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  #11  
Old 08-14-2019, 02:50 PM
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snopercod snopercod is offline
 
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As an outside observer, I'd say that RVs really need a blast of air on their brakes. It would be easy to make a NACA vent on the centerline side of the pants where it wouldn't be visible. I understand that Cirrus's have had similar problems with brake fires. My Lancair brakes are out in the free air, yet I've measured disc temperatures of 700F after maximum braking.
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  #12  
Old 08-14-2019, 03:04 PM
WingsOnWheels WingsOnWheels is offline
 
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Quote:
Originally Posted by F1R View Post
Consider using braided SS over teflon all the way from the calipers to the master cylinders with the external return springs as posted a few weeks past. You can make your own or get TS flightlines to supply professional made lines.

Viton Orings in your caliper pistons and Royco 782 or Aeroshell fluid 31 will raise operating temp limits to over 400F.

Somebody recently posted about installing thermocouples on their brake calipers. Several EFIS and engine monitors have extra channels available that would allow you to monitor brake temps.

Thicker discs have more heat capacity and will not heat as rapidly. I am not sure what make your calipers and brakes are but Bruce hill posted his retro upgrade to thicker discs with his Matco brakes.
http://www.vansairforce.com/communit...d.php?t=172644
Thicker discs provide more braking ability with less fade as they do not heat up as rapidly.

Installing external return springs on your master cylinders at the foot pedals should prevent almost all dragging brake issues.
From Tom in Australia:
I would suggest collar part number 6157K13 instead. It is the clamping type rather than set-screw so it wont damage the shaft.
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  #13  
Old 08-14-2019, 05:18 PM
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Ironflight Ironflight is offline
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Quote:
Originally Posted by snopercod View Post
As an outside observer, I'd say that RVs really need a blast of air on their brakes. It would be easy to make a NACA vent on the centerline side of the pants where it wouldn't be visible. I understand that Cirrus's have had similar problems with brake fires. My Lancair brakes are out in the free air, yet I've measured disc temperatures of 700F after maximum braking.
Hmmmm....10,000+ flying and I hear of a couple of hot brake events per year - not sure that they REALLY need any kind of modifications!
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  #14  
Old 08-14-2019, 08:05 PM
tgmillso tgmillso is offline
 
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snip...
I can perhaps see NACA ducts as a solution to those with nose draggers who are doing long distance crosswind taxiing, but they're definitely not necessary for tailwheels with active steering. Performance of a NACA duct at these velocities would probably be questionable anyway, and to make them large enough to work at these speeds, they're going to be a good drag source at cruise.

If we look at the fires reported recently from brakes, they are predominantly from brake dragging (poor geometry/maintenance/no external springs) or people doing things like unnecessary "bedding in" the brakes under power. Both of these scenarios can be easily avoided.
I'm frankly more disturbed about this supposed requirement to have to disassemble my tailwheel fork every 25hrs to stop the pin sticking. Definitely need to engineer a solution for that one, but that's a whole other thread.

Tom.
RV-7

Last edited by DeltaRomeo : 08-15-2019 at 09:16 AM.
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  #15  
Old 08-15-2019, 09:49 AM
Check6 Check6 is offline
 
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Default Brakes

Having experienced hot brakes with the old plastic lines and doing a lot of formation long taxiing over the years best time and money spent was upgrading discs (good recent discussion here on VAF), using racing hoses from brakes to wing root (used sponsor here on VAF) and use Mobile 1 ATF fluid. Now some will say all this is overkill and I would never question Ironflight along with many others. For me it was peace of mind after it happening to me in a formation run up and seeing it happen to others in run up areas and short, hot landings. Find you a good tech counselor and you will find you will enjoy your RV even more as you repair your air machine.
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  #16  
Old Yesterday, 04:30 AM
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Looks like the brake line is broken not burned through. Perhaps it sprung a leak causing the brake fluid to make its way to the hot rotor or the piston o-ring was leaking. I am only guessing but perhaps the builder thought the bleed nipple should be on the top because they perceived that as being the high point to avoid air similar to car brakes although we bleed from the bottom up not top down.

