Slant Six Forum :: bent torsion bar

Quote:

I should say that the "shape" is very light and you have to hold it parallel to something and have a very good eye to notice. You should perceive the unit as "arrow straight" as dan says if this is your first suspension adventure and have never researched extensively or look moer than 30 consecutive minutes into that

All torsion bars are "indexed". Smaller diameter bars have the hex offset to rotate the control arm down otherwise they wouldn't support the car. Just as a soft coil spring has to be longer to support the car. You have to put more twist in the spring whether it's straight or coiled. Softer springs allow the front end to lift more because lifting the front end 1" may reduce the loading on the tires only 82 lbs for .820" bars, but 195 lbs for 1.00" bars. Has nothing to do with the shape of the spring.

The shape does not affect the spring rate. Even if the spring is bent into a coil the rate doesn't change. You are still twisting the wire along it's length. Having some arc to the torsion spring is not essential to it's function. It's a byproduct.

When you say progressive you are describing a variable rate spring. Variable rate coil springs are possible only because coils are allowed to go solid which changes the effective number of coils thereby shortening the spring. How are you shortening a torsion spring to increase the rate?

Author:	slantzilla [ Sun Feb 24, 2008 6:21 pm ]
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If the bar is really bent, I would check the front mount in the K-frame to make sure it is not broken out.

Author:	Joshie225 [ Sun Feb 24, 2008 6:39 pm ]
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Quote: I should say that the "shape" is very light and you have to hold it parallel to something and have a very good eye to notice. You should perceive the unit as "arrow straight" as dan says if this is your first suspension adventure and have never researched extensively or look moer than 30 consecutive minutes into that All torsion bars are "indexed". Smaller diameter bars have the hex offset to rotate the control arm down otherwise they wouldn't support the car. Just as a soft coil spring has to be longer to support the car. You have to put more twist in the spring whether it's straight or coiled. Softer springs allow the front end to lift more because lifting the front end 1" may reduce the loading on the tires only 82 lbs for .820" bars, but 195 lbs for 1.00" bars. Has nothing to do with the shape of the spring. The shape does not affect the spring rate. Even if the spring is bent into a coil the rate doesn't change. You are still twisting the wire along it's length. Having some arc to the torsion spring is not essential to it's function. It's a byproduct. When you say progressive you are describing a variable rate spring. Variable rate coil springs are possible only because coils are allowed to go solid which changes the effective number of coils thereby shortening the spring. How are you shortening a torsion spring to increase the rate?

Author:	Joshie225 [ Sun Feb 24, 2008 6:55 pm ]
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Another thing on springs. Progressive springs usually are far from optimum. For suspension applications where a progressive or digressive rate is desired you end up with linkages in the suspension to provide the change in rate at the wheel. After all, it's the rate and load at the wheel that's important. Certain motorcycles are good examples of linkages provide progressive or digressive wheel rates.

Author:	argentina-slantsixer [ Sun Feb 24, 2008 7:14 pm ]
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Quote: Quote: I should say that the "shape" is very light and you have to hold it parallel to something and have a very good eye to notice. You should perceive the unit as "arrow straight" as dan says if this is your first suspension adventure and have never researched extensively or look moer than 30 consecutive minutes into that All torsion bars are "indexed". Smaller diameter bars have the hex offset to rotate the control arm down otherwise they wouldn't support the car. Just as a soft coil spring has to be longer to support the car. You have to put more twist in the spring whether it's straight or coiled. Softer springs allow the front end to lift more because lifting the front end 1" may reduce the loading on the tires only 82 lbs for .820" bars, but 195 lbs for 1.00" bars. Has nothing to do with the shape of the spring. The shape does not affect the spring rate. Even if the spring is bent into a coil the rate doesn't change. You are still twisting the wire along it's length. Having some arc to the torsion spring is not essential to it's function. It's a byproduct. When you say progressive you are describing a variable rate spring. Variable rate coil springs are possible only because coils are allowed to go solid which changes the effective number of coils thereby shortening the spring. How are you shortening a torsion spring to increase the rate? if smaller diameter bars wouldn't have shape, they would break because of the massive amount of axial stress that offsetting the hex head has. They're indexed because in the process of offsetting the hex head, they buil in a "bow" shape in that bar wich relieves part of the axial stress. and incresing the rate is achieved by diameter on a torsion bar. Since the lenght is not a variable, that's the reason for different diameters. You "shorten" the torsion spring by aughmenting the diameter. Shape indeed afects spring reaction, not rate. you put shape into a piece of wire or flat spring and it would react differently than a straight piece of the same material. Think of one reason to prove me wrong. If the only reason for indexing a bar is the offset that would push the arm downwards, and being exactly mirrored symmetric (each side) why there's left and right T-bars? And more importantly, have you ever checked about a dozen of OEM fresh .900 or .860 or .99 t bars? I have, and they have a shape. I'm just pointing out what I have observed. I didn't mean "progressive", I mean "sort of", as in "behaves somewhat alike progressive"

Author:	Joshie225 [ Sun Feb 24, 2008 8:02 pm ]
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Small diameter bars like the drag bars on a B-body do approach their strain limit. An acquaintance is a crew member on a late model oval track car. They use very light springs and just like overloaded torsion bars they distort. Again, it has nothing to do with the shape of the spring. The hex ends can be formed at any angle. Putting the hex on the bar does not require twisting the bar. They are indexed only so enough preload can be achieved to support the vehicle. If the bars were twisted and then heat treated I can certainly see the bars ending up with a bow. Or if the bars were simply cold set they will end up bowed. Either way the shape is an artifact, not a necessity. Left and right bars exist because rotating the end of one torsion bar 10Â° clockwise necessitates rotating the other side 10Â° counterclockwise because they operate in different directions.

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Author:	slantvaliant [ Sun Feb 24, 2008 8:35 pm ]
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Quote: I would be concerned with why it bent. Sometimes, the bars get bent when they are used for towing, jacking, or tie-down purposes. Bad practices, all! Quote: i dont want it to ride like a buck board 0.870 bars with good shocks aren't bad.

Author:	dusterdude225 [ Mon Feb 25, 2008 6:03 pm ]
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so i replace the t bars and i am good to go

Author:	NewLancerMan [ Mon Feb 25, 2008 7:47 pm ]
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I think there was good advice from VDART to check to make sure there isn't any crash damage. However, I have seen junkyard bars that do have a curve in them, just from years of use. I can't say I've ever seen a bent bar new, but you can call up FirmFeel or Mancini and see if the new bars they sell have a bend in them or not. MJ

Author:	dank10fenny [ Tue Feb 26, 2008 12:49 pm ]
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when i got my new bars they were arrow staight, they only had a L and R on them, they were beef so no offset on the hex. if they were bent new, they would have to have some sort of indexing to you could instal them right. nada. i think you guys are just gettin into this physics of t bars too much. its a bar. it twists like a spring. not much more

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