valve Gear

You can click on any of the photos to enlarge it.


20 June 2008:

I've now got the sideshaft mountings done and ready for alignment.

Here's the crankshaft end sideshaft bearing mount.

I got the goof-ups today.  I had to make the crankshaft end bearing mount twice.  I got the bushing hole in the wrong face.  Nothing for it but to start all over again.  I was just about done with it, too!


Test fit of the sideshaft.

I still have to fit the taper pins in both the sideshaft gears (the governor gear isn't on the shaft yet) and turn the brass collar O.D. so it clears the head by a little more.

Thrust will be taken up by the shaft collar on the crankshaft end of the cam mount and a bronze washer will be fitted between the cam mount and the cam..........  Either that or I'll make the cam base out of brass and use it as the thrust bearing.  If I do that, I'll make the cam out of steel and bolt or pin it to the cam base.


The crankshaft end of the sideshaft.                                          The head end of the sideshaft.

Note that I had to grind some clearance in the main bearing cap for the driven sideshaft gear.  I knew I'd have to do this and prefer to have the relief in the cap than have to hang the shaft farther out on the crankshaft.  I also had to make an extension to raise the grease cup on the main bearing away from the driven gear.

On the head end, you will notice that the bushing is not long enough to go all the way to the end of the housing.  The bushings are 3/4" long and the housing is 7/8" long.  No matter.  I need the length to get the cam in the right position and I will most likely use the cylindrical end of the housing for the fixed part of the timer.  I'll most likely mount a little rare earth magnet on the cam base and use a Hall-effect transistor to sense when the magnet passes to fire the plug.


21 June 2008:

Today, I made the cam blank, the cam side thrust washer and bored out the governor gear to fit the shaft.  I also cut off the excess from the sideshaft and pinned the sideshaft driven gear to the shaft..

The cam blank mounted on the sideshaft with it's thrust washer.

In order to set and reset the cam timing without boogering-up the shaft, I turned a slot in the shaft where the set screws go so the burrs will be below the shaft level.  I also milled a flat on the shaft for the crankshaft end thrust collar for the same reason.

I need to order another little grease cup. I -thought- I'd ordered an extra (four total) but decided to use grease on the sideshaft bearings.

The governor will have ball bearings all around.  After I finish the rocker arm and roller and contour the cam, I'll do the governor.  Knowing me, if I don't do the governor before getting it running, I'll probably never get around to it.  After the governor, comes the mixer and then ignition.  At that point, it should be ready for a test run.

Motoring along.

After getting everything assembled, I motored it for a while.  The bearing on the head end of the sideshaft is in a slight bind and I hope it will break in and quit getting hot.


22 June 2008:

The rocker arm pivot and rocker arm are done.


The Rocker interferes with socket on head bolt.                                     Shortened rocker pivot.                  

Once I got started on the rocker arm pivot, I deviated from the drawing.  Originally, the block was 1/2" thick with the shaft sticking out another 1/2".  After looking at the arrangement, I thought that the block would try to pry itself away from the base so I increased the block to 3/4" thick.  Also, I changed the diameter of the shaft from 1/2" to 0.453" (29/64") and pressed it into the block instead of letting it float.  This gives a stiffer base for the rocker arm........also, I had a 29/64" bit.

The block was drilled and tapped 10-32 and the base was drilled and countersunk on the head side for temporarily mounting the rocker pivot assembly before welding it to the base.

The first time I checked the fit of the rocker pivot, I came to the realization that the pivot shaft was about 1/8" too long.  It interfered with the socket used to tighten the head bolt above it.  After machining off the 1/8", it worked.  

Rocker arm laid out and partially cut.

The rocker arm itself is a fairly complicated shape so I took the dimensions and relationship between the pivot bore and the follower pin bore and laid out the arm.  I drilled a hole to give a radius to the one inside curve on the part.  It was bandsawed out, ground and filed to finish it.  I have left more metal on the rocker arm that I will eventually need but want to have a bit more metal there to take up for any deviations in machining.


Rocker arm in place.

I changed the retainer arrangement on the rocker pivot to give plenty of clearance for the head bolt.

