Clutch selection

All,

I know if you go new the manufacture will advise.

but in general, how do you know what your looking for?

3000lb ish door car
540bbc
14/71std
4 speed lenco 3.1/1 first

do you go 2 or 3 plate
7"-10"-11" dia

any rules of thumb.

thanks in advance

 

Hi,

I have both an 11" AFT and a brand new 10" Boninfante. Both have run at the 6.0+ level. Let me know if you want either or have any questions about them.

Thanks,
Scott

 

Leanders is a very nice peice and well proven

 

Clutch

Going along with what Mike said, I was always told that each clutch disc has the ability of holding 1000HP (if you use a High friction disc) If you are pushing 2000 HP and running two dics you are going to have trouble. I won't say its a run of thumb but it seems it will get you in the ball park. Plus more discs let you run less static.


My 2 cents
Corey

 

You could get away with a dual disc 11", blown Pro Mods HAD to use them before ADRL came along, and I think they still might when they run NHRA, but I couldn't tell you with 100% certainty.

Also going along with what Mike said, I think you are going to have trouble getting a clutch tune-up to work with that kind of power and 1st gear ratio. 1st will require very little clutch to slip with that kind of ratio, but you will have serious clutch separation as you go through the gears and the torque load increases on that input shaft.

In a 3000lb. car, the clutch becomes less about the horsepower you're making and more about getting all that car moving. That being said, I think a 3-disc 10" would be the smallest I'd go. I know that's what most of the Nitrous cars are using these days. Crower, Molinari and East/West all have some great "pedal clutch" options in that 10-11" arena that are tried, tested and long trusted designs. Generally speaking, the bigger the clutch you have, the bigger the tuning window should be, but it is important to find that proper balance in the inital setup as far as # of discs and size. If you're pushing 3,000+hp, go with a 10.5" 10.7" or 11" 3-disc. If you're in the 2,000-2500hp range, 11" 2- disc, 10" 3-disc. If you're not turning it much higher than 8,500-9,000, you may find that the smaller clutches won't work as well because the levers and counterweight aren't working as hard.

Hope that helps.
-Justin

 

Mike,

we had the 4 speed already setup in the car with a N2O SBC.
We have now moved to Blown BBC.

We did have a 5.0 rear with the 3.1 first gear (left real hard - great fun)
I think we will try like a 3.5 -3.8 rear with the blown engine.

we would be just a little below 2000hp maybe 1800hp but any sort of worth while step up would push us over.

we are not limited to anything with the clutch. we have the 8-5/8 can so that should fit nearly anything. I was even thinking of maybe a lockup clutch as one option may be to get a clutch of one of the Aussie Doorslammers. Just an option depending on all the usual issues ($, avalability, tune ect)

All,

Thanks for the 1000 per plate and the bigger window of tune answers.
so basically get the largest dia and a tripple plate.



What is clutch seperation and causes and fixes it?

 

Clutch separation is when the input shaft of the transmission isn't turning as fast as the motor. Very similar to a torque convertor before it hits it's stall point. Generally speaking, you want the motor to be at a RPM level where it is making power, and slipping the clutch at launch and when you shift the gears allows the motor to be where it is happy and still gain wheel speed. The thing we're trying to avoid is letting the driveline drag the motor out of it's happy place. If the clutch grabs the motor, brings the RPM down out of the power band and it has to recover, costing you ET.

You're generally slipping the clutch hard at launch and just a little when you are shifting. It's all based on load and the torque advantage you have in your tranny gear ratios and your rear gears. Why we were saying that you may run into trouble with that 3.1 first is that the torque load required from the motor and clutch to move the car off the starting line is very little compared to what it will be in high gear when the tranny ratio is 1.0. Even though your wheel speed is higher, it still takes a considerable amount of power to accelerate that car through high gear. So, to recap, the clutch is light to let you slip through 1st gear to get off the line without bogging the motor, but you need enough clutch in the car to pull you through high gear. That light tune-up would cause the separation.

The trick to this whole clutch game is finding the proper gear ratio combination, launch RPM, suspension/4-link tune, tire pressure and the proper static pressure and counterweight on the clutch that will let you slip in 1st gear coming off the line but will keep the clutch locked up in high gear with your particular motor combination.

 

Clutch

If you find that you just can't work with the 1st gear ratio you have with the 4spd, you could always take a section out and make it a 3 spd.

Just a thought

Corey

 

Guys,

I really do appreciate your time in replying.

Yep I know it is no longer a N2O car and that is where I'm lost.

I'm just trying to make the best of what I have got. though obviously some part are going to need changing to make it work.

We will run both 1/8 and 1/4 mile. Probably without any changes to the car between as the 1/8 is more a family fun weekend a couple of times a year.

We are only doing this for fun and will probably only run dial your own so it dosn't really matter if we run 7.50 or 7.80 or 6.99 for that matter.

What I really need is to make this fun. yes the speed bug will probably what 6.99 but reallity is different. I don't want to hurt parts because of bad selection of parts or a tune that just too hard to follow because of bad parts. I also don't want to burn up clutches. I am trying to get close to the mark with everything.

Can I just laungh in second witht he 4 speed with out hurting it? (just a thought to save some cutting and rework) Though I might be best to just remove a pack.




I'm going to re-read your last few post and sort it out in my head a bit more before i ramble on much more.


Tyson.
Australia

 

Clutch

I guess you could just pull the long lever before you stage the car and launch it that way.

Just don't forget to do it everytime.


Corey

 

Push the top button

 

Clutch

Am I the only guy who does it the old fashioned way

Corey

 

We used to row the car down the track.

but when we built the blown engine I also got a throttle control so if we have CO2 we might as well have buttons

 

OK I think that I've got it. With the current gearing 3.1/1 first the clutch setup (lots of slip) would mean that when (if) we got to top that setup just wouldn't work (still slipping to much). What about a lockup clutch? just thinking aloud.

Mike,
the 1.95 first for 1/8mile is that a 2 speed or still 3 speed.

what size rear tyre would you be thinking? as this also effects the final drive ratio.



All,

But what you all agree is that I should be looking at a 3 disc 10+ inch pedal clutch.


now to confuse it all, what a bout a crowerglide??? just a guy here in Austalia has one "cheep" I know even less about them. at least we used a pedal on the N2O

 

Crowerglides are great in pulling tractors and Nitro cars where you're leaving from idle. Blown alcohol generally doesn't appreciate that, and the only reason pullers can get away with it is because they introduce throttle gradually and they spin their tires a ton.

A crowerglide basically works like a big go cart clutch. You set your stall springs to a given load and when the centrifugal force of the levers and counterweight overcome the springs, the clutch begins to apply load.

You get a better advantage with a pedal clutch because you can dictate where the motor is at launch much more easily that with a glide clutch.

 

Justin,

Thanks, Your explination of a crowerglide was great.