Re: Best T-bar match for XHD leafs?
[Re: Kern Dog]
#2686794
08/12/19 10:18 AM
08/12/19 10:18 AM
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Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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Sniper is not only confused, he is too stubborn to see it. I agree.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Best T-bar match for XHD leafs?
[Re: myduster360]
#2686814
08/12/19 10:58 AM
08/12/19 10:58 AM
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Joined: Jan 2003
Posts: 2,094 central texas
krautrock
top fuel
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top fuel
Joined: Jan 2003
Posts: 2,094
central texas
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wonder what kind of torsion bar system they are talking about. Did you see these two notes under the "arm length" data field? not sure what exactly they mean... "Rear - torsion bar (center) to birdcage bolt center Front - center of torsion tube to center of axle." i think you would need to study sprint car chassis designs to figure that one out...
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Re: Best T-bar match for XHD leafs?
[Re: BigBlockMopar]
#2686945
08/12/19 04:47 PM
08/12/19 04:47 PM
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Joined: Jan 2003
Posts: 5,394 Pikes Peak Country
TC@HP2
master
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master
Joined: Jan 2003
Posts: 5,394
Pikes Peak Country
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Sniper isn't totally off as even Mother Mopar claims t-bar spring rate to be wheel rate as the t-bar is the pivot and not subject to the same motion ratio as a coil spring car. As he illustrated in his link, this ratio in a mopar is 1:1. If you look at the loading of a torsion bar, it will apply the same downward force along the length of that control arm because that control arm is all directly 90* from the rotation of the bar. As a simple torsion event, it is reasonable to say torque = force x 1. ie, spring rate is wheel rate. Since the mopar ball joint is on plane with the t-bar socket and the motion ratio is 1:1, I can see where it is one and the same. Logic would also seem to dictate that altering the lever arm length would impact this force measurement. Additionally, adding any degrees of alteration of angle in this twist also changes the formula to require a vector factor which again, changes the force required. I also can see where it is logical that changing the control arm length changes the force. Cranking off that 100ft lb nut with a 12" wrench vs a 24" wrench is an obvious impact of the difference to this force. Perhaps this is why there are some widely divergent claims of rates advertised by suppliers as some are using spring rate=wheel rate while others are calculating a motion ratio into the rate based on the stock control arm length. Don't know, I can't answer for how everyone is measuring their rates when it should be a simple matter of diameter and length. In a t-bar, is that rate measurement the same at the pivot, the adjusting blade, and the ball joint? Does the fact there is an adjustment blade within the control arm effect this? Does the length of this blade and where it sits in the control matter? I don't know, I've never measured the force on any of them. In my other lives using alternate brands, spring rate was simply the force required to compress (or twist in the case of our t-bar) the spring one inch. Wheel rate was typical the motion ratio adjusted spring rate as measured at the ball joint. Adjusted rate was including or deducting wheel offset from the ball joint point If you really want to get into the math of it, here is a short, 13 page read for you: http://web.mit.edu/course/3/3.11/www/modules/torsion.pdf
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Re: Best T-bar match for XHD leafs?
[Re: Sniper]
#2686995
08/12/19 07:00 PM
08/12/19 07:00 PM
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Joined: Jan 2003
Posts: 31,050 Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,050
Oregon
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I didn't create the terms, those are what they are called. A longer lever has no effect on wheel rate or spring rate in our torsion bar suspensions. If you had a Camaro then yeah, that would matter because the coil spring acts in the middle of the arm and not at the inner pivot so spring rate will always be higher than the wheel rate. Basic suspension geometry which you need to understand if you are serious about handling. You have to know the distance from the tire contact patch to the torsion bar pivot point in order to calculate the wheel rate. The farther out the tire is from the torsion bar then the softer the wheel rate. So even things like wheel spacers, wheel offset, etc. will change the wheel rate on a Mopar. Just like it does on a Camaro. I think that different assumptions on the lever arm length is why some charts show different spring rates for the same bar diameter. In my spreadsheet I use 13 inches for the arm length and 39 inches for the effective length of a B/E bar. The overall length is 41 inches but the ends don't count so I use 39 inches. I'm not sure if that number is correct but as long as you are consistent it doesn't really matter. As for the original question I'd say try some bars and see what you like. Shocks are very, very important when the bar gets bigger than 1 inch. My Coronet rode like a dump track with cheap shocks on it but once I put the Koni shocks on there it felt more like a BMW. I used to wince when I'd hit a bump but with Koni shocks took care of that.
