Copper Brake Line?

[prplefilipinoyam]

So I'm designing our brake systems and someone suggested that we use solid copper brake lines. I have no idea if this would work or is an epic fail in the making. I've done some reading but I'm not sure if the sources are legit. What I wanted to know if this is worth straying away from the standard braided or solid steel ? Pros and cons are much appreciated and links would be awesome. The person who suggested the copper brake lines needs cold hard facts to be convinced that his ideas are bad ideas, so I need ammunition to shoot down ideas if they are terrible. Here is the link for his material suggestion:

http://www.mcmaster.com/#8967k1/=47vhky

[prplefilipinoyam]

So I'm designing our brake systems and someone suggested that we use solid copper brake lines. I have no idea if this would work or is an epic fail in the making. I've done some reading but I'm not sure if the sources are legit. What I wanted to know if this is worth straying away from the standard braided or solid steel ? Pros and cons are much appreciated and links would be awesome. The person who suggested the copper brake lines needs cold hard facts to be convinced that his ideas are bad ideas, so I need ammunition to shoot down ideas if they are terrible. Here is the link for his material suggestion:

http://www.mcmaster.com/#8967k1/=47vhky

[Dsenechal]

Are you talking solid lines all the way from your master cylinders to the calipers? Im sure not, but if so that wont work as the calipers move with the suspension. You can however run copper lines from your masters out to your A-arms, and connect to some flexible line , which runs to that calipers. That is what we have done in years past.

[kapps]

Depending on how everything is set up on your car, you might be able to minimize the amount of soft (SS braid) line in your system but you will need some to take up suspension movement.

[Drew Price]

Disclaimer: Some of these reasons are preference issues, but I tried to keep it as quantitative as I could.

Be sure to read the bottom about using steel hard line instead of copper.



1) Copper tubing will easily fatigue fracture if bent on too small a radius, moved around frequently, or re-positioned too many times. Or if a n00b joins your team and invariably finds a way to mess with them.

2) 0.032" wall copper tubing will be very[/] easy to crush. You will have to be incredibly careful when servicing the engine, to not drop wrenches, to not remove sheetmetal guards too quickly, to not cinch down routing clamps too tight, to not step on them, to not lean on them, to not even [i]look at them wrong.

2b) Do you have any idea how damn tiny 0.125" OD tubing is??? You'd be using the equivalent of -2 fittings, I don't want newbie super-mechanics on my team to be trusted with knowing when to say when to stop tightening the fittings.

3) A primary reason for the braided sheath on the nylon lines is for abrasion resistance - do I have to tell you how abrasion resistant copper tubing will be?

4) For the pressures you're talking about, you might want to consider soldered or brazed on threaded couplings for sealing - which would make repairs or alterations difficult and time consuming.

4b) AN fittings as come on many brake components are a 37 degree sealing flare. Pipe and industrial and SAE fittings like will be easy to find for this tubing are a 45 degree flare, you'll have to be sure to get the right flare nuts and flaring tool. Or make a 37 degree mandrel for your flaring tool. Which in my opinion is time better spent doing something else.

5) Re-lining the braking system or making repairs to the car once it is built will require very well thought out paths for the routing of the lines. Flexible lines can be routed around things which may be added or moved during development which could prevent easily replacing hard lines.

6) If they are ever removed from the car, they will be a pain (and nerveracking) to store, move, and have around the shop where you are comfortable that they will not be damaged.

7) You may or may not be able to find flare / braze-on fittings to interface with brake components you will be using. Plumbing or circulation fittings may not offer adapter capability with AN -3 or -4 fittings on most brake calipers and masters. You may not be able to get the correct sealing flare angle or threaded nuts. (I have not, nor will I look for any of these for you - you may well be able to find them, but I already know where to get compatible fittings for flex lines, I learned to not spend more than necessary amount of time sourcing parts - shit needs to get done! I'm sure they could be found, but is it worth the effort?).

8) If you don't have the flaring and bending tools already you will have to buy them. At least two sets.

9) No other schools at comp will have anything you could interchange with in case you lose or run out of any fittings, forget your flaring tool, or bend or break one at comp.



