Torsion bar specs...please add info

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gazza414

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I bought a set of Iron Man torsion bars today
Thought it a good idea to start a thread listing the specs as many shops will simply state " oh yes up graded bars , heavy duty"...never know what dia they are or how much increase in spring rate

anyway all aftermarket torsion bars should be give or take a few mm the same length..893mm

The dia of the Iron Man HD bar is 26mm....it is this dia and a function of the working length that dictates spring rate or angular deflection as a function of applied torque.


If others have any other brands of bar would you mind measuring the dia and adding this info to the thread.
Iron Man..26mm
Dobinsons..26mm dia
Tough Dog...
Superior Eng ....
4WD Systems.....
ARB
TJM
OP
Pedders
Calmini ..27mm
etc etc
 
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depends on the spring steel its made from also, you can't just go by diameter.
 
Al said:
depends on the spring steel its made from also, you can't just go by diameter.
Click to expand...

It makes no difference at all to the spring rate or stiffness

The maths / design goes like this

Torsional Deflection of Shaft
The angular deflection of a torsion shaft can be expressed as

θ = L T / Ip G

where

θ = angular shaft deflection (radians)

L = length of shaft (mm, in)

G = modulus of rigidity (Mpa, psi)

Circular Shaft and Polar Moment of Inertia
Polar moment of inertia of a circular solid shaft can be expressed as

Ip = π R4/2 = π D4/32

where

D = shaft outside diameter (mm, in)

The angular deflection of a torsion solid shaft can be expressed as

θ = 32 L T / (G π D4)
 
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the composition is going to vary from different manufacturers, and depending on just how much carbon in it is going to effect its mechanical properties. That formula even accounts for the rigidity of the steel of which the material specs is a big factor. Maybe we have a industrial chemist on here that can help out. Oh and I am happy to stand corrected if it can be shown, I would be very surprised though. Who knows each manufacturer might specify the exact same compostion of steel.

edit: other factors can also effect it like cold work , heat treatments.
 
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Al,
what you have stated is incorrect and I'm not going to turn this thread into a Materials Engineering 101 tutorial at Uni.

Please see attachment. and you'll notice that both E and G don't change..they are ratio's. The compositions, UTS, and hardness values do change.
SpringSteelProps.jpg
 
gazza414 said:
Al,
what you have stated is incorrect and I'm not going to turn this thread into a Materials Engineering 101 tutorial at Uni.

Please see attachment. and you'll notice that both E and G don't change..they are ratio's. The compositions, UTS, and hardness values do change.
QUOTE]

if you believe that diameter of the torsion bar is all that governs the properties of an aftermarket torsion bar then by means use that info for your selections. E & G will same a constant if there are no alloys present in its composition, this is not a given. Anyway i am not gonna google and try to rely on snippets of info that i may or may not understand, who knows you may be a professor on it. I would think its better to just ask the supply "what are the spring rates mate".

edit: removed IMG from quote
Click to expand...
 
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Torsion bars use JIS SUP 9 alloy steel, aka AISI 5155 - it's not in your table there but that's irrelevant, as an aftermarket manufacturer using something other than SUP 9 for a torsion bar would be an exception - it's easiest just to take the stock torsion bar design, increase diameter by whatever amount for the spring rate they're chasing, and the job is done. So since length is a fixed value, you can compare by outer diameter alone.

For what it's worth, the modulus of elasticity of SUP 9 is 205GPa, very close to the 207GPa of the steels in your table there.
 
yeah if they all use the same stuff then yeah outer diameter should work. as stated in your first post gazza my dobinsons are 26mm, never measured what stock were. And i believe someone once had inside info that there were only 2-3 plants making all the TBs anyway, others just rebadge.
 
that there were only 2-3 plants making all the TBs anyway, others just rebadge.

That's correct
 
So going by this we can pretty much assume all torsion bars are the same so we may as well just buy the cheapest possible torsion bars we can find. That is of course if the dia is the same, which i'm betting most after market bars will be 26mm.
 
ben85 said:
So going by this we can pretty much assume all torsion bars are the same so we may as well just buy the cheapest possible torsion bars we can find. That is of course if the dia is the same, which i'm betting most after market bars will be 26mm.
Click to expand...

Could be 2 category,s there chinese and aussie made
 
I would like to know who makes torsion bars in Australia
Cheers
 
I have been told buy a couple of good reliabel sources that there are 5 companys in the world that make the TB's. They are only made two ways.

1. They cut the bar a bit longer then needed and cold press the steel to give the bulge at eather end and then cold roll the splines into the ends. ( This been the stronger ones)

2. they cut the bar to the right length, then mill the midel of the bar to the right diameter and cut slpines into the end.

If you ask the sales person at the shop how ur TB was made, they wont tell you. They wont even tell you who made it.

You can try and trace the serial number back. If you do this, you will find who has the same type of TB's and just stuck there brand name on it.
 
Where are they made?

be interesting to know which ones are the same, and if any are made in a larger diameter than 26mm for the navaras.

I will check the dia. of the oem bars, see how much difference.
 
I have not found out were they r made. Kts a it of a secret. I gess so that the major stores can charge there own price for the. Say if u found out that the rock crawler TBs r the same as the ironman TB, then u would be able to get them the same price.
 

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