Rob Lane
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| posted on 2/2/06 at 11:16 AM |
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Dual circuit servo ?
Due to a recent operation I now have a weak ankle and need to change my brake bias bar setup for a servoed system.
I believe the BMW 3 series uses a twin circuit servo. Anyone have any info?
Anyone know of another twin circuit servo that's fitted to a car?
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DarrenW
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| posted on 2/2/06 at 11:23 AM |
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Is this what you are looking for. Scroll down to servo. It says they are bendix units. Have you searched brakesint?
http://www.ebspares.co.uk/news49.htm
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Rob Lane
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| posted on 2/2/06 at 11:51 AM |
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Had a search but not found anything suitable.
I believe the Sierra and Escort Mk5 1.4l use a servo dual cylinder without ABS.
Thing is, I clearly remember both the Sierra master cylinder and Escort Mk2 donor had one each BUT I binned them, Doh
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britishtrident
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| posted on 2/2/06 at 11:54 AM |
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Actually Alfas used 2 single circuit Lockheed servos --- same design as fitted to Hillman Hunters, single circuit MGBs, some Vauxhalls.
The servo in the picture is a single circuit Lockheed design although it may have been manufactured by bendix.
If you can get a couple of Hillman Hunter servos they are very easy to rebuild --- and very reliable.
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britishtrident
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| posted on 2/2/06 at 11:58 AM |
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Nearly all cars these days use servos mounted between the pedal and the mastercylinders -- fitting a full size one into Locost would be a tight
squeeze, it might be possible to use one from a Micra/Polo sized vehicle as these tend to be smaller than the Sierra/Escort sized servos.
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Dick Axtell
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| posted on 2/2/06 at 12:42 PM |
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quote:
Originally posted by Rob Lane
I believe the BMW 3 series uses a twin circuit servo. Anyone have any info?
G'day Rob, wotcha done? Sounds like you've had probs?
The "Twin circuit" servo may be a misnomer for a servo + twin circuit mcyl. As British Trident commented, most production cars have a
servo fitted between the mcyl and the bulkhead.
Bigger vehicles, e.g. SUVs, limo's etc., usually have a tandem servo. This simply refers to the double diaphragm arrangement, within the servo
body.
It's a way of increasing the piston area, over which the manifold depression acts. Otherwise, servo's would have to be the size of
old-fashioned steering wheels, and the demand for under-bonnet space just won't allow that!
S-V-C claim to offer a twin-circuit remote servo - at a price.
Work-in-Progress: Changed to Zetec + T9. Still trying!!
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Rob Lane
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| posted on 2/2/06 at 01:11 PM |
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Hiya Dick,
Short version. 25 years ago bad car accident, broken legs, ankle, no kneecaps.
Right ankle now worn down to bone, operation to fit screwed metal plate and lock ankle. Pot 14 weeks, removed Xmas week, now getting better but weak
ankle for a year or so.
Servo
I realise now I had misnamed it. I see its servo then M/C. That's just like the Sierra one I had.
I'm doing a few mods now I'm mobile again and one is to change the brakes.
I have 4 pots fitted with twin M/C plus bias bar. Unfortunately although I can brake, an emergency stop would be extremely painful, assuming I could
generate enough force.
Rob
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NS Dev
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| posted on 2/2/06 at 01:33 PM |
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Would your best option (this may be what you meant anyway!) not be to use a pair of remote servos and keep your bias bar? (or just servo the front,
but that might mean you run out of travel on the balance bar trying to get enough on the no-servo rear brakes.
I'd certainly look at doing it that way. BMW's, but I can't remember which models, had these dual circuit remote servos, it's
a common conversion used on Opel Mantas in order to ditch the std servo which gets in the way when fitting twin weber carbs or throttle bodies.
I would imagine that if you have the battery on the bulkhead panel at the moment, you could move this to the front of the passenger footwell and mount
the remote servo/servos on the bulkhead.
Just a possible solution.....
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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britishtrident
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| posted on 2/2/06 at 03:10 PM |
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If its 0.7" dia master cylinders you are using in your existing pedal box fitting 0.625" shoul reduce the pedal effort by 20%
Thinking about it I seem to remember early Mini Cooper S (the real ones) had a smaller version of the Lockheed servo it might be possible to get
two of those under a Locost bonnet
[Edited on 2/2/06 by britishtrident]
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Rob Lane
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| posted on 2/2/06 at 04:22 PM |
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The Mini idea is interesting. I could fit that lower down the bulkhead and still use the floor mounted pedal with a bit of mod for the leverage.
I did notice a pic of one but discounted it due to being vertical, but now I think about it, it could be the solution.
