H: Hubs, Wheels and Tyres Eight inch brake ?

[Michael Vane-Hunt]

Hi,

Using your setup try pulling the 10 Lb ON THE END OF THE CABLE not the lever - then I predict (with the certainty of Archimedes ) that the SUM of the pull on as many spring scales you care to attach to the other end of the cable will also be 10 Lb.

Now do the same thing but this time pull on the lever with the spring attached to the lever close to the pivot point - You will get more than 10Lb total, but not much more; Now move the spring attached to the very end of the hand lever and again apply a 10 Lb pull - this time, as a result ONLY of the leverage from the hand lever, the total pull at the other end will be much more than 10 LB ., though the lever will travel a much greater distance.

Nothing to do with balance beams!

The earliest remaining writings regarding levers date from the 3rd century BC and were provided by Archimedes. 'Give me a place to stand, and I shall move the Earth with it' is a remark of Archimedes who formally stated the correct mathematical principle of levers (quoted by Pappus of Alexandria).

Baaa

Which end of which cable? Do you mean to remove the cable end from the lever and put a scale on that? Confused. I will be away for a couple days so will try later.

 

[Martyn Goodwin]

remove the cable from the hand lever then pull on the cable (without the advantage of the lever itself. You will find that 10Lb there gives no more than 10 lb at the other end (which could be made up of 2 x 5 Lb if you use a balance beam).

 

[passenger0_0]

remove the cable from the hand lever then pull on the cable (without the advantage of the lever itself. You will find that 10Lb there gives no more than 10 lb at the other end (which could be made up of 2 x 5 Lb if you use a balance beam).

To keep this conversation going MartynG I'm going to take an opposing view of the balance beam operating on the sample principle as a rope block & tackle. Here Work in (force x distance) = work out(force times distance).

Here I'll apply a 10 N force to the cable (as 10 lb is a mass, not a force). My guess is that the you get the same force out on both cables as you put in (10 N) BUT half the displacement. (Velocity ratio 2:1)

While we all seem to have our own theories and I'm interested to see the outcome of experimentation. I like the look of the test rigs so far.
What a good way to spend the days up to Christmas!

 

[Bill Thomas]

You are all to clever for me, But going back to the reason why people take the balance beam off, Is because the brake is too spongy, So to me there must be more leverage with it on. Cheers Bill.

 

[Martyn Goodwin]

You are all to clever for me, But going back to the reason why people take the balance beam off, Is because the brake is too spongy, So to me there must be more leverage with it on. Cheers Bill.

Actually Bill the problem you refer to, a spongy lever, is caused by the balance beam itself flexing under the brake load.

 

[timetraveller]

I think it is simpler than that Bill. First the pivot or the balance beam can flex, which is why so many people have put an outrigger stiffener on it. Secondly, you are applying the whole of the force through the one outer cable which can compress slightly unless you use a stronger one than those used years ago. Using two cables means that the compressive force is now shared by two outers.

 

[Chris Launders]

I don't think you can do this with spring balances, the reason being they depend on travel to give a reading and the balance beam divides the input (cable at lever) travel between the two brakes so spring balances there will read half as much whereas in fact the poundage pull on the brakes is the same as the input poundage (but at half the travel) what is needed are proper load sensors and travel indicators. I am certain this will show the difference between the balance beam and the lever mounted compensator.

Which is the balance beam shares the TRAVEL while maintaining the pull pressure, the compensator shares the PULL PRESSURE while maintaining the travel.

 

[Michael Vane-Hunt]

remove the cable from the hand lever then pull on the cable (without the advantage of the lever itself. You will find that 10Lb there gives no more than 10 lb at the other end (which could be made up of 2 x 5 Lb if you use a balance beam).

I think that is self evident, but will try this later. It also corresponds with the measurements on my lash up. The pull applied to the brake lever, when mechanical advantage is factored in, is equal to the sum of the pull on the other two spring scales.

 

[Vincent Brake]

we cant all be mechanics.....
the world would be a boring place...

 

[greg brillus]

The two main factors here that affect the brakes on a Vincent are...........Lack of descent lining material that is suited to a mechanically operated drum brake.................And two...........The stock 7 inch single leading type brake (even all four of them) are not up to the weight and performance of these motorcycles. They might have been ok in their day, but speed limits and traffic conditions have changed a lot since then. The VSM Brakes go a long way toward improving that, but it is still "only" a 7 inch brake. The talk of the mechanics of balance beams and brake arm lengths is all well and good, but it is the mechanics of the actual brake itself in it's size and efficiency that are what really matter, as anyone who has ridden a bike with decent size four leader brakes would know.