The Homebrew Engine

Part Four

Building the head and other parts.

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


29 May 2008:

A few fiddly bits (as the Brits say) for today.  Using a piece of scrap brass, I made the wrist pin plugs.  They are a drive fit in the piston.

Wrist pin brasses.

I haven't been too comfortable with the crankshaft.  The pins could slip in the cheeks so I drilled through all four press fits, reamed and drove in taper pins.

Taper pins in the cheeks and milling the gib key slots.

The milling of the keyways was tedious.  Since I only have one 3/16" milling cutter, I had to be super careful to not break it.  The keyways are 0.090" deep.  The remainder of the necessary dimension will be broached into the flywheels.

The crankshaft in position with the timing gear mounted and a gib key in place.

I bored the crankshaft timing gear to fit the crankshaft.  There was only about 0.100" of thickness left in the gear between the tooth roots and the shafrt so I turned the teeth off of the end of the gear and drilled, reamed and drove in a taper pin.

The mating gear that drives the sideshaft will be above the crankshaft.  A trial fit showed that the shaft will just clear the water jacket when set-up this way.

Before going to the shop, I worked on the design of the head to get some dimensions.  I'm not going to start on the head until the flywheels are finished and on the crankshaft and the whole works mounted up to the engine.  Then I can design the sideshaft bearing mounts and see where everything falls into place.  That will tell if my present valve arrangement will work.

Today's "Aw-Shoot!" occured when I tried to get the 9" flywheel casing into my 9" lathe.  I just found out that my 9" lathe will really only swing about 8-1/2" so I have to get inspired.  

I'm sorta thinking of mounting the wheels in the mill and facing off and trimming the hubs to length.  Then I'll find the centers and bore them  to fit the crankshaft, about 0.735" or so.  I can then make a broach and broach the keyways into the wheels.  Then, using a piece of 3/4" shafting, I can turn it to be snug fits in the wheels and mill a keyway in it.  I can then insert the shaft into the flywheels, hammer in a gib key  and mount them on the spindle of my mill with a collet.  

I will mount a carbide tool in the mill vise and move the table to move the tool.  I HOPE this will be stable enough to turn the O.D, flanges, etc.


30 May 2008:

Moving right along, I got one of the flywheels mostly done today.  I decided to do them one at a time so I couldn't screw both of them up.  Once I've got the first one done, I'll know what to do to get the second one right.


        On the left, the first setup for flycutting the hubs.     On the right, the second and better setup for the flycutting.

My first thought on flycutting the hubs was to mount the flywheel in the mill vise with spacers to hold it parallel to the table.  After a couple of cuts, I noticed the wheel had moved just a little.  Not wanting it to catch on the tool and be launched across the shop, I tore that setup down, removed the vise and used the setup on the right with the wheel blocked off of the table and clamped directly to it.  1/8" cuts were possible with the clamped wheel so, since I had to take off a lot of iron, the job went faster.

After flycutting both ends of the hub, I found the center of the hub and drilled it to 5/8" then bored it to 0.735, the size of the finished shaft.


An old carbide tool bit was ground to fit in the mandrel to the right, making a pretty fair flycutter.

The flycutter mandrel was made of a piece of 3/4" shafting, turned to about 5/8" then end drilled for a setscrew and cross drilled for the tool bit.  


Broaching the keyway using the vertical feed of the mill.

Since the bit width was about 0.060" under the width I needed for the gib key, I first centered the broach and locked the spindle shaft.  I broached to a little less than the finished depth.  Then, I stepped the wheel to the side in increments 'til it was 0.030" wider in one direction.  I then went back to center and stepped the wheel to the other side the same way.  Close enough to file straight.

Then, I spent an hour hand filing the crankshaft and flywheel so the gib key would jam with a little length left over.


Here's a monster (3/4X3/4) carbide tipped tool I got from a friend.  I ground it and here's how I mounted it to turn the O.D of the flywheel.

