Brakes

[john998]

Hello, lots of good post above. Would just repeat, I think I will use the mod only to allow for the errors in the pivots. With the brake held on I will fully tighten both nuts, and occasionally repeat.
In this way the duo servo will not come into play. John.

 

[passenger0_0]

All good John, I prefer the option you're taking too. As a closing note, duo-servo brake work in both directions of rotation i.e. forward and reverse both give a twin-leading effect. Cheers David

 

[passenger0_0]

Hello 0_0,
You are right with the naming of the brake type. That was just how we called them in Germany 35 years ago. I just realize I am getting old writing like that....
Anyway I found a link to a simple picture that compares the different types of shoe actuation and breaking force per shoe.
It could make things easier to understand for everyone
https://www.google.es/search?q=duo+...ELVAKHThrD_0QsAQICw#mhpiv=9&spf=1497608842279

Cheers Bernd

If it's any consolation Bernd I share that getting old feel too - but what are the alternatives? Cheers David

 

[Simon Dinsdale]

Stu Spalding has been using the Bert W. Modification for quite a few years. He changed the design slightly by omitting the O rings and rather than using countersunk screws on the outside of the brake plate he extended the pivots which is now threaded externally and is secured by nuts. He tightens these nuts fairly tight and finds they whole assembly only moves when the brake shoes require due to wear of the linings. Most importantly he also put a brace on the outside of the brake plate between the brake cam boss and the the pin / boss which engages with the lower Girdraulic blades to transmit the braking force.
I have never used this mod, just reporting what Stu has done. Maybe he will comment on here once he gets reconnected to the internet.
Simon

 

[TouringGodet]

(108 + VAT) x 8 (a set) = near GBP 1000

Ah, sorry. Thanks Bruce for pointing that out.

 

[stu spalding]

Stu Spalding has been using the Bert W. Modification for quite a few years. He changed the design slightly by omitting the O rings and rather than using countersunk screws on the outside of the brake plate he extended the pivots which is now threaded externally and is secured by nuts. He tightens these nuts fairly tight and finds they whole assembly only moves when the brake shoes require due to wear of the linings. Most importantly he also put a brace on the outside of the brake plate between the brake cam boss and the the pin / boss which engages with the lower Girdraulic blades to transmit the braking force.
I have never used this mod, just reporting what Stu has done. Maybe he will comment on here once he gets reconnected to the internet.
Simon

Many thanks to Simon for the comments on the Bert Weisz mod (apologies for mis-spelling his name in MPH). I have been using my version on both steel and alloy plates for tens of thousands of miles with no problems at all, but I must emphasise that the steel plates should be properly braced as per the article in MPH 821. The cam bosses are not very strongly crimped into the plates which is probably why the use of the long rear levers on the front was frowned upon in the past, but with the steel plates fully sorted I can find no appreciable difference in performance between them and the alloy ones. I would have certainly hit that tractor a lot harder if I had been using standard brakes! I hope to be partial weight bearing on my bad leg and working on the bike by the end of next week. Cheers, Stu.

 

[Tom Walker]

This is all brilliant stuff. I don't really understand some of it. And re enlarged pivot holes I would be worried about introducing loose play in case the brakes grab and lock which could be very nasty.
I have put a floating system on my old Ford V8 and it works well but they don't seem to release well.
I don't quite understand with the various incarnations of "floaters" how the mechanism returns to the pre-float position when the brakes are released.
Am I missing something?

 

[stu spalding]

This is all brilliant stuff. I don't really understand some of it. And re enlarged pivot holes I would be worried about introducing loose play in case the brakes grab and lock which could be very nasty.
I have put a floating system on my old Ford V8 and it works well but they don't seem to release well.
I don't quite understand with the various incarnations of "floaters" how the mechanism returns to the pre-float position when the brakes are released.
Am I missing something?

Hi Tom, the mod does not leave the brakes fully floating, rather, they are held firm until uneven wear provides forces sufficient to centralise them. Cheers, Stu.

 

[Tom Walker]

Thanks Stu
I wonder did the bike world follow the car world?
Without changing from SLS, simply adding a 2-piston hydraulic slave cylinder which slides in the back-plate, which became almost universal in the 30's, completely transformed car brakes. Both shoes get the same braking force, and are automatically centred in the drum at every application. All you then need is an adjuster at the pivot end (or snails at mid point of the shoes) and Bobs yer uncle!

 

[greg brillus]

If the slave cylinder had two opposing pistons, then there would be no need to make the cylinder move in the brake plate, as the pistons would move to a position to apply equal pressure to each shoe. Only one is "leading" and the other is "Trailing" that's why the length of the linings on the shoes are different to help compensate this. The major disadvantage of drums on bikes verses cars is they operate mechanically, so you need good linings that are radiused to the drum ID as accurately as possible. Drum brakes on bikes are a complete compromise, on a relatively fast bike like a Vincent the brakes are simply too small. I always tell everyone that "They go better than they stop"...............