B

bifft

Well Known Member
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.

IMG_4693.JPG


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:

IMG_4694.JPG


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.
 
bifft said:
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.
Click to expand...

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.
 
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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.
 
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.
 
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.
 
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.
 
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
 
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...
 
GUYS-----DONT mix and match different types of hose and hose ends. These assemblies are engineered to work together. Different style stems and liners generally are a bad marriage, and cause alot of grief. Even though they may pressure test, there are alot of things involved that could cause an issue later.
If youre going to build your own hoses, use matched hose and hose ends, and DO pressure test them!
Tom
 
GUYS---Dont mix an match different hose, with different fittings. They are engineered to be a matched assembly ( I see this all the time in industrial use.) The hose liner and stem need to be compatible, as well as the retention mechanism. Just because it may pressure test ok, there are other issues that may cause the assembly to fail. Best scenario, is to use matched manufacturers products of Mil-Spec rated parts.
Be careful!
Tom
 
Got the parts to pressure test, and the hose I made passed at 120lbs, which is as high as my air compressor goes. Thanks for all the help.
 
bifft said:
Got the parts to pressure test, and the hose I made passed at 120lbs, which is as high as my air compressor goes. Thanks for all the help.
Click to expand...

Your hoses need to be tested at much higher pressure. Take them to a hydraulics shop and they can test them at several hundred psi.
 
bifft said:
Got the parts to pressure test, and the hose I made passed at 120lbs, which is as high as my air compressor goes. Thanks for all the help.
Click to expand...

Take Sam Buchanan's advice and get your hoses properly pressure tested. But the test pressure he is recommending is way too low.

The hose you are using is presumably Aeroquip AE701-6. It has an operating pressure of 1000psi, a proof pressure of 3000psi, and a minimum burst pressure of 6000psi.

You want to have those hoses hydraulically pressure tested to at least 1500psi. Testing to 120 psi is useless. At any rate pneumatically pressure testing at ANY pressure is extremely dangerous (if a fitting comes off it can act as a projectile).

Some amateur hose fabricators think that they only need to pressure test their hoses to a pressure above the actual service pressure. That is totally incorrect. It needs to be tested to AT LEAST 150% of the manufacturer's rated operating pressure.

If you are not prepared to pay to have your hoses pressure tested at the correct hydraulic pressures, then I recommend that you do not make your own hoses at all. As you are discovering there are quite a few "tricks" to making good hoses and the uninitiated can really stuff them up (and not know they're stuffed). Of course, if they fail in the aircraft that can be disasterous in the worst possible way for you and possibly your passenger.
 
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Just playing devils advocate here, and I remain open minded on this, but what is the logic in testing to pressures far, far in excess of how the hoses will be used? My simple brain says that testing to their intended use pressures, plus a conservative safety factor (maybe 2-3x expected?)would be fine. What's the point in requiring something that is complete overkill? It doesn't necessarily translate to being a better hose or even longer life. Show me how this thinking is flawed.
Erich
 
@Erich, i'm guessing here but i'd say that the purpose is to show that you've assembled the hose to fitting connection properly. If you have it right, it'll take the proof pressures, and not self-disassemble, and you can be sure it will hold at whatever pressure you'll need under the cowl. But if you have assembled it wrong, it may or may not hold at a lower pressure... And you really don't know what pressure that will be or for how long it will hold... The safety factor may drop off rather quickly with only a slight decrease in quality of assembly.

That being said, when I used Aeroquip fittings and steel-braided hose to re-plumb my fuel lines for the Red Cube fuel-flow meter, I didn't have them pressure tested. As fuel runs at a max near 10psi, and the hose is rated for a working pressure 100x that, burst pressure 600 times that, I think it's a pretty safe bet. Maybe I was lucky, but I had no issues with the assembly, the hose didn't want to back out as I tightened the fittings, and i've had no leaks since.

Oil pressure runs around a max of 100psi, only 1/10th the operating pressure of the hose. That's a lot closer to limits than the fuel lines, so I can see that pressure testing is a reasonable suggestion.
 
erich weaver said:
what is the logic in testing to pressures far, far in excess of how the hoses will be used? .
Erich
Click to expand...

Without going into a whole lot of technical details I think that fuel and oil hoses are such critical components that, if fabricating them yourself, it would be best to do what the professionals do, rather than doing what the amateurs do.

All professional aviation hose assemblers hydrostatically pressure test each assembly to the pressure as recommended by the hose/fitting manufacturer. This pressure can vary but is typically about twice the Operating Pressure. Incidentally the "Operating Pressure" of the hose is the maximum continuous operating pressure as stipulated by the manufacturer. It is not the actual service pressure which of course might be far less.

