AeroQuip Fittings Frustration

cln1owner · #1 12-19-2010, 03:05 PM

Spent some time this weekend building hoses and ran across a problem that I think may have been caused by a faulty fitting. I thought I would post in case others may have different suggestions as to the cause.

Fittings and hose came from Vans, so the hose is aeroquip 701. The fitting in question is an 816-6d (3/8)

Here's a couple of shots of what happens. As you can see the nipple is cutting the inside of the hose as the fitting is threaded together.

I thought it may have been my technique, so I build a new hose. Same result. After pulling the second hose apart and comparing fittings I found that the nipple of the fitting rotates freely.

Anybody else seen this? Suggestions for a better style fitting?

T6pilot · #2 12-19-2010, 03:37 PM

This is a very common problem if a mandrel isn't used to assemble various hoses. Check with Aircraft Spruce here http://www.aircraftspruce.com/search/search.php
Good luck.

szicree · #3 12-19-2010, 04:14 PM

I don't think there is a mandrel for this fitting/hose combination. I did mine and did not have this problem. Are you lubing things up a little before assembly?

cln1owner · #4 12-19-2010, 04:25 PM

Quote:

Originally Posted by T6pilot

This is a very common problem if a mandrel isn't used to assemble various hoses.[/url]
Good luck.

Quote:

Originally Posted by szicree

I don't think there is a mandrel for this fitting/hose combination. I did mine and did not have this problem. Are you lubing things up a little before assembly?

I also thought that the 816 fittings didn't require a mandrel. The mandrels on ACS refer to the 491 fitttings.

I lubed up the threads on all the previous hoses I made... when I reassembled this hose I lubed the hose, threads and nipple. Still the same result.

TS Flightlines · #5 12-19-2010, 05:57 PM

you caught this before you put it on the plane. 1--it would have leaked, 2- it would probably have separated once the pressure came up--even at low fuel pressures. These cutter type fittings can give problems, so careful assembly techniques are needed.
Tom

jrs14855 · #6 12-19-2010, 06:43 PM

This type fitting does not require a mandrel. You probably force the hose too far into the fitting, thus closing up the id of the hose and causing the tapered part to cut th id of the hose. You should be able to feel when the end of hose contacts the bottom of the bore. Stop at that point, maybe even back off the hose 1/8 turn or less. The tapered portion of the nut assenbly should slide easily into the id of the hose. I use lubriplate as it is less messy than oil or other lubricants. Mark the hose will some tape to verify that the hose does not pull out during assembly.

panhandler1956 · #7 12-19-2010, 07:11 PM

I noticed this when I built my oil lines, but I assumed this is how the fitting engages the hose for a positive fit. Mine are tight and I used lots of oil in the assembly process. I hope this isn't an issue, I followed the method described on the eaa.org homebuilder hints video on Aeroquip 816 fittings.

swisseagle · #8 12-20-2010, 01:39 PM

Just use oil on the thread and only a very light coat on the nipple. If you apply too much oil, it will flow into the slot between the nipple and the thread and "close" it. This will block the rubber from beeing cut and pushed into the slot.

I do not remeber that the nipple is turning freely, this is suspect to me. If it does turn, it will not cut propper into the rubber. But I'm not in the shop so I can not check that.

Hope someone know it.

Regards, Dominik

JDanno · #9 12-20-2010, 02:07 PM

I was told by my A&P to ALWAYS run a rag through the hose after its been assembled because there will be some of the sidewall shaved off. I was a nonbeliever until I actual made one and noticed that they all had shavings in them. Was he ever right.

N395V · #10 12-20-2010, 02:36 PM

Is this your first time building hoses? If so how did you learn to build them? Reading, videos, someone teach you?

From your photo it appears you truly are slicing into the ID of the hose creating flaps and you are fortunate they were bad enough to see.

This can be a deadly problem in that a more subtle cut of the tubing ID might go un noticed and turn into a fuel obstructing flap during flight.

It is not my intent to criticize you but it is my experience that this problem is almost always operator induced and almost never a hardware problem.

Putting these ends on is fairly straight forward and without problem if done so correctly. If these are your first hose ends I would seek out the help "in person" of someone who has done it before and do several with them present. If you have already made several hoses for your plane I would closely inspect them all for less than obvious cuts in the in the lining.

Quote:

Originally Posted by cln1owner

Spent some time this weekend building hoses and ran across a problem that I think may have been caused by a faulty fitting. I thought I would post in case others may have different suggestions as to the cause.

Fittings and hose came from Vans, so the hose is aeroquip 701. The fitting in question is an 816-6d (3/8)

Here's a couple of shots of what happens. As you can see the nipple is cutting the inside of the hose as the fitting is threaded together.

I thought it may have been my technique, so I build a new hose. Same result. After pulling the second hose apart and comparing fittings I found that the nipple of the fitting rotates freely.

Anybody else seen this? Suggestions for a better style fitting?