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Re: Best T-bar match for XHD leafs?
[Re: AndyF]
#2687005
08/12/19 07:18 PM
08/12/19 07:18 PM
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Joined: Dec 2003
Posts: 22,696 Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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I didn't create the terms, those are what they are called. A longer lever has no effect on wheel rate or spring rate in our torsion bar suspensions. If you had a Camaro then yeah, that would matter because the coil spring acts in the middle of the arm and not at the inner pivot so spring rate will always be higher than the wheel rate. Basic suspension geometry which you need to understand if you are serious about handling. You have to know the distance from the tire contact patch to the torsion bar pivot point in order to calculate the wheel rate. The farther out the tire is from the torsion bar then the softer the wheel rate. So even things like wheel spacers, wheel offset, etc. will change the wheel rate on a Mopar. Just like it does on a Camaro. I think that different assumptions on the lever arm length is why some charts show different spring rates for the same bar diameter. In my spreadsheet I use 13 inches for the arm length and 39 inches for the effective length of a B/E bar. The overall length is 41 inches but the ends don't count so I use 39 inches. I'm not sure if that number is correct but as long as you are consistent it doesn't really matter. As for the original question I'd say try some bars and see what you like. Shocks are very, very important when the bar gets bigger than 1 inch. My Coronet rode like a dump track with cheap shocks on it but once I put the Koni shocks on there it felt more like a BMW. I used to wince when I'd hit a bump but with Koni shocks took care of that. Yup.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Best T-bar match for XHD leafs?
[Re: Sniper]
#2687120
08/13/19 12:26 AM
08/13/19 12:26 AM
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Joined: Jan 2003
Posts: 31,050 Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,050
Oregon
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That would be because you don't understand the terms wheel rate and spring rate.
Learn them, it is not a matter of opinion it is a matter of science. The spring rate on a torsion bar spring is torque/degree which isn't very useful. You need to know the lever arm length to convert that spring rate into a wheel rate.
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Re: Best T-bar match for XHD leafs?
[Re: krautrock]
#2687160
08/13/19 08:48 AM
08/13/19 08:48 AM
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Joined: Jan 2003
Posts: 350 central IL
myduster360
enthusiast
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enthusiast
Joined: Jan 2003
Posts: 350
central IL
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wonder what kind of torsion bar system they are talking about. Did you see these two notes under the "arm length" data field? not sure what exactly they mean... "Rear - torsion bar (center) to birdcage bolt center Front - center of torsion tube to center of axle." i think you would need to study sprint car chassis designs to figure that one out... the only difference from a "mopar" is that a sprint car spindle is at a right angle to "control arm". The calc for wheel rate is identical on both and the length of the "arm" twisting the TB is critical.
Last edited by myduster360; 08/13/19 08:50 AM.
1972 Swinger 3.6L Pentastar Diablo CMR tuner
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Re: Best T-bar match for XHD leafs?
[Re: topside]
#2689263
08/19/19 02:22 AM
08/19/19 02:22 AM
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Joined: Feb 2010
Posts: 18,493 Granite Bay CA
Kern Dog
Striving for excellence
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Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Swapping out some drag-race ft bars on a basically stock '68 383 Road Runner coupe, no options. The car has new XHD rear leafs from Espo, which should be 125# rate. Throw all that + the typical nose-weight bias in the blender, and I guess the .960s come closest - am I right? I appreciate the thought that went into your question. I have wondered if there is a formula to use as a guide. If there is one, it is a guarded secret or one that I have yet to stumble onto so far. Hotchkis probably has it figured out in their TVS line but I never looked at their spec sheet, nor do I know if they have published the science behind one if one exists. Me? I installed Two RH Mopar Performance 440/Hemi leaf springs in my '70 Charger in 2006. Six stage leafs with two half leaves facing forward. I used a 1.0 torsion bar for many years but a couple of years ago switched to 1.15 bars and Bilstein shocks. The ride feels great. It is about as firm as the Wife's car......2015 Challenger R/T 5.7.
Last edited by Frankenduster; 08/19/19 02:23 AM.
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