Search results

wow thanks for the responses. I tore apart my other engines to see what they did, and look at that, all but one use little ptfe pucks stuck in the hollow wrist pins. The other uses impossibly small circlip grooves. I made little plastic ends like you all said, and ran it for an hour (lots of...

I did a small glow two stroke rebuild a few months ago, and things went well till I realized it was losing power as it heated up. I tore it down, and found that my press fit of the wrist pin in the aluminum piston was no longer a press fit at running temps and was wearing a groove in the...

I suppose I am over-thinking it. It should be easy enough to verify my chuck jaws are as they should be. It's not like I need repeatable setups for this engine. The crank case looks to be the easiest part of it, a nice and easy part to re-make if I screw it up. Thanks!

I see, bolted to an angle plate through the crank hole. I don't quite get how you can get the axis of the cylinder aligned with the axis of the lathe though, registering on the crank bore only gets you one of the two axises you need to align. The casting can still rotate around the crank hole...

I recently made a new piston and liner for an RC engine to practice making the tapered cylinder fits, and it runs great! Now I think it's time to try an entire engine. I've grabbed the plans for the Bollaero 1.8, but I'm wondering what the consensus is for the best way to make the cylinder bore...

Or make a cylindrical lap for when you need the nice surface finish and an exact size. Very common in fitting a lapped piston to a bore. There's a certain luxury to not having to have it done NOW. I found my Taig dead on. Didn't have many problems with it. I still use it for really, really...

I accidentally made a wrist pin that's fixed to the connecting rod. Turns out, the bronze bushing in the connecting rod didn't end up the same size as the hole in the piston when I ran the same reamer through it, so I gave it a shot pressing the pin through it. I'm ok with that, I'm still able...

One more question: does high speed steel make an ok wrist pin? I found a drill bit that's the exact size I need. The shank of it is in the softer state that I can cut with a file. I imagine it would have the wear resistance, but does it have the impact resistance?

+1, I'm thankful every time. Especially when I find out I'm doing something in a way that's wrong!

The original was interesting. It used a floating pin, but had plastic pucks on the end to keep from scuffing up the cylinder. If I lock it to the rod, I won't be able to get the connecting rod off of the crank pin to remove it. A press fit on this size seems fiddly enough to be easy to screw up...

is that because in professional work, time is money, so by sneaking up on a dimension you're wasting time? I think it also depends on if you're using carbide or HSS. with a razor sharp HSS bit I can take off minute amounts, but even with a perfectly sharp carbide, I've gotta take 0.003" or...

That;s a good point. I found that my compound, each divison is 0.002", rather than 0.001" like on the rest of the dials. So I needed to set my compound to 2.7something degrees to get tenths instead of 3 or 4.something degrees.

When it's really critical, I start sneaking up on the final dimension. For example, in aluminum on my machine I can tolerate a 0.100" DOC, but I consider that a roughing cut on this machine. When I get within 0.050 or so, I take a 0.030 cut, and re-measure. then a .010 cut, then re-measure. then...

Wouldn't oil have the opposite effect on the offsetting type? It would make it break sooner leaving the cutter futher from where you want it?

Cool math, thanks a bunch! This engine won't turn over 16000 rpm unloaded. But like the others say, it's pretty easy to fix now. Related question: The original was a floating wrist pin. Is there any benifit to making a light press fit, or should I just match the original?

Ok, it's as follows: Piston diameter: .914" Stroke: .724" piston weight: between 0.5 and 0.6oz (my scale has a resolution of 0.1oz). Could you calculate both so I had a best and worst case? The original ran about 9000 rpm on the ground and about 14000rpm in the air unloaded. I could prop it...

The nearest place that sold cig paper is 60km away and it was near midnight ;)

Excellent, I'll go weighing when I get home. Could you share the calculation?

another one I ran into (well, ran into me) yesterday is just as dangerous. I've got a relatively little lathe, takes some time to get up to any reasonable rpm, and I'm still in the "repeat things enough to make them a good habit" phase. I hit start, and something smacked me in the chest giving...

I'm finishing up my two stroke reconstruction, seems to run great! I'll make another thread with details. My question was, I messed up the wrist pin hole in the piston a little. I drilled with a numbered drill bit the same size as my wrist pin, forgetting that I needed to go undersize and ream...