Dynamos

[Steve Baldwin]

> 
> I know I'm off topic, but we are killing our selves here.
> 
> We have a 1934 Riley, and it is fitted with a Rotax three brush dynamo.
> 
> It doesn't work.
> 
> We don't know how it should work, further more we can't find anybody still alive that knows! HELP! 
> 
> Even if you dont know how our setup works, but ya do know how a three brush dynamo should work, please share it with us!
> 
> Mark
> 
> saxon at zymurgy.org
> 
> 

If the dynamo has been sitting unused for some time, it may just need
polarising. You do this by just touching a wire from the battery to the
out terminal. Use some thin, multistranded wire and just wipe it across
the threads so you get a few little sparks. 
This simply sets up some residual magnetism in the core which is enough
to get things going. There needs to be some magnetism to generate some
current that then gets put into the field coils to make more magnetic
field and more current.

If it's not as simple as that, the other thing to check is the brushes.

Most auto sparkies should be able to check a generator. The third brush
part does what a regulator did in later years. It's sort of a second
generator that feeds the field coils. You adjust the amount of current
going to the field coils by moving the position of the brush.

Steve.