Cobra weight distributions?

[vector1]

Originally Posted by scottj

I'd like to hear how that's accomplished also. Regarding install... I built my car from the frame up on a set of Longacre scale pad levelers. First to insure I was always working on a level plane and second so that I was constantly informed of weight distribution when placing components. With the tight clearances in the engine compartment and trans tunnel, I was able to offset my motor 1" to the right and that was only made possible by fabbing my own headers. I also have the drysump tank and battery inline with the RS tires. The P/S tank and all the lines and cables are on the right side as well. With the driver at 160lbs, I'm LS heavy by 40lb.

160#'s? damn! find yourself a 120# trained monkey and you'd be set!

[mdross1]

Originally Posted by scottj

I'd like to hear how that's accomplished also. Regarding install... I built my car from the frame up on a set of Longacre scale pad levelers. First to insure I was always working on a level plane and second so that I was constantly informed of weight distribution when placing components. With the tight clearances in the engine compartment and trans tunnel, I was able to offset my motor 1" to the right and that was only made possible by fabbing my own headers. I also have the drysump tank and battery inline with the RS tires. The P/S tank and all the lines and cables are on the right side as well. With the driver at 160lbs, I'm LS heavy by 40lb.

Wow,Sounds great love hearing how some are more anal than me.Keep telling the wife that when I focus on a project.Having the cars scaled is a major improvement, going to the lengths you did can only imagine the difference in road holding ability.

[scottj]

Originally Posted by Ron61

It could be done with lead weight like the NASCAR cars use. Move the weights until they counter balance the drivers weight. I tried to find my book that has all of the pictures and explanations of how to balance a car for road racing but I must have let it go when I sold my Cobra. It came with the dyno program that I had back then which was the same one that NASCAR and the NHRA used. It cost quite a bit but it was extremely accurate so long as you got the figures for everything right.

Ron

Sure you could... but, he attributed it to... "Just sayin. Stock suspension, good install." Then consider that SPF specs the weight w/460 at 2660lbs + 112 for fuel + 220 driver and it's near 3000lbs already... so it's way over 2900 without any lead... not sayin it isn't possible... just sayin...

[Tommy]

Originally Posted by scottj

Sure you could... but, he attributed it to... "Just sayin. Stock suspension, good install." Then consider that SPF specs the weight w/460 at 2660lbs + 112 for fuel + 220 driver and it's near 3000lbs already... so it's way over 2900 without any lead... not sayin it isn't possible... just sayin...

I, too, was very curious about how that weight distribution could have been achieved without significant modifications.

[scottj]

Originally Posted by mdross1

Wow,Sounds great love hearing how some are more anal than me.Keep telling the wife that when I focus on a project.Having the cars scaled is a major improvement, going to the lengths you did can only imagine the difference in road holding ability.

Personally, I couldn't tell the difference unless I was on the track near the limit. At Gateway (Run & Gun) the car is actually faster being LS heavy... but that track is a roaval. So, there's no improvement, at that track anyway, over guy's that are less anal regarding weight distribution.

[scottj]

Originally Posted by vector1

160#'s? damn! find yourself a 120# trained monkey and you'd be set!

He'd probably drive better too

[Ron61]

Originally Posted by scottj

Sure you could... but, he attributed it to... "Just sayin. Stock suspension, good install." Then consider that SPF specs the weight w/460 at 2660lbs + 112 for fuel + 220 driver and it's near 3000lbs already... so it's way over 2900 without any lead... not sayin it isn't possible... just sayin...

Scott,

You are correct about the weight, but I was running a small block with a lot of aluminum parts. I also never used lead weights as I had a high quality suspension under my car and could adjust it pretty much to achieve a balance. Not perfect but close enough that it handled better than any of the others around here. But like most people I could never be satisfied with what I had and kept tyring things to improve it. I wish I had it back now as that is the only car I ever sold that I hated to see go.

Ron

[Jerry Clayton]

On a Cobra(most of them) the whole body can be offset to the right(or left),the engine/trans offset, and you can use different offset wheels right and left sides---
and you could build or mount fuel cell a little more to r/s

also on those SPF fiqures---they mount the battery behind the left wheel???????

[scottj]

Originally Posted by Jerry Clayton

On a Cobra(most of them) the whole body can be offset to the right(or left),the engine/trans offset, and you can use different offset wheels right and left sides---
and you could build or mount fuel cell a little more to r/s

also on those SPF fiqures---they mount the battery behind the left wheel???????

Jerry,

I did that trick with the body too... just the front- about 1/2". I kept the rear centered so the 335s don't rub. If one was to look for it, they'd notice that the LF tire sticks out farther than the RF. The front is stiff enough that it never rubs a tire.

[Jerry Clayton]

Scott

getting ready to resume work on mine and really would like your list of shock / spring specs as it seems I can't find them---
I'll try to get a picture of the F1-r Pro Charger posted along with the dry sump stuff

[vector1]

Originally Posted by scottj

Jerry,

I did that trick with the body too... just the front- about 1/2". I kept the rear centered so the 335s don't rub. If one was to look for it, they'd notice that the LF tire sticks out farther than the RF. The front is stiff enough that it never rubs a tire.

lets say you move everything further to the right to get the 50/50 side to side, you get the front to back 50/50. i guess you can set the cross to 50/50, even though your ass is over the left tire and the engine is on the right side.

lefthanders do this i believe with the engine offset to the left, but don't they also move the roll center and geometry to compensate? makes me wonder how this would handle.

like you say, pushing the limits might be able to tell.

