V-twin engine from scratch - yet another interpretation of how (not) to build a

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sorveltaja:
'How not to' -act 1:

Both cylinder liners were quite straight, after smoothing. But now, after fitting the pistons, they are badly tapered :scratch:.

Also, neither pistons are airtight.

I used the same methods as on previous project, to fit the pistons. I suspect, that main reason for failure is different liner material.

Also I wasn't able to get good finish, when boring liners on the lathe.

Using correct size reamer would have been an ideal solution, to ensure, that liners surfaces are straight.

NickG:
S, that's what happened on my flame gulper when I used a wooden lap with wet & dry abrasive paper wrapped around with. I got a cracking finish but it went out of parallel. The fix was to use an adjustable reamer with plenty of oil which gave an acceptable finish and straightness / parallelism.

Nick

sorveltaja:
I made grooves to pistons for o-rings. There isn't too much room, so groove's width is only about 1mm(0.039"). Ordinary o-rings are too wide, so I made them out of ptfe. It was really hard to get both piston and o-ring to cylinder. Proper piston ring installing tool would have helped a lot.

At least pistons are now airtight, although quite stiff. Time will tell, how does ptfe last as an o-rings.

Two bars are for connecting rods. White ring is ptfe.

Rob.Wilson:
Hi sorveltaja :headbang:

looking good , great thread .

Cheers Rob

madjackghengis:
Hi Sorveltaja, it distresses me that you had problems with machining your gears, as I just finished doing one in a piece of nasty cutting stainless that looks about similar in size, although it is American rather than a module pitch. To get my cutter on center, I put it down on top of the shaft where the gear was to be, touching it off with a cigarette paper to zero it, measured across the shaft and the thickness of the cutter, divided it in two, and used my "digital caliper down feed DRO" to put the cutter on center. With brass and bronze, as well as aluminium, you want pretty good speed, pretty close to the nominal cutting speed, and no slop at all in the ways, as brass and bronze will "grab" and pull if you let it "climb mill". Brass and bronze need no lube, but aluminium needs a good lube or it gets sticky and balls up. On my pinion, total depth was .068 which I cut in .030 twice, and a final cut of .008 for a good finish. You should be able to cut at least that agressively with the brass or bronze. The real bugger is always slack somewhere, and if you can keep that out, you generally get a good gear. mad jack :beer:

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