Master Cylinder Piping

PostPost by: terryrds » Sat Feb 28, 2004 7:52 pm

On a forum for a different vehicle I'm involved in, there's been reports of failures of the hard tubing where it enters the master cylinder, caused either by vibration fatigue, or movement of the cylinder under hard application. Solutions used have included reinforcing the mounting and including a coil in the hard line, or using braided SS hose instead of the hard line. It occurs to me this could be a problem on the Elan as well, particularly since the cylinder is mounted on the fiberglass while the tubing is on the chassis. Some relative movement would seem inevitable. I recall seeing such a coil on many other make vehicles, but my low milage S2 (reasonably certain original piping) has just a bend, as is shown in the manual.
Is this a legimate concern? Have there been reports of failures on the Elan? If it is a potential problem, using at least a short length of braided hose would seem to be the best solution, as even a coil would flex some, eventually leading to failure. (If this has already been discussed, please point me in the right direction.) Comments? -Terry
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PostPost by: gjz30075 » Mon Mar 01, 2004 2:20 am

Hopefully you don't have a hard line from the master to the slave. With the engine rockin' and the firewall stationary, that will eventually lead to failure of the line. There's got to be some give in the line to allow it to vibrate, such as a braided line.

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PostPost by: rgh0 » Mon Mar 01, 2004 11:03 am

Terry

If I understand the question correctly you are querying whether people have had any problem with breakages in the rigid steel tubes that connect at the clutch or brake master cylinder.

The elan / plus 2 setup seems to be of two types that I have seen.

For the clutch
1. A red plastic tube that runs from master cylinder to slave cylinder. This was on my 1968 S4 with cast iron exhaust manifold.

2. A steel tube from master cylinder to down near the bottom of the RH engine mount bracket, then a flex hose across to the bottom of the bell housing and then a steel tube again across to the slave cylinder. This was on my `1973 plus 2 with tubular steel exhaust headers.

For brakes
Always a direct connection of the steel tube to the master cylinder with naturally a flex hose at the suspension connection end.

I have never seen or heard of any problems with the steel tubing breaking or cracking at or near the master cylinders for either the clutch or brake.

From a theorectical perspective provide you have the correct length free to flex between where it enters the master cylinder and where it is attached to the body or chassis so that any relative movement or vibration induced by other car vibrations is absorbed in elastic flexing of the tube at stess levels below the fatigue limit then no problems would be expected either. How much is that length ? More than 6 inchs (15 cm) less than 3 feet (90cm) would be my estimate. To short and you run the risk of relative movement stresses being excessive, to long and you run the risk of vibration induced stresses being excessive.

my 2 cents Australian ( 1.5 cents US) worth

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PostPost by: terryrds » Mon Mar 01, 2004 12:41 pm

Greg and Rohan- Thanks for your replies. I should have specified I was concerned about the brake master cylinder, the clutch of course has the plastic flexible hose. Also, since my car is LHD, the hard line runs from the cylinder, down along the front cross member (vacuum chamber) to the "T" on the right side, all unsupported until the "T". From what you're saying, Rohan, I guess that unsupported length is intentional, to allow the line to flex within safe limits.
-Terry
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PostPost by: rgh0 » Tue Mar 02, 2004 10:20 am

Terry

It surprises me the brake line Tee is on the right hand side for a LHD car. My current Elan chassis which was an original lotus replacement chassis purchased in 1979 had a mounting hole in the Left side which I assumed was for the brake line tee to be located on that side for a LHD car. Has your car perhaps been convered from RHD to LHD at some time ( perhaps even by Lotus themselves !!).

However to contradict the above, the parts manual implies that the Tee was in the same location for both LHD and RHD cars on the RH side. While it only shows a RHD drawing the only part difference listed is for the master cylinder to Tee bundy pipe which implies the same Tee location for both LHD and RHD cars.

