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| Another version of how not to build a model engine |
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| sorveltaja:
Bogs, the Loctite thing is a fast thing for sure, but it would require cleaning, when changing the needle. So I'll stick with that grub screw -schema stubbornly . Ready for needle shaping: And the finished needle: |
| NickG:
S, Don't know whether it's the camera playing tricks but that needle looks parallel except for a very short tapered section on the end. If you used a sewing needle as bogs said you'd be sure to get a finer adjustment. Worth a try. Nick ps on compression ratios, from looking at Jan ridders designs he seems to aim for about 6:1. I know 6:1 is low for a 4 stroke auto engine these days so it might pay to go through some recognised plans and see what they come out at? |
| sorveltaja:
Nick, it wasn't the camera, needle in the pic had a short taper. Here is the needle with longer taper, after some polishing, and the needle body with grub screw: |
| NickG:
That looks much better, fingers crossed. |
| sorveltaja:
So I got the engine assembled, but as always, at least in my case, it was(is) quite challenging(despairing) to get the spark timing even close to position, where the engine starts to show signs of life. I'm quite sure, that I need to make a spark tester, that shows exactly when the spark occurs. There is a fine example on Jan Ridder's page: http://heetgasmodelbouw.ridders.nu/Webpaginas/pagina_vonktester/vonkentester_frameset.htm |
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