850 Spider restoration- Chasis brace and mounting method to tube

[Frank L. Di Gioia]

The 850 Spiders were based on the sedan platform. Without the roof they were "flexible flyers" so Bertone put a large X brace under the floor and another where the rear seats would have been in the sedan. Looking at it I decided it was a natural to try and connect the two, also I had a steel plate the exact right size. The first pic shows the rear X brace and the tunnel after I drilled a few holes in it. Second shows the Y brace I cut out of the leftover steel. At the gas tank firewall there is a 2" wide existing mount I'm attaching to with two 6mm bolts. At the tunnel end it's also held on with two 2 6mm bolts, one offset to avoid drilling into the heater water lines. Where it crosses the center of the X there is a single 8mm hole drilled through the top and bottom of the rather stout X. to avoid crushing the mounting point an old school aircraft technique is used. The 8mm hole, top and bottom, is drilled slightly undersize and then reamed to an exac t 8mm. The upper 8mm hole is now drilled to slightly under 1/2" and then also reamed to an exact 1/2" allowing the insertion of a piece of aluminum tube 1/2" diameter OD. It's then marked and cut off about 1/32" shorter than the mark. The object is to allow secure clamping of the brace and X brace together without crushing the X center. In actual aircraft construction the bolts, washers, tube, nuts, threaded/solid bolt length is VERY precise to the point the bolt fits so snugly it's inserted with a pigskin mallet (remember my base view is WW2 aircraft so pigskin was the mallet used!) I hope this concept helps any of the X people out there. BTW consult Redracer (Gil) and Jeff Stich if you're looking for "keeper" restoration methods.

 

[Jeff Stich]

Nice work, but it would seem to me that removing the longitudinal vertical sheetmetal panel that's normally directly behind the seats (ie: the "front wall" of the rear seat shelf) would negate much of any "advantage" that your modification would bring. That sheetmetal provides much-needed structural rigidity in that area, helping to reduce side-to-side chassis flex (twisting), which the Spider needs.

Also, if your mod is done to a Spider with the rear seat structure still intact, how does the horizontal upholstered panel (rear seat "base") sit flat with your mod's center bolt head sticking up above the X-brace surface? Or is this mod only meant for a car with a gutted interior?

 

[Jeff Stich]

Oh, that's a beautifully-crafted Y-bracket, btw.

 

[Frank L. Di Gioia]

Jeff,
I had to go out and look at the car to remember there was a vertical cross brace panel there originally. It must have been removed when the roll bar was installed. I only have a vague memory of what/where it was in my last Spider. I seem to recall it had a beaded top edge and several creases to add stiffness. Mod was/is mainly for "Cars & Coffee" to be honest! I had the piece of steel from the original roll bar which used it as a headrest behind the driver. and looked for somewhere to use it. It was an exact fit lengthwise so that's where it was destined to go. The only upholstery this is going to have is a padded leather dash top because I've also got some left over material from a kitchen chair project. My "inspiration" for brackets/braces/gussets comes from looking at a Maserati Birdcage years ago, the ultimate cut and fit car.

 

[myredracer]

Great idea and looks good. Should save a few seconds a lap at Cars & Coffee, lol.

I just wish dealing with weak floors in an 850 coupe due to rust was as easy...

 

[Mark]

Is this the panel in question:

Nice work, but it would seem to me that removing the longitudinal vertical sheetmetal panel that's normally directly behind the seats (ie: the "front wall" of the rear seat shelf) would negate much of any "advantage" that your modification would bring. That sheetmetal provides much-needed structural rigidity in that area, helping to reduce side-to-side chassis flex (twisting), which the Spider needs.

Also, if your mod is done to a Spider with the rear seat structure still intact, how does the horizontal upholstered panel (rear seat "base") sit flat with your mod's center bolt head sticking up above the X-brace surface? Or is this mod only meant for a car with a gutted interior?

 

[Frank L. Di Gioia]

Yes! When something isn't there (like perhaps a memory) it's not missed. The rear area seemed rather spacious but nothing registered as to why. Given that everything else on my 850 was done with little regard for looks it got by me because there were no telltale signs of sheet metal ripped out.