JohnP,don’t worry if you don’t get metric dimentions for one of these engines,as long as you can figure out the approximate size,you make up your own sizes,it doesn’t have to be identicle to plan,its your engine.The only one I built to a plan was at a night class at the local high school,except that I changed the plan and I think got a better engine.Since then i’v made 4 more including a V twin,no plans,but these are not as flash as Davids effort.

I know this post is old… but I'm just making one of these for my first project, and it's teaching me loads, AND better to make mistakes and learn on this, rather than my S50 (yet to start)

What size spring did people use for this?

Edited By Lainchy on 13/08/2019 09:04:09

Edited By Lainchy on 13/08/2019 09:04:25

Thanks Geoff.

I've ordered a spring on the slow boat, 0.5mm x 6od x 15long. That's a real stab in the dark tbh, but if this is no good… Warwick model engineering show is in Oct. Base, flywheel and piston to go.

I did struggle with the 2mm long thread (M3 not 5BA) for the pivot axle, and ended up drilling it out more to 4.5mm depth and M4 thread. I might end up remaking the cylinder, but this is a learning curve for sure. That's the only bit I'm unhappy with at the moment. I really wanted to stick exactly to the plans… albeit metric rather than BA threads (because I have a stock of bolts from R/C helicopters)

Great fun though!

Ian

Edited By Lainchy on 13/08/2019 10:46:56

Cheers Bill. Will keep my eyes open. I tried rifling a few Biro's… but sadly, they're 3mm ID. A friend said about the unpressurised spray bottles so I need to check out some of those too.

Brilliant, thanks Bill

I'm enjoying the build for sure, but also learning heaps. I got the piston OK, I think… there's compression and vacuum when it's dry, but a spot of oil should see it better. It's not a tight fit in the bore… but we'll see. Managed to edge a piece of Sapele yesterday with a router bit in the mill – and that had a coat of varnish yesterday.

I did struggle with the flywheel though. No probs hacking it down to the required outer dimension, but I wanted to put some relief in the faces… I am learning still very much. I'm booked on the Axminster small engineering course next week… I have my list of questions! I managed to do it eventually, but it wasn't a pretty process by any means. I'll see if I can get a picture tonight of what I've done, but I really struggled getting past the relief angle on the tooling. Ended up using a indexable boring bar, which really doesn't take finishing cuts well and was resonating – although I did try various speeds??

Well…short of a bit more polishing…a gasket…and a spring instead of a bit of silicon hose…. it's done First project complete.