lawn mower magneto conversion ,,, ideas

[new2guru]

i wouldnt say its over unity, just a means of improving efficiency *cough ... still using fuel

 

[shortbus=]

new2guru - I miss understood you. Didn't realize what you were saying till I reread you first post.

You are basically wanting to(if I understand right) to use the HV from a magneto to generate a second higher voltage for the plug? You are forgetting that you need to make a spark in the first place, which requires either points or the circuit I linked to. Plus what is the advantage of doing this? Theres a reason why they don't use a Tesla coil to power spark plugs A magneto spark has worked for over a century.

The limiting factor on a small engine efficiency is not the spark but the complete design of the engine. The recent change to small engines to overhead valves is a big leap in engine efficiency.

As far as using the engine to run a generator to run the blades - Every time you introduce a new item into the power transmission line, you loose efficiency. It takes power to generate the electricity - it takes power to turn the electric motor to drive the mower. Even if your generator and mowerhead were 90% efficient(not likely), you have lost 20% of the original engines power (-10% + -10% = -20%)

 

[new2guru]

Shortbus, honestly im unsure if you are having a joke or im just shithouse as expressing the plan ((( As far as using the engine to run a generator to run the blades ))) -

mowing the lawn is not one of my goals - i have several goats too do that for me, i want the motor running more efficiently yes, but its only job is too spin a alternator \ charge battery bank - untill ofcourse somebody works out how too train a goat too run on the stairmaster generator

- but your dead right about the electroincs side of it, ...something i discovered by accident, originally i was unable too get the magneto to trigger any device, i was trying to make it trigger a relay for the IGN coil - via resistors , even diodes and various other transformers.... BUT then i noticed after a strong gust of wind that it breifly worked.. for a few seconds..... one of my 10ish remaining crocodile clip leads has a small area of melted insulation, and it just so happens i was using this wire too go from the magneto too the circuit... and the wind made it blow against the chassis of the lawnmower - shorting the magneto too ground before it had a change too do anything ( in theory) but this actually made it work ! ,,,so i introduced a spark gap in series with the circuit
and kept on playing, however the magneto still not providing enough current for a solid connection in the little relay - and no matter how much i dampen the spark it kills my transistors - even the IRGP - 1000v \ short circuit rated - for motor controllers etc dead..

i need some fresh ideas before this tread dies in the arse

 

[new2guru]

keeping with the KISS aspirations - really the first step (slightly embarrassing) is to get a working circuit then figure out how to trigger it, because the fact is --- that i dont even have a transistor based circuit that can survive my ignition coil \ plasma

aka and IGN coil driver - with sufficent snubbing too withstand the eddy currents kickback from the spark-gap... i have a pretty good selection of electronics component (not chinese tv) stores considering i live in the most isolated city in the world... Perth, western Australia... FIRST STEP TOO OBTAIN A HV SNUBBER DESIGN TO PROTECT MY TRANSISTORS.

time for some more grazing on the interweb...

 

[new2guru]

arrggg blown my trannys again...

i also just tried the following circuit.... magneto > 100winds on a small iron file > hv diode > resistor > LED > ground on the motor

in the hope that i can use the led pluses too trigger a photo-transistor ... thus isolated transistor = reliable

however even with my eyes i can see that the pluses are not very clean,... not sharp and fast enough, so i tried adding a sparkgap between the magneto and coil... unfortunately this stopped the led from working, (which was flashing at a perfect brightness)... so i killed the spark gap and tried removing components from the circuit...

the coil made no difference.... gone,
the hv diode... after removal the led flashs still worked but looked better... sharper...
then i removed everything... just the led running between the magneto and ground... why it i figured... it will only take 30 seconds to try..

and naturally that worked best...

this project always has me spinning in a perpetual loop,

 

[shortbus=]

You need to do more digging on how a magneto or for that matter a battery ignition works. On a small magneto engine(Briggs-Stratton and the like) when pulling the rope/starter the primary coil makes around 6-8 volts, the points open and secondary puts out a higher voltage to spark plug. As the secondary volts collapse it creates a voltage back EMF into the primary storing a high (approximately 400 volt) into the capacitor, combining that with the 6V made by the magneto primary and that makes a even higher spark voltage. the process evens out a certain voltage level in both primary and secondary.