Clutches, Flywheels and Engine Torque

[SPRINTPARTS]

OK, with out sounding like a smart a*rs, this is aimed at anyone with a serious race motor (not a big pair of carbs and a fast road cam) who is prepared to divulge some inner secrets of their race motor.

For many years we have only used "uprated" production based clutches and various weight flywheels. Currently I am looking at going to a "proper race" clutch, be it AP, Tilton or Quartermaster, they all seem to be about the same. There is much conjecture here about flywheel weights (which can vary depending on the weight of clutch type used). Some are saying as light as you can make it, which with a light clutch cover may total less than 40% of the original clutch and flywheel weight, which will help engine acceleration, and others say keep some mass in the flywheel which will help with driveability and launch.

A new flywheel will have to be made to suit the new clutch, just what weight do I make it? I would be interested in what max torque figures a "good" race motor is pulling to help make a clutch type selection easier. I don't wish to run a dual plate clutch unless it is absolutely necessary. The dyno figures I have here a from a few years ago, and I must admit I don't believe their accuracy.

As usually when you speak to numerous people and some so called experts, they all have their own ideas which can have extreme variations. I am hopeful that the people with the best answers are the ones who are using this arrangement on the same type of motor as mine (Dolomite Sprint) and not what works on a Toyota, Honda, McLaren etc.

If you can answers but don't wish to go public (trade/development secrets) you can email me at sprint43@aapt.net.au

Thanks

Mark

[tinweevil]

OK, since I'm not a serious racer I wont point out the flaw in the arguments you are trying to weigh up.

Well, omission rather than flaw.

[SPRINTPARTS]

If you wish to discuss Momentum of Inertial etc fine, there is plenty to consider in flywheel design and clutch selection using these calculations. All the theroists and some so called experts start quoting this, what I am after is real world experience. Theory and calculation are fine for a basic design, but if it is so accurate how can F1 teams who spend millions of $$$$$$$$$$$$$$ get it so wrong every year and make a car so slower and have to continually sort out the basic design once the car reaches the race track. I don't want to know, or care to know what works on a Chev, Ford, Ferrari, it is not important in this discussion, just what works on a Dolomite Sprint in full race trim.

Mark

[Dolly racer 33]

I have used many different types of clutch over the last 20 years racing my Sprint. For the last 15 years or so I have used a custom made steel flywheel,(cannot remember the weight, I will weigh one & post it on here) mated to a twin plate
7-25" paddle clutch. Do not be tempted to go too light on the flywheel or use a 7-25"sintered clutch or you incur problems getting off the line. Probably ok with a light car but not on a Sprint.

Regards,

Ken.

[Hans ten Broeke]

Obvious it did not work so we try again




Hans

[Hans ten Broeke]

Well it seems something went wrong with my reply, the picture should be at the bottom of my post.

Here we go again.

A few years ago there was a member of the UK Dolomite club who made excellent steel flywheels for a 7" clutch, we bought 3
Tony Tewson from Quatermaster UK did gave a good support.
One of the goals was not to end up with a very heavy clutch pedal for my wife's car.
He advised a double plate alu clutch with a light spring, after all these type of clutch is up to 500+ HP with a strong spring.
We never had any problems with that setup, the release bearing is central hydraulic operated.
Could have gone the F3 way, but that flywheel is far smaller in diameter, so than the starter motor had to be reversed to the gearbox, and we run them LHD so there is simply no place, and on the left side you need all the space for a tubular exhaust.
BDW we also use a bit under 3Kg Quartermaster starter engine, now situated just under the distributor.
The whole thing weight a bit under 7Kg.

Well about torque.. sometimes a picture tells the whole story.
The picture out of the German classic magazine Markt shows the first corner of my last Yountimer race at the Nurburg ring.
Standing start, first row, Porsche 3L RSR next to me, I managed to pull 2 till 3 car length away, but his 300+ Hp was a bit to much.
1' in class, my wife Wineke 5'

Hans

[SPRINTPARTS]

Thanks for the info Hans (great photo, wish we could be that far up the grid), and Ken. Your comments and experience is appreciated.

As you stated Ken, my concern is to light a set up and poor launch as well as the ability of the motor to respond to throttle under load. I was considering using Sintered metalic linings, so what would you suggest, Cerametallic Rally (?) plates.

Thanks

Mark

[Dolly racer 33]

Yes Mark, use a twin plate cerametallic rally twin plate paddle clutch. I also use a bell housing mounted slave cylinder which originates from a Saab, (far cheaper than the AP racing unit). This gives you far superior control over the clutch. I also use a starter motor moved to the right hand side of the engine adjacent to the distributor. I use a Peugeot unit. Once again, far cheaper than a Quartermaster unit and geared as well.

I can quote you a price for the complete set up if you wish.

[SPRINTPARTS]

Ken,

PM sent.

Mark

[eightiesflamer]

Mark
I know the guy that Hans is talking about ref the light weight fly wheels, think they are still available. I know that there are a few race cars that are using them successfully.
If you wish I can find out some more.

Darren

[SPRINTPARTS]

Hi Darren,

All info much appreciated. Over the last 20+ years we have had to do all our own development work with no local (Australian) support, so this time I decided to look a bit futher away, but the biggest killer for anything from UK always seems to be the ever changing exchange rate and the ridiculous postage/freight costs.

Thanks

Mark