Rotisserie and unabody bracing

[tharbert]

I wanted to get some feedback about something 962porsche posted in the rotisserie thread

Originally Posted by 962porsche

in my shop we never use rotisseries for unabody cars . they get put on body jigs (frame bench) . if you do want to install a unabody car on a rotisserie then you have to triangle brace the car front to back and side to side . this is becouse of the flex has .a unabodyed cars tolerances are only 5MM that would be 2.5 MM plus and minus . the more you cutaway panels from the car the more bracing you have to install . i had a 911 in my shop this past summer the person that restored it. did it on a rotissorie and only braced the passenger compartment . when the car went back on its wheels every panel gap was off . so if you do have your hart set on using a rotissorie then don't forget to brace the engine and trunk compartments as well and tie them into the bracing in the passenger compartment . before you weld in the brasing square up the car don't just trust the gaps that the car has before its taken apart . becouse hows to say that the panels you're looking at have not been f@%$ with to make them fit ?

I'm doing some rust repair on my 72. After grinding and scraping enough of that infernal rock guard, I decided to go with an octagon rotisserie. The rotisserie is attached at the suspension points, not the bumpers. I want to make sure I don't do more harm than good here I want sufficient bracing to keep me out of trouble.

First of all, my tub is still on blocks, leveled and receiving a new left inner and outer rocker along with some adjacent metal. I will measure it before it comes off the blocks for a base line and to determine if it's close to square out of the gate. My formidable search foo is weak as I've found no procedures or explanation of how to "square up the car" or even measure it for squareness. Can someone please explain this in better detail?

Once square, how do you suggest a DIYer properly brace a tub? I understand front to back, left to right, trunk, cabin and engine compartment. Do I just start welding "X" patterns across door jambs and all three compartments? Anyone have pictures of a properly braced tub? What would you recommend a DIYer use for bracing?

[Fishcop]

Hi Tharbert

I replied to your PM, but here's some pictures. The octisserie format is very unibody "friendly", but definitely brace it up before the sills, floors or other structural elements are removed. And do it one side at a time.

[IMR-Merlin]

I think I went a little overkill on my bracing.

[962porsche]

to square up a car or to check to see if it is . you need the chasses measuring guide of the car so you can check the measuring points . a measuring guide gives you all the places to measure from and to . we do this to all our cars that are getting a resto . if the car is out of it's meaurements at all from spec we them mount the car on the celette bench and give it a pull into spec . if a car is mounted and you brace the crap out of it you can do the work on a rotisserie . i have found over the year of doing resto's it's just not worth it . we have a car right now in the shop that the customer did the resto on him self with the car on a rotisserie . he braced the crap out of it and the doors he can't get the gaps right . the car is out of spec by 1.8 mm . you may not think it's much but it makes it a total of 4.3 MM out . you only have 2.5 MM + and - making it a total of 5MM to be in spec . the sad thing is when the car was turned up side down the tops of the door gaps opened .

[962porsche]

Originally Posted by IMR-Merlin

I think I went a little overkill on my bracing.

if you think that this car is braced right you better think again !!!! the cage and strut tower bracing will not cut it .

[962porsche]

Originally Posted by Fishcop

Hi Tharbert

I replied to your PM, but here's some pictures. The octisserie format is very unibody "friendly", but definitely brace it up before the sills, floors or other structural elements are removed. And do it one side at a time.

john's rotisserie is a good one . this does not hold the car on both ends only . were the car bolts up to the rotisserie is one of the best places to bolt a car up to one .

[IMR-Merlin]

Originally Posted by 962porsche

if you think that this car is braced right you better think again !!!! the cage and strut tower bracing will not cut it .

It actually was sarcasm.

But strange, when I cut the roof off there was no spring in it and the other roof fit perfectly. Some maybe it did "cut it". Either way I didn't take any chances and made sure to square up the car by it's pick up points before finalizing all my cross bracing and stitching the roof on.

[962porsche]

the car should not sag much or at all by removing just a roof skin . it's when the car get's cut up like John's blue car posted here . cars are built on jigs there for i also like to repair them the same way . if you want to do a resto on your car using a rotisserie thats just fine with me . i have stated many times the good and bad about using one and feal no need to get into that again .

[CalvinC4S]

Originally Posted by 962porsche

to square up a car or to check to see if it is . you need the chasses measuring guide of the car so you can check the measuring points

What tools/method would be best for a home restoration on checking this.
I wouldn't imagine the pros using a tape measure?

On your customers car, was it something a novice could spot with the factory service manual measurement pages with the car on jack stands?

[962porsche]

you use a tram gauge to do the measuring . there about 200 dollars for a starter one . if you look at what they real are you can make one your self for about 30 dollars . as we put the panels back on the car we also keep taking measurments to know the cars going together with in the car makers spec .