My Ordinary Little Hit & Miss Engine

[rudydubya]

After drilling the bearing block and tapping the frame, I screwed the bearing block to the frame, put it back in the mill vise, and drilled out some of the excess material in the middle of the block so I wouldn't have to drill and bore through so much.  I then turned the frame on its side and drilled and reamed a hole through the block for the 1/4" OD bronze bearings.

With the bearing block still screwed to the frame, I milled the inside frame walls and bearing blocks to width.

Then the bearing blocks were removed and the center of the frame was drilled and milled out to shape.

The frame base is next.

Rudy

[GailinNM]

Looking Great Rudy,
You know I really like small H-N-M engines.
Gail in NM

[Dreeves]

Rudy, Great Idea making the bearing blocks a one that cutting before drilling. I have done several engines and made them one at a time. Much easier to hold they your way. Great Job and looking forward to a running engine.

Dave

[rudydubya]

Sorry for that missing photo, folks.  I think I have it fixed now.

Gail, thanks, it's great to have you following along.  I'll try not to disappoint.

Dave, thanks.  Maybe a little material wasted, but for me it's worth it.  I usually spend a great deal of time trying to make things easy on myself.  My limited machining skills demand it.   

Rudy

[Don1966]

Nice progress Rudy and I also like the way you made the bearing blocks.............



 

Don

[b.lindsey]

More nice work Rudy. I look forward to your updates on this engine.

Bill

[fumopuc]

Hi Rudy, I am following along too. I like seeing parts to be made with this small Sieg mill. It was my first mill also. Waiting for your next steps.

[rudydubya]

Thanks guys.  I really appreciate your interest.

Here's the frame base.  I hollowed it out for possible use as a fuel tank (I haven't implemented that yet).  The recessed holes at each end are for mounting, and I'll use four long 2-56 socket-head cap screws through the holes in the walls to hold the frame top and base together.

I cut a block of 6061 aluminum on the bandsaw and milled it to size, then put it on its side and profiled the ends with a 3/4" end mill.  The mill protested a little at such a large end mill, but I took light cuts and it finished nicely.

I drilled and hogged out material from the center and then finished it to size.  I also drilled and counterbored the holes at each end for the mounting screws.  I'll put brass inserts in those counterbores for screw seats.

The longest screws I had to attach the frame top were too short to go all the way through the base, so I counterbored recesses for the screw heads deep enough to give me ample threads on top.

My drill bits were also too short and wouldn't go all the way through either.  So here's where I learned to really trust my drawings and my cheap DROs.  I drilled through the bottom of the base as far as I could, turned the base over, and used the DROs to locate the holes from the top.  I drilled through and the holes met right on.

I drilled and tapped holes in the bottom of the frame top to match the screws from the base.  Again, I trusted my drawings and DROs.

And everything fit together nicely.  It looks a little top heavy, but it will look better with the cylinder attached.  Those bronze bearings in their blocks are just there for looks right now.  I won't Loctite them in until I finish the crankshaft.

The seats for the mounting screws are just some brass rounds with a hole drilled through them.  I considered making them from aluminum, but I think brass is classier and adds a little contrast.  I'll use some Loctite when I put them on the base.

We'll do the cylinder next.

Rudy

[cfellows]

I'm learning a few tricks from your thread.  Always interesting and informative to see how other's have done things. 

Chuck

[rudydubya]

Chuck, thanks.  I've enjoyed following along with your projects for a long time, and learned a lot doing so.

Regards,
Rudy

[rudydubya]

Here’s the cylinder, simple and ordinary.  I made it from a single piece of 12L14 steel, no water jacket or liner.  The near end will fit into the end of the frame, and I'll attach it with four 1-72 socket head cap screws.  The bore is 1/2" and the cylinder is 1.5 inches long overall.  The cylinder walls are 1/16" thick.

I chucked a piece of one-inch steel bar in the four jaw, faced the end, and took a light cut along its length.  I center-drilled the end so I could give it some additional support from a tailstock center and cut the grooves with a 1/16" parting-off blade.

I turned down the end to match my frame and progressively drilled out the cylinder until I got close to size, then switched to a boring bar, and finished with a 1/2" reamer.

I didn't have a hone, so I polished the inside of the cylinder with some 1200 grit sandpaper and then some polishing compound.  I'll be using an 'O' ring for a piston ring.

I parted off the cylinder, leaving a little extra on the end to make sure I didn’t cut too short, and finished the parted-off end to length on the mill.  Then I drilled and tapped the frame end of the cylinder for the four mounting screws.  I didn't do any drilling or tapping on the other end because I hadn't finalized the head design yet.

So far, so good.  Still a lot of cleaning up to do, but things fit.  In case you were wondering, I used socket head screws for the frame-end of the cylinder and oriented them that way so I could access them with a long hex key even with the crankshaft in place.

Rudy

[rudydubya]

There isn't much to the cylinder head, it's just a round piece of aluminum with the usual ports and holes.  It's 1.0" in diameter to match the cylinder OD and has a 0.50" diameter, 0.040" thick boss on the inside face to fit in the cylinder bore.  The slot in the lower front is the seat for a pushrod guide/rocker arm mount, and is the only thing requiring a little special setup.  I'll use four 1-72 socket-head cap screws to attach the head to the cylinder.  The spark plug will be a Rimfire Z3.

I chucked a short piece of aluminum in the lathe, turned one end down for the boss, and parted it off to length.  I then put the piece in the mill vise and milled a flat for the spark plug hole.

I turned it on its face with the flat against the fixed jaw and drilled four equally-spaced 1/16" holes where the mounting screws will go (symmetry is again our friend).  The holes aren't large enough for the mounting screws I'll use, I just needed them for alignment during the rest of the milling.  I'll enlarge them later.  I also drilled and milled holes for the valves and guides and the spark plug recess.  The plug recess is deep enough to join the spark plug hole coming in from the side.  The valve guide holes were drilled through, then milled out to port size deep enough to join the ports coming in from the sides.  I won't chamfer the valve seats until the valves are made.

After I finished with the holes, I removed the head and slipped some 1/16" drill rod through the two holes nearest the flat, and rested them on top of the vise jaws and clamped it tight.  With the flat now properly oriented, I milled, drilled, and tapped the spark plug hole.
   

I then moved the drill rods so the sides were up and milled out the intake and exhaust ports.

Almost finished, but I still had to do the slot for the pushrod guide/rocker arm mount.  The slot doesn't align with the flat or any other feature on the cylinder head face, so I made a fixture from scrap to align the head for a straight X-axis cut.  I got the coordinates for the fixture alignment holes from my CAD program.

After the slot was finished I used the flat again for reference and enlarged the mounting screw holes for close-fit clearances.  I counterbored the holes so the shorter screws I had on-hand would go all the way through the head.  I also drilled and tapped a 0-80 hole in the slot to mount the pushrod guide.

The crankshaft will be next.

Rudy

[b.lindsey]

That's some fantastic work Rudy. I am really enjoying following along on your progress.

Bill

[Myrickman]

Just stumbled onto your thread Rudy....neat build. I like the way you slit the tapered hubs using the clamps as a guide. Have to file that one away for later use. Picking up a lot of fixturing hints on this one.  Great job. Paul

[Dave Otto]

Very nice Rudy!

I'm enjoying your step by step and great progress.

Dave