H: Hubs, Wheels and Tyres Eight inch brake ?

[Simon Dinsdale]

Because it isn't applied at one edge?
My statement was admittedly rather dogmatic. The finned 8" drum probably distorts appreciably less than my Rapide drums did, so that also reduces lost motion.
But if "100% of the flex in the system is the shoe bending", why is the standard shoe super flexible and the 8" shoe highly rigid when they have such a similar design?

What clevtrev discovered a few years ago is the machined surface of the brake shoe that the lining attaches to isn't running true to the brake drum. His conclusion was the shoe pivots were 40 thou out of position. When I made my twin leading brake I actually mounted the shoes on the plate and then machined the shoe from its raw casting. I don't know if this was the correct fix, but my brake has no sponge in it at all. With the std Vincent brake plate & shoes it had the usual sponge feeling. I did not change the brake cables, balance beam setup or handlebar brake lever. Only the brake plates and shoes were changed for the twin leading ones and the sponge dissapeared. So from what I found the sponge feeling was inside the brake plate/ shoe assembly.

Maybe Trev will explain more about what he discovered and his potential solution.

 

[hadronuk]

That's very useful information and plainly not a good thing. But how does it follow that the shoes and not the backplate distorts as a result?

 

[clevtrev]

Trev
Do you think steel shoes would improve the situation?

Vince Farrell

Not really, it`s all about geometry.

 

[clevtrev]

What clevtrev discovered a few years ago is the machined surface of the brake shoe that the lining attaches to isn't running true to the brake drum. His conclusion was the shoe pivots were 40 thou out of position. When I made my twin leading brake I actually mounted the shoes on the plate and then machined the shoe from its raw casting. I don't know if this was the correct fix, but my brake has no sponge in it at all. With the std Vincent brake plate & shoes it had the usual sponge feeling. I did not change the brake cables, balance beam setup or handlebar brake lever. Only the brake plates and shoes were changed for the twin leading ones and the sponge dissapeared. So from what I found the sponge feeling was inside the brake plate/ shoe assembly.

Maybe Trev will explain more about what he discovered and his potential solution.

Refer MPH 500, I think, or maybe 499.

 

[hadronuk]

MPH 499 p16. Viewable on WhitakerPedia. Makes complete sense to me. I would think the resultant distortion would be a bit of everything, the drum bulging, the shoe bending, and perhaps the pivot points deflecting.
I did attribute the improvement with the 8" brakes to "better rigidity and accuracy"!

 

[hadronuk]

A thought that occurs is how on earth did the contemporaneous road tests achieve such excellent braking tests? I looked at at least five, none were worse than 30ft from 30 mph, and PCV himself claimed to have tested a Comet at 23ft. That works out at something like 1.5G. I assumed the big difference compared to today was down to asbestos linings, but perhaps the front brakes were also blueprinted?

 

[bmetcalf]

Blueprinting would have kept the .040" dimension, though.

 

[vibrac]

Trev
Do you think steel shoes would improve the situation?

Vince Farrell

Don't forget the Godet shoes I think the spares company may have some but godet prices were very high but they had strengthening ribs AND the correct geometry for incorrect brake plates I belive

 

[vibrac]

A thought that occurs is how on earth did the contemporaneous road tests achieve such excellent braking tests? I looked at at least five, none were worse than 30ft from 30 mph, and PCV himself claimed to have tested a Comet at 23ft. That works out at something like 1.5G. I assumed the big difference compared to today was down to asbestos linings, but perhaps the front brakes were also blueprinted?

Rough solid road to ratchet the tyre. The right road surface. Back then they made proper roads with steam rollers and diddent fanny about tossing a few hand fulls of tar covered sand on top of old rubbish heating it up and putting a Pansy lawn roller on it

 

[b'knighted]

Is the pansy lawn an alternative to a camomile lawn?