iiyama
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| posted on 25/2/07 at 02:54 PM |
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Connecting master cylinders
Is there any reason why I cant link the hydraulics to the inlets on the MC's?
To clarify this I have a resevoir with two oulets, however I have three MC's, front and rear brakes and clutch. So to this end, if I use a
single banjo on the MC furthest from the resevoir and then a twin banjo on the MC nearest the resevoir I can run a single line 'through'
the first MC and onto the second.
The clutch MC can then be fed from the second outlet on the resevoir
Not sure if the SVA man would like this though, although I cant think of a valid reason why he would fail it.......
Opinions please!
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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RazMan
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| posted on 25/2/07 at 02:58 PM |
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There is a valid reason for not having that setup - if the clutch slave blows, you will lose your brakes too (both of them)
A common reservoir is ok as long as you have independent chambers to separate the three master cylinders. That way, if you start losing fluid from any
of the three systems, the warning light will protect all three and you still have enough fliud left to stop the car on one brake system.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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nitram38
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| posted on 25/2/07 at 02:59 PM |
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I have seen cars that share a partitioned resevour but never share hoses.
Think about why the resevour is partitioned. It is for safety if one cylinder/circuit fails.
I would say what you are suggesting is a big no, no.
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iiyama
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| posted on 25/2/07 at 03:09 PM |
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The resevoir is partitioned.
I may be being thick here but I dont understand.
If its ok to share a partitioned resevoir then what Ive described is no different. Is it??
Brakes will be from one partition, clutch from the second.
The resevoir is not under pressure, only that generated by gravity.
The clutch and brake masters will not be joined together, only the two brake MC's.
If the cutch slave blows, why will it affect the brakes? If I lose fluid with in the clutch line, then fluid will drain from a point lower then the
resevoir as this will be the highest point. If the fluid level drops, then the warning light will come on. However this will not affect any fluid in
the braking system will it? If you say it will can you explain how?
Sorry if I am being really dumb!! 
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nitram38
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| posted on 25/2/07 at 03:14 PM |
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If your setup leaks on one resevoir for the brakes, then no brakes!!!!!!!
If your fluid drops below the min mark then you are in trouble. Both brakes in one resevoir means total loss of brakes.
Even if you combine brake and clutch, what about losing one brake circuit and clutch?
Have you tried to stop a car against the compression of an engine?
Even if you switch off the engine you will not be able to bring the car to a smooth stop.
If you think it is safe, why are there no production cars with this setup?
Even dual resevour tin tops have a seperate clutch resevoir.
[Edited on 25/2/2007 by nitram38]
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RazMan
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| posted on 25/2/07 at 03:15 PM |
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Sorry, been down the pub so I'm probably not explaining things too well 
The brakes should have independent chambers too, so if one system blows, the other is still ok.
Here's a pic of my setup to clarify
 
Rescued attachment Brake & Water Tanks.jpg
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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iiyama
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| posted on 25/2/07 at 04:01 PM |
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Nope, still not getting it. Raz, understand your drawing, thats fairly straight forward.
If the resevoir were to drain completly from one line, why would that affect another? There would still be fluid in the system that wasnt drained
would there not?
Are you saying that if one circuit drains then as the brake peddle is used then fluid will be pushed into the drained circuit?
If this is what is being said then I reall y dont understand!!!!
Im not suggesting that Im going to go against advise, but I really have to be straight in my own mind. Not trying to be devils advocate, just trying
to understand!! Sorry if Im upsetting people, this is not my intention!
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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nitram38
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| posted on 25/2/07 at 04:17 PM |
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You are taking both braking circuits from the same partition in the resevoir.
Should you have a leak from one brake circuit, then the fluid would leak from that partition and to the remaining brake circuit.
Minimum fluid levels are on your resevoir to stop you from pumping air into your brakes.
You will then lose the only working circuit along with the bad one.
If you use a combined resevoir, then each cylinder must have it's own partition.
The partitions are there to maintain fluid levels in the unaffected cylinders.
You are not frustrating me, I just don't want to see you fail the sva or have an accident !!!!!!!!!
[Edited on 25/2/2007 by nitram38]
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rusty nuts
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| posted on 25/2/07 at 05:43 PM |
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When main stream manufacturers use the brake fluid reservoir for clutch fluid the outlet for the clutch is ALWAYS higher than for the brakes. This
ensures even if the clutch system leaks there is fluid for the brakes. Common sense dictates doing the same or using seperate reservoir.
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iiyama
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| posted on 25/2/07 at 05:51 PM |
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It would be so much simpler to draw what Im trying to explain! LOL
As a plumber, I understand the effects of osmosis, siphonage and drainage. However maybe these principles dont apply to braking systems!! ??
If I have a container at high level with two outlets and I open one of them, then the fluid will drain from the container and the open pipe. However
there will still be fluid left in the unopened pipe, even though the container is empty.
So if I put MC's on the end of said pipes, one circuit will now be devoid of fluid, the other will still have fluid in it. If I press the brake
pedal, then the fluid on the pressurised side of the system will still pressurise and will only draw air in from the empty container if there is a
loss of fluid from that circuit as well.
If I joined both circuits on the pressurised side of the MC then I can see that if one circuit failed then by pressing the brake pedal fluid would be
forced from the intact circuit into the open circuit.
