 | Home > Off Topic > One for the materials engineers, anti roll bars. |
 
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| lambert.the.farmer Member Since: 11 Apr 2012 Location: harrogate Posts: 2006   
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Hi fellow engineering types. Unfortunately it has been far too long since I was directly involved in this area of practice so i need some help.
How much percentage increase in torsional resistance might be expected in two otherwise identical shafts when one is 25mm diameter and the other is 28mm diameter? In application this is in terms of anti roll bars on a 1000kg sports car build. I know from subarus that stiffening the front bar affects how the back end behaves making it more prone to break away and that conversely stiffening the back makes turning in to corners more difficult. I am also aware that there are other considerations like the durometer of the bushings say a thicker bar in rubber may not actually be any more resistant than a thinner one in polyurethane. Essentially I don't want it to be on three wheels if it drives over a pebble but equally I would like to have a fairly flat cornering attitude. Thanks in advance  Rhubarb and custard let fly with their secret weapon. |
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14th Aug 2017 7:47pm |
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| Disco_Mikey Member Since: 16 Nov 2014 Location: Dundee Posts: 531  
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Stiffening the front end makes it more prone to understeer
Stiffening the rear end makes it more prone to oversteer, but helps massively with initial turn in  |
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15th Aug 2017 2:54am |
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| lambert.the.farmer Member Since: 11 Apr 2012 Location: harrogate Posts: 2006
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Well that's a long held belief overturned. Cheers disco mikey.
Just over one and a half times stiffer and on the understeer end. Hmm cheers leeds, i think that in the first instance i will go polyurethane and thinner I can always go thicker at a later stage if I don't like how it behaves. Thanks. Rhubarb and custard let fly with their secret weapon. |
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15th Aug 2017 4:14am |
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| Ramsay Member Since: 30 Sep 2015 Location: Moffat, Dumfries & Galloway Posts: 627 
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Are you buying off the shelf or having these made? Brendan is right on the same bar different sizes but you can also look at selection of materials and heat treatment to give you variation in stiffness.
My memory from my time at TBL is that the ARB's can have the martensitic structure tempered to varying degrees to alter stiffness. 25mm in high alloy steel would be pretty big on an 1000 kg car. 1995 Defender 110 CSW 1971 SIIA Lightweight |
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15th Aug 2017 8:21am |
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| lambert.the.farmer Member Since: 11 Apr 2012 Location: harrogate Posts: 2006
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Off the shelf in the first instance. I have a choice of 4 that are known to fit directly from 22mm to 28mm. They come with fairly deep /long side arms increasing the effective leverage. Rhubarb and custard let fly with their secret weapon.
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15th Aug 2017 3:39pm |
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