Clutches - Teach me something !

[Chairman Roger]

Both Alan and Alex are upgrading their engines and will both have power/torque outputs similar or greater than my engine (allegedly !).

As part of the upgrade they are sensibly fitting lightweight flywheels and clutches. They have both been told (by people whose opinion I respect) that they should fit seven and a quarter inch TWIN plate clutches and that a single plate clutch is too marginal.

Now I have been using a seven and a quarter inch single plate rigid cerametallic clutch successfully for years with no undue wear or reliability problems (the only problem has been leaking seals in the Caterham slave cylinder which is a known weak area whichever type or size of clutch you use). In addition to that I believe that I am correct in saying that the JPE was built with a single plate clutch and I have heard no reports of problems there.

 

A twin plate clutch is obviously heavier than a single and the dynamic torque ratings of all the single plate clutches that I can see are well in excess of even a high tuned Vauxhall unit

 

What advantages will the twin plate set up give ? Am I missing some point ?

 

[paul jacobs]

I'm a mechanical illiterate, but no Roger, I don't thinkk your are missing anything.

 

I've only got a 7.5 inch single plate in my engine. I had it refaced with a "heavy duty" [whatever that is] clutch material, and use it with a bog standard pressure plate and original cable operation. I've been running it since about 1994, competing regularly, [dropping the clutch at 5K revs.] and about 10k + road miles, using a lightened flywheel done at my local engineering shop, the engine was putting out 245bhp and around 180lb ft when new, although down to around 220bhp now, when it was on Dave Walkers RR last summer, and I was using fairly sticky road tyres.

 

I've had no problems TO DATE [rapidly crosses fingers and toes] so I don't think that fancy twin plate clutches are necesary, but desirable maybe?

[Number Six]

Peace of mind I would say Roger... dumping the clutch at 5/6/7/8k rpm regularly in sprints or Tesco's car park (whatever your choice may be) will inevitably put huge stresses on the whole powertrain so why not just fit the twin plate gubbins while the engine and box are out and the winter nights are long. You don't want to be changing the clutch during competition or touring abroad. Then you can just forget about it and build up your left calf muscle! The twin plates also rattle nicely at tickover and I quite like that sound...teeth.gif

 

Andy

[Tony Martyr]

I feel you are under specmanship pressure Roger.

The clutch plays three roles.

It transmits the range of shaft power from the engine.

It allows the drive to be disconnected and syncronise the two sides of the drive line to via slipping during gear changes.

It acts as a damper of torsional vibration.

Its diameter and therefore friction surface is largely determined by the diameter of the flywheel. In very high speed engines where the moment of inertia of the engine is kept to an absolute minimum the clutch has to be of small diameter and therefore multi-plate to be able to transmit the torque. In the case of the seven, so far as I can find out, the 7.25 inch single plate is able to carry out all three roles, even in the high power units and remain easy to operate.

Clutch materials have got more exotic of late so I'm sure the right choice of materials and the standard configuration is better than a twin plate job of higher inertia.

[Number Six]

Perhaps Tony is right about modern ceramic and carbon materials.

 

This is the spec from the R500, putting out some 230BHP.

 

Caterham ultra-lightweight low inertia flywheel with AP racing light-weight clutch.

Exhaust: Large bore plated 4 into 1 system with carbon silencer.

Max power: 230 bhp @ 8,600rpm.

Max torque: 155 lbsft @ 7,200rpm. Maximum revs 9,200rpm.

 

Is the AP racing clutch a single plate or a twin plate? You boys will be getting circa 250BHP (I'm guessing!) - I wonder what the hillclimb boys are using. They are probably the folks to ask.

 

Andy

[Number Six]

Also if you are using 8.5/9 stickies on the rear that's another huge stress compared to 6/7's.

 

Andy

[Mike Bees]

The SLR/R500 AP is a single plate road-type clutch. It looks pretty much like any other road clutch.

 

AIUI you normally go multi-plate to reduce the diameter (and hence the rotational inertia).

 

Alex and Alan beware that your cars may become horrible to use on the road. Ask PeterC about his 5.25in multi-plate clutch, basically it's just a switch and shouldn't slipped - fine for sprint starts but a bit embarassing around the town or if you have a gravel drive!

 

Mike

[Paul Ranson]

When I was running a 180BHP K with 8.2 inch soft slicks on the rear the stock Rover (not Ford....) clutch never caused any problems, and in fact was in perfect condition when it was removed. Due to its apparent rarity it just got put back in....

 

Anyway if the wheels are spinning the clutch isn't slipping.

 

Paul

[Alex Wong1697456877]

I've asked for a Quatermaster twin plate 7.25" clutch using their "sport" discs which are supposed to be slip friendly. This is after asking one of the hillclimb guys, but to be fair, Roger's abused his clutch as hard as I ever will and it has been ok smile.gif. Having bought a nice lightweight (3.5kg) flywheel, it seems a shame to add an extra plate to it but I have been told it's more than desirable with a 240 to 250BHP engine.

 

Alex Wong

www.alexwong.net

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[EFA]

Well well well,

 

I thing there's perhaps a little confusion here....

