Lucas K2F mag armature.

[Rex]

Is there a good exploded diagram of this armature?  I want to check the assembly order of the slip-ring,steel spacer, oil flinger and brass shims.  Thanks.

[a10 gf]

https://www.a7a10.net/BSA/manual54/magneto.pdf ? page 5

[JulianS]

below

[Rex]

So from the top exploded diagram, there's a steel retaining ring outboard of the bearing inner track?

Thanks!

[groily]

Although you may find things assembled differently, the correct order at the slipring end is slipring - oil flinger - shimming - bearing inner.
No shimming behind slipring, no SHIMS outboard the bearing race; nothing behind the outer race in its housing either, except the insulating washer.
Maybe some large end-housing shim(s) if end-float ends up negative - but ideally shimming can usually be done inside. Only rarely is there negative float with minimum or no shimming on the slipring end.
No shimming (for choice) on the drive end either, although sometimes there has to be something behind the inner race to get everything set nicely. Shims for the shaft ends are easily available in various thicknesses.
The steel spacer goes on last, outboard the race. It's there to support/protect the outside of the armatur shaft on the outermost bit of the female taper for the cb backplate.
You want the HT brushes sitting bang in the middle of the slipring. You want minimal end float, zero perceptible (but not tight) at room temperature is nice.
If you get to that, everything shoud be just right.

And Yes to your last Q.

[Rex]

Thanks Bill. One of your Easy-Cap devices just fitted so fingers crossed it solves the on-going problem.

[RichardL]

EDITED after 15 minutes.

Referring to exploded views in the link, I was surprised/amused by what looks like a disk-shaped cam in the base-mounted mag. At first I thought that the disk was rotating, but on a second look at the cb unit, I guess not. What was the mode of operation there?

Richad L.

I just removed the qouted post beccuse I figured it out (and read the text). I can see why they dropped the face cam.

Sorry, if you were busy typing to straighten me out on this.

Richard L.

[groily]

'Face-cam' operation, Richard, as you just figured, using a static plate (except some AR movement) with depression carefully machined in, and a short pushrod to open the points axially (in line with armature axis). When the pushrod base is in the depression the points are closed to charge the coil; when they come off the dip up the opening ramp, bang, points open against their sprung blade, and voilà! Simple and fairly bullet-proof - and good enough for most Goldies, so can take a bit of stick too. (I can see why they dropped it too, but to be honest, it works really well.)

Found on all MO1 magdynamos (so that's most of our sister beasts in the B series), also on standard N1 mags for singles (but not Comp versions which have 'our' system).

Originally a design from ML, which Lucas acquired about 90 years ago. (A good buy, ML was a smart bunch of guys who made things that were up there wth Bosch in some cases.)
Lucas magdynamos pre-MO1 (eg MN and MS series) used the same rotating assembly we are used to, for singles and twins, and so did the 4 cyl car ones (with rotating coils).

All very anoraky stuff, but there's actually some good history in all this, going back to the Great War, the breaking of the Bosch patents, the development of the UK, US (American Bosch) and other allies' industries etc.  A fascinating off-beat mini-history of military development, commercial intrigue (and gradual technical improvement), but starting from an incredibly strong base, thanks to that superb German engineering.

If I was asked to nominate a product that did exactly what it said on the tin, from Day 1, with very little need of future mods, I'd put the early Bosch high tension magneto in a very special place. They are extraordinarily good.  There's a short book in it somewere - but there'd only be a handful of readers probably!!