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| Bog's Paddleduck Engine |
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| kvom:
I have abandoned the CO2 engine, as I have come to believe that the laws of physics will prevent me from getting it running. Some things don't scale up well. :scratch: I think I will have a go at the Paddleduck plan Bogs posted on HMEM. I'l let this thread be a placeholder until I actually make some parts. My current idea is to scale it up by 1.5 times and use Imperial threads and fasteners (I have a lot of 5-40 and 6-32 screws and nuts). I will also use non-metric drill rod in places where that's called for. Otherwise I will just multiply the dimensions by 1.5 and convert to inches. I have a DRO on both the mill and the lathe, so odd numbered lengths shouldn't be a problem. I will also go somewhat for the "bling" look. I probably won't try the separated cylinders as I don't yet have a good rotary table, and as I will be running it on air and not steam I think I can skip the displacement oiler. I'm pretty sure I have enough scraps lying around for most of the pieces (I plan to do the block in steel rather than cast). I've skimmed through the "book" once, but now I'm going to read it more carefully before starting out. The printer is going as I type. |
| websterz:
Why go up? Scale it down 1:3...that'll be fun! :thumbup: |
| bogstandard:
K, John S did a double sized V twin, the same as yours. He had a little trouble getting it to run. A change to running on high pressure actually got it turning over OK. The lift pin lengths are super critical. Shred over on HMEM is building one of my engines at this moment, and he is doing the Imperial conversion as well, but he isn't finding it too difficult, except metric has a better range in the smaller sizes of screws, so he is basically sticking to two Imperial ones. Darren on here is getting along fine as well, but he is doing the metric version using purely marking out and manual handle settings on the machines. So you having DRO's is a distinct advantage. If you are enlarging it, you should find no problems, as the engine has lots of adjustments in critical areas, and on the valve gear itself, you make the spools to the correct spacings by measuring between your drilled holes. Good luck with your project, and if you have any troubles, you have the correct person reading your postings about it, and will help if it is needed. Because you are running on air, you can make it out of almost anything you have in your scrap box. As long as it will take the pressures involved, use it. Bogstandard |
| kvom:
--- Quote ---John S did a double sized V twin, the same as yours. --- End quote --- Unfortunately mine is 3x, as I was seduced by a cube of aluminum that was "just the right size" for the crankcase. :bang: My other build was Elmer's bream engine in double size, with the plans that Brian Rupinow provided. I followed his dimensions but varied the style quite a bit. It ran fairly quickly after I finished the assembly. Your engine has more parts, but I don't see any that are significantly more complex. I'm used to making the harder ones over and over anyway. ::) |
| bogstandard:
Kvom, There is only really one difficult part to make, and that is the crosshead, but if time is taken to think about it as it is being made, even that becomes a simple job. The normally difficult bits, like the crankshaft, uses the method of, a few simple things, that when brought together, make one complicated part. With your experience, I don't see you having any problems at all. When finished, it is a lovely runner, even more so if it was to be made larger. Bogs |
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