How to turn the rim of the flywheel?  Since my lathe wouldn't swing it and after thinking on it a bit, I took a piece of 3/4" shafting and turned the O.D. on one end to what I think was a couple of tenths over the hub bore diameter.  With a file, I made a very slight taper on the diameter.  I then drilled the end and tapped it for a 1/2-13 bolt.

I drove the shaft into the hub of the wheel and it was a nice tight fit.  I added insurance by torqueing down the end bolt against the hub face.  Then I slipped the big end of the shaft into a 3/4" collet in the spindle of the mill.  I gave it a spin and there was no noticeable wobble.  What I DID notice is that the ends of the hub are not concentric nor are they concentric with the outer diameter of the casting.  It looks to be around 3/16" off.  Since the hub was already done, there was nothing to do but to turn the outer rim of the wheel.

If it looks too bad, I may stick it in the lathe (it may be small enough to swing by then) and turn the inner diameter of the rim to make that part concentric, at least.  It all depends on how bad it looks and my mood at the time.

A while back, a good friend in Kentucky gave me a box of used tool carbide tipped tool bits.  Some of them are 3/8" and work well in my tool post.  There are a few 1/4" bits that I can use with shims and a couple of monster 3/4" bits that I didn't think I'd ever use.  That is, until this project.  I selected the bit that was ground close to what I needed and ground it to do the turning.  I stuck that moose of a bit into my mill vise and it works like a champ when running the mill at it's slowest speed.  I make a cut by stepping the table then cranking down the quill.  It'll do 0.015" cuts without too much complaint although I've decided to be cautious and do 0.010" cuts.  I had to quit for the evening after partially cleaning up the face of the rim.

Tomorrow, I hope to finish the first (cam side) wheel and get the second (off-side) wheel done and fitted to the crankshaft.  Then, it's on to the sideshaft layout.


30 May 2008:

I've almost finished the flywheels.


 Turning the outer rim edge.                                                  Turning the inner rim edge.

By repositioning the tool in the vise, the rim edges could be turned.  The inner edge was done by reversing the tool and running the spindle in reverse.  The "crust" on the castings is really tough and there were probably some sand particles embedded in the outer layer of metal so, I had to remove the tool and resharpen it before doing the final cuts on the rim.  After turning the rims, I used a file then coarse and fine sandpaper to put a nice finish on them.

The off-side wheel, ready for gib key fitting.

I now remember my time working in the machine shop back in the mid 1960's.  Working with cast iron is DIRTY!  When I finished the wheels, I was covered with black iron dust and the shop was a mess.  When I oiled the wheels to keep them from rusting, the iron dust on my hands transferred some of itself to the wheels as you can see above.

Before boring the hub on the off-side wheel, I checked both sides to see if I could find the center more accurately.  I found that I can get either side centered but the other side would be off-center.  This is because the boxes the wheels were poured in were not aligned very well at the foundry.  The sides are shifted almost 1/4", making centering both sides impossible.  The first wheel turned out with the centered side on the outside face and I figured that the outside of the wheels needed to be centered so that's how I did the second wheel.

I ran out of time today before I could get the gib key fitted in the off-side wheel.  One reason is that my broach fell apart.  I now know not to use a carbide tipped tool bit for something so small.  The force of pulling the tool through the cast eventually ripped the carbide tip off of the shank.  I ended up making the bit out of an old steel bit and it took a while.

Tomorrow, I'll mount the crank and test fit the wheels to see how the sideshaft will lay-up.  I can take dimensions and use CAD to come up with the bearing mounts for the sideshaft.

Another thought occured to me.  If I'm going to be using a flyball governor, I'll have to drive it at a right angle to the sideshaft and if I were to buy another set of helical gears, I'd be out another $45.00.  I think I'll arrange a round belt - possibly an O-ring - as a right angle drive for it.


30 May 2008:

The flywheels are done and the first coat of paint is on.

I also made a gib key puller today.


Gib key puller.


Milled-out steel scrap with 1/4-20 nut welded on.                               Puller with key inserted.                  

Since I was having to insert and pull the gib keys numerous times to get them fitted, I wanted to keep from beating them up so I made a puller out of some scraps.  


Here's the engine with the sideshaft laid up to see how it will fit.