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theconrodkid
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| posted on 2/2/06 at 04:36 PM |
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E21 bmw,s had twin servo,s,doubt if you would find any around now,also fiat 131,s i belive.
who cares who wins
pass the pork pies
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DIY Si
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| posted on 2/2/06 at 08:16 PM |
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The later mini's had a horizontal servo and twin line cylinder, should be just the job. They're fairly small, and if even that's too
big, why not get a remote servo? Also fitted to the proper Cooper S's at some point. But don't go looking for anything Cooper, S or
otherwise, as it'll cost a fortune due to the name. Just look for a standard remote servo. Shouldn't be too much if buying new.
Hope all that helps
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britishtrident
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| posted on 2/2/06 at 08:47 PM |
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1990s Min Brake servo
 
Rescued attachment ScreenShot004.jpg
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iank
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| posted on 2/2/06 at 09:17 PM |
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New 90's mini servos seem to run £120 ish new.
http://www.minispares.com/Product.aspx?pid=34058
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NS Dev
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| posted on 2/2/06 at 10:44 PM |
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as I said in my previous post, surely easier to keep the existing cylinders as they are, and fit a remote/pair of remote servo(s)
If you can't get a BMW E21 remote servo (thanks Conrodkid!!) then surely you can get an aftermarket one for this car.
I know car builder solutions do them but they are pricey, as do Europa.
Link to remote servo from Europa
as I say, not cheap but there must be alternative ones.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Syd Bridge
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| posted on 3/2/06 at 09:19 AM |
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I think I posted this previously, or u2u'd someone about it.
Anyway, a remote setup can be made using most modern servos, by using a hydraulic clutch slave to actuate the servo, and use the standard master
cylinder on the pressure side, and plumb normally.
IE single m/c at pedal>clutch slave>pushes servo rod>pushes standard m/c of your choice>plumbed to your brakes. This system works with
vacuum or positive pressure in the diaphragm chamber. On opposite sides, obviously! 
Seen it, done it more than once. Not on normal road cars though.
The only difference between this and the commercial remote servos, is that the commercials have the slave and master in one cylinder on the same side
of the vacuum chamber.
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chrisg
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| posted on 3/2/06 at 11:08 AM |
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quote:
Originally posted by Syd Bridge
I think I posted this previously, or u2u'd someone about it.
Anyway, a remote setup can be made using most modern servos, by using a hydraulic clutch slave to actuate the servo, and use the standard master
cylinder on the pressure side, and plumb normally.
IE single m/c at pedal>clutch slave>pushes servo rod>pushes standard m/c of your choice>plumbed to your brakes. This system works with
vacuum or positive pressure in the diaphragm chamber. On opposite sides, obviously!
Seen it, done it more than once. Not on normal road cars though.
The only difference between this and the commercial remote servos, is that the commercials have the slave and master in one cylinder on the same side
of the vacuum chamber.
That would be me Sid.
I've been trying to sort this for my own car I've got arthritic knees and I REALLY need to sort this out.
Any suggestions for clutch slave cylinder?
Or a single M/C for the pedal end?
Cheers
Chris
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NS Dev
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| posted on 3/2/06 at 11:27 AM |
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Best to let Syd answer, but from my experience I can say that the std Mini slave cyl is the longest stroke and cheapest one available, hence why most
use them!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Syd Bridge
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| posted on 4/2/06 at 10:41 AM |
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I'll deal with this on a 1-1 basis with those wanting more help. (Far too many watching this forum endeavour to make commercial gain from what
is offerred freely here.)
To start with, put your lateral thinking hats on, and erase all of what you see under a bonnet from memory. (Some are excused from reading further
at this point. )
To explain the background thinking....The wife's Fiesta has the brake pedal on the RH side, but the servo/m-c is on the left, and they are
connected with a mechanical linkage. This is no more or less than a remote servo system, with a mechanical link.
When we first tried the remote thing at the workshop, it was attempted with a clutch cable and a lever assembly on the servo. So, a mechanical
connection using a cable. One more option.
The hydraulic setup was derived to cut down weight, and for spacial considerations. It is a remote setup, with a hydraulic connection.
So, three options for a remote with connections.
On the slave cylinder; I recall that the first used was from a european car, as the work is in France, but not sure. Anyone have any suggestions??
Further slaves were, and still are, made on a bespoke basis down in the workshop. Machined from barstock, reamed and honed, then put together with
industrial seals.
The early Mini clutch slave that I have is 7/8 bore, and so is the Sierra m-c that I have. So, they should be able to be made to work together, or
just use an aftermarket 7/8 m-c. There are a few nuances to be worked on those parts before the system is workable though.
Those wanting to take this further, u2u me please.
