Classic Revival Square tube vs Round tube chassis.
 

Hi All

There are a few folks on here building or who have built CR Cobras. Dave W mentioned it's interesting to see the evolution in chassis design over the years.

Mine is one of the early square tube chassis cars but even it had some changes from the first Square tube chassis.

The square tube used a donor rear suspension from the AU falcon which was still a current model when t came out. Complete new rear ends could be bought from Ford. I sourced mine from a wreck and it took some finding as there weren't that many in the wreckers at that stage. I liked the double wishbone rear end as it seemed a significant move forward from the traditional Jag rear end or live axle designs.

http://www.clubcobra.com/photopost/d...hassisdone.jpg

Front end components were the more traditional Jaguar sourced items.

Mine had some changes from the very first square tube cars in that it had pendant pedals rather than floor mounted.

http://www.clubcobra.com/photopost/d...1409front3.JPG

The next update after mine had a dropped boot floor and redesigned rear subframe. Pedals also got 3 mounting holes to move them forwards and back.

The round tube saw a complete redesign with suspension being a mix of donor Holden components and bespoke CR manufactured items.

So lets look at the differences in generations. Post up your CR square and round tube chassis pics and we can see the development.

Cheers

Mine is a year or so after Mikes.
Here is the 3 hole hanging pedal assy.
[IMG]http://www.clubcobra.com/photopost/d...PICT000110.JPG[/IMG]

here is my round tube while under construction at Classic Revival;
http://bencobra.files.wordpress.com/...-1600x1200.jpg

Chassis tour video
http://youtu.be/awNdFCT78HU?list=UU3...dnRkJXnNIB84Xw

Front Suspension Sway bar
http://youtu.be/E8gdShe_qe8?list=UU3...dnRkJXnNIB84Xw

Front Suspension Assembly
http://youtu.be/ZHrPwk3RURs?list=UU3...dnRkJXnNIB84Xw

Interesting stuff. Thanks Ben!

I forgot you did the chassis tour video. Thanks for the reminder.

Cheers

I'll try and match with similar pics from mine so people can see the differences.
Mine is chassis number CR3514, so i assume 14th round tube.

From the rear, the lowered boot floor, and totally different chassis structure.
The diff is VE, the half shafts are custom from Classic Revival, 67mm shorter than stock VE, but the stocks cant be shortened due to the taper in the shaft beyond the splines.
There is a trap here for the unwary, there are 2 different splines depending on the VE diff version, mine was from a HSV and has more splines and larger diameter shafts.
The knuckles and brakes are VE, or custom as in my case.
Lower Arms (front and rear) are stock VE as the tie rod, but the upper wishbone is custom CR.
Hand brake lever is BA~BF ford, cables are custom CR

http://i1060.photobucket.com/albums/...ps7f0aee4e.jpg

http://i1060.photobucket.com/albums/...psb01d7495.jpg

The fuel tank fits up with a raised triangular section between the chassis, its custom To suit CR.

http://i1060.photobucket.com/albums/...ps36fdfa66.jpg

Front is VZ Knuckle, hubs and brakes or custom brakes, the upper and lower arms and sway bar are custom CR.
Rack is VP, but needs customizing with mods to VZ tie rod and ball joint to suit the VZ Knuckle.

http://i1060.photobucket.com/albums/...ps32cba008.jpg

This is the pedal support as a comparison to Daves pic, ill find some that show it without the body on.

http://i1060.photobucket.com/albums/...ps0d8a7533.jpg

In that last pic of the pedal support, you can also see another mod where the steering rod exits the body to the left, instead of straight out through the foot well end panel.

Here's a pic from the engine compartment side.

http://i1060.photobucket.com/albums/...ps3c874167.jpg

Very nice. What offset wheels can you fit to the rear?
Bugger, looks like I'll have to sell my square tube, and go round. lol.
Will your front sway bar fit a square tube? I'm still trying to source one.
JD

Get yourself some 19mm conduit and a heat gun and bend it to the shape you need and take it to the local pedders or suspension place and they should be able to do you a custom job.

Cheers

Here is a square tube car.
The steering shaft comes straight out the end of footwell, in comparison to Dave W's
[IMG]http://www.clubcobra.com/photopost/d.../PICT00162.JPG[/IMG]

Another comparison with Dave W round tube.
Here is a stock VN Commodore fuel tank as recommended by Ian at CR for the square tube cars.
I don't think I have a lower floor than Mikes, but I am not real sure.
[IMG]http://www.clubcobra.com/photopost/d...t_2007_034.jpg[/IMG]

This is a stock square tube rear diff and suspension assy.
It has the heavy cast AU IRS upper and lower arms, this shot is also pre "Aussie Mike bump steer kit" and still has the factory tie rod fitted.
[IMG]http://www.clubcobra.com/photopost/d...ar_of_car2.jpg[/IMG]

I think that was one of the real visual changes when looking at the car is the round tube now has more dish on the rear wheels.

