How were/are the alloy bodies attached to the tube frame?

[wrist_pin]

Hello everyone,

This is my first post and first question. I hail near Pittsburgh, PA.

I don't have a cobra so, owning one is still a pipe dream.

I just freed a locked up 289 which took 6 weeks of patience and penetrating fluid to do so. In addition to rings stuck to the bores, the wrist pins were tightly stuck in the pistons. The crank just would not budge. I knew this engine had run albeit poorly which is why it was removed from the car. I have problems throwing things away. It sat on a wooden dolley in a basement for more years than I wish to admit.

289s are getting harder to find around here. Most of the Mustangs I see at local car cruises have 302s in them.

It's a 1966 with matching heads so I'm looking for something to put her in.

Back to my question.

• Were panels screwed to tabs on the frame or what?
• Do the fibreglass bodies have thin plates bonded so they are attached the same way as the alloy ones?
• Can someone provide links to pics?

Forrest

[1985 CCX]

Pictures are all over the web.
Rivots were attachment to the discrete frame tubes.
I used SS rivots to make it work.
Also I used a poly bonding to enhance rigidity.
Help?

[CompClassics]

The aluminum sheet metal was rolled around the substructure tubes and riveted so that the rivet heads were not easily seen.

[Three Peaks]

Depends on the location on the body. Where it was possible, the aluminum skin was wrapped around the tubing and riveted in place- the hood edge, cowl edge and rear cockpit edge, door edges, and a couple other discrete places. In other places, the body birdcage was formed close to the edge and rivets fastened the body to the superstructure- the hood opening edges, trunk opening edges, and the rocker panels.

From what I can tell, the door edges had tabs that were formed from the edge of the door to the door frame so there would be some adjustability before attaching with rivets. I believe this gave them some room to adjust the doors to the fender lines, but I could be wrong.

The quickjacks front and back gave some amount of support and attachment at the front and rear but it really wasn't their function.

Bob

[CompClassics]

The hood, doors and trunk outer skin panels were fixed by bending or pinching the aluminum outer skin around aluminum sheet metal framing that was riveted to the steel tubing that formed the superstructure of the particular part,

[wrist_pin]

Thanks for the input guys. I am having trouble posting.

Well, now I can post again. A moderator must have read one of my many pleas for help. Thanks!

~~~~~~~~~~

I am not seeing this in pictures, but I'll pay more attention when I look at builder's pics. I am seeing bulkhead supports but no rivetting going on.

I have only seen one alloy bodied cobra since the 70s and that was in Moon Twp. If I see another one, I'll have to check it out more closely.

I was reading a FiberFab manual for a Cobra and they didn't do a thing like your saying with the fibreglass.

Forrest

[1985 CCX]

Can see it on the edge of doors.

[Dwight]

Each company that produces fiberglass body do them different. Unique and Lone Star mold the interior, trunk, inter fender wells to the body.
FFR uses aluminum panels to make the interior, trunk.
Hurricane has a fiberglass interior / trunk but they are not molded to the body.
Below is a pic of a Hurricane body

Dwight

[wrist_pin]

Thanks for the pics.

Can you fellas tell me how thick the aluminium body metal is and how thick the fiberglass body is?

[MAStuart]

Most old aluminum cars .050 thick. Newer aluminum cars .060

[LMH]

You can see in this Kirkham video how the body is attached to the frame. This is on the billet chassis car but the tube/principle is the same as an original.
This is the bottom of the car below the doors. Also, note the fender lip wire.

[ame]https://www.youtube.com/watch?v=VjdlAWtN5ac[/ame]


Larry

[wrist_pin]

MAStuart,

Thanks for your input. I can see now why they say "Look at the cars, just don't lean on them".

Larry,

I watched the vid on youTube and found links to more vids on the same topic. Thanks for getting me started.


Forrest

[wrist_pin]

Seeing the Clecos in the video reminds me of a time when I had a job with the aircraft industry.

Does anyone know if they used and/or are now using Cherry Max Rivets for the fasteners?


Forrest

[LMH]

Doubt it on originals. Cherrymax is a U.S. company and original cars were built in England.
Kirkham may though.
Larry

[wrist_pin]

Larry, that's a very good point.

I was Googling on "British rivets" last night and found

Aluminium monocoupes and kit cars - PistonHeads

Of course unless the adhesive fails (which it shouldn't), it will stop the degradation of the structural stiffness at a certain point, whereas a purely rivetted monocoque will just get baggier and baggier until it becomes intolerable and/or falls to pieces, but even with bonding the stiffness of a traditional ali monocoque will degrade to the point where it is significantly worse than a (much cheaper and easier to fabricate) steel spaceframe.

If this is true, then that quells my enthusiasm for trying a rivetted monocoque for a chassis on some other car.

Does anyone know if the aluminum bodies on the cobras "loosen" with time and vehicle use?

Forrest

[LMH]

Not that I've noticed and that's on a 50 y/o car. (I've been working on an original) The body is pretty well attached and doesn't show any sign of loosening as far as I have seen. It's never been off the chassis.
Going to depend a lot on how the car has been used though.
This is in terms of an original car. David Kirkham could probably tell you if it's been an issue with his cars but I'd be surprised if they have a problem. Less frame flex than an original car.
Larry

[wrist_pin]

Well, I'm glad to read that, Larry.

Do you have an estimate of how much the entire aluminum body weighs? Which alloy was used ? 6061?

Forrest

[LMH]

I'm not sure what the original alloy was or how much it weighs. 50 pounds for the main body skin rings a bell but I could be totally off.
Cobra's borrowed a lot of parts and fasteners from the British aircraft industry, so my guess would be the bodies were shaped from whatever they were using at the time to skin aircraft in England. Body thickness is/was .050" I think.
Larry

[MAStuart]

Now days here in the US most would use 3003 H14

Mark

[wrist_pin]

Thanks Mark.

I had to look this up.

Speedy Metals Information for 3003-H14 Aluminum

3003 Aluminum is alloyed with 1.20% manganese, which increases the strength of 3003 over commercially pure aluminum (1100 series). 3003 has excellent workability, weldability, and good corrosion resistance. It is used for drawing, forming, spinning, fuel tanks, sheet metal works and other applications that require moderate strength for an aluminum with good weldability. H14 designates the temper, and means that 3003 has been strain hardened and partially annealed. In this condition, 3003 can be easily formed.

I have been following you on metalmeet. You are doing some pretty work.

MAStuart's My Daytona Coupe (cobra) scratch build

Do you have a guesstimate as to the total weight of the body when finished?

Forrest