Syd.
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britishtrident
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| posted on 4/2/06 at 11:03 AM |
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A hydrualic connection would convert the system effectively into single circuit. Jaguar used just such a hybrid system in the 1960s on the E Type
using a bendix remote servo.
On the E type the Benix servo was operated by a single htydraulic circuit but the output was dual circuit --- bit of a bodge of a system.
A leak anywhere on the sytem would result total loss of fluid.
[Edited on 4/2/06 by britishtrident]
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Syd Bridge
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| posted on 4/2/06 at 02:08 PM |
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Trying to take over from that other fella, are you Trident? You show the limits of your understanding far too often.
Read what I put again, and you'll see that it is NOT a single system, but two very separate systems, separated by the servo. It can even
have dual m-c's on the output side of the servo, and an adjustable balance bar if sir desires!
The whole setup can utilise a single reservoir, and in the application where I see it used, it does. But with individual reservoirs, is no more
susceptible to fluid loss than any brake system in any car.
This setup is little different to what is found in larger commercials, with remote systems.
The system I outlined above is good enough to be used by a major manufacturer in its competition dept., for quite a while.
Maybe any detractors should broaden their personal databases.
Syd.
[Edited on 4/2/06 by Syd Bridge]
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chrisg
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| posted on 4/2/06 at 04:16 PM |
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Can anyone suggest a single master cylinder to get the ball rolling?
Cheers
Chris
Edit:
Looking on ebay, would a Triumph spitfire/tr6/7/landrover one be suitable?
If so then as I understand it I'd need A triumph M/C attached to the pedal>a mini clutch slave cylinder > servo>M/C
can anyone suggeast a compact servo and M/C?
[Edited on 4/2/06 by chrisg]
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britishtrident
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| posted on 4/2/06 at 05:01 PM |
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quote:
Originally posted by Syd Bridge
Trying to take over from that other fella, are you Trident? You show the limits of your understanding far too often.
Read what I put again, and you'll see that it is NOT a single system, but two very separate systems, separated by the servo. It can even
have dual m-c's on the output side of the servo, and an adjustable balance bar if sir desires!
The whole setup can utilise a single reservoir, and in the application where I see it used, it does. But with individual reservoirs, is no more
susceptible to fluid loss than any brake system in any car.
This setup is little different to what is found in larger commercials, with remote systems.
The system I outlined above is good enough to be used by a major manufacturer in its competition dept., for quite a while.
Maybe any detractors should broaden their personal databases.
Syd.
[Edited on 4/2/06 by Syd Bridge]
You have many detractors I wonder why that is ? I have witnessed your many tantrums in this forum and have only been impressed at the volume bile you
manage to throw at anyone who has a valid point that dosen't fit in with the world according to Syd Bridge.
The (much revised from original description) system you describe above is awkward and uses a load of space more than using two small Mini Cooper S/
Early 1275Gt style remote servos. Why re-invent the wheel remote servos already exist.
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Syd Bridge
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| posted on 4/2/06 at 05:57 PM |
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The system I describe is versatile, and can be made 'Locost' at a fraction of the cost of commercial units, and maybe even with Sierra
parts to hand, plus a Mini slave.
Not reinventing the wheel, just giving it a different centre pattern.
I've got the bits in my workshop NOW to make one of these, and so have many on this forum. How many early Cooper 's' servos are
there floating about? And how much would they fetch these days?
Syd.
My detractors are mostly people who lack the ability to think laterally, they only see what they know or is directly in front of them. How many would
attempt to make a remote servo this way, when nothing else was on hand to fit? Same with most things people want to argue about. They'd all die
in the bush, when a bit of intuitive 'bush engineering' would save their lives. I've been brought up to think 'outside of the
envelope' as the yanks say. Intimidates some, because of some of the solutions that come out. Then again, my per diem is more than what most
earn in a week, and is that way because of the difference in the way I think, as most would be aware of by now. Crazy, insane, ....intuitive?? Call it
what you want. To me it's simple problem solving with a shoestring budget or limited resources. Or making something to fit a purpose when a
ready made is just not available. I've been down this road on here before, and won't go there again. Think laterally.
[Edited on 4/2/06 by Syd Bridge]
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NS Dev
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| posted on 4/2/06 at 06:26 PM |
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To reiterate my point for the third time (maybe eventually somebody will listen!!)
Keep the twin master cyls!!!
Servo the front circuit, don't servo the back. You can still balance the brakes with the balance bar, it will just be wound more to the rear, as
long as you are using equal front and rear cyls (prob 5/8" for both)
Use a remote servo of the various types described by Syd Bridge on the front circuit.
Job done.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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