Spools used on a road race cars...

[racer726]

I'll get flamed for this I'm sure, but I'm considering the following setup for open tracking and eventuall roadracing (as briefly mentioned in the other post):

* Richmond full spool, 31 spline, lightened with IRS clip grooves machined into the spline.
* 3:55 Ford gears, lightened ring gear, micropolished and cryo'd gearset.
* IRS with all delrin bushings, 31 spline Cobra axles
* 600# rear coilovers with Cobra R Bilsteins
* 375-400# front coilovers with Bilstein struts
* 52% front and 48% rear weight distribution, 3000# car with driver
* Cobra R rear wing, under body aero (aero is important for a spool setup) * 330 RWHP at 6100rpm, and 340 RWTQ at 4600rpm

Anyone try anything similar to this before?

Thanks,
Dave

op:

 

[ShelbyGuy]

spools are for drag racing, not turning. think about what a differential does.


good luck getting the car down to 3k#. you realize thats 700+ pounds to remove from an 03/04, right?

aero and spool have nothing to do with eachother.

start with an on-track driving school with the car as-is and then see what you want to change. also, only change one thing at a time - its easier to sort things out and quantify whether the change worked or not.

 

[Cobra-R]

spools are for drag racing, not turning. think about what a differential does.


good luck getting the car down to 3k#. you realize thats 700+ pounds to remove from an 03/04, right?

aero and spool have nothing to do with eachother.

start with an on-track driving school with the car as-is and then see what you want to change. also, only change one thing at a time - its easier to sort things out and quantify whether the change worked or not.

John,
Dave had a 94/95 Cobra last I knew, although it will still be a challenge to get it down to 3000 lbs. Dave is an experieced driver, I think the question deserves more credit than what we are used to getting in here. No way you could have known, just pointing it out.

Brian

 

[ShelbyGuy]

oh sorry.

im still having a hard time getting my brain around the rationale behind a spool on the road course. locker, sure, as a relic from the old days...but a straight up spool??

 

[kevin]

i had a spool on my race car for about three years. i went to an open end rear.

with the spool, you will have one side fighting the other side in turns (the tighter the worse) as the wheel rotation tries to be the same when they should not be. i much prefer the open and, tho it takes a bit of getting used to, the car handles much better. this is not to say i woulld presume this works for all cars and all setups.

road america is a good example from my perspective in turn 5, canada corner and the carousel.

 

[racer726]

Thanks for the backup there Brian.

It does sound like one of those "crazy idiot" ideas, just remember that the CanAm cars had spools back in the day, as did a lot of other roadrace cars... one reason was that they made a lot of power, and they haven't invented any posi differentials that could withstand the power. It was either a spool or an open differential. There was a good tech article somewhere on the net on which type of differential is the fastest around a road course... from a race car builders standpoint, and the spool was actually a very close second to the Torsen Gleason type of differential, the main difference being driver preference as it requires a specific driving style that many people are not comfortable with.

And think about this... shifter carts buzz around the track pretty fast, and essentially have a spool... unless you count the episode of "Pinks" with the shifter catrs, they aren't meant to go in a straight line.

The biggest reason for it, for me would be the fun factor of how they would be driven... trail braking deep into the corner and nailing the gas right at the apex.

The reason for aero is that if the car is setup properly for the slower corners (higher spring rates in the rear), it will be too loose on the fast ones... aerodynamics is the solution to that issue.

The weight and the indicated front/rear bias takes some thinking, and setting priorities. Those have been one of the big priorities, especially unspring weight and rotating weight. The forged steel crank is lightened about 10lbs... it's an aluminum block motor with 2 valve heads and a plastic intake... and a spool will weigh at least 14 lbs less than a T2R (although the 31 spline axles are heavier than 28 spline axles). Since the car is light, I can get by with the Cobra brakes, a T45 I hope, and 10 inch wheels instead of having to go wider.

I thought about this a while back, did some research... and then there was a thread about spools on the Club Cobra forums where Richard Hudgins talked about the spools in roadrace cars...

http://www.clubcobra.com/forums/showthread.php?threadid=20084&highlight=spool+canam

Same thing though, most people assume they are only good for the drag strip for launching the car.

