# How much cable can I pull with a brake lever in another custom mechanism, and how can I achieve it?

I am not sure if this is the correct community for the answer, but since this part is about a bicycle part, I thought it's okay. If this is better posted in physics, or anywhere else, please let me know.

I am working in a custom mechanism for a cosplay prop (which is not relevant here, if you want to know, it's the blades from Attack on Titan). I need to pull a pair of pieces, that work in a lock mechanism. They lock themselves around the piece that goes inside the mechanism with springs, and the way of freeing the object is pulling from them, with the same mechanism as a brake lever.

The matter is that I need that pieces to travel back about 2 cm, which is the length of the pieces, and I don't know if it is posible to pull that length of cable with a simple brake lever (long, I suppose) that I can buy. Would it depend on the length of the lever? The tyoe of lever? The angle? All of them?

• Thanks so much to every answer. I didn't think about another lever, to change the ratio again. Actually, it seems a very good idea, I think that I have enough space. The problem is that the lever also collides, not with the handlebar of a bicycle, but with the object, which is a handle, that covers the mechanism, so I can't extend the angle all that I would want. Commented Aug 22, 2018 at 14:05

I believe a typical V-brake lever (so called long pull) has enough action to pull 2 cm of a cable.

V-brakes are known for they greed for cable length - e.g. if replacing cantilevers with V-brakes one needs to replace the levers as well.

EDIT: I may be wrong - see this thread: What is the actual cable pull of brake levers?
There it says that long pull has the action of 14 mm which is not enough for you. A solution for you would be (depending on how technical/machinist savvy you are) to use the brake lever to engage another lever that increases the advantage of the cable pull.

Since one picture saves 1000 words...
This contraption would increase the pull of the secondary cable by the ratio of the arms of the extra lever at the cost of increased force required to engage the brake lever. Of course the extra lever can be in any shape and the distance between the rotation point and the cable attachment point determine the arm lengths.

I hope you get the idea.

• yes, he would need to demultiply the lever so he can have more motion. user39085 should make a pivoted pole(o wheel) where the cable ataches near the pivot, and attach the locks for the blades far away from the pivot. Anyway 30mm should be enough for the task.
– dmb
Commented Aug 22, 2018 at 13:05
• It would be simpler to use a class 3 lever as a distance multiplier. Commented Aug 22, 2018 at 13:05
• If you don't use a (full) standard handlebar to mount the lever you may get away with only the lever, since the limiting factor is usually the lever hitting the handlebar. If there is no handlebar to hit, you can pull more cable. Commented Aug 22, 2018 at 13:28