4 June 2008:

I've spent the last few days watching paint dry and doing some more fiddly bits.  Got the grease cups mounted on the rod and mains and have spent some time in CAD, working out the governor, cam and valving arrangement.

Here are some conversions of the AutoCad drawings I've been working on.

Elevation view of engine at this point in the design.

The governor and sideshaft designs are coming right along.  I haven't located the crankshaft end bearing of the sideshaft yet but, since the governor is mostly done, I can put it close to the hub of the driven helical gear.  I'll use a bronze thrust washer between the bearing block and the gear hub.  

The whole governer assembly, driven from miter gears, runs at one half crankshaft speed on ball bearings.  I also use a larger ball bearing as a thrust element on the vertically moving collar.  Depending on how it seems to work, there are a couple of places I can put compensating springs and an adjusting mechanism for controlling speed.  

I ended up with a tall governor but I wanted to allow an inch vertically between the bearings and didn't want to get my hands caught up in the weights and other gizmos when pulling over the wheels.  As it is, there is a close fit between the miter gears driving the governor and the side of the flywheel but a quarter inch is as good as a mile.

The ignition timer can be mounted on the sideshaft between the governor and the cylinder.  There seems to be enough space for it and a timing adjuster there.


Plan view of engine at this point in the design.

The cam arrangement is kind of unusual but it's what I've come up with and is subject to change until such time the urge to cut parts becomes irresistible, then it's time to "Shoot the engineer and start production!"

I've got the cam and rocker arm ratio set up to give about 0.70" lift to the exhaust valve.  I'll probably make the cam to give about 1/8" lift then, if it's too noisy, I can always remove some of the high side.  I've yet to work out the cam profile but I think I want about 200 degrees of exhaust opening (Open at 165 degrees ATDC and close at 5 degrees ATDC.  Again, if it doesn't work, I can always make the opening angle smaller with a file.  


Elevation and plan views of the head so far.

You can see a swivel on the cam follower.  This keeps me from having a funky angle on the cam face.  The roller follows the cam and swivels on the rocker arm.  To keep the rocker shaft pin from interfering with one of the head bolts, I've got it cantilevered off the mount.  I'll most likely make a pin with a flat head for the rocker shaft and use a cotter key to keep it in the mount.

I've got a couple of valves out of a defunct lawnmower engine I'll cut down for this engine.  I may use one of the valve springs although I may have to cut some turns out of it to ease back on the pressure. I really don't want any stronger spring than I can get by with because the cam and roller are not going to be hardened (that is, unless I find a nice little ball bearing in my junque to use as the follower).

Since this isn't going to be a production piece, I can be kind of relaxed about totally finishing the drawings.  All I need is enough to extract dimensions from to make the parts.

If I get the "fiddles", I may scoot the rocker arm mount toward the exhaust valve.  That will make the ratio more favorable (closer to 1:1) and allow closer match between the cam lift and the valve lift.

I may not get much more done in the next week or so but stay tuned.  This project will go faster once the head is finished.


13 June 2008:

I'm back at it again after some "home improvements".


    The cylinder head blank faced and turned from the piece of scrap shafting.

                         Cutting the cylinder head blank from the shafting.                            

A few days ago, I turned the O.D. and faced one end of the cylinder head material.  Then, I mounted it in my freebie bandsaw and cut the blank off.  

The finished head.

After facing the other end and squaring it up to dimension, I did some drilling, milling, reaming, and tapping and now have a finished cylinder head.  I had to bore down into the outside side of the head to within 1/4 inch then drill and tap a 10mm plug thread.  The recess for the plug (seen below and to the left) is big enough in diameter so I can get a socket in to install and remove the plug.

Intake and exhaust ports are 3/4".


The finished head mounted on the engine.

I just looked at the assembly drawing (the last drawing before this entry) and find that I've got the head reversed.  Looking toward the crankshaft, the intake is on the left and the exhaust is on the right.  I'll have to go back in and get it flipped before I dimension the rocker, cam and sideshaft parts.

