H: Hubs, Wheels and Tyres Eight inch brake ?

[greg brillus]

Even with the VSM twin leading shoe brakes, you can keep the balance beam, as you just run each cable through the stock adjusters, though you need to drill them out so the cables just pass through. Another tip.........If you go this way, use a pair of the stainless adjusters (you can buy separately from the VOC spares co) as the alloy originals are too weak. This is because once you drill out the centers, there is very little material left, but it is only a visual thing anyway. Cheers.................Greg.

 

[nkt267]

Even with the VSM twin leading shoe brakes, you can keep the balance beam, as you just run each cable through the stock adjusters, though you need to drill them out so the cables just pass through. Another tip.........If you go this way, use a pair of the stainless adjusters (you can buy separately from the VOC spares co) as the alloy originals are too weak. This is because once you drill out the centers, there is very little material left, but it is only a visual thing anyway. Cheers.................Greg.

That's what I did for a section member..John

 

[Martyn Goodwin]

If you can get hold of a set of these linings and have them bonded to your brake shoes I can assure you the results will surprise you.

With just standard shadow finned drums with alloy brake plates at ANY speed you can get the front tyre squealing under brakes plus unless you take care you can also lock up the back wheel - and there seems to be amazing resistance to brake fade.

Hard to find but persistence on ebay will get results. Don't worry about what the particular bike or car the sets you track down were meant to be installed on - the bonding process will ensure a perfect fit to Vincent shoes. Always good to have an extra set for both wheels in reserve in your home parts stock.

 

[davidd]

I have never received a good answer to this question, but a proposition has been published many times in MPH:

"Consider a pull of 100 lbs in the cable. This is applied directly to the left front brake. The reaction to this is taken by the balance beam which then applies 100 lbs. to the right front brake [and also 100 lbs. for the left front brake]. For the same force with a twin pull lever only 50 lbs. applies to each brake." R. Cordy MPH 629 at 31.

This came up in MPH during a discussion of brake levers and their effects by Neville Higgins. He and George Spence, among others, assert this as true. That is, the Vincent balance beam and cables are designed in a way that the force transmitted by the cables is doubled when they reach the brake arms on the drums. Thus, if you use a stock Vincent cable and balance beam and you tied concrete blocks to the cable ends instead of the brake arms, you would be able to pick up two 100 lbs. blocks with the Vincent while the dual cables could only hoist two 50 lbs. blocks.

I find it difficult to believe that the two cables running to the handlebar produce half of what a balance beam system produces. I have had many discussions about this and I have lost all of them. Mr. Higgins and others are winning the day.

My first argument has always been "If Vincent balance beams somehow double the force on the brake arms compared to two single cables, how is it the the stock braking is so crappy?" It just seems to me that the doubling should produce more impressive results.

In this same vein, I am shocked that no one else used this system. If factory racers could double the pull on the brake arms by using a balance beam why were they not used on the factory racers on the TLS racing drum brakes?

Additionally, if the balance beam makes this doubling, why couldn't you line up more balance beams, cris-crossing the Girdraulic to get a quadrupling or more? This sounds like something Mr. Newton would not have allowed.

I have argued that the balance beam is really a splitter. It is not a lever, but a see-saw. The whiffle tree is simply a narrower version of the balance beam located in a different place. The whiffle tree is also a see-saw.

I realize that all the smart people are arguing against me, so I don't necessarily think I am correct, but I would like to know the answer to this question. It would be nice to know if the gents using twin cables are really at a disadvantage.

David

 

[greg brillus]

I see all your points David, I could not be convinced that the balance beam is as effective as it might be, only it works by the same principle as that found on push bike brakes. I feel the main difference over a lever/twin cable pull set up is perhaps not indifferent to the extra travel needed in cable pull travel for a multiplate clutch. Perhaps the lower "Pull figure" for the twin cable set up is more a case of a handlebar lever that has 1 1/8" pivot centers over a stock Vincent's 7/8th s.........Thus travel over actual "Pull" figures change quite dramatically. I would say the stock set up has quite a lot of
Pull not unlike the rear set up that has enough strength to bend parts of the brake plates, not least the anchor pins that secure the shoes themselves. This just shows that the Vincent brakes are far too small to cope with such a speedy machine. The 230 mm twin leader Ceriani I ran on the racer gave excellent braking, even though i never pushed it hard enough to suffer from "Fade" too much. Any twin leader is always going to be superior to a single leading shoe brake. Cheers...................Greg.

