Hose assembly woes.

bifft · #1 12-16-2012, 04:55 PM

Trying to build my own, using the parts provided by Van's. I can't seem to keep the host from backing out of the fitting when screwing it together. Tried three times so far, it always backs out around 1/16" or so.

Also, it gets about as far as shown in that picture, than gets really hard to screw in. I went ahead and forced one, trying to see if I could get to the minimum 0.031" gap specified by aeroquip:

This is as far as I could get it to go, pushing the wrenches as hard as I could (shouldn't work when angry). I'm not a small man, so this was probably into 100's of in/lbs. It slipped at this point, causing the damage shown. Still a gap of .064.

The online videos make it look so easy, with just "make sure hose does not push out of socket". I did make sure that no oil went between the cutter and the inner tube section as shown here:

http://www.sacskyranch.com/hosemistakes.htm

Any other hints?

On the plus side, the hose does seem to fit where I want it, so I at least got the length right.

Sam Buchanan · #2 12-16-2012, 06:02 PM

Quote:

Originally Posted by bifft

Trying to build my own, using the parts provided by Van's. I can't seem to keep the host from backing out of the fitting when screwing it together. Tried three times so far, it always backs out around 1/16" or so.

Also, it gets about as far as shown in that picture, than gets really hard to screw in. I went ahead and forced one, trying to see if I could get to the minimum 0.031" gap specified by aeroquip:

This is as far as I could get it to go, pushing the wrenches as hard as I could (shouldn't work when angry). I'm not a small man, so this was probably into 100's of in/lbs. It slipped at this point, causing the damage shown. Still a gap of .064.

The online videos make it look so easy, with just "make sure hose does not push out of socket". I did make sure that no oil went between the cutter and the inner tube section as shown here:

http://www.sacskyranch.com/hosemistakes.htm

Any other hints?

On the plus side, the hose does seem to fit where I want it, so I at least got the length right.

Here is the way I assemble stainless Aeroquip hoses, you can decide whether or not you want to use this method. I've built several hoses that have been in service on my RV-6 for 13 years (hoses were replaced at seven years).

I dip the end of the hose in STP oil treatment prior to inserting it in the fitting. The mandrel will screw into the fitting with only moderate effort and the hose doesn't get pushed out of the fitting. An A&P told me about using STP, that stuff is unbelievably slippery. My hoses have always passed the pressure test and have never had any service problems.

Bushcaddy · #3 12-16-2012, 06:21 PM

You should also be using a vice to hold the end of the fitting that you don't want to move. Using two wrenches is not a good idea...the end of the hose has to be completely immobile.

aerhed · #4 12-16-2012, 06:48 PM

I use DC4 on the ferrule instead of STP ( because I have it). Try it with a fresh hose end, lube, and don't bottom the hose too tight to start.

Kahuna · #5 12-16-2012, 07:10 PM

Let me see if I can't run down Tom at TS Flightlines. Since he does this for a living, he should be able to help. I made my own 303 hose assemblies for years on several planes. After seeing how the pros do it, I have turned over my needs to Tom.

bifft · #6 12-16-2012, 07:17 PM

Thanks, just tried dipping the hose in the oil (don't have STP), used the same munged up end I already had, it seems to have made the difference.

Also put it in the vice, after replacing the hardwood jaws with the steel ones. The hardwood doesn't mark the fitting, but it does allow it to turn (had already tried that before). Will try folding some sheet al as a spacer before working with a new end.

TS Flightlines · #7 12-16-2012, 07:20 PM

Biff---what you are seeing is the 'cutter' part of the fitting stem actually cutting into the liner of the hose. You should lube the hose very well, so the cutter can do its job. And Yes, you need to have about a .030 gap between the hex on the stem, and the collar on the hose.
Too large a gap ( or not tight enough) will not allow enough retention between the stem taper, the hose liner, and the collar, and the possibility of a failure exists. Recheck it, slow down. DO pressure check the assembly.
Tom

vjdslk · #8 12-16-2012, 08:27 PM

Vise jaw inserts. They will make life much easier and not mark up your fittings.

http://www.summitracing.com/parts/aer-fcm3661/overview/

Sam Buchanan · #9 12-16-2012, 08:45 PM

Quote:

Originally Posted by vjdslk

Vise jaw inserts. They will make life much easier and not mark up your fittings.

http://www.summitracing.com/parts/aer-fcm3661/overview/

The Summit vice jaws are slick and I should buy a set. But I use two pieces of aluminum angle over the vice jaws and they work ok.

RWoodard · #10 12-16-2012, 10:59 PM

I made up a bunch of Aeroquip hoses last year and have to agree that the vice jaw inserts made all the difference in the world.

As an aside, I would caution anyone making hoses to make sure the fitting is compatible with your specific choice of hose. I used Aeroquip "aerolite" hose with a combination of Earl's fittings and Aeroquip fittings. After the second hose failure, subsequent loss of oil and second engine-out landing, I came to the conclusion that one of the fittings was cutting the lighter-weight hose. I dutifully pressure tested the second set of hoses and they passed with flying colors. Still failed.

I threw everything away and started over with new stainless braided hose and new Aeroquip only fittings, and haven't had any problems since.

FWIW...