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bent torsion bar
https://slantsix.org/forum/viewtopic.php?t=27376		 Page 1 of 2
Author:  dusterdude225 [ Sat Feb 23, 2008 2:38 pm ]
Post subject:  bent torsion bar
I have a bent torsion bar. It is crooked as a dog’s hind leg. It is on the passenger side. Is it supposed to be like this? :?: Do I need a new set? Please help me in my first suspension rebuild. Please give any rebuild tips too.
Author:  SlantSixDan [ Sat Feb 23, 2008 2:51 pm ]
Post subject: 
The torsion bars need to be arrow-straight. If you've got a bent one, you'll need to replace it. Good opportunity to upgrade to thicker bars.
Author:  Matt Cramer [ Sat Feb 23, 2008 3:48 pm ]
Post subject: 
You didn't say what year Duster this is, but unless it's an F-body Duster (Volare) it's time for new torsion bars.
Author:  dusterdude225 [ Sat Feb 23, 2008 4:33 pm ]
Post subject: 
it is a 73

what size should i shoot for
Author:  VDART [ Sat Feb 23, 2008 4:53 pm ]
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I would be concerned with why it bent. Check your suspension pieces closely, if ok then get new bars. I believe your bars to be the .850 thickness--- I put some .870 bars in my 62 valiant & it seemed to firm up the ride quite a bit. Lawrence
Author:  argentina-slantsixer [ Sat Feb 23, 2008 5:50 pm ]
Post subject: 
torsion bars aren't straight. This is the greatest mistake I have been encountered when people talks bout them. They have shape. They're a section of a very large spiral shape. that's why they have to be installed in certain way and in certain side of the car. If you look at say your left T bar, properly installed, it should somewhat point down and inward. THEY're NOT STRAIGHT!
Author:  dusterdude225 [ Sun Feb 24, 2008 1:39 pm ]
Post subject: 
torsion bars aren't straight. This is the greatest mistake I have been encountered when people talks bout them. They have shape. They're a section of a very large spiral shape. that's why they have to be installed in certain way and in certain side of the car. If you look at say your left T bar, properly installed, it should somewhat point down and inward. THEY're NOT STRAIGHT!

they are bent in a U shape like it is bowed down in the middle

Quote:
I would be concerned with why it bent. Check your suspension pieces closely, if ok then get new bars. I believe your bars to be the .850 thickness--- I put some .870 bars in my 62 valiant & it seemed to firm up the ride quite a bit. Lawrence
i dont want it to ride like a buck board i dont want a to firm ride[/quote]
Author:  SlantSixDan [ Sun Feb 24, 2008 2:21 pm ]
Post subject: 
Quote:
torsion bars aren't straight. This is the greatest mistake I have been encountered when people talks bout them. They have shape. They're a section of a very large spiral shape. that's why they have to be installed in certain way and in certain side of the car. If you look at say your left T bar, properly installed, it should somewhat point down and inward. THEY're NOT STRAIGHT!
Interesting...I've never run into this. All the bars I've handled have been straight (though perhaps I wasn't looking closely enough), and my understanding was that the left vs. right was due to the indexing of the hexagonal ends relative to each other.
Author:  dank10fenny [ Sun Feb 24, 2008 3:04 pm ]
Post subject: 
new t-bars are straight yes, and you want to put them in proper sides becuase of the preload needed with the offset hex's. used t-bars WILL curve after a period of time, this is why it is importland to re-install them in the same place. you dont want to mess with the integrity of the metal by makin them have to hold weight the other way/side. it sounds like THIS t-bar has been signifigantly damaged and needs attention. just make sure to swap both sides
Author:  Matt Cramer [ Sun Feb 24, 2008 4:08 pm ]
Post subject: 
Quote:
Interesting...I've never run into this. All the bars I've handled have been straight (though perhaps I wasn't looking closely enough), and my understanding was that the left vs. right was due to the indexing of the hexagonal ends relative to each other.
It's also because they are pre-stressed. This leaves areas of tension and compression in the metal that make them better suited to handling loads in one direction.
Author:  argentina-slantsixer [ Sun Feb 24, 2008 4:43 pm ]
Post subject: 
Quote:
new t-bars are straight yes, and you want to put them in proper sides becuase of the preload needed with the offset hex's. used t-bars WILL curve after a period of time, this is why it is importland to re-install them in the same place. you dont want to mess with the integrity of the metal by makin them have to hold weight the other way/side. it sounds like THIS t-bar has been signifigantly damaged and needs attention. just make sure to swap both sides
no, sir. They need to have some shape BEFORE. The shape will result in less thickness needed to do the spring work. This would be a mistake only comparable to state that coil springs comes straight and gets winded over use. Also, the shape allows the bars to produce a more gentle movement without being saggy.

