Another version of how not to build a model engine

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madjackghengis:
Bluechip,
Just for background information, dwell angles of about thirty degrees are standard on points operated engines, so the flat on the round cam should be sufficient, dwell angle being adjustable by point gap with a degree wheel, a light bulb of the right voltage, and a pointer to set when the bulb goes out, and to show the degrees when it comes on with the points open. Typical primary voltage in a twelve volt system is two amps for a car engine, anything close to an amp is sufficient for small engines. Thirty degrees will allow full coil "saturation" at eight grand on a racing engine, thus a full "fat" spark at the plug. Plenty of dwell for an old Harley.
mad jack

madjackghengis:
By the way Sorveltaja, with the vellman transistor kit, you should be able to use a micro switch to trigger the ignition without any problems of burning it up, as there is very little current in the trigger circuit. I've used one of those conversion kits in a truck to good results. It should give you a fixed dwell angle established by the circuitry. Are there any magneto experts out there who have managed a miniature magneto? I'm looking at the possibility of one for my radial, never made one before so any insight would be appreciated.
On the fuel tube, you might try putting it right below the surface, with a tiny hole right above surface level, that's what some regular carburetors appear to use to control low speed mixture. A slash cut end, with just a bare bit of opening showing above the fuel level might work as an alternate. Quite a lot of dedication, getting this engine running up to snuff, looking good :bang:

NickG:
Madjack, I have also wondered about miniature magnetos. I have a book which must have belonged to my grandad, model petrol engines by edgar t westbury. It has a section in there about them. I will see if there's anything useful in there and let you know.

Nick

madjackghengis:

--- Quote from: NickG on January 25, 2010, 08:08:32 AM ---Madjack, I have also wondered about miniature magnetos. I have a book which must have belonged to my grandad, model petrol engines by edgar t westbury. It has a section in there about them. I will see if there's anything useful in there and let you know.

Nick

--- End quote ---
Hi Nick, I've got an old book of ETW's on miniature ignitions and magnetos I'm studying, it has a lot of information and gives dimensions and numbers for winding miniature coils and the like, as well as some ideas on miniature magnetos. It was written in the thirties of forties, with the new "rare earth magnets" available, I think I can get a working magneto in scale size certainly for a single cylinder hit or miss, and with one of the chapters on the Scintilla magneto, and how it works, maybe one that would run nine cylinders in at least close to scale size. ETW was the mother lode for model engines for forty or fifty years, and designed some stirling engine generator/radio sets which were dropped behind occupied lines in WWII and used by the French resistance, to comm with the Brit forces.
It's getting hard to find any of the books he's written, at least here in the states.
mad jack

Bluechip:
Folks

Got this myself, absolutely excellent.

Was sold by Camden in UK, no longer stocked by the looks of it tho.

scroll down the site a bit ..

http://www.bobshores.com/

Dave BC

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