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Torsion bar science

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Old 04-01-2011, 09:34 AM
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Default Torsion bar science

Here are the facts about torsion bars:


AUTOMOTIVE TORSION BARS

There exists a great misunderstanding about tweaking torsion bars (or using lift “keys”) to lift a vehicle. Many people believe that by rotating the frame end of a torsion bar there is an increase in force on the bar and therefore more twist on the bar. That is not true.

Moving the fixed end of a torsion bar to a new rotation point without increasing the load on it will cause the free end of the torsion bar to rotate the exact same number of degrees as the fixed end was rotated.

I will not delve into the physics and math of this phenomenon so that people without that background can still understand what is happening.

I have devised a model torsion bar apparatus using a wooden torsion bar with levers at both ends supported on ball bearings. One end is fixed to a scale to measure force on the bar, the other end is free to move. The end with the scale represents the frame end of an automotive torsion bar and the free end represents the suspension end.

As can be seen in the unadulterated photographs this particular system with it’s fixed spring rate wooden bar with a force of 10 ounces deflects 11.15 degrees in the un-lifted position. When the system is “tweaked” to raise the free end there is still 10 ounces of force on the bar and the twist measures 11.1 degrees. (There is .05 degree less measured rotation in the lifted condition that could easily be measurement error)

As can also bee seen in the photographs the only way to put more force on the bar is to increase the weight on the free end of the torsion bar causing it to deflect more.


Copyright 2011, Michael Campbell


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Old 04-01-2011, 12:38 PM
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hmmm I'm wondering if any of the guys that commented on the "my 4x4 dakota" thread have looked here and if so what say you now?


The world is not flat, get over it accept new knowledge and move on....
 
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Old 04-01-2011, 02:02 PM
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I'm moving this to off-topic since it isn't a specific question about our trucks.

And I'm not convinced... the mounting points don't match the design of our trucks, so its not a good representation of whats going on. In that setup, the "torsion bar" is in line with both pivot points. Like I mentioned in the other thread, on our trucks, where the torsion bar mounts to the lower control arm, its offset from the pivot point which means there cannot be a 1:1 pivot ratio at the control arms as you turn the keys. And if there is not a 1:1 turn ratio front to back, the bar must twist to compensate. So sorry, but broaden your mind and remember that in math, x does not always equal y.
 

Last edited by 95_318SLT; 04-01-2011 at 02:12 PM.
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Old 04-01-2011, 03:04 PM
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Thanks for moving this.


I really don't care if you are convinced or not, I have nothing to gain or lose by anyone believing or not beieving the truth.



As you can plainly see there is an offset in my model also, it doesn't matter. As long as the offset doesn't change (which it doesn't) there will be no change in the load.
 

Last edited by verdesardog; 04-01-2011 at 04:03 PM.
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Old 04-01-2011, 06:06 PM
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Another interesting point that might be confusing to some.

The end of the key will feel more force than the end of the suspension due to the different amount of leverage. The key is very short compared to the suspension arm. The torsion bar has equal foot pounds of torque on both ends, but because the Key is a short lever it will have many times more force on the end of it. Equal foot pounds of torque, different amounts of leverage equals different amounts of force on the ends of the levers. That's why it's benificial to jack up the front of the truck when adjusting the KEY, to unload it as much as possible.


If you were to put a scale under a front tire and weigh the force on it and were able to measure the force on the end of the key you would see the end of the key has many times more pressure than the wieght of the vehicle. But it's the same amount of torque, measured in foot pounds.

None of the above will change by tweaking the torsion bar, it's all set by the suspension gemoerty, the force won't change, the leverage won't change, the only thing that will change is the rotation of the t bar therefore giving you more or less vehicle height level depending on which way you rotate the t bar. This difference in leverage is why a small linear change in the key gives a much larger difference in position of the end of the suspension arm. Small change on key = large change of vehicle height. All measurments are in relation to the frame of the car, just upside down from my model.
 

Last edited by verdesardog; 04-01-2011 at 06:38 PM.
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Old 04-02-2011, 10:16 PM
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Another thing you need to remember is when doing a t bar lift is that you are not gaining any suspension travel, what you gain on one end you lose on the other end. Your suspension can only flex the same amount that was designed into it. Doing a t bar lift will put your truck closer to the upper end of suspension travel.

That's why t bar lift keys are usless waste of money, you can gain as much lift as can be safely used free and with much less work by tweaking the original keys.
 

