Anyone with experience with the Hegar brake master cylinders? Given they are a sealed system, how do they relieve the fluid pressure when the pedal is released? i.e. do the brakes ever drag due to pressure not being able to return to a reservoir?
I’m using the simple Hegar cylinders for toe brakes, and I’d advise against them due to the fact that they have no option for connection to a reservoir like most master cylinders to. The problem isn’t dragging, since the fluid is free to equalize through the whole system. Maybe if the fluid got hot it would increase the pressure, but that was never a problem for me.
The problem is just the opposite. When the brake pads wear even a little, that creates extra space in the hydraulic system. For a normal system with a port for a reservoir, that just pulls fluid in from the reservoir. For a sealed system, it lowers the brake pedal. As the pads wear, you have less and less brake pedal travel until you’d eventually have no brakes. I lived with that for a year or so until I got tired of having to bleed the brakes every few months to get more fluid in the system.
My solution isn’t something I’m proud of, or would recommend, but it works. I added a small reservoir on each side of the cockpit that’s Tee-ed into the pressure line from the master to the calipers. Ideally you’d have a one way valve on the bottom of the reservoir, but I couldn’t find one that seemed like it would work. Instead, I added a manual valve on the reservoir. My preflight is basically to open the valves a few seconds, then close them. There’s no need to do that every flight, but it keeps the brakes full and consistent.
Rusty
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