Posted on October 17, 2012:
Hello again folks! The next step in getting the Red Wing engine running is to mount the magneto on the engine. Before I can do that I will need to decide where the magneto will fit on the engine and how will it be driven by the crankshaft. The answer to the first part of that question really depends on the answer to the second part so I must first decide on how I will drive the magneto.
Traditionally a magneto is driven off of the timing gears so that the magneto pulses (sparks) are synchronous with the piston reaching top dead center on the firing stroke. The rotational relationship between the crank and the magneto must be consistent for this to happen. My mini magneto will also need to be synchronous with the crankshaft so I must drive it with either a roller chain and sprockets or a set of timing gears to keep it in-time with the crankshaft (1:1).
The roller chain method mentioned above has been used successfully by many Falcon magneto builders. This type of system uses a sprocket on both the magneto and crankshaft of which the two are connected with a miniature timing chain. The only drawback to this system is that the timing chain would have to mount on the non-governor side of the crankshaft which would be in plain sight. This would not lend well to the scale look of the Red Wing engine.
I want a drive system that will be somewhat hidden so the basic look of the engine is not altered. This is why I have opted to use an additional set of timing gears to connect to the existing timing gears under the cam follower assembly of the engine. This setup will somewhat hide the drive gears behind the flywheel and allow me to mount the magneto inside the base of the engine as to not ruin the scale look of the engine.
I do, however, have a concern about using a timing gear system. I am not quite sure how noisy the gears will be considering the magneto is a bit notchey when it turns. By this I mean the magneto will surely cause backlash in the gears as the magnets on the rotor swap poles over the core of the coil. This means the gears will chatter as the rotor pushes and pulls (twice) every time the crankshaft turns over.
I am not sure how noisy this chatter will be and wont know until I have a prototype system developed. I guess I will find out shortly ;0)