Correct brake hose types

Captain Avgas · #1 10-15-2006, 04:46 AM

A good number of builders who have been unhappy with the leaky plastic tubing and fittings that Vans supplies for the brake lines have opted to use Aeroquip 601/AE701 stainless steel braided hose instead.

However it is my understanding that although cheaper and lighter, 601/AE701 is not recommended for hydraulic lines due to its low pressure capacity (1000 psi). The two hoses that Vans supplies that travel from the pilot pedals master cylinders to the firewall are both Aeroquip 303 (3000 psi). Given that 303 is more expensive (and heavier) than 601/AE701, and given that Vans are penny pinchers, it doesn't seem to me that they would opt for 303 when 601/AW701 would do the trick.

So why are builders using 601/AE701. Is there engineering evidence to suggest that 1000 psi is a satisfactory hose pressure for this application...or is this just another case in the RV world of the blind leading the blind.

rocketbob · #2 10-15-2006, 05:50 AM

We have several local RV's and Rockets flying with Nylaflow plastic hose throughout the entire brake system with thousands of hours between them with zero problems. Last year three of us measured pressure at the brake caliper with a pressure gauge, just to see what kind of pressures are actually at the caliper. If you stand extremely hard on the brakes (harder than one would ever do in the real world), there is about 500psi in the system. Typical hard brake pressures are around 300psi. Nylaflow is rated at 1000psi so there is a 2X safety margin over the worst possible pressure scenario.

Regards,
Bob

rocketbob · #3 10-15-2006, 06:04 AM

Actually clear Nylaflow is good for 1500psi, not 1000psi as I misstated in my previous post.

Regards,
Bob

Captain Avgas · #4 10-15-2006, 06:51 AM

Quote:

Originally Posted by rocketbob

Actually clear Nylaflow is good for 1500psi, not 1000psi as I misstated in my previous post.

Regards,
Bob

Bob, I looked up the ACS catalogue at http://www.aircraftspruce.com/menus/ap/tubing.html

Nylaflow sems to be rated at 1000 psi. Nylo-seal NNR is rated at 1500 psi. What specific product are you referring to and specifically what associated fittings are you referring to.

rocketbob · #5 10-15-2006, 10:12 AM

I just went out in the hangar and checked, its Nyla-Seal.

Regards,
Bob

Captain Avgas · #6 10-15-2006, 07:37 PM

Quote:

Originally Posted by rocketbob

I just went out in the hangar and checked, its Nyla-Seal.

Regards,
Bob

A google search on Nyla-Seal hose does not seem to reveal any such hose product. Can you refer me to a website that supplies this product and do you have a part number. And can you advise me specifically what fittings you used to attach the hose to the master brake cylinders.

The problem with this area is that an archive search reveals that builders are calling their hose by many names, some of which don't even exist. Nylaflow, Nyloflow, Nylaseal, Nyloseal, Polyflow, Parflex...it goes on and on....very confusing.

RV8Squaz · #7 10-15-2006, 08:21 PM

The leaky plastic tubing is used on the reservoir (non-pressure) side, according to the RV-8 plans.

Jerry

Captain Avgas · #8 10-16-2006, 04:47 AM

Quote:

Originally Posted by RV8Squaz

The leaky plastic tubing is used on the reservoir (non-pressure) side, according to the RV-8 plans.

Jerry

But if you have brake cylinders on the passenger side then the Vans plans call for the "leaky" plastic hoses to travel from the cylinders on the passenger side to the cylinders on the pilot's side (that's a pressure situation).

rocketbob · #9 10-16-2006, 06:29 AM

Boy you can't find good help anymore. Its spelled nylo-seal.

Tube (3/16):
http://www.aircraftspruce.com/catalo...s/nyloseal.php

Brass Fittings:
http://www.aircraftspruce.com/catalo...lofittings.php

Regards,
Bob

rocketbob · #10 10-16-2006, 06:31 AM

BTW, there are certified aircraft that use plastic brake lines. Take a look at an Extra 300, it has plastic lines throughout.

Regards,
Bob