Torsion bars are shaped and that's the reason why they have side and orientation.
Author:  Joshie225 [ Sun Feb 24, 2008 5:20 pm ]
Post subject: 
Juan,

I have to disagree on torsion bars needing to be in a shape other than straight. What determines a spring's rate (lbs/in or kg/mm, etc) is the effective length of the spring and the wire diameter. The other variable which isn't considered variable is the modulus of the steel used in the spring. It doesn't matter if the spring is wound into a coil or is straight like a torsion bar.

The 1.04" and larger Mopar Performance torsion bars are identical for right and left. The .990 and smaller are indexed for right and left to allow for enough preload to support the vehicle. The idexing or preload in a torsion bar can be equated to the free length of a coil spring. For a lower rate coil spring to support a given load at a given height it must have a longer free length than a higher rate spring. Lower rate torsion bars have to be indexed to allow more twist just as the coil spring would be compressed more.

Swapping torsion bars side for side would be akin to stretching a coil spring rather than compressing it. Coil springs distort in use just as torsion bars do. I have a story about someone trying torsion bars that were not properly heat treated and they ended up in the shape described. Looked like something from a giant iron barber pole with hex ends.
Author:  argentina-slantsixer [ Sun Feb 24, 2008 5:39 pm ]
Post subject: 
Quote:
Juan,

I have to disagree on torsion bars needing to be in a shape other than straight. What determines a spring's rate (lbs/in or kg/mm, etc) is the effective length of the spring and the wire diameter. The other variable which isn't considered variable is the modulus of the steel used in the spring. It doesn't matter if the spring is wound into a coil or is straight like a torsion bar.

The 1.04" and larger Mopar Performance torsion bars are identical for right and left. The .990 and smaller are indexed for right and left to allow for enough preload to support the vehicle. The idexing or preload in a torsion bar can be equated to the free length of a coil spring. For a lower rate coil spring to support a given load at a given height it must have a longer free length than a higher rate spring. Lower rate torsion bars have to be indexed to allow more twist just as the coil spring would be compressed more.

Swapping torsion bars side for side would be akin to stretching a coil spring rather than compressing it. Coil springs distort in use just as torsion bars do. I have a story about someone trying torsion bars that were not properly heat treated and they ended up in the shape described. Looked like something from a giant iron barber pole with hex ends.
you just made to my point. Thicker torsion bars aren't indexed because they're just a thick piece of steel. There's more to it than a chunk of tempered steel with hex heads, as you say. Thinner ones are shaped because if you pre shape a thinner section of spring tempered "wire" it would have sort of a "progressive" effect, meaning, it would react the same as a thick chunk without the harshness in the action, permitting the same reaction times without the big shake that thick bars have. I see this all the time in sax and clarinet needle springs. Thinner torsion bars would also allow the car to lift the nose more than a thick one (proportionally) and that's because of the shape.
Author:  argentina-slantsixer [ Sun Feb 24, 2008 5:42 pm ]
Post subject: 
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 :wink:
Author:  NewLancerMan [ Sun Feb 24, 2008 5:55 pm ]
Post subject: 
point being, you need new tbars =) swap both sides, and you'll be good.

BTW I have several good sets, so if you're interested, let me know. Both softer and harder (.83 or .87) sitting here gathering dust. I put in .92s and won't go back (in fact am probably going up to .99s)

MJ
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