Questions on the Elmer 33 Engine

[Heffalump]

Hiya chaps,

I'm building Elmer's 33, and have come to the radiused slot in the base. I saw stan did this with a tool I do not have! What options are there for cutting this slot?

[Jo]

Take a piece of 1/2" diameter drill rod, grind the end to the half width line and profile it to give some clearance at the back. Harden it. Then use it as a flycutter, sticking sideways out of a "boring" bar at the appropriate diameter.

Your cutter will have one tooth, Stan's had many more so take it very slowly and steadily as you cut.

Jo

[Heffalump]

One other thing we are lacking is a boring tool for the mill!

Aside from not looking as pretty, would this feature function as well with a flat bottom instead of a radius?

[b.lindsey]

It shouldn't affect the function at all...just a matter of aesthetics. Looking at the plans, the slot is for clearance of the crank disk and con rod. The flat bottom will show but the engine will still run fine. It looks like the side to side clearance (or width of the slot)  is far more critical.

Bill

[mklotz]

Just wondering out loud here - if I'm being stupid, just ignore...

Assuming the base is aluminum...

A (woodworking) dado head

or

a small carbide-tipped 2.5" saw blade - the type used on small panel saws.

[b.lindsey]

That would work Marv, even a non carbide slitting saw would do, it would just take repeated cuts until the width was achieved, and a little more clean up at the end. The 2 1/2 diameter doesn't appear to be critical so even a 2" saw or 3" one should work if available...the wider the better of course.

Bill

[mklotz]

That would work Marv, even a non carbide slitting saw would do, it would just take repeated cuts until the width was achieved, and a little more clean up at the end. The 2 1/2 diameter doesn't appear to be critical so even a 2" saw or 3" one should work if available...the wider the better of course.

The flywheel is 3" diameter so I don't understand why the radius is less than half that (1.5").  Esthetically, I would expect it to be larger.

[Alan Haisley]

One other thing we are lacking is a boring tool for the mill!

Aside from not looking as pretty, would this feature function as well with a flat bottom instead of a radius?

I used a flat bottom, then angled the piece and cut a ramp. It doesn't look too bad that way.

Alan

[Heffalump]

One other thing we are lacking is a boring tool for the mill!

Aside from not looking as pretty, would this feature function as well with a flat bottom instead of a radius?

I used a flat bottom, then angled the piece and cut a ramp. It doesn't look too bad that way.

Alan

Ah that's quite a nice halfway house, I might do that as the cheapest option. The nodding / tilting head on the Bridgeport will make that easy.

[b.lindsey]

Marv, the flywheel on this engine sits outside the "base."  The radiused slot is for the crank disk and connecting rod. Even so, it is more than generous at 2.5" diameter.

Bill

[kvom]

Make the base from 3 pieces fastened together.

[Heffalump]

Hiya Chaps,

I've annotated the drawing attached below, are these holes meant to be tapped?

[sshire]

Jim
No tapping there. Those are clearance holes for the screws that affix the cylinder.(which is tapped). The side view shows them  as countersunk for flathead screws. I used SHCS, so mine are counterbored.

[Jo]

Would you like me to put all of these little query threads together into a single "Questions about the Elmer 33" thread?

Jo

[Heffalump]

Yes please Jo! I am likely going to have many more - That's a much better idea.

Thanks Stan, does the #4-40 just refer to a drill size? I'm pants with imperial!