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Captain Avgas

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

Regards,
Bob
 
rocketbob said:
I just went out in the hangar and checked, its Nyla-Seal.

Regards,
Bob
Click to expand...

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

Jerry
 
RV8Squaz said:
The leaky plastic tubing is used on the reservoir (non-pressure) side, according to the RV-8 plans.

Jerry
Click to expand...

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

Regards,
Bob
 
Which hoses

In answer to the very first post on hose ratings....

I thought folks were using the teflon auto racing hoses such as these pre-made ones from Pegasus and other race car suppliers...

Pre-Assembled Size 3 Braided Teflon Racing Hoses
If you need some of the common hose lengths, you can save yourself the bother of having to assemble them yourself by ordering our pre-assembled braided stainless Teflon hoses. The straight and 90 degree ends have 3AN female swivel fittings for easy installation and service (the banjo fittings do not swivel). These hoses use crimped (not reusable) hose end fittings. All hoses are proof tested to 3,000 psi.
http://www.pegasusautoracing.com/productselection.asp?Product=3

They are tested (not just rated) to 3000 psi.

These are the ones I'm going to use..... :)

gil in Tucson
 
One guy's experience

For what it's worth, I had the plastic brake lines between the passenger and pilot brake cylinders on my previous RV. On the 7 I'm building now, I had custom Aeroquip 303 hoses made to go between the two sets of cylinders. Having been through the hassle of making it work, I'd probably just use the Nyloseal lines per the plans on the next airplane.

good luck,
mcb
 
Brake lines

Gentlemen,
I gave up on the plastic line long ago-too many leaks and failures. I use braided stainless steel with Teflon internal tube. Good for high PSI (3000) applications and resistant to everything. The stainless is also resistant to chaffing and around the wheels, rocks and other debris that could damage your hose. PLUS the lines are flexible will not fatigue like alum lines will after time. You also will not have to mess with flaring tube. All of the fittings are AN and stainless steel and very easy to work with. I've never had to replace them and never had any leak. I use all #3 AN fittings and the stuff is great for all of the engine assy lines too, like for fuel press, oil press, manifold press, and fuel return lines. Call Jeff or Dave at Columbia Airmotive 1-503-665-4896 and they will hook you up. IF you know the fittings and line length they can also make the lines on their swaging machine for the brakes on the RV-4,6,7,8,9,10. I use all steel #3 AN fittings around the engine and brake calipers also. Good luck, Aden Rich.
 
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Hydraulic shoppe

Once again, same stuff or better but MUCH cheaper...Although I have not taken a brake hose to them as of yet.

Frank
 
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