Having an unsupported line from the master cylinder on the left hand side down to the front cross member, across and back to the tee on the right hand side sounds to long to me. On my chassis there are a couple of clips on the front cross member to hold the brake lines and i would have expect the lines crossing the front cross member to be supported in these before the tee. The unsupported length being from the master cylinder to the front cross member is within the range I would consider OK all the way around to the Tee sounds to long.

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PostPost by: nebogipfel » Tue Mar 02, 2004 10:25 pm

Could this be the problem?

In the UK there has been a trend for a while to fit pure copper brake pipe instead of mild steel partly because of its corrosion resistance and also because if you polish it it looks pretty.

That said, copper is fine if it is well supported so that it cannot vibrate, work harden and become brittle. I have also seen the flared end of a copper pipe fall off because it had been forced too much in the flaring process and susequently became brittle

My own preference is for copper nickel alloy pipe which does not corrode and is much more durable than pure copper (Kunifer in the UK) It's not so shiny though!


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PostPost by: terryrds » Wed Mar 03, 2004 4:15 pm

Rohan- Thanks for the tip on the clips, mine must have gotten lost over the years. Will try to find a source. I'm reasonably certain my car has always been LHD, at least since it left the factory.
John- Interesting point about copper brake lines, but I think (not certain) the failures were with steel lines.
-Terry
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PostPost by: type36lotus » Wed Mar 03, 2004 6:10 pm

I have always heard that copper WILL work harden and should not be used for brakes. If beauty and corrosion resistance are desired there is Stainless Steel tubing produced for brake lines. I have seen it, just haven't a clue where.

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PostPost by: nebogipfel » Fri Mar 05, 2004 7:56 pm

Yes although copper undoubtedly work hardens it is widely used in the classic car world.

Quite a few of the ready made kits are pure copper :(

As I say I stick to copper/nickel which has never let me down. It will polish fairly nicely and of course doesn't corrode. It is fairly easy to hand form into nice curves and flares easily too.

Stainless sounds interesting, but I bet it's a b*gger to put flares on!

If you have copper brake pipes make sure they are clipped firmly and cannot vibrate and if you are making your own be careful with the flaring tool :)
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PostPost by: gjz30075 » Fri Mar 05, 2004 8:05 pm

Yes, and if you do get the flare done on stainless, its a b**gger to get it to not leak. Its so hard, that it doesn't want to conform to its mating seat.
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PostPost by: richboyd » Fri Mar 19, 2004 3:33 pm

re: Tee locations on my 1969 S4, LHD from factory, tandem master cylinder. This car had three tee fittings, all originally on right side of chassis. One tee is for the front wheels. It is(was) located on right longitudinal chassis member, just behind the front crossmember. A second tee, located just behind the front wheel tee. This second tee does not functions as a tee, only as a right-angle junction (one branch of this tee is plugged). The third tee is on chassis "Y" branches near differential.

This set-up was, to my mind, the factory plumbing all cars (both RHD and LHD) the same between wheels and tees, then adapting the plumbing from tee to master cylinder. The common plumbing is most suited to a RHD car; the original master-to-front wheel plumbing traverses the chassis cross member too many times for LHD logic: once from master to tee, then back again from tee to left wheel. At least all of my original plumbing was well supported with clips welded to chassis. The lines appear to be "bundy" tubing, a plated steel tube.

With a new chassis, I moved the front wheel tee to the left chassis side. I removed the tee-functioning-as-junction, replacing it with a real junction (now a straight-through "bulkhead" fitting). I kept its location, and the connecting line to the rear, along the right side of car - mainly to avoid exhaust heat. More plumbing, less heat.

I used steel bundy tubing again, but switched to 37degree flares and AN-3 fittings (steel, not aluminum). Six Banjo fittings at wheels and master cylinder handle the only remaining non-AN (non-JIC) junctions; those threaded into the cylinders themselves. The wheel hoses are teflon/stainless, which have AN-3 ends.
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