Any way you look at it, a fulcrum is just a fulcrum. If you want to use a shorter brake pedal then every fulcrum in the system has to be shortened by the same percentage. What is missed in this discussion is the length of the drum brake actuator. It’s really just a simple mathematical formula. If you shorten the brake pedal by 50%, then the pull rod arms at both locations must also be shortened by 50% to retain the original final leverage ratio at the drum.
As SCM says, if the ratios in the brake lever stay the same then the force on the brake rod will be the same and there's no need to change the length of the brake drum actuator lever.CC
Actually true for force and travel as long as the ratios remain constant.
Assuming the brake drum lever has to travel 0.5", then the stock brake lever arm also travels 0.5" which at 3" results in about a 10* rotation of the brake lever which works out to about 1.7" of travel at the toe pad.To get 0.5" of travel at the 1.5" custom brake lever arm it has to rotate about 20* which works out to about 1.7" of travel at the toe pad of this lever also.So as long the new lever has the same ratio of arm lengths as the old lever, things will feel about the same.
The ratios are NOT constant if you leave out the brake actuator arm. Period!According to your own math, the difference between 10* rotation and 20* is double! Does that sound constant? Do you know what a 1.7” of brake pedal travel feels like?It feels like you’ve got no rear brakes. Especially on rear-sets where your foot is angles down.
Non-tech guy thinking here:If my rearsets mean my new, shorter brake actuator pulls the brake rod a shorter travel than it used to (by virtue of being a shorter lever), albeit with the same force, I'd need a shorter arm at the brake drum to accomodate that shorter distance of travel, no?MD
The rotation of the lever is not constant, but I don't care about that, I only care about how much I've got to move my big toe and that IS constant.Why does the drake drum arm care what's going on at the brake lever? All it sees is a force being applied to it through a brake rod.My math just shows that both foot brake levers apply the same force and the same travel to that brake rod for the same amount of force and travel of my big toe. The numbers were arbitrarily chosen for easy math, so they won't reflect the actual travel of a properly adjusted brake system.CC
What I'm concerned about is how much leverage I'm going to get on the rear drum. Dealing with both a shorter brake lever and a shorter actuator. Can anyone assist with science and/or experience? Will this work out? (Edit: Waitaminit. A shorter actuator is going to give me MORE leverage, no?)