Remote Servo for Clutch

[brdee]

Hi Guys,

Just thought I would pass on some pearls of wisdom I came across when exploring the possibility of reducing the exersion needed to operate the Ultima Clutch, which seems to have been a topic from time-to-time!

You may be aware that there has been some adverts and articles in the Kit Car mags recently regarding remote servos and the main offering appears to be a lockheed unit (with brackets and lines, one in particular from s-v-c ltd.

However on checking elsewhere on price (as you do!) I spoke with Ken Ewers at AP Braking and he strongly suggested that a ratio of 1.65 to 1 would be ideal, rather than the 1.9 to 1 that was more widely offered.

Ken suggested that the 1.9 to 1 variety would be far too strong and would greatly reduce 'feel'.
Ken also put me in touch with several sources so, if you want to go with his suggestion, here are the details:

Part Number 4257-812P and available from:-

Leacy MG Ltd
Aston Lane
Perry Barr
Birmingham B20 3BW. Phone [phone]
Fax [phone]
OR

David Manners Ltd
991 Wolverhampton Road
Oldbury
West Midlands B69 4RJ Phone [phone]
Fax [phone]

I have ordered mine, so will let you know how I get on!

Thank you Ken of AP Braking - a very nice man!

Keith

[peterpsg]

I'm suprised that he didn't suggest that you change the clutch instead!

Would a 115 - 140mm 3 or 4 plate carbon fibre unit not be a lot lighter on the pedal?
(Not the wallet!)

Though, I guess a CF unit would be a bit more on/off than the normal cera-metallic ones...

[brdee]

Have you used one of these alternative clutch plates?

No idea what it would rush me....and how long they last in comparison with the std unit?

keith

[peterpsg]

No, I just have the normal heavy clutch... which I'm getting used to, but due to all the extra work my left leg is doing, I find myself sometimes walking in circles! (;-) joke!)

I think a CF clutch is somewhere between 2K-2.5K (£, but they apparantly have very good wear characteristics, and according to the AP website can last as long as 10 normal clutches. I guess that's all down to what your driving style is like!

Still, the CF clutchs are much lighter, hence the engine will pickup speed faster due to the lower intertia mass - same phyics applies to the use of CF/Ceramic brakes - improved transient response.

My prime concern was the drivability of them in normal use, i.e. do they have much slip, or are they really on off, which could make hill starts and crawling in traffic interesting...

So, ANYONE with a CF clutch feel free to comment!!!!

[davefiddes]

Some of us have replaced the stock clutch master cylinder (3/4" dia) with a smaller one (5/8" dia). This gives a bit bigger pedal throw but is much much easier on the left foot.

Might also be worth double checking the clutch linkage. I discovered that the connecting rod on the master cylinder was binding with the clutch pedal because the slot was too small. It actually bent the connecting rod!!! Fixing that did improve things quite a lot but not as much as swapping to the smaller cylinder.

[peterpsg]

Ok, just spoke to the guy next door, who's a bit a mechanical type, and apparently the clutch plate release springs are the problem, i.e. in order to hold the pressure plates together hard enough to cope with the torque, they have to be pretty heavy... so scrape the idea of the CF clutch (well I'm still dreaming!)

[gtrclive]

Have driven a Mid engined Chevy with a Super Clutch Triple plate organic clutch.. It's a good deal lighter, almost as light as a normal car..... Am building a GTR with the same clutch unit...

Oh and by the way its alot lighter than a normal G50 clutch unit, over 10kgs lighter... Wouldn't fitt anything else now....

Only down side is it does not slip as easy as a single plate unit, but then again it's also rated at over 600lbs so rated higher than a normal G50 unit...

Have also rebuilt a GTR with a Kennedy engineering H/D G50 Pressure plate, also rated to 600lbs but your leg tends to fell it.....

[gtrclive]

Also fitted a Servo to my GT40 Clutch ( Yanky big pressure plate unit etc ), but it was irratic at best... A Clutch needs flow not pressure, and a servo is best at Intensifying pressure not flow....

I know that they have designed a servo for Clutches but why add wieght when you can loss it instead.....

[andygtt]

peterpsg said:

Ok, just spoke to the guy next door, who's a bit a mechanical type, and apparently the clutch plate release springs are the problem, i.e. in order to hold the pressure plates together hard enough to cope with the torque, they have to be pretty heavy... so scrape the idea of the CF clutch (well I'm still dreaming!)

This is correct for a single plate clutch, however multi plates increases the pressure for the same weight spring..... thats why tripple plates are rated higher than twin plates etc..

Also as Clive says they are hugelly lighter even if they are not carbon fibre as they are significantly smaller.... I'm also using a tripple plate in my project.

They will be a little snatchy at slow speeds (like the Porsche GT's tripple plate clutch) but I'd prefer that to a heavy Porsche unit.

[peterpsg]

Ah cunning, so there's a bit of mechanical advantage in the multi-plate systems...

Where did you get your clutch again? I've been eyeing the AP racing ones up!!!

[andygtt]

Gardner douglas... they do a kit that fits an Ultima BUT it will involve changing a lot as you will need a new flywheel/ringgear maybe starter/adapter even.....
but that will be true with the AP setup which you will also have to develope yourself.
As I'm doing the BMW v12 thing I had to design it all myself, but I would much prefered to have bought off the shelf.