H: Hubs, Wheels and Tyres Eight inch brake ?
- Thread starter Julian R.
- Start date
It all sounds like schoolyard German too me!
"a 100 Lb pull on the lever will put 50 bl on each cable."
As Martyn sez. With one cable in equilibrium, there is 100lb throughout the system - tension in the inner cable and compression in the outer which pushes down on the balance beam and causes a 100lb tension on the other end (RHS on a C and LHS on a B) pulling up. Adding more balance beams just spreads 100lbs elsewhere. No doubling.
With a whiffle tree 100lbs is split between 2 cables giving you 50lbs each and the need to double the length of the brake arm to achieve the same moment at the cam.
Mr Vincent was indeed ingenious.
As Martyn sez. With one cable in equilibrium, there is 100lb throughout the system - tension in the inner cable and compression in the outer which pushes down on the balance beam and causes a 100lb tension on the other end (RHS on a C and LHS on a B) pulling up. Adding more balance beams just spreads 100lbs elsewhere. No doubling.
With a whiffle tree 100lbs is split between 2 cables giving you 50lbs each and the need to double the length of the brake arm to achieve the same moment at the cam.
Mr Vincent was indeed ingenious.
Hi Hugo. I have no experience of the 8” brakes but have heard other opinions from those that have. I have the TLS ones on the Prince outfit, but before fitting, spoke to Vincent about them in Austria and was invited to sit on his bike, put the front brake on while he tried to push backwards on a hill. The brake held well and I was quite impressed. If I stop on a steep hill, I use both front and back brakes, as long as the rear brake is not stamped on, because the torque bar can bend. Very pleased with the brakes, and the odd time that I have had a quick stop when traffic lights change, they were on the verge of locking up. Easy on the hand as well.
I'm embarrassed to say that I do not have a front end sufficiently assembled to carry out the following simple experiment. With the standard Vincent set up, remove the lower end of each brake cable from the brake cam arms. Attach two similar weights to the end of each of these cables and allow to dangle. Now put a spring balance on the handlebar brake lever at a known distance from the pivot and measure the force needed to lift the two weight with known values. There will be some frictional losses but it will give you some idea of how much force at the handlebar end gives a known force at the brake arm end of the cables. Now do the same with the left hand end of the balance beam locked into place so that it cannot pivot. This way you will lift only the left hand weight. If you now have access to another bike with the double cable set up and no balance beam do the same. There will be different frictional losses but you are looking for a factor of two difference. Let us all know what you find. Bu**er the theory, let us do it empirically.
Just to put a spanner in the works, here is what is fitted to my Rapide. They are twin leading, and still using the balance beam because I think its a Vincent quirk a bit like the twin clutch. The brake plates are an alloy casting with the "water excluders" a part of the casting and machined from one. Its not easy to see but there are cast in strengthining ribs and the pin which engages with the bottom of the girdraulic forks is also a part of the casting and heavily supported with cast ribs. It still uses the original brake arms which have only rotated a few degrees backwards from their original position allowing the balance beam to still be used. Works very well.
They were designed by a VOC member over 20 years ago who had 5 sets of castings made and these were the last set which I purchased 2 years ago as raw castings and then machined them up. Interesting is the original brakes had a lot of sponge feeling in them, but these have none at all, but it still uses the same balace beam and the exact same cables that I had fitted previously. So my conclusion all the sponge feeling was from something inside the original brake plate setup and not external.
They were designed by a VOC member over 20 years ago who had 5 sets of castings made and these were the last set which I purchased 2 years ago as raw castings and then machined them up. Interesting is the original brakes had a lot of sponge feeling in them, but these have none at all, but it still uses the same balace beam and the exact same cables that I had fitted previously. So my conclusion all the sponge feeling was from something inside the original brake plate setup and not external.
Are these plates using standard Vin brake shoes?
No. They are similar to std but slightly shorter to allow you to get two seperate cams and two seperate pivots inside. The linings are the same length though as standard. The castings for the shoes were provided as raw castings with the plates all as one kit.
Simon