Kunifer Brake Pipes

[Andy Borris]

Need some advice on making brake pipes from a reel of Kunifer pipe please.

http://www.rallydesign.co.uk/popup_image.php?pID=13935

While I can form the ends (and even get them leak proof!), I can't seem to get the pipes straight! Because the pipe is curved into a reel, I always end up with a “slight wave” to the pipe.

Any suggestions on how to get a wavy pipe straight?

Thanks

Andy

[thebrookster]

Fasten it to the chassis regularly was the best I got to when I did my Spitfire.

Cheers,

Phil

[Beans]

First make them to the correct length and straighten them by hand  ...

[Beans]

Then roll them between two wooden planks ...

[Beans]

Giving a nice straight pipe, ready to bend in the proper shape,
using th eold pipes as template ...

[Andy Borris]

Thanks Beans, that's something I never thought of.

[nicmk1est]

old ways are the best  :P

[TedTaylor]

Glad someone is using proper pipe and not the copper rubbish.  Just had to undo some copper brake pipes on the LSE and two of the three unions destroyed the pipes by binding - still it saved me having to decide whether to replace them for cupronickel - had no choice.

The secret of getting straight pipe from the coil is to roll it out along a bench or other flat surface.  Hold the one end flat on the bench and roll the coil out along the bench - second person can help but I use a hefty weight/clamp on the end if needed.  While you won't necessarily have an absolutely straight pipe (probably with a slight curve) you can either gently flex the curve out or simply put your unions and bends into the pipe while the curve is still present because by the time you clip it all into position it will go straight.

If I have some bad wavy bits I place the pipe in a vice, not clamped up tight but so it slips through and with something soft (aluminium/cardboard/wood) to protect the pipe.  Then slowly move the pipe along through the jaws flexing them gently when you get to curved bits with moving the pipe through the 'padded' jaws to act as a guide.  Beans idea is also a good one especially once you have rolled the coil out as flat as you can.

Bending can be difficult especially on tight bends - the extra toughness of cupronickel makes anything other than gentle bends by hand tricky without creating kinks.  I have a selection of four or five hand benders to give me different bends, though the piers type got chucked out many years ago because as you work the bend though them they have an infuriating habit of creating a nip which is (or should be) and MOT failure.  I also use large diameter tube (e.g. large diameter exhaust pipe) to work bends around.

Ted

[piman]

Hello Ted,

"Just had to undo some copper brake pipes on the LSE and two of the three unions destroyed the pipes by binding -"

were the unions steel?  Personally I've used copper for a great number of years and providing it is supported properly and you use brass unions, no problems. Copper brake lines are a heavier gauge than cupro nickel and easy to form.

Alec

[heraldcoupe]

Copper is highly susceptible to work hardening. I've worked on many cars fitted with copper pipes and the failure rate when dismantling is alarming, even when support appears to be good.
With the design of the Spitfire swing-spring, the short pipes to the wheel cylinders have some movement by design as the cylinder slides, which with copper pipes becomes a serious safety issue.

Cheers,
Bill.

[TedTaylor]

piman wrote:

Hello Ted,

"Just had to undo some copper brake pipes on the LSE and two of the three unions destroyed the pipes by binding -"

were the unions steel?  Personally I've used copper for a great number of years and providing it is supported properly and you use brass unions, no problems. Copper brake lines are a heavier gauge than cupro nickel and easy to form.

Alec

Hello Alec

Some unions that were fitted to copper pipe and I had to undo were brass and some were steel.  The failure rate (i.e. the copper binding to the unions within the joint) have been the same - something like 80 or 90% (over the 15 years or so I have had to do this I have not bothered to keep count).  The problem is caused by the soft copper being forced into the sleeve hole in the union as it is tightened so that it fills and jams in it, and the complete lack of inherent strength of the copper means that it has had little torsional resistance to the turning action of the union nut so sticks in there.

The point about cupro-nickel (e.g. cunifer) is that it is a much tougher material which is resistant to knocks etc. and simply does not need to be as thick as the softer copper pipe to give a much stronger pipe line.  The reason it is easier to form is that it is such a soft material, but that does not stop it being damaged when being bent - the reason I was having to change the pipes was because of an MOT failure because one was kinked.

Also as Bill says, copper work hardens and this in itself causes additional problems.

I am not disputing that you have had no problems with copper but I have had so many when undoing these joints (fitted by other people).

Ted

[piman]

Hello Ted,

I'm aware of the properties of copper, I've been in engineering all my life and like all things it needs an understanding of materials and how they are used. To say it is rubbish is a bit of an overstatement. I'm not even sure if cupro nickel was available when I started changing steel lines because of corrosion problems but I just bought a stock of fittings and copper pipe and made my own. I guess that I've just stuck to it.

Alec

[TedTaylor]

Hi Alec

Sorry if you feel that I am overstating copper as being rubbish - may be I am going a bit over the top but I am afraid I hate it when apparently perfectly good items destroy themselves on removal.  This is an experience shared by others.

In the early days of hydraulic pipes in the 1930s copper was the choice (there was nothing else as an old Morris 8 I had testified) but the industry moved to steel based pipe on the grounds of cost and strength.  When vehicle testing was introduced in various parts of Europe in the 1960s the problem of corrosion was highlighted and Volvo moved to cupro nickel in the 1970s - copper was rejected I understand on the grounds of its poorer strength characteristics - cupro nickel is at least 50% stronger in its comparable properties than copper and in a number it is the equivalent of steel pipe.  I believe pure copper pipes are banned in the USA, Canada, Australia and New Zealand but not sure if this applies to cupro nickel - Forum members from these countries can perhaps advisel.

In my work as a teacher of physics, technology and motor engineering from the 1970s I became aware of cupro nickel piping and at the beginning of the 1980s bought the proper equipment to form it and have never used anything else since.

While I have no doubt that you have had no problems with using copper your engineering background obviously helps, and the reports of copper pipes failing may well be due to poor fitment by people using it inadequately supported and overtightened - a problem that steel and cupro nickel are much less likely to be prone to.

While there are thousands of cars running around safely on pure copper pipe, the problems found by some people in its use make me steer well clear of it.

Ted