Refurbished dynamo and other surprises

Biscuit · Post by **Biscuit** » Sun Nov 25, 2007 5:52 pm

The locking device on the dynamo sprocket is an interesting subject, have we ever stopped to think about it?

There isn't a lock washer, spring, serrated or otherwise on the magneto sprockets and nothing on the mainshaft nuts, either end, so why is one needed on the dynamo?

Observing the twin, there are no locking devices on the magneto gear, camshaft gears, halftime pinion or driving end of the mainshaft, only on the dynamo. Is it a Lucas thing?.

SPRIDDLER · Post by **SPRIDDLER** » Sun Nov 25, 2007 6:11 pm

There wasn't a lock washer or spring on my dynamo sprocket ('54 G3LS) the first time that I had to remove the dynamo. I seem to remember that the parts were not in stock at JSL or others at the time so I just refitted the original sprocket onto a new armature (with new woodruff key) and the original nut.
Had it apart recently to fit new dynamo and primary chains and it was still Titus Aduxarse after about 6k miles.
P'raps it was indeed just a Lucas thing.

Biscuit · Post by **Biscuit** » Sun Nov 25, 2007 7:25 pm

To add to that Sprid, I have never fitted a lock washer of any description to the single dynamo, not in my youth and not now. But human nature being perverse, I always use the lock washer on the twin.

Perhaps somewhere in the recesses of my mind I know the single is locked on to a taper, whereas the twin is on a parallel shaft.

Merlin · Post by **Merlin** » Sun Nov 25, 2007 9:07 pm

Just a bonus for being old Alan.
Regards as always.
Merlin

SPRIDDLER · Post by **SPRIDDLER** » Sun Nov 25, 2007 9:21 pm

Which has just reminded me Alan, that the supplier of the new armature (can't recall who it was without the frightening task of trawling through probably a million quids' worth of receipts!) told me he recommends not fitting the Woodruff key at all. I suppose the turning resistance / inertia of the dynamo would be much the same as for the unkeyed, non-spring washered etc magneto sprocket nut - and the dynamo doesn't have to hold it's timing. Still, the key does provide a bit more security.

Biscuit · Post by **Biscuit** » Sun Nov 25, 2007 9:39 pm

Well, relatively speaking, dynamo 6V around 7.5 Amps magneto 20,000 odd V, current negligible. So there is far more load on the dynamo drive.

Hope I'm right!!!!

Don Madden · Post by **Don Madden** » Sun Nov 25, 2007 10:56 pm

Don't forget the magneto primary windings generate approximately 6v & perhaps 2 Amps peak current when the plug fires. Due to the shape of the armature core, the primary generates for less than half the revolution, but the load is significant. I agree that it is less than the dyno.

Cheers, Don.

Circlip · Post by **Circlip** » Mon Nov 26, 2007 6:55 am

Timing the dynamo centre to the coil is a neat trick but is not necessary unless you want to run without a battery and certainly not required when the plug fires. The plug fires from the discharge of the secondary windings of the coil. The coil is charged when the points are closed this period is measured in degrees called the dwell angle. Its the duration of dwell that the coil needs a charge. In any case the accumulator (battery) will keep supply up to requirements.

Discarding the woodruff key for the dynamo centre will render the centre to suffer harmonic shock from Harmonic torsion. Its not the load but the accelaration and decelaration of the crank shaft. Its there for a reason!!!!!

Lock nuts or devices may not be necessary if the rotation is in your favour.

SPRIDDLER · Post by **SPRIDDLER** » Mon Nov 26, 2007 11:08 am

quote:
Timing the dynamo centre to the coil ......

??

56G80S · Post by **56G80S** » Mon Nov 26, 2007 2:09 pm

Thanks a lot for your comments.

The sprocket for the dynaomo is almost new and the engine sprocket is in good condition.

There were no locking arrangements on the dyno sprocket when I first bought it, but I'm reluctant to do without it now.

Just by way of more fuel to the fire, Tony Surbey included a plain nut with the reworked dyno.

Johnny B