Thanks for the replies, gentlemen, and particular thanks for the description you gave, David.
From all of the reports about the alloy fwh brake I've read/heard, this covers everything succinctly. Probably most importantly, it is first-hand experience - excellent. The variability of material used in the brake drums of these wheels leads me to think that trying to make a good reliable brake out of the Ariel alloy fwh is flogging a dead (iron?) horse....
This variability of the braking surface does make me wonder if the hydraulic conversion would be a total solution, Paul. Has anyone experienced the dreaded damp-morning grab with one of these conversions, I wonder...
One point regarding this brake. At first I thought that both cams opened both shoes together, but they do not. The cams are 'single-sided,' if that makes sense. There is a lobe on one side only. Therefore the 'plain' part opposite to the lobe acts as a stop for the shoe to 'float' against. So, by definition, it is a twin leading shoe.
As a one-off, there has been a degree of engineering applied to it. The machined, wedge-shaped pieces on the ends of the shoes seem quite complex. Not sure about those washers, Roger. I'll have a closer look.
Ultimately, though, I do feel that it has been a lot of work which may not produce the desired result
However, I am tending towards trying it on the bike, which is a Square Four-engined Huntmaster, which should give the brake a decent workout, I suppose.....
Regarding binning it, this is still a consideration. The inherent weakness of the alloy plate is a concern. I've looked at BSA/Triumph 7" and 8" brakes, John. It would seem that a pair of fork legs (or just the sliders?) with bolt-on end caps would be necessary for the spindle - or have people who have used these brakes made a spindle which passes-through, like the original Ariel one? If so, what about the torque stay?
Apart from the work involved fitting one of these brakes/hubs, there is the fact the these things, generally, are now silly money. Also, I'm not keen on how these brakes look. The large peripheral flange which protrudes beyond the diameter of the hub looks like someone has fitted the wrong brake plate.....(I understand that this flange gives rigidity to the plate, so it's something you have to live with.)
I've read somewhere that an Ariel owner fitted a tls drum front wheel from an 'airhead' BMW. Does anyone have any information about this? (I think that my delicate sensitivities may be less offended by a German brake than a Japanese one......I have even considered an Indian Enfield tls. The problem of these is that, it seems, no two brake plates are machined alike at the factory and they are even more problematic than the Ariel brake....)