Brake questions from my hangar.

[SHIPCHIEF]

If you are enlarging the pipe thread in a closed bottom hole, you can do it by carefully grinding off the end of the pipe tap. Then tap a little deeper until it bottoms out. Then grind off a little more of the end of the tap and do it again until your fitting can fit properly.

[bret]

With the NPT I remember this being a pain to get the correct TQ and have the fitting pointed in the correct direction. I erred on the tight side for no leaks, one more turn errrr Come on!

[sblack]

It sounds very much like a thread issue. You don't need to be out of tolerance on a tapered thread to have it go too deep or not deep enough. The NPT fittings from Summit Racing are very popular because they are from China and are way cheaper, but I bought some for my oil cooler lines and the 90 deg ones only went 1 1/2 turns into the acc. case. They were a few thousanths too big in dia. If you had a fitting that was a few thou too small you would bottom out and it would never seal. I don't know if that is your problem, but that is where I would look. If threads are damaged that is a sign that something went wrong. NPT threads in good shape with sealant don't leak. If yours do the threads are damaged or not well formed etc. Try different fittings, try cleaning up the threads very carefully with an NPT tap, make sure you are not bottoming out. It could also be that the thread is poorly formed in the cylinder so it goes too deep.Those are the things I would look for.

If that doesn't work buy new cylinder bodies. You need clean undamaged threads and good fittings and you should have no problems.

[AndyRV7]

Thanks Scott.

Maybe I need to take a step back and understand better what I am doing. I struggled with the appropriate tightness of the fittings the last time I did this. They may have been too loose because I was afraid to try to go past the proper final direction and still be able to get a full turn more out of them without stripping something. It sounds like you want more than a couple threads of depth but not so many that the fitting bottoms in the threaded portion of the bore. Is this correct? Accomplishing this sounds like a challenge for sure! This time I got them to "snug up" and then still too my chances on 3/4 - 1 full turn further. But I have no idea if they could have gone even further.

I think to be safe, I am going to start from scratch and order the new fittings and some new cylinder bodies. Can anyone confirm that these are the fittings I need?

http://www.aircraftspruce.com/catalog/hapages/an822.php

I'm guessing 4D size!??? I looked on my plans but I have braided steel lines so the fitting isn't listed on the plans.

Thanks for the help! Andy

[bret]

That fitting looks odd? it listed for a flared tube, is that a 45 deg, our JIC fittings are 37 deg.

[AndyRV7]

Originally Posted by bret

That fitting looks odd? it listed for a flared tube, is that a 45 deg, our JIC fittings are 37 deg.

I'm not sure I can even answer your question.

All I know is they are 90 degree elbows and one end is the NPT threads. I don't have any information on the brake lines so I can't look up the proper fitting. You guys are all smarter than me!

EDIT: OK, I just looked up JIC fitting and I see what you are speaking about but I still cannot answer your question. I see that they are not interchangeable with 45 degree fittings. Would there be a mark on the line that would help me know what fitting I need?

[JanRV6UK]

If you ever think of buying new cylinder - Consider Grove : http://www.groveaircraft.com/rvmc.html

They have internal return spring - and the end is adjustable to you can set up a suitable tilt for your brake pedal ... Yes they are expensive ... but good ..

[bret]

Originally Posted by AndyRV7

I'm not sure I can even answer your question.

All I know is they are 90 degree elbows and one end is the NPT threads. I don't have any information on the brake lines so I can't look up the proper fitting. You guys are all smarter than me!

EDIT: OK, I just looked up JIC fitting and I see what you are speaking about but I still cannot answer your question. I see that they are not interchangeable with 45 degree fittings. Would there be a mark on the line that would help me know what fitting I need?

take the two fittings, put the bevel sealing area together, if it makes a right angle, 90 deg, those are the wrong ones for our plane. those wrong ones are SAE 45 deg, not JIC 37 deg

[AndyRV7]

Originally Posted by bret

take the two fittings, put the bevel sealing area together, if it makes a right angle, 90 deg, those are the wrong ones for our plane. those wrong ones are SAE 45 deg, not JIC 37 deg

OK, let me go a little further. What makes them wrong for the plane? Provided they meet the required spec of the brake system (AN or mil-spec or some similar standard) wouldn't the type of female nut on the end of the brake lines themselves determine the appropriate fitting (45 or 37 degrees) on the line side of the elbow??

Maybe I'm just slow but it seems like we are trying to determine if the fittings are appropriate for the steel lines the builder used on the plane. Beyond that, I may still have some substandard brake component but at least we would know if the builder's chosen elbow fittings are the correct ones for the lines??

I won't be near the fittings until the weekend to check them.

EDIT: From Wikipedia

The refrigeration and air conditioning industry usually uses 45° flare connections while hydraulic hoses are usually 37-1/2° flare connections.

OK, so I hope I actually have 37 1/2 deg fittings but I won't know until Saturday.

[AndyRV7]

Ok, so I do have 45 deg SAE fittings.



Here are a couple pics of the female fittings. There don't appear to be any markings on them to help with identification.





Any ideas? Next steps?

I'm trying to get some info from the builder but I'm not sure that will be quick.

Thanks! Andy