Straightening Coiled Tubing - DIY Easily and Cheaply

[Tomnistuff]

Here in Quebec, I couldn't buy pre-bent and "terminated" fuel and brake lines for my 230SL.  All I could buy, even from the U.S, was short, straight lines with connectors in various lengths (also available here).  That required that I cut them to the exact correct length, bend them myself and "re-bubble flare" one end.

That wasn't a big problem but the long lines down the center of the car (3/16", 5/16" and 3/8" O.D.) were only available coiled, even from Mercedes-Benz.  I have no problem reproducing the bends of the original tubes with a simple tube bender or terminating the tubes with a bubble flare kit, but straightening coiled tubing and making it look nice seemed beyond me.

So I found a solution, not fun, but a solution that is easy, inexpensive and that works almost perfectly.  The attached procedure with photos describes how I straightened the three tubes that run the length of the car, prior to re-bending them to match the original tubes and adding bubble flare fittings to the ends.

If it helps someone else who lives in the up-north, out-back, over-yonder or anywhere else not near and automotive center, I will be pleased.  If it is worthy of being put in the TM, that's OK too.  However, I don't consider myself competent to do that.

It's a five page long WORD document with color photos, and even contains a bit of stress/strain behavior of bent tubes, which is pretty easy to ignore.

Good Luck if you should decide to try it.  It's attached below.

Tom Kizer

[dirkbalter]

Hi Tom,

I am about to buy below for the same reason.

http://www.eastwood.com/eastwood-handheld-tubing-straighteners.html

Dirk

[Tomnistuff]

Hi Dirk,
Those prices, $80 U.S. per size times three sizes = $240 U.S. or about $300 Canadian are the reasons why I decided to make something myself.
Tom

[dirkbalter]

Yup, it adds up quickly.
I just printed your instructions and will give it a try first.
 

[stickandrudderman]

There are other tube straighteners which are adjustable but still, straight tubes is an essential detail in my book.

[merrill]

Hi
About 11 years or so ago I replaced all brake lines and both main fuel lines running from the rear to front of the car.

all lines were delivered in a roll.   

what I did was carefully unroll the lines on a cement floor and then using the old lines as templates I would align the lines length wise and start taping the old and new together and bend the new to match the old. 
I believe I taped the long straight center runs together first and the worked toward the ends where most of the bends are.

it worked out fairly well.

[Tomnistuff]

Hi Merrill,

If you rolled them out on the floor and did not bend them even farther backwards (beyond straight), what you did is like the first tube photo in my write-up.  They should have sprung back to a curved shape like the tube in the second photo.  I don't know how you got them straight before bending them to match the original tubes.  Is there something else that you did?  Maybe I missed something.

Tom Kizer

[mdsalemi]

Adjustable tube straighteners run around USD $100-$150. There are a number of styles and manufacturers; here's a domestic one:

https://www.ebay.com/itm/Mini-Brake-Fuel-Line-Tubing-Straightener-Coiled-to-Straight-Tube-Tool-TLF11/202116535890?epid=4009748719&hash=item2f0f159652:g:nOkAAOSwldRaDf45&vxp=mtr

What I might try first is drilling a hole in a 2" thick piece of soft wood (probably with countersunk entry and exit points), to the size that will accommodate the tubing you are working with (should be a snug fit) and either pulling the tube through, OR, affixing one end of the tube to a hold point and pulling the wood down the length of your coiled tubing. I've straightened various kinds of wire assemblies like this with good results, and the wood block is one favored by some lo-tech DIYers on the muscle car forums who don't like to buy costly tools and prefer home-brew solutions.

Don't rule out buying the requisite tool, using it to straighten as much tubing as you think you will need in your project, and then turning around and selling the tool. I've done that with some peculiar tools that I've needed for important projects, and found a ready market for tools in excellent condition. You'd probably get about $75-$80 back, in a sense renting that tool. I did a massive flooring project a couple of years ago which required a non-standard flooring nailer. I could rent it for $20 a day at some places, but I needed it for 6 months. I found one "new in box" on eBay, but opened, for about 75% of the new price. I bought it, used it for close to a year to execute that one flooring project, and resold the tool on eBay for exactly what I paid for it..

[merrill]

hi
its been quite a while since i did the job.

I recall getting the tubing as flat as possible then rolling on a cement floor

when making my "bends" i would find a can or container with a similar curve to the old lines and use that as an aide when bending.

to ensure a close fit I did tape the old line to the new as I went

matt