Last edited by verdesardog; 04-02-2011 at 10:20 PM.
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Old 04-04-2011, 10:56 AM
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Still no further discussion here? I've been wracking my brain trying to figure out where you guys are coming up with a stiffer ride, I think I've got it.

After tweaking your t bars you have however much you lifted your truck more downward travel on your suspension, once you go past where it was bottomed out before tweaking then yes you are putting more FORCE on the t bar and causing it to twist more giving you a firmer upward torque than during normal driving. So I agree you might be feeling a firmer ride IF you are using that extended downward travel of your suspension. However if you are driving so that your suspension never flexes lower than the original flex you have the same ride..so on the street normal...off road a bit firmer, for sure less bottoming out.

OK? See I'm not a stubborn closed minded person.
 
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Old 04-04-2011, 02:38 PM
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Originally Posted by verdesardog View Post
I'm not hijacking this thread, I'm done arguring with stubborn fools.
The t bar science thread is about information, where do you see any arguing there? Why not respond there instead of in other threads?

I've been driving my dakota with t bars tweaked for many years, the only stiffer ride is because of the higher spring rate t bars I installed.
I personally haven't responded since I don't have any proof/links to support my findings. I still haven't seen a link to your first post. Other than that is all your info. Like I said post links with info!!

I personally don't care about the physics to much. The BUTT test is what proves it. And others too.

I am open minded I see your side maybe your right and by clocking one side the other side does too. But also found a few things around the net that say torsion bars are a progressive spring. Nothing more than that so I didn't care to post it up.

Also you do agree you have a stiffer ride. How do you know that it ALL from the HD bars? Maybe 50% is bars 50% is having above stock height.

Also you just don't have the bars raised up as must as the rest of us do (where we feel it that is). Most of us that feels it have the indexed keys installed. Since you don't you can't feel what we all feel.

Yes I know the "PHYSICS and world is round and you see it flat" ect. Like I said the world is not round. The atmosphere is the closest to a sphere and the world way far from round/sphere. If you try to roll it it wouldn't go straight due to tons of mountains and valleys/oceans if you minus the water. Also for hundreds of years the humming bird defied the PHYSICS and Gravity. So there is tons of arguments per topic. So you don't know or even look at every possibility.

You get too hurt if people don't see it your way, if you didn't you wouldn't be posting and posting and posting in this thread alone. I don't care to argue about this at all, you don't have your truck where we do so who cares what you say, you can't feel what we can. It's like saying you know what a Jet feels like when it takes off without being in it and only thinking about the physics about HOW it would feel. 2-3G's(what ever it might be) is way different on paper vs in person. Expecting since you only flown in a single engine aircraft vs a Jet.

Yes we all know that by cranking them up we loose downward travel and gain upward travel. NO ONE IS ARGUING ABOUT THAT!!! So don't use that as one of your points. I will admit I only had maybe a inch tops of downward travel with the lift key and how much I had turned. But now I have a SAS a good 9-10in down travel.
 

Last edited by Crazy4x4RT; 04-04-2011 at 02:52 PM.
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Old 04-04-2011, 04:00 PM
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Forget all the other posts I have made concernig T bars, I have deleted all pics except for these here.

How do I know the firmer ride is due to higher spring rate t bars? Cause I drove it tweaked for about a year with the original T bars before going to the heavy duty suspension V8 bars from the dealer on my V6 truck, it wasn't firm enough for my use in Arizona back road search and rescue missions.

All springs are "progressive", the more force you put on them the more they will "resist" that force.

You got it just backwards lifting your truck gives you more downward travel not up.

The "butt dyno" is very unreliable and subjective as has been proven on many other sites regarding HP and torque in comparison to true tyno tests.

My feelings are not hurt at all, I'm just trying to understand where other people are coming from. That's why I did the experiment, to PROVE the physics behind spring behavior to myself as well as anyone else intelligent enough to comprehend the results.


As for the difference between a single engine civilian air plane and being catapaulted in military plane off the flight deck of a carrier...been there done that!

And you know the reference to the world being round was just that, a reference, of course it's not totaly round but it is far from being flat.

Another interesting factoid...If the world was the size of a cue ball, it would be smoother than a cue ball....
 
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Old 04-05-2011, 02:25 AM
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Where is the link to the info you posted??
How much do you have yours tweaked?

Since you don't have it close to maxed our or an indexed key you don't know what we are talking about.

I will leave it as that!
 

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