The Homebrew Engine

Part Three

Making The Cylinder And Liner

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


13 May 2008:

I've decided that the water jacket and the decks will be welded together.  The cylinder will still be a wet sleeve with an O-ring at the bottom joint to seal the water in.  The top end of the cylinder will have a step on it that will fit into a step in the bore of the top header.  I'll get a drawing posted when I get the time.


14 May 2008:

I worked on the water jacket and the head-end deck today.


                         Indicating the pipe that is to become the water jacket.                                                               Facing one end of the jacket.

Cutting off the pipe was almost a challenge.  My bandsaw just barely was big enough to cut it and, as it was, I had to turn the pipe about 3/4 of the way through to finish the cut.

I got lucky with the lathe.  I was not optomistic about being able to hang on to the pipe in the lathe but ended up reversing the jaws on the 3-jaw chuck and sliding the pipe over the entire chuck, leaving just enough room to tighten it with the key.

I then indicated it to get it to run as true as I could.  Being pipe, the radius is not constant, changing about 0.020" in a revolution.  I got it as close as I could, then faced one end square.



                                 Cleaning up the inside diameter.                                              Chamfering for welding

I bored the inside diameter just enough to mostly clean it up for a depth of about 1/4".  Since the jacket is to fit over the deck plates and be welded to them, I wanted a good fit before welding so everything stays concentric.

Doing it the hard way, a bit at a time, I cut a rough chamfer about half the width of the face so the welds could be smoothed.


                 Boring the head-end deck for the liner.        The semi-finished head deck with the recess for the liner.

To do the bore for the cylinder liner to slide into the head-end deck, I drilled a hole with a series of increasing diameter bits until I had a 3/4" hole.  Then I used the boring bar to bore it to a slip fit with the liner.  I will turn the O.D. of the liner to fit the deck with a lip at the head end which fits into the counter bore shown.  The head gasket will hold the liner tight against the deck and seal the coolant from the combustion chamber.

After the decks and water jacket are welded together, I will put the assembly back in the lathe and true it up, taking a light clean up cut over the outside diameter.


16 May 2008:

Yesterday, I spent all my time working on dimensioning the CAD drawings of the cylinder assembly, liner and cylinder rails.  Since the jacket is made of schedule 40 pipe, it didn't clean up close to where I thought it should.  To keep confusion from reigning (which, in my case is easy!), I changed the pipe dimension and had to re-dimension everything else to be sure it came out right.

I got back out to the shop this afternoon and made the rear or crankshaft-end deck piece and fitted it to the water jacket.


Semi-finished crankshaft-end deck and water jacket.



Here's the crank-end deck and water jacket laid together.

I should have the head-end deck done tomorrow then, on Monday, since my little MIG outfit hasn't got the horsepower for this, I will take it to the welding shop.

After it's been properly warped at the welding shop, I'll figure out a way to get it back in the lathe and mill to straighten up what I can.  I haven't put the final dimensions on the cylinder mounting rails so I can make them to fit whatever size the cylinder ends up being.


19 May 2008:

I've finished both decks now and have cylinder assembly ready to weld.  I'm getting the welding done later today.


The cylinder with a 1/2" threaded rod holding it together for welding.

Here are the cylinder mounting rails.

I also drilled and tapped the 1/8" NPT hole in the jacket for the oiler pipe to come out and have drilled and tapped the 1/4" NPT hole in the bottom of the jacket for the cooling water to enter.

I've got a brass compression fitting for 1/8" tubing that I will drill out for the 1/16" oiler pipe to exit the jacket through.  I'll fit an O-ring around the oiler pipe and give it a little squeeze with the compression nut.  This will keep cooling water from leaking out and will allow the pipe to slide a little as the cylinder liner and jacket move from thermal effects.  

The oiler pipe will thread into the liner.  I'll use a 1/4-28 tap and die to cut the threads into the pipe and liner.  I priced the tap and die for 1/16 NPT and think I'll pass on them.  1/4-28 will work if I only partially run the tap into the liner and die over the pipe.

The cylinder mounting rails haven't been trimmed yet.  I intend to put the welded cylinder assembly into the lathe and turn the O.D. and face the ends flat before measuring to cut the mounting rails.

I may then clamp the cylinder to the frame with the rails in position and take the whole works to the welder.  That way, nothing can get out of position while moving it to the welding shop.  That may happen tomorrow.


20 May 2008:

The cylinder is welded and turned to look nice and the cylinder mounting rails are fitted to the cylinder and it will be welded to the rails tomorrow morning.

The welded cylinder before cleaning up.


Here it is faced and turned and ready for the die grinder and file on the crankshaft end.


The cylinder, mostly finished and clamped for welding.