I'm not saying that I'm putting a spool in the car to be faster than a similar car with a Torsed diff... but I would like to set up and drive one on the track. I never have, and that's why Im looking for those here that have tried it.

 

[Jimmysidecarr]

Wouldn't a Helical gear type slip limiter be easier to drive and easier on all the parts than a Spool???

Like a Torsen T2R... or a Detroit Locker- True Trac???
The price on the Tru Trac is semi-reasonable...



How about a lightened negative camber enhanced housing w/ 28 spline aftermarket axles???...IF you retain the "stick".

Like that guy used in his FOX track rentals... those things were supposedly quite fast...


:shrug:

 

[Jimmysidecarr]

OOPS.... that took so long to type up at work with all the interuptions.... that your explanation NOW renders my post somewhat meaningless :bash:

I can see where an extremely high torque car could be driven very fast with that set up and driving style...

I think it would require some very serious low end though ... don't you??

 

[13 Cobra Toy]

What about the Eaton E-Locker? I'm not sure if it would work in the IRS .....

http://www.drivetrain.com/eatonelecposi.html

 

[Jimmysidecarr]

I just had another thought...

The outer splines and CVs are going to take a real whoopin with a high torque sticky tired car...

You might want to do DSS level 5s and the Billetflow IRS cover brace...

To avoid this-->

 

[93SVTCobra]

Couple things:

first off using two piston vs four piston front brakes have little to do with the weight of the car and more to do with the consistency of the wear on the brake pads.

Adding the DSS level 5 and the billetflow IRS cover are just two ways to add a bunch of unnecessary weight to the IRS. That might be needed for an 03/04 drag race Cobra with 600 hp but for the hp levels that you are talking about I'd recommend something like this:

Nice solid mount AND removes about 2 lbs off the IRS. If you're going to get it below 3000 with driver you are going to need to tear the car COMPLETELY apart and optimize EVERY piece.

All that being said I'd just put a T2R in it and be done with it.

I'd be interested in hearing more about a lightened 8.8 ring gear set. I've done a bit of research on it and the only ones I've come up with that LAST are quite expensive.

 

[racer726]

i had a spool on my race car for about three years. i went to an open end rear.

with the spool, you will have one side fighting the other side in turns (the tighter the worse) as the wheel rotation tries to be the same when they should not be. i much prefer the open and, tho it takes a bit of getting used to, the car handles much better. this is not to say i woulld presume this works for all cars and all setups.

road america is a good example from my perspective in turn 5, canada corner and the carousel.

Yeah, I hear that a lot from people about how bad it is... does kind of have me worried a bit, especially since I'm hearing it from someone who's tried it at the track. What kind of car was it, and how was it set up if I may ask? Not talking about the 93R I'm sure. Some people run them in A-Sedan, and I suspect some of those that do don't admit to it, and may even laugh at how ridiculous that would be. I've got the late Mark Donohue's book "Unfair Advantage" ... and it's pretty inspiring in some ways. Donohue dumped the limited slip setups to go with a spool, and the results were... well, written in the history books. Most drivers couldn't drive the car set up that way.

Not that my ego's telling me that I can because I'm better than most drivers... well, maybe it's at least telling me to try to make it work. Most people definately can't drive my car the way it's set up now... but for me it's right on the money. What I'm thinking is that the spool would be an interesting experiment to say the least.

Couple things:
first off using two piston vs four piston front brakes have little to do with the weight of the car and more to do with the consistency of the wear on the brake pads.

I never made the comparison... I'm just happy if I can minimize the need to upgrade the braking capacity... the lighter the car, the less heat needs to be dissipated. Regarding wear on the pads, on the Mustang I've worn out 8-9 sets of front pads, and never experienced any uneven break wear. That's due to being lucky perhaps, but I'd like to think that it's because fo proper brake maintenance. The ol' PBR's are pretty light by the way, and caliper weight is unsprung weight.

Adding the DSS level 5 and the billetflow IRS cover are just two ways to add a bunch of unnecessary weight to the IRS. That might be needed for an 03/04 drag race Cobra with 600 hp but for the hp levels that you are talking about I'd recommend something like this:

I agree on the DSS and Cover. About that rear brace... I may fabricate something like that... I need to think about that one, nice idea, first time I've seen the picture, thanks for sharing that.