 

Firstly the JPE uses a 228mm road car clutch with a Calibra Turbo cover and an AP 4 paddle unsprung centre plate. This is OK, but the drive flange springs are stressed and will snap eventually. These covers lasted only 2000 miles average on my car before the straps broke. Helix Autosport make a range of uprated covers (they are stil the road clutches but they use thicker and more drive flange springs, and will also increase the clamping force if required.) See www.helix-autosport.com for more info on these uprated covers - I never managed to break one.

 

It should be noted that many of the later Vauxhall engines sevens have a pie dish flywheel which is a very heavy undesirable item - all the notes above apply to the conventional type flywheel.

 

The single AP cerametalic 4 paddle drive plate the JPE uses is a CP3431. The version of this plate with the sprung centre is not capable of the shock loads a powerful Sevn can put onto it, the centre rips out! Stcik with the unsprung version and you won't be needing a tow home!

 

There are a bunch of 7 1/4 clutches on the market in both single and twin plate designs. The main difference betwen a single and twin plate is increased torque capacity, although this is at the expense of "feel" The twin plates are more on/off in operation. A twin plate in a car with a 3.92 diff and a 5spd heavy duty box with a 2.04 first is not an easy car to pull away from uphill traffic lights in.....Still its a race clutch and is really not designed for this purpose.

 

I will report soon on the Quartermaster 5.5" clutch which I have just fitted to my engine. (Engine due back in car in about 3 weeks) This gives the advantage of lower weight (3.1kgs for the flywheel, 2.5 kgs for the clutch) but more importantly reduces the power required to overcome inertia of the flywheel. This setup uses a std ringgear and starter and also has the advantage of very much speeding up gearchanges as the synchros have less work to do due to increased engine braking the low inertia brings.

 

Peter C has a 5.5inch QM in his car and its gearchange is now very impressive!!

 

Quartermaster clutches use a special sintered material which is claimed to dramatically outlast that used by their competitors - we'll see.......

 

 

 

 

 

 

 

Arnie Webb

The Fat Bloke blush.gif in a Slow Old Vauxhall wink.gif

[Tazio]

Well as the Alex's partner in crime - it all seems clear now doesn't it?

 

Not!

 

( or more budget overspend than sense? )

 

Alan

 

L7 FUN

 

Edited by - Tazio on 19 Feb 2001 20:33:24

[Slipper man]

My only experience of a twin plate clutch was on my BDG, which was horrible - the only really nasty part of the car. By contrast the R500 unit just feels like a normal car clutch, and as Mike says, looks normal too. I'd stay with what you know works, if I were you.

[paul jacobs]

As Keith said, if it works, stick with it. I forgot to mention that I had a brief flirtation in the early days of my engine,['92] with an unsprung paddle clutch which was quite simply horrible in any kind of slow road situation, and wore out after my trip to the Swiss meet and back, say, no more than 2500 miles, causing some fairly severe scoring to the flywheel.

 

Really, save your money and go for a slightly uprated but essentially standard item, the others are nothing but trouble and expense.

[EFA]

Got to say that with the 4 paddle AP unsprung and the Helix cover clutch action was easier and lighter than most "normal" cars.

 

Arnie Webb

The Fat Bloke blush.gif in a Slow Old Vauxhall wink.gif

[Number Six]

I liked the twin plate clutch action on the BDG. It was bullet-proof and after you got used to it it was never an issue (apart from once or twice when my foot bracing slipped and the car took off like a bat out of hell). Agreed it was almost on/off but not quite as bad as that. I could easily live with another one. But Arnie's got me thinking now, the QM sounds like the business - anything to speed up gear changes has got to be a good thing.

 

Andy

[Roger King]

Personally, I'd go for a twin plate. Whether or not it is horrible to drive depends on the spec of the plates etc, it has nothing to do with being twin plate.

 

Over the years we have found that a twin plate tends to last aroud four times as long as a single.

 

If you look through the AP clutch catalogues (or whatever make you are using), you will often find that a single will theoretically be OK, but it will depend on the driver's technique as to how long it will last.

 

Our normal policy for highly tuned engines (not a hard and fast rule) is to use a single plate on a Crossflow and a twin plate for a Vauxhall. Remember that it is torque rather than power that dictates the clutch's capacity.

 

There is extra inertia with a twin plate, but the extra mass is at the same diameter as a single plate and is not too big an issue, certainly not when compared to the inertia of a 'road' clutch.

 

In the end, so long as you are within the specified capacity of the clutch, the choice has to come down to the driver's mechanical sympathy and the type of use. Hillclimbing and sprinting will always see heavier wear rates and make a good case for a twin.

 

To illustrate the difference the driver makes - we had a driver who used his car regularly on the road and did a full season's competitive racing. At the end of the year there was no appreciable wear to his clutch. Another driver in a similar car and with the same clutch managed to destroy three clutch plates in the year while racing and he never once used it on the road.

[Alex Wong1697456877]

Roger (Swift),

 

If you look through the AP clutch catalogues (or whatever make you are using), you will often find that a single will theoretically be OK, but it will depend on the driver's technique as to how long it will last.

 

There's your answer!

 

Alex