 

[vibrac]

We are not alone with the balance beam the Scott also used it on some machines and the conclusion on their "technicalities" was the doubling of force was a falicy. The balance beam pulling on two balance beams is a good mental analagy for me. What are the individual strands of a rope if not miriad balance beams? flexture is the real enemy and there is less movement on a 2 inch beam at the bar than 8 inch on the beam.

 

[erik]

i transformed the speet Brakes to Balance beam working with the helpof a friend.he has a water cutting machine.and it is true that the Balance beam doubles the force on the brake arms.therefore i had to shorten the original speet arms to nearly the half length.without doing this the way of the handlebar Lever was to Long.but this modification works really good ,and the original parts are still in use.why because there is less force on the cables ,there is less Flexion on the parts.

 

[Bill Thomas]

In the old days, People could squeal the front tyres, Ron could, But I feared braking the cable !.
It's the linings that are not fit for use, I made longer brake arms for my Comet, And to me they feel much better.
The first Norton Commando with disc, Had small soft pads, They was the best, They wore out quick, But they were super.
I am not talking brake fade, That is something else, Just that standard brakes can be made to work. Cheers Bill.

 

[erik]

in the mph october issue ,on page 9 there are two photos of my conversion made by Marcus Bowden.regards Erik

 

[Martyn Goodwin]

i transformed the speet Brakes to Balance beam working with the helpof a friend.he has a water cutting machine.and it is true that the Balance beam doubles the force on the brake arms.therefore i had to shorten the original speet arms to nearly the half length.without doing this the way of the handlebar Lever was to Long.but this modification works really good ,and the original parts are still in use.why because there is less force on the cables ,there is less Flexion on the parts.

Hi Erik, seems that you may have discovered a new physics solution that 'magically' increases force applied to a single cable. Just kidding.

The balance beam cannot increase force - it simply shares or spreads it. example = apply a 100 Lb pulling force on the brake cable at the hand lever end and that cable tries to apply 100 lb to the brake arm at the wheel but at the same time it also applies a downward force on one side of the balance beam which in turn puts a upward force on the second brake arm at the wheel - so the 100 Lb pull at the hand lever end is converted into two 50 Lb pulls at the brake arm at the wheel. Actually there is some friction losses in the balance arm pivot so it will never be exactly distributed. If you do away with the balance arm and replace it with a twin cable arrangement with a (I think its called) a waffle bridge at the hand lever - a bit like a mini balance beam - you will get exactly the same effect - a 100 Lb pull on the lever will put 50 bl on each cable.

With a mechanical brake it is only levers that can change the force and levers do that by modifying the amount of travel. Here is a long discourse on the topic https://www.thoughtco.com/how-a-lever-works-2699400 . It is the brake cables that carry the force from one lever to another.

With our Vincent brakes there are at least 3 levers to take into calculation.

1. The lever created between the hand lever pivot point and the end of the brake cable.
2. The lever created by the brake arm at the wheel - the length of the lever being the distance from the hole for the brake cam and the end of the cable, then there is the 3rd -
3. the actual brake cam on the inside of the brake plate itself. If you make changes to ANY of these levers you will change two things - the force applied to the brake shoes and the travel range of the handbrake lever. Generally more handbrake lever travel = more force applied to the brake shoes and the reverse is also true ; Less handbrake lever travel means less force on the brake shoes.

I use a balance beam on my Comet with finned shadow drums, alloy backing plates and NOS FERODO MZ41 linings. With the stock setup my brakes were not all that good BUT I increase the length of the brake arms at the wheel end by 1" and now my brakes are much better - though it was at the (expected) cost of increased brake lever travel at the handlebar.

For the record I am not a physicist, my formal training is in Economics and Law however I am happy to attempt to address your questions and invite other readers of this topic to add their thoughts.

regards

Martyn