| Author |
Message |
    
Jay Villalva
New member
Username: Jay
Post Number: 19
Registered: 11-1999
| | Posted on Sunday, February 05, 2012 - 03:34 pm: | |
We experienced a hot brake issue that caused a brake fire in an RV-8. The pilot taxied from the hangar at the South end of the field (PWT) to the North end for take-off. The pilot didn’t realize the brakes were dragging, the heat produced caused the o-ring to fail and the leaking hydraulic fluid (MIL-5606) caught fire. We replaced the hydraulic fluid with a synthetic and replaced the o-rings with a higher temperature material (the rudder pedals were also modified to make it more obvious if the pilot's feet were on the brakes). The type of o-ring material to use for higher temperatures is Viton. The fluid for a higher flash point (which is also compatible with MIL-5606) is Royco Synthetic 782. Something to consider in combating your heat issue. I have included some reference links.
http://www.marcorubber.com/viton.htm
http://www.marcorubber.com/materialguide.htm
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Louie Lacy
New member
Username: Llacy
Post Number: 107
Registered: 10-1999
| | Posted on Sunday, November 04, 2012 - 02:15 pm: | |
Has anyone used the Viton O Rings in their brakes and did they work. I have to replace the o rings in my Cleveland Brakes(wish I had never bought Clevelands) about once a year. |
Jimmie Kevin Alderman
New member
Username: Vikingpilot
Post Number: 11
Registered: 07-2011
| | Posted on Sunday, November 04, 2012 - 05:24 pm: | |
I had Clevelands on my Viking and wore out 2 sets of tires and over 300 landings, with no problems with the brakes and no rebuilds. I have them on my wheeler now- but she isn't flying yet. The viking is a retractable i.e. no wheel pants- so is it the heat that is the issue?
As far as viton o-rings, we sometimes used viton seals in hydraulic systems in our construction equipment, but rarely. How are your seals failing- leaks, etc?
We use viton seals in our oxygen tanks because they do not burn and are basically inert to help reduce the risk of explosion, and they are more heat resistant than neoprene or rubber. I would assume they would help guard against failure due to excessive heat, but would think finding a way to cool the brakes would be a better option. |
Al Kittleson
New member
Username: Al38kit
Post Number: 59
Registered: 07-2007
| | Posted on Sunday, November 04, 2012 - 06:21 pm: | |
I kind of looks to me that the answer is to not keep your feet on the pedals, and ensure you don't have a dragging brake...Lou ,what don't you like about Clevelands?...I've got a set of Matcos I don't plan to use... |
ali moghaddas
New member
Username: Amoghadd
Post Number: 36
Registered: 09-2003
| | Posted on Sunday, November 04, 2012 - 09:51 pm: | |
I installed the brakes from "Grove" & are very happy with them. As I understand they are similar to Cleveland's & are cheaper. |
Reinhard Metz
New member
Username: Reinhard_metz
Post Number: 96
Registered: 03-2003
| | Posted on Monday, November 05, 2012 - 07:22 am: | |
I have Cleveland brakes as well and have had the same over heating problem, and have had to replace the o-rings several time. One time, after a super long taxi at Milwaukee General Mitchel, the brakes leaked out all the fluid on the ramp, due to the over-heat flattened o-rings, and I had to leave the plane there, and come back, re-build and bleed right there on the tarmac!
In case you think this is an Express anomaly or pilot problem, it is not. Cirrus has been fighting this problem for some time, including several fires and lawsuits and ADs. This is caused by the tight fit of the wheel pants, and is also testimony to the poor Cleveland design, and undoubtably the legal and cost environment overshadowing any notions of an improved design. Cirrus changed their o-ring material, but unfortunately, you can't get any info as to what they chose - they just have a new part number.
Underlying this is the woefull inadequacy of nitrile/Buna-N as the o-ring material. Having gotten tired of this, I did some research on materials and just recently changed my o-rings to Viton 75, from oringusa.com. I also replaced the brake fluid with synthetic DOT 5 silicone fluid. So far, so good, but have only had the change since the last annual. I also used a far more effective bleeding process this time - the Express brake bleed can be daunting - I drew a vacuum on the brake fluid reservoir, which drew all the air out of the lines. Most firm brakes I've had to date. |
Ben Baltrusaitis
New member
Username: Freepistol
Post Number: 34
Registered: 09-2005
| | Posted on Monday, November 05, 2012 - 07:38 am: | |
Great tip, Reinhard, drawing a vacuum on the reservoir! |
Al Kittleson
New member
Username: Al38kit
Post Number: 60
Registered: 07-2007
| | Posted on Monday, November 05, 2012 - 08:46 am: | |
Reinhard...great tip. I think you're missing an "s" in the url....
http://oringsusa.com/
Any chance you have the part numbers? I take it you changed o-rings in both the brake pucks and the master cyls?
I've had the best luck with filling systems from the bottom up using a pump on the brake...blow it up or suck it up, I guess it doesn't matter...! |
Reinhard Metz
New member
Username: Reinhard_metz
Post Number: 97
Registered: 03-2003
| | Posted on Monday, November 05, 2012 - 11:12 am: | |
Yes, thanks for the correction on the URL.
The ones I bought are Viton 75 brown,
http://www.oringsusa.com/catalog/product_info.php?cPath=26_122_101&products_id=1 01001700
I changed only the rings in the brake pucks, not the master cylinders, as my research said silicone synthetic fluid was compatible with Nitrile/Buna-N. If that turns out to be wrong, then I will have some more work to do!
Though it may be tempting to use silicone o-rings, given their temperature capability, they are truly not compatible with synthetic/silicone fluids - they swell up pretty badly.
When you take apart those expensive "aviation quality, certified" Cleveland brakes, it is a real disappointment how simple and crude they are, leading to some of the problems - poor tolerance - piston to bore fit not tight enough - single rather than dual o-rings, mounting bolts squish the aluminum housing, causing them to get stuck. Ripe for an improved design, but probably impossible to introduce. |
Louie Lacy
New member
Username: Llacy
Post Number: 113
Registered: 10-1999
| | Posted on Saturday, January 12, 2013 - 05:55 pm: | |
Has anyone replaced the bronze bushing in the nose gear. Mine seem to be worn so would like to replace them.
Lou |
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