T

Tcheairs

Well Known Member
Could someone tell me the bolt head size, bolt size and thread count of the bolt and castle nut that attaches the piston of the brake master cylinder to the rudder/brake pedal? Metric? Sae?

Yes, I've searched the forum but can't come up with my specific specifications. Would like to know before I crawl under the dash to install a brake return spring on the master cylinder piston.

Thanks
 
Plans for the RV7 (which would be same for 6/8/9 & probably same for the later models) call out for an AN3-10 which would be 3/16 x 1 National Fine thread. 3/8" wrench
 
The master cylinder has its own internal return spring, so you may not need an additional spring. If you've tried using the brakes and it's not springing back, you may want to check for binding--assuming it already has brake fluid in it. If it is binding, make sure everything that moves is square to its respective connection point. If it's not, it can get in a bind.
 
When I pull the pedal back by hand, the master cylinder piston has to move approx. 1/8" to fully close. This does not happen from the copilot pedal. took the wheel off and and it spins perfectly straight. The return spring kit (McMaster Carr parts) is the easiest thing to try at this point. It can 't hurt anything for it to be installed.
 
Sure, a lot of people have put booster springs on there. It shouldn't have a detrimental effect on anything.

Not sure if you're the original builder or if you bought the plane used. My point was that you might also want to look to see if anything else is going on there. Is a tab bent or damaged on the rudder pedal? I've read that some people have apparently stood on the brakes so hard that it bent a tab. Is the master cylinder stroking straight up and down, or is it offset and may require a washer to space it out correctly?

If you look at some of the pics of items Vic Syracuse and others have come across, some people have snugged up the mounting nuts and/or used a Nyloc nut instead of a castellated nut with a cotter pin. The pivot hardware should be just loose enough to allow the parts to stroke without binding. And while it is uncomfortable to get under there to work on, it's doable. Looks kinda funny, but it can be done.
 
Everything straight..spring kit did the trick..no more brake drag..Bought plane from builder..new in 2012..had 125 hrs TTAE on it when bought it 2 years ago..
Still like new..PITA for my 77 yr old body to slide on my back up under the panel. Thought I was going to have to use my cell phone for an SOS to get pulled out of there feet first..Thanks for all of the advice.
 

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