Hi Chris, Thanks for the feedback. I wouldn't use DOT 5, but it is approved by some of the manufacturers, and I have seen it used successfully on a Long-eze. His concern was about flammability of MIL-5606, so he switched to DOT 5. As far as I know, he didn't have any issues, but I've lost track of the plane long ago now, so I was only able to track if for a couple of years after he switched.
This does bring up another point as long as we are talking about brakes, and that is the issue of the plastic based brake lines and brake heat. If you run the nylaflow/nyloseal/nylon/plastic brake lines all the way to the brakes, they may be exposed to a lot of heat, especially if you have wheel fairings as they interfere with brake cooling. I have seen two failures of the plastic brake lines due to brake heat. One was a simple rupture and loss of both brakes at low speed. The other was a rupture and ensuing fire causing complete destruction of the aircraft after the MIL-5606 fluid sprayed onto the hot brakes. I made a transition from from the soft brake lines to aluminum lines at the lower gear leg outside of the wheel pants. Others may have other solutions, but it is something to ponder when designing your brake lines. Best regards, -Jeff Scott > Sent: Wednesday, November 12, 2014 at 5:12 AM > From: "Chris Kinnaman via KRnet" <krnet at list.krnet.org> > To: krnet at list.krnet.org > Subject: Re: KR> Brake use of loctite Or teflon tape. > > I've never had good results with DOT-5 silicone-based brake fluid in any > ground vehicles. Maybe seals in A/C brake systems are compatible with > it, but in the (one each) motorcycle and car I used it in, the seals > dragged which in turn caused the pads to drag on the disks. Aircraft > brakes are not too good at "bouncing" the pads off the disks during > rotation, the way it works on ground vehicles, to begin with. The pedal > height / lever travel was inconsistent too, no doubt due to the pistons > in the master & slave cyls sitting in varying positions after letting > off pressure on the lever. When I used it the systems were flushed, > disassembled and dried before adding the DOT-5, so mixing of any amount > of DOT-3 and DOT-5 was not a factor. Likewise, when going back to DOT-3, > everything was flushed, disassembled, and dried. The seals were > undamaged and not replaced, and once DOT-3 was back in the system, > everything worked fine. This being said, I wouldn't use DOT-3 in an A/C > due to its eagerness to grab and retain moisture. > > Chris > > > On 11/11/2014 10:27 AM, Jeff Scott via KRnet wrote: > > If MIL-5606 Hydraulic is exceedingly expensive or difficult to get in > > Europe, DOT-5 Silicone based Brake Fluid is an acceptable replacement > > fluid. Just don't ever mix the two, and if you change from one to the > > other, the system has to be flushed clean. > > > > -Jeff Scott > > Los Alamos, NM
