Mystery Spring

[Steve Simmons]

Has anyone ever seen a spring like this? Supposedly it's a TC spring, and the length/width is identical, but notice how there is a double main leaf. The arc is a little flatter than an original TC spring but I'm not sure if that's by design or if it's just old and saggy. It has the same leaves as a TC spring, with the addition of that extra main leaf. I'm sure this double main leaf design is much stronger, but I can't help thinking this would make it too stiff. Anyone ever hear of an aftermarket manufacturer doing this? It's a rear spring by the way.

TC main leaf is beside it for comparison. Also, the double leaf seems to be permanently attached, like it's welded on or something. Or maybe I just need to pull harder. It's doweled.

[Rob Reilly]

Well, the leaves won't be welded together, because they have to move relative to each other. There will be a pin in the center to keep them in place.
The spring rate or deflection for any given load is dependent on the width, length and number of leaves, but especially on the thickness of each. The beam deflection formula is d = PL**3/48EI where I is the section modulus I = wt**3/12 and thus takes into account the cube of the thickness, i.e. t x t x t
If the intermediate leaves are shorter or more in number or especially thicker you can expect less deflection, a stiffer ride.

[Steve Simmons]

Yeah, I realized right after I posted that "welded" was definitely not the right word.

I'm sure you're right that there's a dowel there. But that still begs the question, what are these for and why do they fit a TC perfectly?

[Ray White]

...
The spring rate or deflection for any given load is dependent on the width, length and number of leaves, but especially on the thickness of each. The beam deflection formula is d = PL**3/48EI where I is the section modulus I = wt**3/12 and thus takes into account the cube of the thickness, i.e. t x t x t
...

With respect you may know what you are talking about but I would put money on it that no one else - including me - has a clue.

[Rob Reilly]

Sorry, that's the way to calculate how much a spring will bend under any given load. I was thinking how to identify and characterize it, assuming it is an aftermarket spring made for racing and would in that case likely be stiffer than normal.

[Martin Johnson]

Hello:
Maybe a "Y"-type saloon? Or another MOWOG vehicle?

[Steve Simmons]

As I recall, Y-Type springs were wider like the TD/TF springs. But maybe a Woolsely or similar from the 40's? Or a saloon?