Recent content by f2cf1g

The leakage past the contrapiston suggests it's much too loose, it should be a firm press fit in the cylinder. A loose contrapiston is a no-no. You shouldn't need a locknut on Midge if the fit is OK. Contra hitting piston is a definite big deal. Before you make a new contra, try expanding...

Working in 29/64s and suchlike is beyond me so I redraw parts in metric with dimensions from what i think will be DRO reference edges. Less scope for mistakes too.

Diesel fuel will last indefinitely provided (a) that the container is airtight and (b) that the container is opaque or nearly so, as per Bluejets brown bottle. Glow fuel is tolerant of daylight, diesel is not. Nice Midge, mine runs well. In your 2nd video yours sounds overcompressed.

Try metal polish.

Please don't run it on that prop, it may throw a blade which is extremely dangerous. It is made for electric motors and not designed to withstand the vibration inevitable in an i/c engine. Good luck in getting it running.

Well done. Did you make a new piston?

Yes, but I only heat once and let it cool, then re-lap. I have never found any problem with the pin fit afterwards, though I suppose if it was retained with a light interference fit it might become noticeably looser which might have to be dealt with. Roy

Rather than make new, why not try "cherry-bombing" the piston and contra to make swell a bit? Often works for me.

Hi Pat. I'm following your thread with interest because I'm also building one. My scrap bin is far from empty! The drawings show two methods for cutting the transfer ports, the one you are contemplating and another with the flute extending from a hole drilled at rightangles into the bore. I...

I'm a control line and free flight man too, don't know much about throttles! What I've found in doing Nelson glow head conversions is that getting the compression ratio right can be difficult and often takes a bit of experimentation. When it's in the right ball-park, setting the needle...

Well done on getting it running, it sounds strong, revs sound OK to me. The motor is on the boundary between 2 and 4-stroking in the second video. If you can lean it out to pure 2-stroking, the compression ratio is OK (though you might get more power by increasing it). If it won't 2-stroke...

You have described the classic symptoms of an under-compressed glow engine, i.e. stops when plug disconnected and unwilling to 2-stroke. Try skimming the head 0

Can I ask what was wrong with the original piston/liner set? Only running will wear it out, not sitting in a box. I doubt that it's clapped out sufficient to stop it running or pulling a combat model round at 75mph. The process of enlarging a cast iron piston is often called "cherry bombing"...

Those things are no use for the tolerances applicable to pistons and liners. To have any hope of measuring taper accurately you need a bore gauge. However, that's not necessary provided you follow Ken's advice and lap the liner and the piston using the techniques described on Ron's site. I...

After you mentioned it in your last post I watched your video (not sure why I didn't see it before). The motor appears to be oscillating not fully rotating. I've not seen this on a glow before but in a diesel it is caused either by too high compression ratio or too much fuel causing too much...