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| Another version of how not to build a model engine |
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| sorveltaja:
Thanks for replies and suggestions :wave:. Today I was testing the engine with different carb settings, and suddenly it just refused to start or run. So I double-checked every possible things. Fuel system was ok, ignition system was ok, but the new spark plug started causing shortcuts, no matter what. Yesterday it worked just fine :scratch:. As gasoline itself doesn't conduct electricity much, in this case it was enough to cause almost electrochemical pair between spark plug and its core. Resulting black goo between them. With previous plug, that never happened. It must have something to do with new spark plugs body material. It is made of an ordinary M6 screw, as was the previous one. Apparently they aren't same material. Old and new plug: Two cores, left was made of an M2 screw, right is stainless steel. Both was tested with new plug, but no difference. The battery-led combination is a poor man's continuity tester. The 9V battery in picture is old, and it has low enough voltage, so it doesn't burn the led. |
| sorveltaja:
Old plug is on the left, new on the right: Right one might have too little sparking surface, when compared to the left one. That also could be one thing, that causes the shortcut phenomena. edit: I remember seeing great spark plug build tutorial on HMEM, and there it was: http://www.homemodelenginemachinist.com/index.php?topic=5653.0 When making the next spark plug, I think I'll follow gbritnell's advices :dremel:. |
| sorveltaja:
New spark plug body, made of stainless steel, except the nut, that was silver soldered: Finished work: Anyways, now it seems that the engine testing can continue :wave:. |
| Andy:
Sorveltaja, I've been following this with interest, and I admire your persistence. :headbang: I'm afraid I can't offer any advice, but hope you get it going to your liking very soon! |
| sorveltaja:
Andy, thanks for your reply :thumbup:. I did running tests with new plug, and it seems to work ok. But the engine still has quite a reckless behaviour. I have read the previous replies, and there is good suggestions about that carburetor thing. Hopefully I finally can concentrate to test different carb variations, besides stomping bugs. One by one, if needed :coffee:. |
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