After this is all done, I will machine the liner and fit it to the jacket.  I'm waiting for O-rings for the crankshaft end of the liner.  The top end of the liner will have a step that will fit into the recess on the head-end deck.  The head gasket will seal this joint.

It will be necessary to remove the cylinder from the engine frame at least one more time to drill coolant passages and drill and tap for the head bolts.  I won't know exactly what to do here until I have made a drawing of the head.  I'd like to drill some water passages in the head but that will mean that I will have to drill and plug some blind holes which I think I can place on the bottom of the head where they won't show.

I may have to re-visit my idea for a sideshaft.  I'm having trouble finding a source of helical right-angle gears.  I tried Berg but they don't seem to want to do business in onesies and twosies.  Anyone got a suggestion?

If I can't get the gears, I may just make it a gearless.  With a gearless setup, the cam is on the crankshaft and there is a funky every-other-time cam actuator/lockout to make the valve work every second revolution.  This is better suited to a hit and miss engine but I don't see why it couldn't be applied equally well to a volume governed design.

THEN, I've got to work out the governor.  With the gearless arrangement, it will have to have the flyweights on the crankshaft with linkage going to the mixer.

Stuff to think about.


21 May 2008:

The cylinder has been welded to the rails and cleaned up. Since the TIG welding caused the mounting rails to get a bit wavy, I had to put the works in the mill and take a cut to even things out.

Milling the rails straight.


Here's the works mounted up and ready for the liner.

You can see the liner blank in the above photos.   That's what's on tap for tomorrow is to do the liner and maybe get started on the piston.


22 May 2008:

Well, yesterday afternoon I went and bit the bullet and ordered a couple of 9" flywheel castings.  I also got some grease cups, an oiler and a set of helical gears among other things.  I figure if I have to make everything, this project's gonna take forever.

Today, I started on the cylinder liner and didn't get very far.

Cylinder liner blank with plug for live center.

First, I made a tight fitting aluminum plug to fit into the bore of the end of the pipe to use with the live center so I could turn the cylinder liner.

Trial fit of plug into recess in head end of cylinder jacket.

I used the aluminum plug to find the diameter that the liner has to have at the head end to fit into the step in the head end of the cylinder jacket.

Turning the O.D. of the cylinder liner.  The end of turning is where the liner will be cut to length.

I think I've found the limit of my little lathe.  In trying to turn the O.D. of the liner, I got a LOT of tool chatter!  I tried several tools and angles and tightened up the gibs as much as I dared but still had chatter and it was making the cut look really bad.  I did find that, if I only took about 0.005" per cut, the chatter was very minimized.  At 0.005" per cut, it would take about 20 passes to remove the 0.200" from the diameter.

After cutting off the excess of the liner blank.

Finally, I got disgusted with the look of the cut so I removed the blank from the lathe and cut it to length.  Then I put it back into the lathe and tried a cut.  It seems to chatter less now.  I also have re-set the tool as close to the toolpost as I can get it which also seems to help.  

I ran out of time so I'll get back to it tomorrow.


24 May 2008:

The liner is about done.  All I have to do to it is to machine the chamfer in the bottom of the bore and drill and tap for the oiler line.

The liner, almost done.   The aluminum centering plug is still in place.

It took about four hours to finish turning the O.D. of the liner because of all the tool chatter.  I ended up turning the diameter at the head end on the right (snug fit into the deck), the diameters where it fits into the headers (0.001 loose) and the diameter where it slips through the back (crankshaft) end of the the deck (snug fit).  I turned the area of the liner between the decks to 0.005" clearance so the liner won't have to be hammered all the way.

The largest diameter at the head end is 0.200" long and fits into a counterbore in the deck that's also 0.200".  The head and gasket will hold the liner against the step in the deck (says so right here in the 'fine print!).

When I turn the chamfer at the crankshaft end (in order to be able to insert the piston and rings into this end), I'll have to chuck the liner at the head end and use a steady rest to hold it so I can work on that end.  Although I don't think I'll have a chatter problem, if I do, the tool marks won't be a big issue because the surface is only for compressing the rings on assembly.


25 May 2008:

Moving right along, today I finished the liner by drilling the oiler hole in it and checking it's fit in the jacket.

Then I went for my hone and found that it is just about 1/4" too big to fit the bore.  I did the next best thing.


Here's how I honed the bore.  Redneck Engineering at it's finest!

The bore still has some "granularity" but is smooth and I think the rings will seat fine.


Laying out the water passage and head bolt holes in the deck.

Since I'm basically lazy and also because I have a CAD system and can plot drawings at exact size, I simply made a drawing of the deck with the holes positioned, then laid the drawing on the deck and used it as a template to center punch the hole centers.

