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I'm having a problem with the brakes not holding when I do a runup. At about 1800 rpm the plane starts to move and I can't stop it until I idle back to 900. I installed a foot pedal attached to the hand brake to assist and it still isn't enough. What's my problem? What are you guys doing about brakes?

Which brake system have you installed in your Onex? Is it the mechanical brakes with the upgraded drums? The hydraulic system?

It's the original system, mechanical with steel drums. I'm going to pull a wheel and see what's going on in there. They feel like I have grease or oil on the bands. They hold up to 1800 rpm and then break loose and go.

I think I solved my own problem. The brake levers are bottoming out on the small block that traps the end of the cable sheath. Either I haven't tensioned the brakes enough or, and this is what I'm going to do, I'll move the block up higher on the plate.

Thanks for finding this problem. When I read your post I checked my brakes and found I had the same problem. Glad I didn't find it on my first flight. I raised the blocks and that solved the problem. After reviewing the prints I believe a change may be in order here.