The next thing I will do is to lay out and contour the cam lobe.  I've made a 1:1 CAD drawing of the cam profile for a 200 (crankshaft) degree duration.  If it's too long, I can always take a file to it.  After finishing the cam profile and checking it, I think I'll get it red hot and throw it into a bucket of oil to harden it as much as possible.  Then, it's on to the follower assembly.


23 June 2008:

The valve train is nearly done.  I need to do some touch-up on the cam profile then I can move on to the governor.


The cam follower in various stages of completion.

I marked up the drawings of the cam follower quite a bit to make allowance for what parts I had on hand and because some of the dimensions just didn't look right when I started laying it out.  I'm glad this isn't going to be a production engine because I would have to spend a LOT of time refining and cleaning up the CAD drawing.


To round off the cam follower, I used washers and the grinder to rough them out then filed them to finish.


The valve adjustment is an eccentric on the shaft of the cam follower roller bearing.

The eccentric was made by first turning the large diameter for the finger wheel and drillling the bolt hole in the 3-jaw chuck.  I then switched to the 4-jaw chuck and indicated it 0.020" off-center and machined the 0.250" diameter for the bearing to slip over.  Returning it to the 3-jaw chuck, it was parted off of the stock.  It took some whittling and fiddling to get a nice fit for the bearing and to get the length of the eccentric to just fit in the follower block.  The adjustment will be held by tightening the bolt which will squeeze the eccentric and hold it in position.........Or so it says here in the fine print!  We'll see how it works.

Milling the cam profile.

I made a fixture for milling the cam profile and it worked fairly well.  The cam is setscrewed to a shaft that turns in a piece of stock that is held in the mill vise.  After lines were scribed to define the transistion between the valve closed part and the valve open part of the lobe, the cam was rotated as the milling cutter took off material.  After doing the cam, I figured out that this method is fraught with pitfalls.  Luckily, I didn't fall into any of them and the cam turned out pretty well.

I'll have to do some filing to clean up the profile but  it should be all right.

Cam, follower and rocker in place.

Just before quitting for the day, I laid the valve train together and rough-timed it. The cam angle is about right but I may have to re-do the cam because the rocker is cocked a little and the valve lift isn't what I expected.  The engine should run as-is so I'll leave it for now.

I'll take a couple of days off and get back to it toward the end of the week.


28 June 2008:

Well - I'm back.  During the interval, I had a re-think about the cam follower roller.  I've replaced it with a larger bearing and eccentric and had to cut away some more of the roller frame.

The old, smaller roller on the left and the new, larger one on the right of the modified roller frame.

I figured that a larger roller (bearing) would make the follower track the cam better.  Not so.  Tracks about the same so I made a little spring to push the roller frame in the direction of the roller following the cam better and it worked.  

New roller and eccentric in place with spring shown.

The notches on the new eccentric are for using a screwdriver to peck the eccentric around to make the adjustment.  I tried hardening the cam but was only slightly successful.  I can't believe that I've actually taken all of my used motor oil to the recycler!  I used water for a quenching medium but it didn't seem to work well.  In the running-in that's been happening, the brass thrust washer has been producing a lot of wear product from running against the cam.  I may have to make a thin, hard steel or Delrin washer for it to run against.

THEN, I started gathering the materials I'm gonna use for the governor assembly and found to my disgust that the new cam roller bearing was supposed to be one of the two that I was going to run the governor shaft in.  Drat!  Did some rooting around and found a ball bearing and a bushing I'll use.

THEN, I looked for a piece of 3/8" X 1-1/2" X 6" hot rolled to make the vertical governor frame out of and found that I didn't have a big enough piece!  Okay, so I'll use some of the 5/8" cast aluminum I've got sitting around!

It looks like the next time I go to Panama City, I'll have to visit my friendly scrap yard to get some 3/8" plate and other stuff so I won't run into the same situation later.

I'm gonna be soooooo glad when I get this thing finished.  It's to the point that it's getting a little boring.  Once it makes smoke, I'll get all enthusiastic again.  


30 June 2008:

I got started on the governor.

The governor frame and shaft.

Looking at the photo, it looks like the governor frame is not square with the engine frame.  I just noticed it.  I -think- it's due to the camera angle but I'll check it tomorrow.  It could also be because I only have one rather worn bearing of the two that will be on the shaft.

I ended up ordering two of the correct ball bearings from McMaster-Carr rather than cobbling up some bearings out of the junk pile and making a hash of it.