Brake fires on our RV's are pretty rare and my guess is most of it is pilot braking technique. No need to stand on the brakes when landing, let the plane roll out and slow naturally. If you need to stand on the brakes you probably landed at too high an airspeed. Do not drag the brakes which is a perfect way to overheat them. If you are in situations where brake heating could be an issue such as long taxiing or extended formation taxiing perhaps go with a higher wet boiling point fluid.

Going with SS brake lines is a luxury but really not needed. There are thousands of RV's perfectly happy without them.

I would inspect everything to see what is salvageable. The caliper can easily be cleaned and rebuilt with a Viton o-ring (do both sides at the same time). Gear leg will need to be either repaired or replaced, it may be easier to just replace it. New brake line, you can splice in a fitting up inside the gear leg fairing. If the wheel pant is salvageable just repair it which will probably be easier than replacing it.
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  #17  
Old Yesterday, 08:55 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by tgmillso View Post
I'm frankly more disturbed about this supposed requirement to have to disassemble my tailwheel fork every 25hrs to stop the pin sticking. Definitely need to engineer a solution for that one, but that's a whole other thread.
In my opinion, "supposed" is the proper statement. Apparently based on a few opinions?
Unless being operated in very harsh conditions and/or a huge # of hrs per year, there is strong evidence that for most people, a good cleaning and inspection at the yearly condition inspection is adequate. Surely not more often that every 100 hrs. Which for most people would not be more than twice per year.....
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  #18  
Old Yesterday, 04:47 PM
tgmillso tgmillso is offline
 
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It's all good Scott, it's not your tailwheel. It's an aftermarket tail wheel that I installed because we have rabbits living on our airstrip and I was concerned that the stock tailwheel may drop down a rabbit hole and catch. After 60 flight hours I had the pin stick in the extended position, so I disassembled and found it full of grit and not much grease. I contacted the manufacturer to propose that I drilled/installed a grease zerk into the body of it so that I could always keep it pressurised with grease and expel any grit, and he said that I was better off doing 25hr disassembly/resulbrication. He said that this was a common procedure.
Seems a little crazy to me, so I contacted some other non RV tailwheel owners. None have these types of issues. One Kitfox owner I spoke with who operated in identical conditions has disassembled his tailwheel once in 1500hrs, but he as a grease zerk on it and always keeps it full of grease. He has the same locking pin setup to us, but a different bearing configuration.
As I said, it's worthy of another thread, I just hadn't got around to posting it yet. I'm just interested in the experience of others that are operating in similar conditions (grass/wet) and if someone has come up with a more ideal solution.
I'm sorry I didn't clarify that it was an aftermarket tailwheel earlier. I would say I have not experience with the Van's tailwheel assembly, however when I did my transition training with Mike Seager I positively sucked on the first day and had a tough time keeping things straight, especially on rollout. He told me the next day that he found the pin had stuck in the retracted position. I'm not sure if this is just a freak coincidence, as it was the first 3 hours I had ever spent in an RV, and here was the same issue. Mike operates off a similar stip to ours, but only 1 in 10 of our landings were at Veronia, the rest at sealed Scappoose. 95 percent of the landings I perform are on grass/dirt/gravel runways. I'm just looking for a solution to what will otherwise become one of the highest maintenance items on my entire aircraft. Perhaps Doug's going to chime in and tell me I should have built that RV-15 bush plane. I would, but I've decided to wait for the RV-16 electric version instead.

Tom.
RV-7

Last edited by tgmillso : Yesterday at 06:22 PM.
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  #19  
Old Yesterday, 07:18 PM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by tgmillso View Post
I'm sorry I didn't clarify that it was an aftermarket tailwheel earlier. I would say I have not experience with the Van's tailwheel assembly, however when I did my transition training with Mike Seager I positively sucked on the first day and had a tough time keeping things straight, especially on rollout. He told me the next day that he found the pin had stuck in the retracted position.
Mike is a true gentleman and diplomatic instructor.....he was probably just trying to make you feel better......
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  #20  
Old Yesterday, 07:50 PM
tgmillso tgmillso is offline
 
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Excellent point. He did seem like a good bloke. Im still not sold that weve got the ultimate configuration yet in terms of tailwheel maintenance in harsh conditions compared to our other taildragging counterparts. My quest for a solution will continue...
Tom.
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