cln1owner

cln1owner

Well Known Member
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.
201012191430_54_2_m.jpg


201012191430_54_0_m.jpg


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.

201012191430_54_1_m.jpg


Anybody else seen this? Suggestions for a better style fitting?
 
No Mandrel for 816

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?
 
T6pilot said:
This is a very common problem if a mandrel isn't used to assemble various hoses.[/url]
Good luck.
Click to expand...

szicree said:
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?
Click to expand...

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.
 
good thing---

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
 
fittings

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.
 
Me too

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.
 
Not too much oil!

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
 
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. :p
 
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.



cln1owner said:
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.
201012191430_54_2_m.jpg


201012191430_54_0_m.jpg


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.

201012191430_54_1_m.jpg


Anybody else seen this? Suggestions for a better style fitting?
Click to expand...
 
How does the tube looks when you remove the fitting?

Nate,

how does the tube looks like when you remove the fitting?

Did you see a concentric "cut ring" or is the "cut ring" out of center?

I have a tube where I removed the fittings in the shop, there you see the cut ring really good. I try to make a picture and post them here.

Can you post a picture of the tube also where you removed the fitting?

Thanks, Dominik
 
N395V said:
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.
Click to expand...

This was the fifth hose of the bunch I had assembled. Two -4 hoses for the brake lines and two other 3/8 hoses. I inspected them very closely after assembly. No signs of problems. The problem hose was on one end, and after comparing this fitting with the rest, the only difference was the loose/rotating nipple. The cutting camphered edge did cut into the hose, like the other end. There was no rubber remaining in the cut groove prior to the second try.

I can handle constructive criticism, thats why I posted, and why I ask questions. My only direction was the little instruction I could find on the net.. EAA video, Koul Tool video, but like you said, it's pretty straight forward.
 
swisseagle said:
Nate,

how does the tube looks like when you remove the fitting?

Did you see a concentric "cut ring" or is the "cut ring" out of center?

I have a tube where I removed the fittings in the shop, there you see the cut ring really good. I try to make a picture and post them here.

Can you post a picture of the tube also where you removed the fitting?

Thanks, Dominik
Click to expand...

Dominik,

I'll take a closer look after work today, and post a photo.
 
Recreation and Education

True, it's not a place to save a few bucks, but neither is the rest of the build. If a guy wants to learn I say let him learn. I found the following link that contains a nice picture at the bootom of the page showing what goes wrong when too much lube is used. The lube prevents the cutter from cutting and instead the hose gets smooshed back. I can see where this would create a bulge that would narrow the I.D., thus causing the inner nipple to cut the hose. Just some additional info that might help. In any case, have em pressure tested.

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

Hi Nate

Look at Steve's link, they show exactly what I meant. Hydro-Lock cause the rubber push-back, so the "ring-cutting" cannot happen propperly and it will leak.

Enclose is a photo of mine tube end after taking the nipple off. Have a look at yours, inspect the inner cuted ring. It should have even thickness and a smooth surface.
Tube.jpg

Do not reuse the hose, cut off and do it again (if long enough)

Oil only the thred and the inner tube very sparingly.

Go to a hydraulic shop, let show you how it works, let yours pressure tested before any use in an airplane.

Hope it helps,

regards, Dominik
 
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One thing that the Koul tool stresses is rotating the hose as you install it on the fitting, and lubrication, of course. I didn't have any problem installing it with the tool, though the hose ended up being too short for my infamous attempt to install a fuel line on a vertical updraft, A model IO-360 without hitting an engine mount tube. But that's another story. Anyway, Alex Peterson came over with his neat testing equipment and the hoses tested fine.

I'm rebuilding now. I'm assuming I can't reuse these fittings once installed.

By the way, the note that isn't a place to save money is an interesting one. I occasionally wonder what it would be like if Tony Bingelis were still alive and stopping by here occasionally. (g)

Anyway, would be interested in an update from you on how this turned out for you.
 
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Bob Collins said:
Anyway, would be interested in an update from you on how this turned out for you.
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TS Flightlines said:
lets us know how you are doing with your hoses. There is alot of help here for you.
Click to expand...

Sorry I haven't updated my status. I'm certain that the loose nipple in this one fitting is enough to cause problems. I made two hoses using these fittings. The other fitting worked both times... this "spinning" fitting failed both times. The plan is to order new fittings and hose to redo. (I have to order two because when I disassembled the last failed hose assembly, the good fitting retained rubber between the cutter and the nipple. With the -6 fittings the two are so close together, I can't get the material out, even with a few dental tools I've collected over the years.) I'm just waiting to get a few more items to add to the order. Meanwhile I've had some distractions... Stein sent me a bunch of stuff and it's WAY more fun than hoses. :D

I'll post an update as soon I've got the new fittings.
 
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Wow, it's hard to believe that it's been almost a year since I ran into this issue. I did get replacement fittings shortly after my last post, however other build items have kept me distracted.

I finally got back to the fuel lines, and the new fittings worked great.
 
jrs14855 said:
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.
Click to expand...

I agree but, I close down and then back off 1/2 turn, just to make sure you are not collapsing the hose.
 
cleaning hoses

Here is the method I have used:
Obtain a small diameter brush used for cleaning coffeee makers etc. A google search will turn up hundreds of these. I use some heavy rubber gloves, very hot water and dish soap. Scrub the inside of the hose with the brush with soap and water, then rinse with hot water and brush some more. I put the hoses in the oven at around 200 degrees to bake out any water. Inspect by looking thru the hose at a strong light.
 
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