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| Another version of how not to build a model engine |
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| NickG:
I think this is the same sort of cam as you find in a car distributor for opening / closing the points - been so long since I've seen one though i'm not 100% sure! Nick |
| Stilldrillin:
A car points cam has a peak (or 4) not a flat (or 4)...... The points should be together for the maximum time..... Not held open! I think! :scratch: David D |
| Bluechip:
Dave SD Quite right. I doubt if there is sufficient 'dwell angle' to allow the coil core to reach a high enough magnetic field to give any sort of reasonable spark when the points open, and the field collapses to give said spark. You may need about 120 deg., depends on the coil and the internal resistance of the source of DC. Has yours got a currrent limiter? The instantaneous current may be causing that to kick in, and that may drop your apparent DC input voltage. I had a cheapo Chinese PSU, limited at 5A, if I took pulses out of it at near 5A, the output voltage bounced all over the place. CARP !! Briefly demoted to battery charger, on it's way to the Wheelie Bin. Don't know whether you have one, but you should have a capacitor across the points too. About 47nF or 100nF usually work. 100VDC rating will usually survive long enough. Dave BC |
| sorveltaja:
Thanks for the replies and suggestions :wave:. Ignition circuit, that's in use, consist: 12V/2,5A PSU from an ancient (DEC/Digital)computer, that has a shortcircuit protection. That bugger seems to last, no matter how hard it is abused used. standard 12V automotive coil Velleman's transistor ignition kit K2543 Besides all of those bells and whistles, reducing the ignition cam's flat part/ignition points close/open sequence, as mentioned earlier, has given positive results. Spark plug stays a lot cleaner than before. Meaning, that I don't have to make a new ptfe insulator every other day anymore :thumbup:. The vapor carb is still under testing, engine runs with it, but especially the idle adjustment is bit tricky. Anyway, I'm working on it :dremel:. |
| Bluechip:
Sorveltaja Not sure what the kit is, but if it uses a power transistor to switch the coil primary, then NO capacitor is needed. In fact, it usually stops it working if present. Dave BC |
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