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  #21  
Old 12-29-2019, 02:54 PM
BillL BillL is offline
 
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It sounds like a check of the master cylinder plunger return on the right side is in order along with the other unplanned restoration. Brake pads should wear relatively evenly, anything else means something else should be checked. If the pedal is sticking and fluid is not returning, then it is likely the brake (self) dragging added to the heat, may have been the last straw.

Good the "lesson" went no further. Catch me sometimes and I'll tell you about pressurizing a fuel line that had water frozen in it and the accidental ignition of an 18" flame shooting out of the (open) gas tank onto the garage wall. Funny how your mind can run a 1000 scenarios of the natural progression in a second. All's well that didn't burn down, or something like that . . .

So how do you stop the flame while preventing it from chasing back into the nearly empty gas tank??? All while the A/F in the tank is moving rapidly to the explosive regime? At a later time . . .
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Last edited by BillL : 12-29-2019 at 05:24 PM.
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  #22  
Old 12-29-2019, 03:26 PM
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snopercod snopercod is offline
 
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Quote:
Originally Posted by DanH View Post
Let's not get carried away here.
Who's carried away? I've read at least two threads here about brake fires on RVs and you want to dismiss it as pilot error? Whatever... On my Lancair, when I read about incidents related to the poor design - yes, there were several - I did something about it. The great thing about Experimental aircraft is that builders can do what thy think it prudent (peace sign).
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Last edited by snopercod : 12-29-2019 at 03:33 PM.
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  #23  
Old 12-29-2019, 05:30 PM
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F1Boss F1Boss is offline
 
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Default New brakes/break in procedure

1st, a brake pad break in procedure is not really needed on our RV machines if the system is up to spec on final assy. If you feel like such a procedure is warranted, do it without wheel pants in place. The fire will be much easier to put out.

I repeat: 1st, If you feel like such a break in procedure is warranted, do it without wheel pants in place.

2nd, if you are worried about the brake fluid catching fire because you want to disregard #1, use Dot 5 fluid (it will not burn) tho it will boil.

3rd Dot 5.1 is NOT Dot 5. Dot 5.1 can ignite. Do not mix these two.

Dot 5 cannot be used in (some of) the new brake systems with anti-skid, and Dot 5 cannot be mixed with any of the petroleum based fluids, including 5606.

Dot 5 will keep your O rings in good shape, as long as you don?t cook the system to max temps. Dot 5 will not hurt your paint if spilled or splattered.

To change to Dot 5, flush the empty system with Isopropol Alcohol and blow out with air before adding Dot 5 to the system. Best you also change the O rings at the same time.

If you have a brake problem ?on the road?, you can find Dot 5 fluid at any Wal-Mart, and the O rings at Home Depot (plumbing dept). That eliminates any searching for 5606 if you are stuck, tho Synth ATF will work fine (Wal-Mart again).

If I had a trike RV, I would dang sure use Dot 5.

Please go back and read #1.
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  #24  
Old 12-29-2019, 06:19 PM
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FORANE FORANE is online now
 
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Hmmm
Looking up flashpoints I find references:
Dot 5: >248 F, >252 F and one listed as 274 F
Royco 782: 445 F
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  #25  
Old 12-29-2019, 06:46 PM
McStevens McStevens is offline
 
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Quote:
Originally Posted by snopercod View Post
Who's carried away? I've read at least two threads here about brake fires on RVs and you want to dismiss it as pilot error? Whatever... On my Lancair, when I read about incidents related to the poor design - yes, there were several - I did something about it. The great thing about Experimental aircraft is that builders can do what thy think it prudent (peace sign).
I think the point was more along the lines of why put cooling fins on wheel pants when all of the heat is generated while stopping. Which kind of makes sense, to me at least.
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  #26  
Old 12-30-2019, 06:52 AM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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Wow. What a story. I can't recall ever been so engrossed by a VAF post.

I know everyone is pointing to aluminum brake lines but I can't figure out why if there was a puddle under the brakes before you replaced everything, there wouldn't have been a soft pedal AFTER you replaced everything when you were testing it. Clearly something was wrong beforehand.

Please keep us updated when you find the cause.

And thanks for the reminder to buy a larger fire extinguisher.
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  #27  
Old 12-30-2019, 07:45 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by snopercod View Post
Who's carried away? I've read at least two threads here about brake fires on RVs and you want to dismiss it as pilot error?
I dismiss the notion that cooling air scoops on the wheelpants would be useful. They would not improve braking power or safety margin during a typical single stop landing, nor prevent fire if dragging the brakes during taxi.

The reasons are fundamental. There is no significant dynamic pressure (a function of velocity squared) available at the relatively low RV braking speeds, and effectively none at taxi speed. As a result, mass flow would be limited. Even with mass flow, the little aircraft rotors don't incorporate any features to increase heat transfer by conduction...no fins or channels, and nothing to promote boundary layer turbulence. Laminar flow is ineffective for heat transfer.

Flowing air through the wheelpants would create aerodynamic drag in flight, when speed is high...and the brakes are cold.

Quote:
The great thing about Experimental aircraft is that builders can do what thy think it prudent (peace sign).
Sure. My own brakes incorporate polyalphaolefin-based fluid (the MIL-H-83282 Royco 782 noted earlier) to increase flash point, and viton o-rings to keep the fluid in the calipers at temperatures which turn standard nitrile o-rings to rocks. The o-ring change is primary, as again, most fluids are safe if retained in the caliper. The fluid change makes it less likely to ignite if it does get out.

I could probably still induce a fire if I dragged the brakes far enough under power. Even viton has limits.

Speaking of limits, the only downside to common viton o-rings is a reduction in sealing at low temperatures, one reason Cleveland doesn't make them standard. That said, there are specific compounds available with ratings in the -40F/-40C range, worth investigating if operating in the Arctic.
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  #28  
Old 12-30-2019, 11:01 AM
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snopercod snopercod is offline
 
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Quote:
Originally Posted by DanH View Post
I dismiss the notion that cooling air scoops on the wheelpants would be useful. They would not improve braking power or safety margin during a typical single stop landing, nor prevent fire if dragging the brakes during taxi.
Any you have the engineering data to back up that assertion?

A member the Lancair community (aerospace engineer) has actually instrumented his brakes and recorded the hard data on brake temperatures during taxi, landing, and rollout. I have his graphs here on my computer. So when I tell you that peak brake disc temperatures are over 700F on landing and 400F on rollout, I have data to back that up. Someone in your community should instrument his brakes and you could go from there.

Oh, and I've been running the Royco 782 for many years.
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  #29  
Old 12-30-2019, 11:03 AM
Mich48041 Mich48041 is offline
 
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At the local airport, a practical joker put a few drops of brake fluid on the hangar floor under someone else's aircraft brake.
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  #30  
Old 12-30-2019, 11:46 AM
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KatieB KatieB is offline
 
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Wow, I'm glad you are OK and your plane can be repaired! That was a great story, thank you for sharing it.
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