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| ian_in_the_midlands:
Following people kind enough to answer my questions, and requesting I do a log of the build, here it is. Be aware - this is not a "how to". I have no idea what I am doing as I have only owned a lathe for a couple of months, and the only engine I have built so far is the simple Elmer's wobbler. I am using the poppin as a project to learn about machining, so any constructive comments will be welcomed. First the pictures of where I am now. The cylinder and cylinder head are finished, and the piston has been made. My first attempt at lapping the cylinder by hand ended in disaster with the centre becoming a larger diameter that the two ends. I used an adjustable reamer, taking very light cuts to get back to a cylinder. I then turned the piston to be a tight fit, and brought it down to size using very fine abrasive. It is now a lose but airtight fit. In the picture the cylinder looks quite rough, but I think this is an optical illusion. I will wait to see if the engine runs before trying any lapping again. |
| ian_in_the_midlands:
This afternoon I started on the crank. The plan calls for 7/32" x 1/4" steel. I had some 1/4" key steel, so this was faced down in the lathe to the size required. This was then sawn in half, and marked out. The holes were then drilled in the lathe with the two parts held together in the chuck. The holes will be reamed to final size when my reamer arrives next week. I plan to silver solder the crank parts together - something else I have never done before. |
| dawesy:
Looking good. Must have a ho at something like this. Keep up the good work ;) |
| Stilldrillin:
Hi Ian. Watching.... Reasonably quietly. :thumbup: How did you lap the cylinder? I often find mine are slightly small, in the middle...... :scratch: David D |
| ian_in_the_midlands:
For the attempt at lapping that failed I made an aluminium lap, and using fine grinding paste, held the lap in the drill at slow speed, and held the cylinder in my hand, trying to feel for tight spots. I had read there is a danger of opening out the ends too much. That is probably why I concentrated too much in the middle. After correcting the problem with an adjustable reamer, the piston feels a constant fit all the way through. |
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