Once these holes are finished, I can mount the whole sheebang onto the frame and make the piston.


27 May 2008:

A little more progress today.  I finally finished the cylinder assembly.

The oiler tube and fitting for the oiler.

I got some 1/16" steel tubing to go from the liner to the oiler adapter.  The thread in the jacket is 1/8" NPT.  The oiler tube goes about halfway up into the ball and the oiler goes about halfway down into the ball.  I'll make a little vellum gasket to seal the joint between the oiler and the tube.  I drilled out the fitting so the oiler tube was a loose fit.

The ball is out of my junk box.  It was originally a chain pull for a ceiling fan that is now deceased.  I drilled it and threaded it halfway 5/16-24 to fit the thread on the fitting.  The other half way is threaded 1/4-28 to match the thread on the oiler.  I think it looks kinda neat.


The cylinder finished with the oiler fitting in place.

On assembly, the oiler tube is screwed into the liner after the liner is in the jacket.  Then the adapter thingy is threaded into the jacket.  

Note that I've got the the cooling passage holes drilled and the head bolt holes drilled and tapped.  It looks like I have room in the head to have three vertical cooling channels that connect the bottom and top sets of holes.  The water outlet is in the head and connects with the passage in the head from the top center hole in the deck.  I'll have to think on how to be sure to get the holes in the right place.  There will be ports, valve seats, valve guide bores and a spark plug hole to miss.


Drawing of the piston and the raw material for it.

The piston drawing is done and it is being made now.  I haven't exactly figured out how I'm going to get a press fit of the wrist pin in the piston.  The pin is 0.500"+.  I think I'll see how close I can get with a 1/2" reamer.  If the reamer makes 0.500-, I should be in business.  To make sure, I'll drill and ream a hole in a piece of scrap to make sure I don't end-up with an "Aw-Shoot!"

Instead of using snap rings to hold the pin in place, I think I'll make a couple of brass plugs to push into the ends of the pin bosses.  If the pin does move, the brass will keep the pin from moving enough to score the cylinder liner.


28 May 2008:

I think I can consider myself finished with this part of the project.  The piston's done and hung on the rod.

It took a while to hog-out most of the piston.  Note the high-tech masking tape depth gauge.

I made a lot of chips today and they are the kind I like.  Nice machining aluminum.  It cuts free (not like chewin' gum!) and it's easy to get a nice finish.  



The finished piston.

You will notice that I've done some artistic filing on the little end of the rod.  This is to make it clear the inside of the piston without my having to remove too much meat from the piston.

I opened out the inside below the wrist pin bosses to allow about a 1/8" thickness of the skirt down to about 1/4" from the bottom where I left it thicker.

The part of the piston around the wrist pin bosses was bored to about 0.875" diameter to give clearance for the little end of the rod.  After boring the inside, I swapped ends of the piston, faced it off to length (4.00") and made a center for turning the O.D.  I removed the piston from the lathe and mounted it in the mill where I hogged out the length of the hole between the bosses (perpendicular to the pin) to about 1.125" so the rod could move.

The piston was then repositioned in the mill and the wrist pin hole was lined up.  I drilled the wrist pin hole to 0.375", as big a bit as would fit lengthwise in the chuck of the mill.  Then, using various collets, I used a graduated set of reamers to laboriously increase the size of the hole to exactly 0.500. 

I turned the piston 90 degrees in the mill and used the same centerline as for the wrist pin.  I then milled a 1/8" slot that corresponds to the oiler hole in the liner and ran the mill all the way through to come out right over the wrist pin.  When I set the depth of the slot, I made allowance for the reduction of the diameter of the piston so there would be about a 0.050" depth in the slot.  I figure this will capture most of the oiler oil and feed it to the wrist pin. 

The piston went back into the lathe and, using the live center, I turned the piston to 1.988" allowing for 0.004" clearance in the bore.

The last thing to do was to use a parting tool to cut the ring grooves.


Heating the piston prior to driving in the wrist pin.

The wrist pin is about a 0.0005 (half a thousandth) tight fit in the piston so I used my trusty heat gun to get the piston hot enough to sizzle spit (a scientific way to measure temperature).  Then I laid the piston and rod together, quickly inserted the pin and hammered it into place.   I don't think it's gonna move but tomorrow, I will make a couple of brass buttons to press into the ends of the wrist pin bore.  That way, if the pin wanders, the brass will keep the bore from scoring.


The assembly so far.

I just had to put the piston in the bore and lay the rod against the crankshaft.  I made a complete turn and there's no interference between the rod and anything else.

Now, to the next page.


In Part Four, I will work on the cylinder head and other parts.


Comments?  Suggestions?  Email me at:

[email protected]