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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rusty nuts
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| posted on 25/2/07 at 05:57 PM |
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Try it your way and see what the SVA inspectors has to say about it.
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iiyama
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| posted on 25/2/07 at 06:02 PM |
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quote:
Originally posted by rusty nuts
Try it your way and see what the SVA inspectors has to say about it.
Not very helpful, but thanks anyway.
All Im trying to do here is understand the physics.
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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blueshift
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| posted on 25/2/07 at 06:12 PM |
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the little fluid that is left in the pipe is not enough. That is why there is lots of fluid in the reservoir.
A setup which will pass involves a reservoir of sufficient capacity (I don't know what this is, in the SVA manual?) for each circuit. With your
setup, if one circuit failed and drained the reservoir, your other brake circuit would have no reservoir with fluid in it. That is an SVA fail and is
why you must not do it.
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nitram38
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| posted on 25/2/07 at 06:13 PM |
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You are obviously not going to listen, so do it your way.
Keep a link to this thread for when you fail sva.
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iiyama
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| posted on 25/2/07 at 06:24 PM |
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quote:
Originally posted by nitram38
You are obviously not going to listen, so do it your way.
Keep a link to this thread for when you fail sva.
Absolutly not. As I stated Im just trying to understand the physics. Just because something fails SVA dosent make it logical! there are plenty of
threads on this site to prove that! And more to the point I have never said that what I have described would pass SVA. Also havent at any point said I
would plumb up this way regardless!
Maybe I need it spealt out in words of one syllable. Maybe its because I have a mis understanding of how a master cylinder works. However no one has
yet described why if one circuit failed then the other would as well just because the low pressure inlets are conected. It has just been stated that
it will.
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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Liam
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| posted on 25/2/07 at 06:27 PM |
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I can see what iiyama is saying. We're obviously talking remote reservoirs here so there is some length of hose between the reservoir and the
MCs. In the event of the reservoir draining, the hose to the working circuit is effectively a mini reservoir.
It's true as far as I can see that indeed you wont suddenly loose both circuits. You'd have to have a leak in the other circuit and go
some way with one circuit failed to pump air in and loose both circuits. I guess in production cars it's quite feasible this could happen with
a failed rear circuit going unnoticed. Although this is less likely in an enthusiasts car, it's just not good practice to allow single point
failures leading to catastrophic results.
Another way it could be a serious problem is that if the mc drains with really hot brake fluid (after a good caning) the fluid will be expanded. When
the fluid cools and contracts the fluid left in the working circuit hose could all drain out too.
Best to follow conventional practise - a 3 outlet reservoir isn't expensive.
Liam
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RazMan
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| posted on 25/2/07 at 06:30 PM |
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quote:
Originally posted by blueshift
the little fluid that is left in the pipe is not enough. That is why there is lots of fluid in the reservoir.
Got it in one! The fact is that you must have MORE than enough fluid and the reservoir is designed to do just that. If you look at all of the SVA
compliant reservoirs that CBS etc sell you will see exactly what is involved - 3 chambers, 1 for clutch (also the highest level) and 2 separate
chambers for front & rear brake systems. Therefore if you blow the clutch, you have BOTH brakes available, if you blow the front brakes you have
the rears available and vice versa.
Hope that clears it up 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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nitram38
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| posted on 25/2/07 at 06:34 PM |
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By the way I have a 3 way one that I bought from CBS that I want to sell.
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iiyama
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| posted on 25/2/07 at 06:36 PM |
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mmmm. I think Ive got it! Thanks for the last two contributions!!
So if I put another oulet into the resevoir I have, at say 3-4mm down from the max level for the clutch, is this acceptible??
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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iiyama
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| posted on 25/2/07 at 06:42 PM |
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quote:
Originally posted by nitram38
By the way I have a 3 way one that I bought from CBS that I want to sell.
this one? http://www.nfauto.co.uk/fluid_reservoir.htm
I have the second one down! Problem I have is that the resevoir needs to be higher then the MC's and Iam a little limited in the height that I
have to play with.
At least I guess it has to be higher??
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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nitram38
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| posted on 25/2/07 at 06:49 PM |
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Yes it is the top one!
And the real bummer is that I ordered your one yesterday !!!!!!!!!!!!!
I also ordered a seperate dumpy one for the clutch.
Bought them from Rally design.
[Edited on 25/2/2007 by nitram38]
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iiyama
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| posted on 25/2/07 at 06:54 PM |
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Does the clutch circuit have to have a warning light ala the brakes?
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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nitram38
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| posted on 25/2/07 at 06:57 PM |
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quote:
Originally posted by iiyama
Does the clutch circuit have to have a warning light ala the brakes?
No, only the brakes.
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RazMan
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| posted on 25/2/07 at 06:58 PM |
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quote:
Originally posted by iiyama
At least I guess it has to be higher??
Not neccessarily but it helps - gravity doesn't really come into the equation as fluid is drawn through by suction.
btw - no warning light is required on the clutch
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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iiyama
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| posted on 25/2/07 at 07:30 PM |
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So in that case I can put a screw in resevoir on the clutch MC.....
Ok guys, thanks.
Once again sorry if I upset anyone!
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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