I have just obtained a reconditioned dynamo and need fasten the sprocket on.
The nut which holds the sprocket on is a bit stiff, so when I attempt to tighten it, it breaks the sprocket taper and the dynamo turns.
I can get the nut on by about 1.5 turns before this happens.
Does anyone ave any idea how to keep the dynamo static.
I notice two slots on the ring at on the end of the armature under the sprocket, are these or a special tool?
Any help greatly appreciated.
Adrian
Hi Adrian,
I believe that the slots you see are in the end of the armature retaining nut so not there to assist with sprocket mounting.
Could it be that the threads are different on thread and spindle causing the problem you describe? I'm not sure if the dynamos were made with different threads for different bikes but it's possible.
Can you let us know what is the dynamo model and what bike is for?
Cheers,
Bernie
Thanks Bernie,
The dynamo is ann E3L and the b8ke is a '53 plunger A10.
I was wondering if I'd been given the wrong nut. It is castellated and the spindle has a suitable hole if that is any use.
Regards,
Adrian
I'm still guessing a bit but if you look here: http://www.davelindsley.co.uk/assets/pdf/CATALOGUEMASTERWEBSITE02.01.2017.pdf
on page 8 it shows different part numbers for the armatures for Triumph, A10 and magdyno E3Ls. Might not be different threads but maybe worth giving them a call in the morning - they may be able to shed some light on any variations there and confirm the thread used.
Does the armature thread look damaged at all? That's the other common reason why the nut would tighten up and if so you might be able to dress it out with a needle file or fine disc on a Dremel.
Cheers,
Bernie
The armature thread is 3/8 BSF. I would run a die down the thread and a tap through the nut.
The difference in the armature between BSA and Triumph is a taper fitted sprocket for BSA and a straight end for a pinion for the Triumph.
Not unusual to find that an original armature end has been hit with a hammer to remove it from the bearing thus burring the threads. It is usually hard to remove the armature from the end bearing due to it being a very tight fit hence the use of the hammer.
To refit a sprocket or pulley I remove armature complete with the end piece from the main body and hold it in fibre vice jaws to hold it whilst the nut is tightened.
Thanks to both of you, the nut I was given is supposed to be 3/8 BSF, it's just tight.
All the threads look good. I'll check to make sure they are the same.
I think I'll have to try Julian's idea of removing the armature.
Regards,
Adrian
I've sent off for BSF taps and die, I think the nut thread is not too good around the bottom of the castellations. It also occurred to me to heat the sprocket before putting it on the taper in the hope of a better grip on the taper when cold. I could then use a chain on the sprockt to keep the thing still.
Adrian