Brake Fire

[DanH]

<<It turns out that in the RV-8, the pedals are designed in such a way that any pressure on the pedal at all -- even just to use rudder -- exerts a force on the brake cylinder. This is true for every 8 built to plans.>>

Totally true, and if you have big feet it is worse. I've done the "rod mod" before. I seem to recall a more elaborate pedal mod also. Anyone have pics? I'm going to do something with the new bird's pedals even if I have to weld up a new assembly. The catch to the rod mod is that it steals 3/4" of legroom, and concentrates pressure across your foot if you wear soft shoes.

Dan

[m_warfel]

When I installed my brakes from Vans, I modified them by replacing the standard Nitrile O-rings with Viton (sometimes refered to as Flourocarbon) O-rings of the same size, the Viton has an upper temperature limit about 100-125 degrees F higher than Nitrile, however it is only good down to about -15 degrees F (I'm not too worried about that in Calif.). The other modification i intend to make is to use either the Mil-H 83282 hydraulic fluid or Mobile one Synthetic automatic transmission fluid for an increased flash point temperature. (the temperature at which the fluid will burn in an open container.) If you compare the specification data between the Mobile One synthetic Automatic transmission fluid and the Mil-H 83282 hydraulic fluid, you will find that they are very similar and the I have found that the Mobile one trans fluid is more readily available.

I hav found the best source for O-rings (if you don't need tracability or special compounds) to be Mc Master Carr.

Mike Warfel
RV-8
Finishing

[Geico266]

Originally Posted by DanH

Totally true, and if you have big feet it is worse.

I can stay off the brakes by using the sides of the peddle "frames", and I have # 12 EEE's. It's a little awkward at first, but it beats the heck out of replacing o-rings, or running for the fire extinguisher.

[Jamie]

Part of the problem is people mount their rudder bars completely vertical. Ideally they should be sloped away from you a bit so your toes aren't hitting the brakes when you're working the rudder. This is part of the problem with people dragging brakes. If you shorten the rudder cable 'links' and mount the rudder bars a little more forward there's no problem. I have had no problems so far in 160 hours and my pads look like they can go another 160 or more. I also installed auxiliary return springs on the master cylinders which I feel helps with brake life.

[Ironflight]

Originally Posted by DanH

I seem to recall a more elaborate pedal mod also. Anyone have pics? I'm going to do something with the new bird's pedals even if I have to weld up a new assembly. The catch to the rod mod is that it steals 3/4" of legroom, and concentrates pressure across your foot if you wear soft shoes.

Dan

Here is a picture of the "pedal extension" mod (scroll down to my first panel picture, and you can see the pedal extensions). It is pretty easy to do, and gaurentees that you are taking pressure OFF the brakes, as long as you have your toes low on the pedals. But....it doesn't fit everyone's ankle geometry, so I don't consider it a universal solution. I like it, but have flown -8's without it as well.

It's important to remember that the -8 pedals are different from those on the side-by-sides (and the -4's, and the -3's...), so what works for them might be different than what works on an -8.

Paul

[learningtofly]

during my search for a airplane (rv) i came across an article about brake fires and i believe it was on this site, anyway the solution was to use automotive dot fluid , it is non-flamable-- but here is the critical part-- you must use o-rings compatible with the dot fluid. i will try to find the contact info for this guy as he had to buy a pretty large quantity. good luck

[tonyjohnson]

There is a lot of info in the archives on the topic of brake fluid, brake modification, and brake fires:

http://www.vansairforce.com/communit...ighlight=brake

Based upon the info here I replaced the seals in my 8a project with those compatible with automotive brake fluid and plan to use that.

[hughfi]

Please send pictures.

[IowaRV9Dreamer]

Originally Posted by m_warfel

When I installed my brakes from Vans, I modified them by replacing the standard Nitrile O-rings with Viton (sometimes refered to as Flourocarbon) O-rings of the same size, the Viton has an upper temperature limit about 100-125 degrees F higher than Nitrile, however it is only good down to about -15 degrees F

Hi Mike - did you change the O-rings in the master cylinders also? I'm planning on running the "other" milspec fluid and am thinking of changing O-rings. Is the Viton only for heat or for fluid compatibility?

I've flown a C150 at -15F, so that might actually be a problem... BRRRRR

dave

[Jim Wright]

Hi Rich,
Thanks for your reply. I would greatly appreciate you pictures of your brake pedal modification. I feel that this is definitely a part of my problem.
Many thanks for your reply.
Jim