Elmer's Kimble engine

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arnoldb:
:doh: My work life has been keeping me pretty busy of late, so shop time is hard to come by.

This afternoon I drilled a 2.5mm hole through the center of the engine top:

That was tapped M3 for the air inlet.

I next milled out the excess metal that was still left on the bottom of the engine:

The bottom mounting holes were not tapped yet, so I also tapped those M3, and gave the block a final flat-lap on both sides. That pretty much completes the engine block part of the build.

Next I started on the vane; I milled a section of 4.8mmx12 brass flat bar down width of 9.65mm - that's the same thickness as the engine block. I didn't quite get it, and ended up at 9.7mm. I wanted the vane 0.01mm thinner than the engine block, so I sat down and flat-lapped it down to 9.64mm on some 600 grit paper, frequently checking with a micrometer that I was keeping it parallel and not lapping one end down more than the other. Quite a bit of manual work, but it turned out well in the end:

Next I faced the one end square, cut it of just over length (the bit of flat bar was more than twice too long), and then squared up the other end as well. The vane top needs a slot where a seal with a small spring will be installed, so I started cutting that with a 2mm cutter. after about the 7th pass, a bit of a disaster; just a second of inattention and I increased the rate of feed just too much:

Oh well, that poor end mill has been doing duty for more than six months now, in everything from plastic to a bit in stainless; it was getting a bit blunt. So I fetched a new one from my stock and finished the job. There's only one left now, so it's time I fired off an order to RichOn - I need some other cutters as well...

Back when I started this project, I mentioned the fact that Elmer's plans has a measurement error with the mortise and tenon joint. I was still undecided whether I was going to use this method for joining the vane to the main shaft.
This joint is most likely the weakest link in the engine, and would see quite a bit of torque transferred through it, so just soft-soldering the vane to the shaft without some form of additional strengthening would very likely lead to failure.
Many moons ago, John Bogs suggested that silver soldering the joint would be his way to do it - I agree, but then there's one teeny little problem for me; this joint has to be done ultra-neat as any excess would be very difficult to clean up, and that's something I'm still having problems with when silver soldering.
So it was either the mortise and tenon for me, or I had to find another solution. I did the latter, and decided that three pieces of 1.5mm piano wire running between the shaft and vane would be just as strong - if not stronger than - a mortise and tenon made from brass. The main loading on the joint is radially, and the wire would cope well with that - while loctite would be more than adequate to keep things from coming apart.

I drilled three 1.5mm holes spaced 2.5mm apart in the bottom of the vane:

Next I cut a section of 6mm silver steel to length ( :dremel: I restocked earlier this week) and cleaned it up on the lathe. Then I drilled matching 1.5mm holes in it - offset to compensate for the one thicker cylinder cover so that the ends sticking out from the engine would be equal:

I used the Dremel with a cut-off wheel to slice off three sections of 1.5mm music wire, and pressed those into the vane with some loctite, and with more dabs of loctite, pressed the lot into the shaft. The middle hole on the shaft had wandered a tiny bit, but this actually helped things; I had to use the mill vise to press it together the last bit - and the vise aided in getting everything nice and square. It won't come apart easily, but if needed, I can get it apart again with some heat. Some of the excess loctite running between the two pieces also help to make the seal air tight:

and

A quick assembly, and things are looking good; some oil smeared on the vane gets distributed evenly everywhere on both the rear and front covers, and there's no binding :ddb::

:beer:, Arnold

Rob.Wilson:
Lookin Great Arnold :clap: :clap: :clap: :clap:

Looks like it will be a runner soon :headbang:

Rob

PS those parts look friggin small :palm:

doubleboost:
Like Rob said friggin small :bugeye: :bugeye:
Beautifully proportioned though :thumbup: :thumbup:
Once i get below m6 i start to worry :lol: :lol: :lol: :lol:
John

Stilldrillin:
Arnold.
I've been sitting here, scratchin' me head for the past few weeks. Wondering what all those unfamiliar parts would add up to. :scratch:

But, now I've got it!! I think..... :D

Nice, different project, and well shown. :clap: :thumbup:

David D

DaveH:
Arnold.

Coming along just dandy :thumbup: :thumbup: :thumbup:

Well shown as usual. :clap: :clap: :clap:

:beer:
DaveH

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