1 July 2008:

More parts have been made for the governor.


The governor shaft finished with the 1/8" wide slot.              Governor weights, collar and thrust bearing.       

Since I used LeadLoy steel for the governor shaft, milling the slot wasn't too bad.  The governor collar (the part that has the ball bearing on it and the governor shaft goes through) was made out of a piece of galvanized 1/4" pipe.

The vertical rod that takes the governor output down to the bellcrank that goes to the mixer rides on the bottom edge of the outer race of the ball bearing.  This will nicely handle the thrust as the governor pushes against the compensating spring that I will put on the lower part of the vertical rod.  Speed will be adjusted by changing the compression on the compensating spring.

The governor shaft bearings came in today so, once I've made the links that go between the weights and the governor sleeve, the bellcrank and the compensating spring compression changer, the governor will be essentially done.

Technical question:

Does anybody watching this know what the formula for figuring the diameter of the venturi of a mixer?  I think it is a percentage of the bore diameter.  In lieu of any other information, I think I'll try for a venturi diameter of 1/4" or 1/8 of the bore.


2 July 2008:

The governor's almost finished and I think I need to do some rethinking on it.  My design of the governor was just based on a wild guess as to weight size and the speed it should run.  


The weights after changing to stronger rods.

I didn't like the look of the rods that I'd originally made out of 6-32 all thread.  I found a long 1/4" brass standoff and cut it into two new rods which have been soft soldered into place.

The nearly complete governor.

I made the rest of the governor parts today with the exception of the bellcrank.  There is so much stuff working in the governor that it is a bit stiff in operation.  As it is, I don't think it will work well for three reasons.

Stiffness is one reason and the other is that I goofed in either not running it at crankshaft speed (it's now 1/2 crankshaft speed, geared 1:1 off of the sideshaft).

Then there is the matter of the amount of mass in the weights.  Now, they are 1" long pieces of 3/4" brass bar stock.  I think I probably need about twice the weight for it to work correctly.

What I think I'll do is to work the stiffness out of the governor and go ahead and try it.  I can always double-up the weights if they aren't heavy enough.

I couldn't resist making a photo of the engine in it's almost complete form.


5 July 2008:

Took a break for the 4th and figured out some changes to the governor to make it work at slower speeds and not bind.

The improved governor with extra weights and reworked linkage.

Since the governor didn't want to work at any reasonable speed, I added some weight.  Not having enough brass like I made the original weights out of, I simply turned a piece of 7/8" HRS bar to clean it up and threaded the ends of the brass weights and one end of the steel weights 8-32 and, using a piece of steel 8-32 bolt, screwed them together.

Since the weight linkage was binding, I removed the screws formerly in the weights and made pins, threaded for acorn nuts on both ends.  Much smoother.  I also made a new central pin by turning a piece of 0.175" (I have a piece of the stuff and have no idea where it came from) steel rod down to .125, leaving a head on one end and grooved the other end for a snap ring.  Much better.

I think it will respond down to around 200 RPM (crankshaft).

Getting started on the bellcrank.

The last item in this part of the project was the bellcrank to change the vertical governor movement into horizontal movement for the throttle plate bellcrank.  The raw material is another piece of that 0.175" rod, threaded 12-24 on one end to fit into the engine frame with a locknut and washer and on the other end for a nut to hold the bellcrank on the shaft.  The bushing is a reject from a long-past project (NEVER throw anything away!) and the material that the arms are made of is some 0.062" brass parts removed long ago from a telegraph switch box.

The bellcrank after a bit of cutting and drilling.

After reaming the big ends of the arms and drilling the mixer arm for the throttle rod (which is going to be a piece of coat hanger wire [remember about never throwing anything away]), I soft soldered them onto the bushing.

The finished governor.

I temporarily hooked a spring to the mixer end of the bellcrank and spun-up the engine and I think the governor will work.  How well, we won't know until the engine is running.

It's now onward to the next part.  In Part 6, I will try to have the engine running.  The mixer, exhaust pipe, fuel tank, timer and cooling tank will need to be made before commencement of the push to make smoke.


In Part Six, I will work on the mixer, exhaust, timer, cooling system and other parts..

Comments?  Suggestions?  Email me at:

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