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Fire (Brake during taxi)

David Paule said:
My '55 C180 has aluminum tube to the brake calipers. It allows sufficient flex so that the brakes move freely on their posts. The tube is inside a housing until shortly before leaving for the brake, certainly less than a foot of free tube, probably closer to 6". The tube is 1/4". I plan to use 3/16" for a similar tube on my RV-3B project.

Dave
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as long as it is the soft annealed stuff like 3003, it can handle a bit of movement.
 
I don't see data on it, but I think it's the other way around; 3003 might get into the yield range when flexing when a stronger alloy would remain elastic. In any case, the tube design should allow for some motion.

Dave
 
David Paule said:
Has anyone affixed a temperature sensor to the brakes? If so, please tell us about it.

Thanks,
Dave
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On a hot summer day in Florida I've seen up to 145 F temps but that's inside the tire at the center of the 2 piece hub after braking and turn off. Berenger SensAir system.
 
David Paule said:
I don't see data on it, but I think it's the other way around; 3003 might get into the yield range when flexing when a stronger alloy would remain elastic. In any case, the tube design should allow for some motion.

Dave
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Not my understanding. The soft annealed stuff, like 3003, is very far from yield strength when bending and can bend a LOT. This is the stuff Vans supplies and you can bend it back in forth in any direction. The more alloyed and hardened stuff is what doesn’t like the constant moving. Not about yield strenth, but work hardening that makes it brittle, then cracks,
 
Taltruda said:
Since experimental don’t have ADs like the certified world, all we Have are Service bulletins, service letters, and service instructions. Vans has published a Service Letter (SL-00047) addressing this. I really wish more owners and mechanics would just look these up and comply with them..


I would also add that it’s a great saftey engagement to replace the brake lines with steel braided Teflon lined versions.. TS probably makes a set just for your plane.
Learning to taxi and minimize brake usage (abuse) is also someone I’ve seen lacking out there. Like someone said above offering their technique, but sometimes the crosswinds just don’t allow it. On the 500x5 RVs, there’s a thicker disk mod that you can do.. I wonder if there’s a version for the larger 600x6 wheels?
Thread 'Cleveland upgrade kit 199-93'
https://vansairforce.net/threads/cleveland-upgrade-kit-199-93.153627/
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I thought dragging brakes was causing unnecessary wear on the pads and rotors but a potential fire takes this to a whole new level.. Always learn something new..
 
ve0kog said:
I thought dragging brakes was causing unnecessary wear on the pads and rotors but a potential fire takes this to a whole new level.. Always learn something new..
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Yeah these little aircraft brakes are not designed to handle much heat.. look at beefy automotive disks that are vented vs tightly enclosed and very thin aircraft brakes.. they don’t have much heat capacity..
 
lr172 said:
i can't understand how anyone would think a nylon tube is acceptable connected to a brake calipar. over time, i guess we see it all in EAB.
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All the canard have used nylaflo since the 70's.... It has to be replaced every 10-15 years depending on exposure to UV. However, most have (or should have) a heat shield between the axle and gear leg or as a minimum wrap the leg and brake line with fiberfax and metal tape. We have the issue that the gear legs are 100% fiberglass and can soften or melt if the brakes get too hot.
 
lr172 said:
Not sure I understand the recommendation for hose here. Both of my planes have aluminum lines out near the caliper, per plans. I would expect these lines to have a much higher melt temp than PTFE lines. Maybe the stainless braiding will absorb enough heat to actually make that not correct. Please elaborate.
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bwestfall said:
I recently had a brake incident that almost reached the fire stage as well in my RV-10. It was due to a newish pilot taxiing so heavier on the brake steering followed by heavy braking after an aborted takeoff. Shutting down it smelled like a semi truck descending a mountain path. Hoped out and the right brake was smoldering smoke out of the wheel pant. No flames and no damage but the brake master cylinder is now a nice brown patina and the label is all but melted off. The nyloc nuts took one for the team and I probably should have used all metal ones in the beginning.

During the build I replaced the o rings with vitton's, used the royco 782 fluid, and braided stainless brake lines. There is no doubt in my mind that had I not done the o ring and 782 swap the situation probably would have ended much differently. The o ring on the brake cylinder did not appear damaged but I replaced it anyway. The brake pads were just about at their limits and were swapped out. Fresh brake bleed and put it all back together. No issues now after several flights.

The Cleveland's are adequate until they are not. I am seriously considering the Matco upgrade. It seems with the upgrade the system may be able to withstand more heat before this sort of thing could happen. The question remains though would this same situation have caused an issue w/the matco's?
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In this case, look at the clear PVC abrasion sleeve over the hose braid. Clearly got hot. What saved the hose is its located behind the wheel pant bracket, so alot of the heat from the rotor is re-directed. Teflon has a temp rating of 450*, with limited exposure to 500*. YEP, you could even use a firesleeved hose ( like some military planes) , BUT even firesleeve isnt fool proof from fire. Once the heat transfers to the fiberglass wheel pants, well its just fueling the fire. Aluminum tube has a higher temp rating, but is prone to flare cracking, and side loading the calipers. YES---it varies from plane to plane and the PILOTS use of the brakes. Just a thought here for those going to OSH-- Long taxis, then going to grass. Imagine a hot brake picking up cut grass.

Tom
 
lr172 said:
Not my understanding. The soft annealed stuff, like 3003, is very far from yield strength when bending and can bend a LOT. This is the stuff Vans supplies and you can bend it back in forth in any direction. The more alloyed and hardened stuff is what doesn’t like the constant moving. Not about yield strenth, but work hardening that makes it brittle, then cracks,
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I used 5052-O/.049 on the brake lines from fuselage to caliper, std 3003 for everything else.
 
lr172 said:
Not my understanding. The soft annealed stuff, like 3003, is very far from yield strength when bending and can bend a LOT. This is the stuff Vans supplies and you can bend it back in forth in any direction. The more alloyed and hardened stuff is what doesn’t like the constant moving. Not about yield strenth, but work hardening that makes it brittle, then cracks,
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5052-O has far better fatigue life than 3003. Just because 3003 is "soft" doesn't mean its very good in cyclic loading applications.

Skylor
 
My rule of thumb is that if brakes are needed for taxiing, such as a strong crosswind with a swiveling nosewheel, to use the brakes intermittently. This can result, in effect, S-turns while taxiing, but it gives the brakes a chance to cool.
 
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