Testing to these pressures ensures that the hose has no defects and that the end fittings are properly engaged. Typically the test pressure is held for about 30 seconds. If the pressure drops it may be an indication that the end fittings are slipping.

Incidentally, in actual service, constant flexing under normal operations can cause a poorly fitted end fitting to fail, even at very low pressures. Testing to higher pressure improves the chances of detecting such a fault.

As for not testing home-built hoses at all.....well that's just plain crazy. :eek:
 
Captain Avgas said:
Take Sam Buchanan's advice and get your hoses properly pressure tested. But the test pressure he is recommending is way too low.

The hose you are using is presumably Aeroquip AE701-6. It has an operating pressure of 1000psi, a proof pressure of 3000psi, and a minimum burst pressure of 6000psi.

You want to have those hoses hydraulically pressure tested to at least 1500psi. Testing to 120 psi is useless. At any rate pneumatically pressure testing at ANY pressure is extremely dangerous (if a fitting comes off it can act as a projectile).

Some amateur hose fabricators think that they only need to pressure test their hoses to a pressure above the actual service pressure. That is totally incorrect. It needs to be tested to AT LEAST 150% of the manufacturer's rated operating pressure.

If you are not prepared to pay to have your hoses pressure tested at the correct hydraulic pressures, then I recommend that you do not make your own hoses at all. As you are discovering there are quite a few "tricks" to making good hoses and the uninitiated can really stuff them up (and not know they're stuffed). Of course, if they fail in the aircraft that can be disasterous in the worst possible way for you and possibly your passenger.
Click to expand...

Bob nailed it: if you can't do it right, then let someone else who is qualified and has the necessary equipment do it for you. I'm a big believer in letting "specialist" do what they do best.
 
Walt said:
Bob nailed it: if you can't do it right, then let someone else who is qualified and has the necessary equipment do it for you. I'm a big believer in letting "specialist" do what they do best.
Click to expand...

And if all this fabrication and testing stuff sounds too complicated....just buy commercially manufactured hoses. They are readily available at reasonable prices. :)
 
Hoses

Your hoses are too important to do yourself. Get Tom at TS Flight Lines to make them up for you!! :eek::)
 
Get them from Tom!

My .02..
I just ordered hoses from Tom.. I watched the video on the EAA website on putting together hoses.. looks easy peasy right? I priced hoses on all the auto racing sites.. nitrile rubber over stainless braid.. they are about $7 or $8/foot and straight fittings are about $8 each or so. Not exactly the stuff you find at Spruce for $15/foot but close and made by Aeroquip. All the posts on here about non-aviation teflon hose without the conducive liner swayed me away from the teflon auto racing hose. I tried to source some Parker 919b hose from industrial suppliers based on some posts I have read on here (teflon with liner and stainless braid) and finally found some and price would be about $10/foot and each fitting (straight) being about $10/each and they didn't pressure test the completed hose. Found that Tom's prices to be right in line with building them yourself.. except a professional does it and pressure tests and mails them to you the same day or next day.. no brainer for me. Go with Tom.
 
Erich---
I go by the rated working pressure of the hose, not by what you are going to use it for. A hose may be ok at 30 psi, but come apart at 100.
Tom
 
What happened?

The OP wanted to know how to properly assemble a hose, something hundreds of us have done on hundreds of Experimental airplanes.
Suddenly the hoses are too important of a component to do yourself?
Isn't the wing kind of important too and for that matter the elevators and trim tabs? Some of course have those items built by professionals too.
As for price, I am quite aware that custom built hoses are almost the same price as those that you can build yourself.
I am certainly in favor of doing hoses properly and testing them, but talking someone out of making his own is simply "un experimental".:(
 
Ernst, as far as I'm concerned, ALL components of an airplane are important. And, alot of guys are perfectly capable of assembling their own hoses from either 303 or 701 series hose, with the appropriate hose ends. Most guys, do not have the proper equipment to CRIMP teflon hose, which is what I do. There are reusables for teflon, and with care CAN be assembled in a home shop environment, just like 303 or 701.
My point was to pressure test them to a sufficient enough pressure to assure a reliable assembly. Some guys do, some guys dont. I have seen all sorts of hoses on experimentals, and not just RV's. I've seen pictures of your hoses, and they are great. But--I have seen clear hose from the aviation aisle at the Blue Home Improvement Store on oil coolers. I have seen push lock hose on oil coolers. I have seen these on planes that were FLYING, not just a mock-up. How they got past an inspection concerns me.
Alot of guys on this forum fab their own hoses. They chose to do their own, but were alittle apprenhensive, and thats ok. For some, it was a easy as building a fuel tank. The idea is safety.
Tom
 
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