[Jerry Clayton]

just remember that all this weight placement ratios is just a starting point if your racing(or is necessary to meet the rules)

Out top fueler and funny car frames were welded in an certain pattern to give about 1/2 inch of twist to them to then compensate for engine torque

[Silverback51]

Originally Posted by RET_COP

......Is 50/50 optimal?
I think of a car like the GT40. with the mid engine, it must have been rear heavy yet I read where it cornered great
Lou

Is 50/50 optimal?

That is a yes/no question. There are so many factors in the equation that there is no one answer. The variables range from tire size and spring rates to the CG of the vehicle. For that matter tire pressure can have an influnce on how the vehicle handles.

Let's take the GT40 as an example. It is far from being 50/50 as it's a mid engined car. But then you look at the tire sizes. Much larger in the rear than the front. Not unlike a F1 or Indy car. Now look at a NASCAR (as much as I hate to refer to them) car. All four tires are the same size and I'm willing to bet the car is close to 50/50 weight distribution, with a side to side bias due to them only turning to the left.

Since a Cobra is not able to run same size tires front and rear (and by size I mean tread width) you would generally want a little more weight on the rear. The spring rates would be such that under acceleration you transfer the weight to the rear of the car for traction. The same is true under braking for a corner. The weight is transferred to the front to help in the braking and turn in at the beginning of the corner if you are trail braking.

Hope that helps a little, and didn't just confuse you more.

[scottj]

In steady-state cornering, such as a skidpad, the heavier end will lose traction first, everything else being equal. Road racing is more about transitions than steady state cornering. Since heavy braking transfers weight to the front tires, road race setups favor a static rear weight bias to counter weight transfer that would otherwise result in a turn-in push. Rear bias also helps forward bite off the corner. Being a short wheelbase car increases weight transfer.

[RET_COP]

Good stuff here guys, I'm taking notes.
Thats why the QA1 Proma Star double adjustable are $300.00 for one!!!
Its tough to set up for cruising with sometimes a passenger and then go autocrossing. Either its a compromise sacrificing on both ends or have two completely different setups.
I just set up for cruising, very neutral without a driver at this time. Next winter could be a different upgrade.

Two Cobra's would be the answer

Lou

[vector1]

think you can do better then that.. bought my qa1 dbl adjustables from autofab race cars for 250 ea. in md. close to you. there's probably different brands if you shop around, like behrents, lefthander chassis, coleman, etc.

if you need extra spring clearance and want to use 2 1/4 springs theres a place in florida, van steel, inc. 727-561-9199, that makes the adjusters for these shocks for 2 1/4 springs, or you could use a lathe and make your own from 2 1/2 perches, i didn't have the option.

i have the above, and they are adjustable, i don't know how good they are though.

[Dominik]

I also built one car on scales, but I gave up on 50/50 left and right. It's quite amazing how weight adds up: Body, chassis, aluminium engine, differential, trans +/- 1.000lbs, and you think you are "done". Next moment it doubles...

The chassis (RAM) did not encourage offsetting the drivetrain, but placing the battery on the far right probably has the same effect.

[RICK LAKE]

RET_COP Lou Here is the easy thing to do, The front shocks you will drive on the street with will give you an easier smoooth ride and drive at the track front shocks will have different settings (stiffer). You want the car to squat in the rearend a little when accelling the car. I get about 1-2" drop in the back end. The tires, 335's are not rubbing on the frame or body. This gives me good traction on take off. There is still too much weight transfer on hard braking. I raised the spring rates 30% in front. The easy thing to do is get the car scaled with both sets of front springs and try and keep the car at the same ride height. This way the alignment will not have to be adjusted. Swapping springs will take any where from 3-4 minutes up to 10-15 minutes depending on mounting fasteners. Some guys run quick pins. I stay with aircraft nuts. Rick L Ps IMO unless you are running the same company replica with everything beening equal, You are going to have to street the car, then race it and watch film of it to learn what it is doing on the track. Taking heat temps of the tires is a good place to start. Record all this info and DO ONLY 1 ADJUSTMENT at a time to see if it's better, same or worse. It's alot of work but having a great handling car at the end makes all the trouble worth while.

[dlampe]

The most important number is diagonal balance according to what I have read and felt from the seat. You can't move weight from left to right or visa versa or you can't move weight front to back and visa versa with spring adjustments on the scales. You can adjust the diagonal balance with the spring adjustments. That is why I just don't believe a stock or even mostly stock cobra from any manufacturer with a driver in the seat is going to be 50/50. I have the scales and I have played with this stuff for days at a time. In the end, the best I could do was 50/50 diagonal weight distribution and 48/52 front to back. By the way, my GT40 was a seriously race prepped car and it was 49/51 front to back.

[STL Mark]

For the side to side measurement - I was not in the car.
Sorry for the confusion.

My main point was that the SPF was basically perfect right out of the box.