Now - if you were considering steel hard line tubing rather than copper, you can get rid of most of the fragility concerns, but the maintenance and serviceability concerns are still there. Hard lines with threaded couplings to flex hoses and nice bulkhead connectors could really tidy things up, and would make for a nice package, but I liked being able to move mine around to make sure that I wasn't going to drop the engine on it and squish it against a frame tube, or that I could re-route them around things if needed, and all I needed was more hose. The fittings are re-useable, same as hard line flare fittings, but you have to cut the flare off.


Best,
Drew

[Tech Guy]

From past experience, the tech inspectors will not approve copper for brake lines. If they find them, they will send you home without a moments hesitation. Copper is NOT an appropriate material and not worth the risk.

Bundy tube is the proper material to use for the "hard" brake lines. Don't mess with a basic safety item.

[VFR750R]

What would be gained over steel lines? Copper is heavier, not as strong, and not as stiff. It's only advantage is heat transfer which is a insignificant design point on the lines.

And from the posts above, reliability may also be an issue.

I've heard of copper being used for gas lines on old tractors and stuff, mostly due to the fact that it can be easily bent, and I think the softer material seals better then steel on steel (hence water piping, oil drain gaskets, etc. being made from it). I wouldn't trust it for racing though.

[Michael Royce]

I have to agree with the Tech Guy. Copper has no place as a brake line material on an FSAE car (or any real race car!) And personally, I don't like aluminium for brake lines either.

Some sanctioning bodies don't even want copper or aluminium lines for direct reading oil pressure gauges due to the problem of fatigue failure. As an example, the SCCA GCR 9.3.27 says "All fuel, oil and water lines, including gauge and vent lines, that pass into or through the driver/passenger compartment, shall be of steel tube or metal braided hoses."

[prplefilipinoyam]

Thanks y'all. Pretty much what I've read on the internets.

[kapps]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Michael Royce:
I have to agree with the Tech Guy. Copper has no place as a brake line material on an FSAE car (or any real race car!) And personally, I don't like aluminium for brake lines either.

Some sanctioning bodies don't even want copper or aluminium lines for direct reading oil pressure gauges due to the problem of fatigue failure. As an example, the SCCA GCR 9.3.27 says "All fuel, oil and water lines, including gauge and vent lines, that pass into or through the driver/passenger compartment, shall be of steel tube or metal braided hoses." </div></BLOCKQUOTE>

Hmm. We've had aluminum hard lines for the past 2 years and they haven't said a thing about them. Buy Several long straight one's, cut to length, put a new fitting on the cut off end and re-flare.

[Pete Marsh]

Be carefull using bundy tube with 37 deg AN fittings. The stuff is designed for a 45 deg double flare, and can split if used with the AN 37 deg single flare. My favourite stuff is stainless steel CDS tube, with AN 37 deg flares. Simple, robust and they do it like that on planes, so can't be too bad an idea.

Pete

[Marco Antonitti]

Just to give my 2 cents,

In the aerospace industry, copper tubing was used for fluid lines, but is no longer the case due to it's obvious weight disadvantage and can become very brittle when it is subjected to vibration.

Although we are not talking about the aerospace industry, these cars do see a quite a bit of vibration. My opinion is to stick to an aluminum alloy.

It's too bad there is no brake-by-wire, would be really cool to see some electric brake systems that are currently being developed...(maybe one day there is 100% safety). Good luck!

[R. Alexander]

Brake lines should be light and stiff, much like the vast majority of things on a race car. Copper is neither.

[MD Co]

I agree with everyone elses comments above about using pure copper for brake lines. Bad idea there.

However, Copper-nickel alloy brake lines were successfully used on our car, and was well accepted by the design judges when we were at Michigan in 2008. I designed and built the entire braking system for our car.

Check out Cunifer brake line from FedHill:
http://www.fedhillusa.com/

This stuff is DOT approved and is MUCH easier to work with than stainless or conventional steel brake lines. It was very easy to flare and bend, but maintained its integrity. It's also much more fatigue resistant according to the literature on FedHill's website, but I never did any testing of my own.

The guys over at FedHill were extremely friendly and helpful. We're using their stuff again on this year's car.