Love it or hate it one of the more striking things about the square tube chassis was the lack of dish on the rear. I think it gave a modern car look with the same dish front and rear.

I kind of liked the Ben Hurr style with the spinners sticking out.

http://www.clubcobra.com/photopost/d...ear_wheel2.jpg


Cheers

That's my favourite pic of your car Mike!

Classic Revival suggested wheel specs for the round tube are as follows,

Front;
8" Rim. (9" total width including Beads)
Backspace = 6"
Front space = 3"
Offset = ET38, or 1.5" towards outside of the wheel from the centerline.
Camber = 1.0 to 1.25 deg negative
Caster = 6.0 to 8.0 deg positive
Toe In (total) = 2.5 to 3.0 mm

Rear;
10" Rim. (11" total width including Beads)
Backspace = 6.5"
Front space = 4.5"
Offset = ET25 or 1.0" towards outside of the wheel from the centerline.
Camber = 0.75 deg negative
Toe In (total) = 1.0 to 2.0 mm

Ground height is measured under the main frame rails and is designed at 120mm

I don't have any details for the square tube.

It was a real struggle to get any accurate Square tube wheel specs back in the day. I believe they were 2.5" or possibly 3" front space all round. I think mine are 2.5" but you could risk 3" if your body was perfectly centrally mounted. I hate wheel rubbing so went with the more cautious 2.5"

I had 3 piece wheels built and on the rear I reckoned I could fit an 11" rim in there (12" total width) A lot of guys were running 9.5" rims but I really wanted to run the 315 tyre and they look a bit distorted on a 9.5" rim. The problem I found though was the bump steer was so bad on the rear that it would make the wheel rub on the inside of the body. With the rear end mods and the relocated coil over mounts I reckon I could fit a 12" rim in there now with no clearance issues.


The rear rims were originally a 9" back half rim and a 2" front half. That presented some problems to make as there was such a deep draw on the sheet of aluminium that he had to make them from thicker sheet. The material got to thin out near the edge. I also got him to weld the rim halves together as I was concerned about their strength.

I like the rear wheels now with a more central offset as I think they make for a stronger wheel. Also makes for a more central load over the wheel bearing.

Cheers

Here's a similar pic to Mikes wheel pic but its Gregg's Round Tube,
I love the stance of Greggs car, i'll be very happy if i can get mine to sit the same.
If you look through Bens pics of the Nats(thanks for that Ben, they were fantastic for people like me that couldnt get there this year), you'll see some pics of Gregg's car on the move and its got the look with that Voodoo Blue.

http://i1060.photobucket.com/albums/...ps8a523d14.jpg

Mike, I've got 10" rims on mine running 315's, 11 would be better I reckon or I did run 295's on the rear which is probably better, but I couldn't find them last time.

You say about the body not being square. Mine is weird. The body appears to be centred but the guards are not (go figure). On Phils car the guards are centred but the front opening is not.

Vagaries of fibreglass etc etc - something which AP have spent a lot of time on I believe.

Mine does rub ever so slightly on the passenger side under hard cornering (you can hear it in my latest videos from Nationals). Cheers Gregg

The range of tyres up in that width is pretty limited. It seems to jump from 275 to 315 with nothing much in between. Are you running the Kumho KU36? I'm looking forward to running in the new control tyre classs.

I agree with Dave. The stance on your car is great. A real credit to you.

I don't think the symmetry on the original cars was anything to write home about either.

The bump on the rear of mine was so bad it wore a hole right through the fiberglass in one spot :o Probably would have cleared with 10" rims though. There was a change in toe of more than 20mm through the entire travel.

When I modified It I had everything bolted up and checked clearance through the whole travel. Fingers crossed there will be no rubbing. That sort of thing really irritates me.

Cheers

mmm this may make the case to run a 17" tyre. According to this in 17" there are 285 and 295 available, yet in 18 it goes from 275 to 315.

http://www.kumhousa.com/tire/categor...7-2BEA0466BD5C

Gregg is there any room to move the wheel outbound by 10mm, or would it start hitting the guard?

Ben

I've got a pair of the 285/40/17 on the shelf at home. They are actually a bit taller than the 315 and should fill the guard a bit better.

Cheers

I could easily make up some different width spacers, then we could take a rear wheel and the shock off one of our cars and put the wheel through its suspension movement with say, 1/4" 1/2" and 3/4" spacers and see what looks good, and where & when it hits.

whoops, wrong thread

Dave