19-12-2020, 02:55 PM
A Muddle of Magnetos!
I don't know what the collective term is for a quantity of magnetos but in this case, muddle seems appropriate.
I'll probably get shot down in flames by the purists but I like to use the post war Lucas "Tractor Mag", the SR4. I have had bad experiences with vintage magnetos, including
a four mile walk when the Watford on my RF saloon exploded. Using the SR4 is a good solution for a driving mag engine car, being strong, reliable,
holding their magnetism well and having most spares available. The downside of course is that there is no manual control of the spark so you have to run with fixed timing.
The pile of bits seen here has been tested, several of the HT coils are open circuit and need rewinding. The key is to find one that is about 5K ohms from the
HT connection to the primary wire. Much more indicates a bad connection, much less, shorted turns. I found a coil at 4.8K Ohms and built it into a casing with a good
rotor. Lubricated the bearings with HMP grease and tested. It gives a good spark at 60 RPM, so I'll try that one on the car. The problem is getting a rebuilt, stiff engine
turning over fast enough to get the magneto sparking.
I have one magneto with the "Flick" drive, otherwise known as an "Impulse Starter". Unfortunately, it has a drive flange with 20 teeth on it intead of the 19 we require,
so will take some re-engineering to use. The Flick drive operates at speeds below 250 RPM where it retards the magneto and then spins it quickly over the point that the spark
is timed, helping to start the engine. Maybe I'll try and incorporate that on the Mag for the Top Hat if I have time
Here's the finished product, ready to fit.
Whilst I'm rebuilding SR4's, I must have a look at the one fitted to my Chummy, which has been operating for a few years now and needs the bearings greasing.
I'm still hoping to attempt to start the Top Hat engine over Christmas but I also have to remove the RK saloon engine to sort out a badly oiled clutch.
I don't know what the collective term is for a quantity of magnetos but in this case, muddle seems appropriate.
I'll probably get shot down in flames by the purists but I like to use the post war Lucas "Tractor Mag", the SR4. I have had bad experiences with vintage magnetos, including
a four mile walk when the Watford on my RF saloon exploded. Using the SR4 is a good solution for a driving mag engine car, being strong, reliable,
holding their magnetism well and having most spares available. The downside of course is that there is no manual control of the spark so you have to run with fixed timing.
The pile of bits seen here has been tested, several of the HT coils are open circuit and need rewinding. The key is to find one that is about 5K ohms from the
HT connection to the primary wire. Much more indicates a bad connection, much less, shorted turns. I found a coil at 4.8K Ohms and built it into a casing with a good
rotor. Lubricated the bearings with HMP grease and tested. It gives a good spark at 60 RPM, so I'll try that one on the car. The problem is getting a rebuilt, stiff engine
turning over fast enough to get the magneto sparking.
I have one magneto with the "Flick" drive, otherwise known as an "Impulse Starter". Unfortunately, it has a drive flange with 20 teeth on it intead of the 19 we require,
so will take some re-engineering to use. The Flick drive operates at speeds below 250 RPM where it retards the magneto and then spins it quickly over the point that the spark
is timed, helping to start the engine. Maybe I'll try and incorporate that on the Mag for the Top Hat if I have time
Here's the finished product, ready to fit.
Whilst I'm rebuilding SR4's, I must have a look at the one fitted to my Chummy, which has been operating for a few years now and needs the bearings greasing.
I'm still hoping to attempt to start the Top Hat engine over Christmas but I also have to remove the RK saloon engine to sort out a badly oiled clutch.