Re: KRnet> KR -2 brakes.

[Jeff Scott via KRnet]

FWIW, the 3/32" Nylaflow brake lines in my KR were 24 years old when I sold it.  In 24 years and 1400 hours, I never lost any fluid.  Never once had to add fluid to the brake system or bleed, which is highly unusual.  One caution is that one should switch to Aluminum or rated hydraulic line near the bottom of the gear leg if you have wheel pants.  A landing with hard braking or extended taxi with a bit of brake dragging will melt the nylaflow tube causing a brake failure.  I've seen this happen multiple times with the plastic lines inside of wheel fairings.

 

As stated below, the ferrules on the nylaflow lines work exactly the same as the water lines.  Incorrect seating will cause them to leak.

 

-Jeff Scott

Arkansas Ozarks

 

 

Sent: Thursday, July 21, 2022 at 3:41 AM
From: "Daniel Branstrom via KRnet" <krnet@list.krnet.org>
To: krnet@list.krnet.org
Cc: "Daniel Branstrom" <4dan.branst...@gmail.com>
Subject: Re: KRnet> KR -2 brakes.

Lulubelle, I don't have experience with plastic brake lines, but I have encountered leaks in plastic plumbing lines to appliances because I left too much plastic line beyond the ferrule. Tightening the nut doesn't stop the leak. That may be your problem. The extra tubing prevents the ferrule from seating all the way into the fitting, thus causing a leak.  You can see for yourself if it is seating properly into the fitting by just pushing it in without putting the nut on the tubing so you can observe what happens. If it doesn't seat all the way, that's the problem. The cure is to cut the tubing a bit shorter, so that it only sticks out ~1/8"

 In general, if you do continue to use plastic line, my opinion is that you should inspect it fairly often, at least during your annual inspection, because I've read reports of older plastic brake lines (installed years earlier) on experimental aircraft weakening and expanding over time. It is certified in plumbing for use with water and air, but I I don't know about long term contact with brake fluid that operates under high pressure. Some brake fluids may have some chemicals that aren't compatible for long term immersion in the tubing. Inspection will make sure it is still in good shape. The pressure in brake lines is far higher than what it would be in a water system.

On 7/20/2022 10:33 PM, Lulubelle Pitts via KRnet wrote:

It looks like this... In case you couldn't picture it...  And the reservoir is behind the seat.    - Scott.

 

On Wed, Jul 20, 2022, 9:34 PM Lulubelle Pitts via KRnet <krnet@list.krnet.org> wrote:

I'm having brake line leaks in the 1/8" plastic tubing, I think because the ferrels  won't seal the plastic ... any anyone else deal with this?   I'm thinking of replacing some of it with aluminum tube at the reservoir but I'll have to connect to the plastic down the line - I don't want to fish tube through to the wheels because I'd have to cut or drill ... don't want to do that.

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