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Urgent Jig Help


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#1 Steve220

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Posted 28 April 2017 - 12:02 PM

Guys and girls,

I'm at an emergency stop with my project. Started cutting out the floor and the car made a large bang whilst on the jig. The gaps have parted by 2mm (now 3mm) and spinning it around to sit upside down it closes the gaps. The car is jigged as per pics but I'm worried it's not enough. Which direction should I go?

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This ones closed

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CA78D732-53D5-4ADD-ADB6-530C7C2E5B8B.jpg

This rear quarter has started to ripple just like the other.

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#2 DomCr250

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Posted 28 April 2017 - 03:11 PM

The jig looks a little flimsy to me - mine ran a scaffold pole through the car, it was located to the tunnel on the handbrake mount and then ran cross braces diagonally from each door opening that also met at the handbrake mount.

 

Maybe try rotating it until the gaps close, tack weld them up and then add a cross brace in your 'H' section between the doors - it still might sag as it's not sitting on a pole through the car.



#3 AndyR

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Posted 28 April 2017 - 04:44 PM

The question is also, whats happening to the roof?  Looking at the whole unit structurally, its your jig that is the problem.  As it is made of two separate "legs" with the shell suspended between it, it's creating an accordion effect, with the shell being exerted to the compressive / retractive forces; and pushing the legs essentially away from each other.  Especially when rolling it in the orientation that you have it, there is not enough of the side structure with the big door and widow apertures to resist the bending, placing it on its side with your supports and the big roof panel may be what does it.  Like mentioned above, tack it back together and weld a few diagonals into your current brace bars, both within the square made by the shell interior and a triangle into the door apertures.  And i would also consider welding the two "feet" together with some box section to prevent them wanting to move away from each other.

 

Andy



#4 sonikk4

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Posted 28 April 2017 - 04:55 PM

Steve where you have the drops downs to the crossmember tie each of those together with another section of box while the car is upside down.

 

Is the spit bolted in solidly?? Mine does rock slightly so worth double checking all of the bolts to make sure they are tight as well.



#5 Steve220

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Posted 28 April 2017 - 05:58 PM

The spit is free standing either side. I've taken the car off the spit and onto the wheeled palet, the gaps have gone back to normal. Might have to approach this from another angle.

#6 sonikk4

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Posted 28 April 2017 - 06:08 PM

Add more bracing as mentioned I think is the way fwd.

#7 ukcooper

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Posted 28 April 2017 - 06:08 PM

as AndyR said how's the roof :) movement gota gone some where ??:(



#8 Steve220

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Posted 28 April 2017 - 06:20 PM

Roof's fine. No creases that I can see.



#9 nicklouse

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Posted 28 April 2017 - 06:21 PM

I do not see any triangulation in there so it will move about as much as it wants.

#10 Steve220

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Posted 29 April 2017 - 10:10 AM

Will get some more metal in there. I'm surprised how much flex is in the entire shell if I'm honest!

#11 tiger99

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Posted 29 April 2017 - 12:08 PM

Crossed diagonals, joined at the middle. across the door apertures should solve the bracing problem. It is torsional stiffness that is needed the most.



#12 minidaves

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Posted 01 May 2017 - 08:31 AM

shells are very flexable, and are a bugger for twisting, i am a little more old school, as most of the cars that are being repaired have been run rusty and week, i jiggle the shell till the doors fit nice, and everything lines up sweet, then work out how to get some strength back as quickly as possible.



#13 minidaves

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Posted 01 May 2017 - 08:34 AM

and the roll over jig that bolts on the rear shock mounts and turrets at the front, needs some major thinking in my view as it pulls all over the place and will make the floor pull it the right way up. 



#14 tiger99

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Posted 01 May 2017 - 11:42 AM

Indeed! But that is because rust and the temporary removal of certain parts of the monocoque during the repair process greatly reduces the normally very high torsional stiffness of the shell. In normal use a good Mini shell twists rather less than a lot of much more expensive exotica. Torsional bracing of the door apertures by crossed diagonals puts a lot of the stiffness back in. Linear bracing can't do that.






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