I’ve been doing quite a bit of work honing the description of TrueBrake to get the message across to people. Because the product description needs to be reasonably concise its hard to get all the information across. Here’s some more of my thoughts on TrueBrake…
Why is TrueBrake a thing?
I designed TrueBrake because I realised there was a vacant middle ground for modifying the Logitech brake pedal, somewhere between overspending $120+ on a load cell and $10 on a spring or some bits of foam. Also, like most of the things I design, I do it because I really want one.
How does a load cell work?
There are several types of load cells. The ones commonly used in sim racing pedals are strain gauge load cells. Strain gauge load cells are springs, or to be more precise they contain a spring element. Spring elements that don’t move very much, but springs nevertheless.
Strain gauge load cells use an electrical strain gauge to measure the bending of a metal beam (spring element) when a load is applied. The deformation of the beam is very small, but deform it does (following Hooke’s Law). In this case the load cell is used to measure the load being applied to but not the position of the brake pedal.
Because real brake pedals move when you press them, something squishy and springy must be put between the pedal and the load cell. Usually this is a long stack of polyurethane buffers. And because real brake pedals usually have a certain amount of free play before the master cylinder engages with the pedal, the stack of buffers has a spring between them and the pedal.
It is a common belief that a strain gauge load cell is the best solution for a sim brake pedal. They certainly have a lot going for them and I think that for an expensive high-end set of pedals they probably are the best solution. For the Logitech pedals probably not, because if you need endless adjustability, up to 100kg of braking load and budget is not an issue then you have the wrong set of pedals!
How does TrueBrake work?
TrueBrake doesn’t use a strain gauge load cell, but then that’s the whole point of it! TrueBrake measures the deflection of the spring inside the cylinder (Hookes Law!) which is what a load cell does but the movement is larger. This movement and the force required to create it are of similar amounts as found in a real brake pedal (that is by design!). TrueBrake is not connected directly to the brake pedal. There is a small spring and polyurethane buffer between it and the pedal, this is to create the free play and the following transition into braking. TrueBrake measures the load being applied to the pedal and not the position of the pedal. Sound familiar?
Why is the stock Logitech setup not very good?
The stock Logitech potentiometer measures the brake pedal position. Because the pedal is spring loaded, it follows that it also measures the load applied to the pedal (Hookes Law again!!), but the load is small and over a large amount of travel. It is essentially an accelerator pedal trying to be a brake pedal.