Tomorrow, I'll make the valve guides and machine the valves down to size.  Springs and keepers will be either made or taken out of the junk box.

Geez, guys - it's starting to look like an engine.


14 June 2008:

It seems that some of the jobs in this project take way longer than I figured they would.  Today, I thought I'd get the valve guides made and in, get the valves made and lapped, get the valve springs, keepers, etc. done and get the head gasket done so I could put the liner in permanently and get the piston in.

I didn't get all of that done.  I got the valve guides done and in the head, made the valves and got as far as the intake valve spring and keeper.  The valves took a lot longer to cut down than I figured they would.

The guides are in and the valves are ready to be cut down.

These two valves came out of a defunct lawnmower engine several years ago.  Following my usual practice of being a packrat, I saved them thinking they might come in handy sometime.  They did.



   Making a center in one of the valves.                                     Cutting down the diameter of the head.


After reworking the head, taking the first cut on the stem.                  Taking one of the last cuts on the stem.           

The most tedious part of cutting down the valves was turning the stems.  The smaller the stem got, the less I could take off per pass.  When I got down to the final cuts, the middle of the stem was a couple of thousandths bigger than the ends because of the stem pushing away from the tool bit.  I had to lay a piece of plywood behind the stem to keep it from flexing.

The guides were reamed to 13/64" (0.203125").  After I got the valve stems down to 0.204", I had to use 400 grit carborundum paper to get the last 0.001" off and get rid of the little fatness in the middle of the stems.  That took some time, too.


               The finished valves.                                              Checking the fit of the valve guides.

Since the intake valve is "automatic", I turned more material off of the head end of the intake valve to reduce the weight.  I also made the stem shorter so the exhaust valve rocker arm won't interfere with it.

Then came the lapping chore.  The intake valve lapped-in easily but the exhaust valve with it's wide face just didn't want to seat.  I ended up cheating a little by putting the valve back into the lathe and changing the angle from 45 degrees to about 47 degrees.  This made a narrorer seating face and I think I've got it lapped-in.


The intake valve spring and keeper parts.                                   The intake valve keeper in place.      

I found a likely spring for a first try at the intake side and made a keeper and pin.  The 0.050 hole in the stem was made with a small solid carbide bit.  I got lucky there.  Often, when working with hard materials and the little carbide bits, the bits get in a tiny bind and will break.  This time, I clamped the workpiece down and ran the drill press at 4.500 rpm and made both of the holes without mishap.

The keeper pin is the shank of a worn out #56 (0.0465") drill bit.  Now I know why I've saved a box of worn out small bits.

Before quitting, I selected a spring for the exhaust valve and ground the ends flat.  The keeper is in the lathe.  I'll finish it tomorrow.

THEN, I can make the head gasket and button up the cylinder and get the piston in.  I've got a 12 volt motor and a cog belt pulley and belt that I think I'll slip around one flywheel and motor it for a while to start breaking in the rings and finish running in the bearings.


15 June 2008:

After making the exhaust valve retainer, I checked the sealing of the valve using alcohol.  It leaked like a sieve.  Somehow, the seat tooling got shifted a little and the valve hadn't lapped-in correctly although the pattern looked pretty good.  I ended up making a mandrel for an old valve seat cutter and carefully recut the seat.  After a lot of lapping, I got it to seat.

Then, I made a head gasket and permanently installed the liner.  I put the piston in for the first time and find that there is a minor alignment problem with the rod.  The little end of the rod is not centered in the piston and the rod bearing runs warm.  What I may do is to shim the bearing out 'til it doesn't bind and run it like that for a while to see if it will run-in true.

Motoring it to break in the rings.  It DOES have compression!

I had a motor taken from a broken marine washdown pump so I made a couple of funky mounting rails and hooked it up to the little engine.

I'll probably take another break from the project for a week or so.  When I get started again, I'll do the sideshaft, cam, follower and rocker,  the governor, mixer, timer and maybe some other parts on the next page, The Homebrew Engine Part Four.

Stay tuned!

In Part Five, I will work on the sideshaft, governor, valve gear and other parts..


Comments?  Suggestions?  Email me at:

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