H: Hubs, Wheels and Tyres Eight inch brake ?

[Tom Walker]

Its all very interesting and as Greg and David have pointed out to me, getting everything "right" is half the battle. A bit of wear here and there in every joint and bush, correct set-up etc. is all vital if one wants proper functioning of the brakes.
If the Vincent brakes are as "out of the factory", plus with a couple of the mods made over the years, they no doubt work well. (As I have read here. Not personal experience, of which I have little).
I have, locally, a motorcycle brake specialist, called Bob Coley, who has the correct equipment to skim drums, and turn newly lined shoes to the best possible fit. But because its not top of the list, I havnt had the Raps brakes done by Bob.
Also from reading this thread, I will now go out and centre the shoes. I understand that it will be impossible to get that close adjustment necessary as Greg described, without the shoes being as concentric with the drums as possible.

 

[Tom Walker]

Vincent
if the brake shoes flex when operated, are you not machining them to the wrong radius by mounting them unstressed on the lathe?
Or is it just a case of its better than not doing it at all!!

 

[Tom Walker]

Tom,

The linings today tend to be much better, but they are generally not offered for drum brakes because nobody uses drum brakes.

On the lever, I usually do it the way Greg does, start out with the linings just short of touching the drum and I try and take all the play out of the system so the lever does not have to take it up before the shoes hit the drum.

I take it you measured your lever pivot distance? It should be 7/8" from the lever pivot center to the center of the cable barrel. If it is longer than that the lever will touch the bar for sure.

Reasonable braking is quite good!

David

Ok David, now I am a little confused. I would have thought that the longer the distance between the lever pivot and the cable, the more movement you get at the brake arm, less at the lever, and a less good leverage ratio?

 

[Vincent Brake]

Vincent
if the brake shoes flex when operated, are you not machining them to the wrong radius by mounting them unstressed on the lathe?
Or is it just a case of its better than not doing it at all!!

And here comes in the experienced machin-ist, as wel as brake-ist

 

[greg brillus]

There are several trains of thought about setting up the shoes to skim on a lathe........You either machine the OD of both shoes/linings down say 20 thou smaller than the ID of the drum........ Or........Place a 10/12 thou shim between the cam face and the shoe plate, machine the linings so it just slips into the drum, then when the shims are removed the shoes move inward slightly giving a running clearance...........Or the best way I was told by an ex- racer here is.......You assemble the shoes as per normal, mount the assembled plate in the lathe, and use some kind of fixture to actually "Pull" the brake lever on slightly so that this action duplicates exactly what the cam is doing when the brakes are applied. You then skim the lining material so it just slips into the drum. This is also why each brake plate and drum needs to be done as a matching pair/set as it is rare with original parts for all of these parts to be the same. Even new drums are all over the place with their ID's............Cheers.......................Greg.

 

[Tom Walker]

And here comes in the experienced machin-ist, as wel as brake-ist

Many apologies Vincent I can assure you there was no offence intended.

 

[david bowen]

In the next few months there will be a supply of original made correctly brake shoes.

 

[davidd]

Ok David, now I am a little confused. I would have thought that the longer the distance between the lever pivot and the cable, the more movement you get at the brake arm, less at the lever, and a less good leverage ratio?

Tom,

See the No. 6 post in this thread: https://www.vincentownersclub.co.uk/index.php?threads/handlebar-levers.9648/#post-90470

I think it is a common misconception that the 1.25" pivot distance provides more pressure for the same distance. Generally, they provide less pressure over a longer distance and that longer distance may be getting you into the handlebar.

I think this thread has shown a lot of consensus that the Vincent braking system is a short lever throw high pressure system (single cable lever with balance beam) as opposed to the long lever throw lower pressure system (double cable lever with no balance beam). Unfortunately, the high pressures in the Vincent system seems to damage the system itself. The shoes are woefully under designed and made with very soft material, something that Trever has been saying for decades. It is very difficult to find shoes that are not bent.

The stock backing plates seem little better. They do appear to be more robust, but I have found so many that are misshapen in so many ways (some have the brake anchor, cam boss and shoe posts all bent). Considering that the shoes are so soft it is hard to believe that the backing plates can be so obviously damaged.

I think Greg's statement is true about good original brake systems working fine, but I don't think that many of these survive. I think it is great that you have "reasonable" braking because your system may have survived and is doing well. I think most systems have bent shoes at a minimum and possible some warpage in the plate, or a bent post.

I think that aftermarket brakes like Vincent Speet's or the 8" are the best upgrade that can be made.

David

 

[vibrac]

My take
http://www.saftek.co.uk/ very fast turnaround just ask for extra depth
packer on operating cam when turning
ensure clearance on central spindle
dump the beam on the front :-0
use alloy plates on front

 

[david bowen]

The guys making these brake shoes are Vincent owners for many years, one is A Metallurgist working in alloys the other guy tool maker