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Installing Aeroquip fittings

mburch

Well Known Member
Patron
Hi folks,

I bought some Aeroquip 303 hose and fittings for same, to use in place of the plastic brake line in the cockpit of my RV-7. I also have the correct mandrels required to install the fittings. However, I'm having a little trouble with the assembly, in reference to the instructions in the ACS catalog or this copy here. I screw the hose into the socket, back it off a quarter turn, secure the socket and hose in my rubber-jawed vice, thread the mandrel into the nipple and tighten, and smear Lubriplate everywhere. So far so good. However, I often have trouble getting the mandrel/nipple combination far enough down into the hose for the threads to engage the socket, no matter how much pushing/twisting/threading I try. The instructions just say "screw nipple into socket and hose using wrench on assembly tool" like it was no big deal, which makes me thing I'm doing something obvious wrong. Is there a secret?

I'm just making practice hoses now; I'll take the real pressure-holding hoses to a hose shop for testing. I may have to have them make up the hoses for me too, but I'm hoping I can figure out the secret.

thanks,
mcb
 
Ted Farmin said:
Push hard, real hard and turn at the same time.

Yeah, I tried that first. :) I wonder if I am using too much lubricant or something...

mcb
 
If it were easy, everyone would do it!

I did all my hoses, and I hear ya, man. Getting some started was a bear, and others just went in. I did hoses from the -4's all the way up to -8's for my inverted oil system. The big boys are muscle builders.

I played with lubricant (didn't have Lubriplate) and found that the best was straight 40 weight Aeroshell oil. Cut the hose ends square, use some dykes to snip any fibers hanging off the outside edge then thread the collar on. Lube the daylights out of the inside of the hose, the mandrel, as well as the hose's B-nut that tightens onto the mandrel, to keep from stripping the threads. Put in the mandrel, and push push push while turning. It will start threading just when you're about to give up. Once started, I found that I had to use two wrenches, one on the B-nut and one on the mandrel to keep the two from slipping relative to each other. Halfway down, lube the exposed threads on the hose end, and keep going.

After you're done, remember to rig up some sort of pressure testing. At SnF, I talked to the Aeroquip guys who said that the proper practice was to test the hose to 1.5 times it's rated pressure to avoid any mishaps. So, I went to Northern Tool, and for $35 for a hand pressure pump which I filled with 5606 hydraulic fluid, tee'd in a pressure gage. I tested all to 3000psi. Overkill for a 100psi application? Definately, but the hose is rated for it, and I had the tools, all of which will deliver peace of mind. BTW, I did have one fuel line that did not leak below 300psi, but dripped quite a bit at 2000. I replaced the end gladly.

Have fun!

Art in Asheville
 
You could also go the route of getting aeroquip racing hose (TFE for brakes), and fittings.

These do not require the use of a mandrel, are rated for the appropriate pressures, and are less expensive. I buy them through Summit Racing or Pegasus racing.

Before all the purists jump on me, these hoses are rated for various pressures, temperatures, and fluids, and frankly their natural application is a whole lot more demanding than aircraft use.

YMMV, but I find them much easier to assemble than the traditional aircraft stuff, and hence easier to assemble properly.
 
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