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| Another version of how not to build a model engine |
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| sorveltaja:
Thanks for replies! Today I made a new carburetor, and tested it. First was 0.7mm throat, then bored it to 1.0, and finally to 1.5mm. None of them brought the engine alive. Most likely reason for that is the fuel that I used - it was an unopened can of well known brand lighter fluid. I have used that succesfully before, but this time even the odor was different. It smells more like teen spirit mouth-wash, than gasoline. Did the burning test on a small steel cup with it, and the amount of smoke and smell told already, that it was something else/heavier, than pure gasoline. To keep the engine's fuel thing straight, avoid lighter fluids, unless you are sure, what you get. Anyway, next I'm going to obtain real gasoline. And start the carburetor testing -phase from the start. Learning curve might be quite steep, but I'm getting used to it. Having the engine, that really wants to run, is the source of inspiration :thumbup:. |
| bogstandard:
How are you starting it S? If you look at the pic of the back of my engine (opposite to flywheel), you will see a lump of bar with a hole in it. That holds a one way clutch bearing. Stick a bit of 6mm rod in my drill, put it into the bearing and turn on. When the engine fires and runs, the rod just pulls out. It saved hours of finger aching starting during setting up trials. Bogs |
| sorveltaja:
Bogs, at the earlier stage I used a Dremel with rubber wheel against flywheel for starting. Recently it hasn't been necessary, since the engine starts easier. If it doesn't even kick, I know it isn't going to run. During this project, I have learned, what the general faults are, that prevent running. Mostly it's flooded spark plug, or failing breaker points. Earlier the biggest problem was the cylinder head cover not being leak proof, due to my somewhat faulty design. But more of that later. One by one, I've managed to stomp the bugs as they appear. On the left is previous needle system, that snapped right where the needle tip comes out. In the middle is newest carburetor body with 1.5mm throat. On the right side is a new needle, that I made off of compass needle. It however might need some tweaking. |
| bogstandard:
S, A lot of people use sewing or darning needles in their carbs. Cheap and cheerful, but very accurate. Bogs |
| sorveltaja:
I tested the new carb, and it floods the engine too easily. Most likely reason for that is the M3 thread, that holds the needle, being too coarse(0.5 mm pitch), preventing any tuning. The glow engine needle, that I used earlier, has 0.35mm pitch on its thread. It seems that even finer thread (~0.1-0.2mm) pitch would be better in this case. I can make that fine thread on the lathe, at least outer thread. Small diameter inner threading is more of a problem. It would require threading tap. Is there any other way to accomplish that? Easiest way could be to buy a whole new needle system. But not yet. In the meantime, I'm going to make a vapor carburetor, as it surely can't flood the engine :dremel:. |
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