If you're going to get it below 3000 with driver you are going to need to tear the car COMPLETELY apart and optimize EVERY piece.

Your right. After the years I've spent motorcycle roadracing, believe me... I know how to make things light the right way. I also think I have a pretty good understanding of the value of making things light, and the car responds extremely well to weight savings on the front.

All that being said I'd just put a T2R in it and be done with it.

You'r probably right... on the other hand it's not like I can't simply swap it back later.

I'd be interested in hearing more about a lightened 8.8 ring gear set. I've done a bit of research on it and the only ones I've come up with that LAST are quite expensive.

Motive makes them for $2XX, but I'm doing the lightening myself on the lathe, and also having the spool/ring balanced. We'll see if it lasts. The gears teeth aren't touched... but the lighter gear will have less heat capacity. Micropolishing should reduce heat generated, and cryo treating will hopefully increase wear resistance. The gears themselves are already heat treated, and the machined areas will not be working surface areas.

Dave

 

[racer726]

VVVVV Spool on the champ's car. Everyone else had limited slip.

Little trivia... I think I got the right car.

Dave

 

[93SVTCobra]

How muc lighter are the lightened gear sets? Do you have a website for motive?

 

[kevin]

Yeah, I hear that a lot from people about how bad it is... does kind of have me worried a bit, especially since I'm hearing it from someone who's tried it at the track. What kind of car was it, and how was it set up if I may ask? Not talking about the 93R I'm sure. Some people run them in A-Sedan, and I suspect some of those that do don't admit to it, and may even laugh at how ridiculous that would be. I've got the late Mark Donohue's book "Unfair Advantage" ... and it's pretty inspiring in some ways. Donohue dumped the limited slip setups to go with a spool, and the results were... well, written in the history books. Most drivers couldn't drive the car set up that way.
Dave

the spool is not real "bad" to handle per se just a different technique. but now that i run the open i certainly feel the difference. there's less desire on the car for the back end to break loose and it seems (at least to me) i can get thru the turns faster with the open. i have run both set ups at several different tracks so i think i can make the comparison. it took a while to get used to the open and how much freer it seems to be in the turns. i run an open roadster that is 2200 pounds (certainly lighter than a mustang) and is well balanced from front to rear and corner to corner.

i do run a torsen t2r in my mustang track car and that is certainly better than the limited slip it came with (great reduction of inside wheel spin in the turns)

 

[racer726]

How much lighter are the lightened gear sets? Do you have a website for motive?

http://www.motivegear.com/pages/performance_gate/performance_division.htm

The 3.90 is a good ratio for light weight gearset compared to 3.73 or 4.10.... and not too many others make them, but Motive does... pretty good ratio overall I think.

Dave

 

[ShelbyGuy]

ive never heard of a motive 3.90:1 gearset NOT whining to beat the band. lots of 03/04 guys have tried them.

ymmv.

 

[93SVTCobra]

Where do you see that the 3.90 gear is available in with the lightweight option? I only see the 3.73 available with this option.

 

[racer726]

Where do you see that the 3.90 gear is available in with the lightweight option? I only see the 3.73 available with this option.

I think these are the ones, better call them to make sure... problem with places like this is you never know what i6t is with generic pictures and explanations:

http://store.summitracing.com/defau...=MGR-F888390&N=115+401013+316454&autoview=sku

Ignore the generic picture of the 9" gearset. The AX gears are lightweight, as referred to in the general description of the product line.

I would call Motive to make sure.

Dave

 

[1995COBRA-R]

This may have little to do with your car.

I use a spool on my '65 vintage race car. The old cars do not like to turn and the spool allows you to help get your car to turn (since you want the rear end to come around;ie: it's loose as heck). We also use bias tires (required) which gives you plenty of "sliding ability". If you ain't sliding, you ain't going fast.

We all change to an open rear diff or limited slip for Daytona. You don't want your rear end loose there. The wall can really hurt, and it will scare you to death if you start sliding the rear at 150mph. You have to change rear gears anyway for Daytona so you just remove the spool.

I prefer some sort of limited slip on my '94 car. I use the Hoosier radials, and they don't allow much forgiveness. If they start sliding; it's harder to correct.

I guess it also depends on your driving style, and the tracks you plan to run.