The MGA With An Attitude
BODY SILL Replacement Parts, Commercial - RT-224

On 2/1/2010, Jon Tillman wrote:
"I just got off the phone with Scarborough Faire and I think I'll be getting the parts from them. The one thing that concerns me is that they told me the parts are 22 gauge metal, 'factory specs'. Is 22 gauge correct for original"?

ROTFLMAO. Gimme a minute to pick myself up off the floor and stop laughing. Hell no. 22 gauge is like the outer body sheet metal on some recent Oriental econo cars where you can dent it by pushing on it with your thumb.

Original sheet metal in MGA body sills is 18-ga, 0.048" thick, 2-pounds per square foot. You could break your foot if you kick it. I was worried about 20-ga being too thin. 22-ga is only 0.028" thick, and you can bend that stuff with your fingers. Bending strength of sheet metal varies as the cube (third power) of the thickness. So, ....
    (0.028/0.048)^3 = 0.198.
Does that give you a hint? The thinner metal reduces weight by 42% and reduces bending strength by 80%. Even with the box section structure it has to be at least 50% to 60% weaker in beam strength. I wouldn't put such thin sheet metal in my MGA body sills even if it was free.

On 2/1/2010, Jon Tillman wrote:

"When they told me 22-ga I was a little surprised as I was told even Moss uses 20-ga (and I've heard that their stuff is too thin). The person in the phone went into this long explanation about how the inner sill is made in England and has the extra gussets for strength. I contacted the company you mentioned in a previous email and although they charge 149.00 for inner sill their material is 18 gauge".

The gussets are original issue, four places directly below the front and rear surfaces of the door pillars. The gussets add greatly to crush resistance of the box, and therefore torsional stiffness of the body sills in assembly. See RT-615 and 3092.jpg

Someone sent me some pictures of the Moss parts, and there were only three gussets in those pieces, only one below the rear door post. I guess the people making and selling these parts have little or no engineering design understanding of how they work.

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