Chesnut new C5 Cobra pics

[john chesnut]

I always have loved Shelby's 427 Cobra, and wanted one! But, I didn't want to use 60's technology.
I started in June to build one with a steel and aluminum space frame that uses the 1997-2003 Corvette suspension,
brakes, wheels, tires, and diff. I used an LS6 with a T56 trans. Ford engines can be used too.
I eliminated the Vettes rear mounted transmission and converted the diff to take a driveshaft. I got the car running at Run n Gun. It handles like a dream!
Here are a few pics for those that are interested. John

[john chesnut]

[john chesnut]

I apologize for screwing up the posting of the pictures. Moderator feel free to delete the thread. Could you please let me know the proper way to post pictures. Thanks, John

[computerworks]

...fixed the posts... the last one was a good size... the first I had to resize, then I put it in your Gallery.

ron

[john chesnut]

Thanks ron, I am going to try and post a frame photo.

[vxurazz]

John,

What are the dimensions of the car?

Thanks

j

[FUNFER2]

John, it looks great. The only,..........thing I would change are the wheels.
Ah,...ya should go ahead and pop in the 640 HP Vette motor.

The paint color is awesome and this shade of orange is very popular.

Can you tell me how much the suspension travel is front and rear, compared to the typical 2" to 3" with most Cobra's ?

Actually, please explain the entire suspension.

I would love a ride in it !

Cool car John !.

Kev

[john chesnut]

It was important to me to keep the dimensions accurate. The car has the stock 90 inch wheelbase. The body is the accurate size. I am 6'2, 230lbs so I needed more cockpit room. I accomplished this by doing 2 things. The traditional Cobra uses a 4inch tall frame rail. the floor of the car is on top of that rail. My chassis has the same 5 inches of ground clearance but the frame wraps around you and the trans tunnel is a structural part. This allows my floor to be dropped by 3 inches.
I designed headers that wrap up and over the footboxes. This allowed me to move the engine further rearward, lets me have long and wide footboxes, and keeps the footboxes cooler. With the seat in the full back position I can not reach the pedals!
The front of the chassis comes to a vee. The air coming through the radiator is forced to the sides of the car. It exits out of the double stacked side vents. This eliminates the lift and heat build up that most Cobras suffer from. The second vent opening is the only "non original" aspect of the body.
With fuel the total weight is 2247lbs. With out driver it has 53.9% of the total weight on the rear tires. I wanted a front engine car with a mid engine balance.
The Cobra has almost a 4 inch narrower track in the rear and almost 6 inch narrower track in the front then the Vette. Custom rear axles were made and a new front steering rack was made that kept the correct Vette geometry. The steering in this car is incredible. It is light, quick, but not twitchy. It is completely stable at speed. It has the tightest turning radius of ANY car I have ever driven. And, It feels like it has power steering even though it's a manual rack. This is because of the position of the ball joints well into the wheel. This car with 58mm offset wheels has a Zero scrub radius.

Feel free to ask any other questions. I love to talk cars! John

[maxum_101]

wow great looking car and set up... any more pics of the car?

[john chesnut]

Suspensions have come along way from the 60's. The older suspensions and mustang based suspensions have relatively short control arms. The lower control arms are mounted high and the spindles are relatively short. The old cars used 15 inch wheels with a deep off set to get big tires to fit. The short control arms result in fast camber changes as the wheel moves through it's travel. This causes unpredictable handling and less grip. The high lower control arm mount results in a high roll center which causes the car to want to skate across the road surface rather than bite into it. The off set wheels and the position of the upper and lower ball joints meant that earlier cars had a large scrub radius. This results in hard steering, increased bump steer, and a lot of kick back felt through the steering wheel.
The Vette has 3 and 7/8 inches of travel at the shock. The Vette lower control arms are long and mounted to the chassis very low. The spindles are tall. And the ball joints are placed in the center of the wheel. The Vette control arms are attached to the chassis at precise angles. Except for the rear upper control arms none of them are mounted parallel to the ground. In the front the lower control arms are mounted angled down in the front. The top are mounted angled up in the front. They are mounted in this manner to keep the car from nosing down under braking and to keep the camber constant.
The Vette has a very low roll center and with 58mm offset wheels a zero scrub radius. If you draw a line through the upper and lower ball joint it should intersect the ground in the center of the tire contact patch. This is Zero scrub. If it doesn't then there will be a lever effect which you feel through the steering. It makes the steering hard. If you have driven a car in which every time you hit a bump the steering wheel shook and the car felt darty, it's probably because of a bad scrub radius.

In my opinion the Vette rear suspension is the best production one available. It is a true double aframe design. This means that the axle is splined and changes length as it goes through it's travel. Jags and old vettes used the axle as a control member. The wheel travels in an arc as the suspension moves. This causes decreased tire contact and less grip. Further as the ujoints wear the rear end will feel loose and less positive.
The old independent rears also could transfer to the power as good as a live axle. If you watch one under power you will see the rear of the car squat. As it does the tires move up in an arc. As they go to negative camber, tire patch is lost and you get less traction. Another problem with these rear ends, especially the old vette is that the roll center is high. This causes a snap oversteer condition.
The new Vette independent rear solved all of these problems. It has 50% anti squat desined into it. This effectively allows for up to 1/2 of the vechiles weight to be transfered to the rear tires under acceleration. The double aframes allow for pretty constant camber through out the range of travel and the wheel base stays constant. The older rear ends that use control arms to locate the rear hub to the frame feel twitchy because the wheel base actuall changes as the wheel moves up and down.
I am able to use the vette sway bars in the car as well. I use the stock vette rear bar and use a rear , heavier Z06 bar in the front.
The handling on the car is impeccable. It can be adjusted from slight understeer to slight oversteer. It corners flat. You can feel the rear end working and can power slide it if you want.
Wheels can be a limitation with my car. With out flaring the body you need to use a 58 mm offset. Up to 10 inch in the front and 12 inch in the rear can be used. Vintage Wheel makes a 18inch wheel with the older wheel look with the correct offset. Otherwise there is a good selection of Vette wheels.
I am running the stock Vette brakes. They are more than enough for this car unless it is going to be heavily raced.
The C6 vette has the same suspension geometry as the C5. As far as mounting to the chassis the only difference is the upper rear control arm mounts. This can be accomodated for when the frame is built. By using the Vette parts I knew that I would have a good supply of these great parts for years to come.

[alfy65]

John,
Very nice...I hope you took a "LOT" of build photos..would like to see a history of the build in your gallery..
Thanks
Al

[Hoofa]

John,


The body I would like to use on your chassis started as a Factory Five. I've widened the rear about 4" to about 73"and the front roughly 3" to about 69". Could I make up the space with different backspacing? Would that have any averse affect on the handling?

[john chesnut]

Hoofa, Your widened body would work out perfectly. You wouldn't want to use spacers as this would effect handling. I would change the suspension pickup points so that the stock vette track width would be used in the rear. I narrowed the rear by 4 inches so your width is perfect. In the front, I would change the pick up points to match your body and have a new steering rack made. I have a FF body in the shop. It isn't widened but I had intended to make it fit my chassis. Call me at 603-504-4106 or email at jmcbigbelly@yahoo.com if you would like to discuss further. The handling of the new chassis with the vette parts is incredible. You wouldn't be disappointed! Have fun planning. John