An Interesting Q TT.
I think I'll amuse myself with an experiment when I get A Round Tuit.
I have amused myself this morning. Little things and little minds.
Result of a brief play showed equivalent performance of air gap and carbon brush on a K2F, in the sense that sparks up to 6mm were available in line with the Lucas test specs. Fat sparks every time at the flick of a wrist too.
A slightly fiddly job to try to get a, say, 2-3 thou gap between not-a-brush and slipring using a standard Bob Culver-quality pick-up and a light interference fit of a brass rod with shiny nose, at 5.13mm. Not the exact same setting in the pick-up for both rods and gasket choice obvs critical, so we'd have to be careful. If the makers had ever gone this route they'd have made the not-a-brush adjustable for depth I think and issued appropriate fitting instructions to avoid a foul-up.
Didn't run at high speed for long as didn't want to risk a problem on my best spare K2F, so dunno if there'd be dimples or tracking problems on the slipring segment in prolonged use owing to the arcing.
Given that a mag will run with a disintegrated carbon brush quite often, arcing away to the spring if that hasn't fallen out, I wasn't expecting it not to work, but was quite surprised at how 'the same' both sides of the mag performed when running it with one brush and one not-a-brush.
But, not wanting to risk the new slipring, or even maybe stress the rewound coil's insulation, toys are now back in their cupboard.
Does say though that if a brush fails on the road, a bit of something metallic rammed tight up the pick-up will at least get you home.
And thanks to you TT for raising the question.
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