Bending brake lines

[kens_cockpit]

I've been making the brake lines to run from the centre and then down inside the landing gear legs on my RV8QB.

I made the LHS beauthifully if I do say so myself (on the third go!). I thought I would use the LHS as a template for the RHS and just do the required bends in the opposite directions.

You know what happens next. I bent RHS one the wrong way at the first 90 degree turn. I decided I would just bend it back the other way using my tube bender. I figured if it cracked I could still use it to get the fit just right and make up another one.

Problem is I've run out of tube and it didn't crack and I finally got the bends just right and installed and after bruising my forearms inside the landing gear box I'm reluctant to take it out and redo it if I don't have to.

Will bending the 1/4" tube 90 degrees one way and then back 90 degrees the other way make it so weak it will split at the first sign of vibration? Or if it didn't crack during the bending will it be OK?

I'm inclined to replace it if there is any doubt.

Thanks for your thoughts.

Ken Stanton
RV8QB
Fuse plumbing and wiring

[airguy]

I'm assuming your using stainless tubing here? I've done close to what you describe with 1/4" OD 316 stainless, .035" wall thickness. I've had pieces bent in 2" radius 90's that I later straightened out by pressing in a vise inch-by-inch to remove the bend, and then later bent that same area again in a different configuration. I've done this many times, have had no failures to date, and I pressure test all my tubing pieces to 10,000 psi before putting in service at 6,000 psi. Granted, most of my installs are low vibration with static pressures.

I recently had an pressure switch malfunction that took one of those bent-again pieces over 14,000 psi. The pump stalled, the tube held.

My 2 cents....

[Mel]

I would not reuse this aluminum tubing after 2 opposite 90 degree bends. The brakes carry quite a bit of pressure.
Make a new one and be comfortable.

[kens_cockpit]

I will do it again. I suspect I would have done it again anyway. I will be happier with the next one.

And if I can say Mel, though we have never met, due in large part I suspect to the fact we live on the opposite sides of the world, I have found your advice on these forums to be exceedingly helpful.

Cheers

Ken Stanton

[Ted Farmin]

I made a pattern with welding rod first to get the exact pattern for both sides so as to not make a mistake for the second side.

test flew our 4 Fri. 13th
hands off no trim needed.
Ted and Tim Farmin