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Want to determine how much weight your frame has lost due to rust?
David Howard has a brand new NOS 69-1973 frame. Extremely mild surface rust only. We just weighed it today at 265 lbs.
I have weighed my 1972 frame earlier, with 100K miles on it and 25 years of abuse, but garaged for the last 25 yrs, at 242 lbs.
Mine had some surface rust, some pitting, no flaking, a couple of cup fulls of small rust flakes inside, zero rust holes anywhere, and was what I would consider a very good solid frame. It measured the same thickness everywhere. Still it had lost 23 lbs over the years, due to rust.
He had this NOS frame available so we carefully measured it if anyone wants to weight their frame and use that as a guide as to how solid it may still be.
The thickness of it measured either .110 to .113 at many different spots using a 1.000" micrometer. Interestingly the motor mount brackets are much thicker at 0.160" It was painted and Eastwood coated inside.
Using two of these scales we also weighed a very complete rolling 68 chassis, at 1140 lbs. with full suspension, gas tank, steering, PS ram, Rally wheels and Cooper tires.
We used these or similar:
We got calibrated and repeatable results within a pound or so.
How good is that! But I'd be afraid to weigh my frame! My car is originally from Wisconsin.
Not to mention I am not inclined to completely dissassemble a running car just to find out.
However extremely useful information for those doing a frame off restoration.
I measured mine again carefully today and I got a bunch of 1.03 to 1.06" thicknesses. So it has thinned out from the original 1.10" and that makes perfect sense with my 24# frame weight loss. That's a 9% weight loss. And presumably strength loss as well.
FWIW
I measured mine again carefully today and I got a bunch of 1.03 to 1.06" thicknesses. So it has thinned out from the original 1.10" and that makes perfect sense with my 24# frame weight loss. That's a 9% weight loss. And presumably strength loss as well.
FWIW
You've got to be careful trying to make determinations like that based off a single frame. These things had production tolerances that would easily eat up 24 lbs. Hell, even your wall thickness is within spec for A36 sheet thickness or A36 square tubing wall thickness. It could have come out from the factory with that thickness for all we know.
Just curious do you know the spec for this thickness steel?
I just found an ASTM chart that says the normal thickness tolerance of 12 Gauge steel is from .0994 to .1174 "
So that certainly seems like the gauge that was used for the frames.
So you are absolutely correct, the .112" on one frame and the .104" on another, built a decade apart, might mean nothing at all!
Last edited by leigh1322; Jul 21, 2023 at 12:22 PM.
Just curious do you know the spec for this thickness steel?
I just found an ASTM chart that says the normal thickness tolerance of 12 Gauge steel is from .0994 to .1174 "
So that certainly seems like the gauge that was used for the frames.
So you are absolutely correct, the .112" on one frame and the .104" on another, built a decade apart, might mean nothing at all!
I do not know the spec. I honestly don't even know which steel they made the frame from. I mention A36 because its as common as dirt, but the factory could have used any number of low carbon alloys. There are also some processes that will yield better tolerances than others. I don't generally work with steel (too effin heavy), but I know drawn aluminum has tighter tolerances than extruded aluminum. It wouldn't surprise me for steel to have different tolerances for different processing.
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NOS Bare Frame Weight Documented
