Anti-Roll Bar Question
08-28-2001, 12:32 PM
#1
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Anti-Roll Bar Question
A couple of questions prompted by Puhn's "How To Make Your Car Handle".
I realize these questions a bit over the top, but I'm curious.
P.150
Can the OEM anti-roll bar be significantly stiffened by heat treating? I am assuming
not given the overwhelming function (4th power) of diameter on stiffness. Still, 4130/4340 can be greatly changed by heat treating.
On a 993, would replacing the anti-roll bar bushings with something stiffer and keping the bar the same make the bar more efficient?
Puhn talks about a test where a 0.80" bar with solid bushings performed like a 1.00" bar on rubber bushings.
tim
I realize these questions a bit over the top, but I'm curious.
P.150
Can the OEM anti-roll bar be significantly stiffened by heat treating? I am assuming
not given the overwhelming function (4th power) of diameter on stiffness. Still, 4130/4340 can be greatly changed by heat treating.
On a 993, would replacing the anti-roll bar bushings with something stiffer and keping the bar the same make the bar more efficient?
Puhn talks about a test where a 0.80" bar with solid bushings performed like a 1.00" bar on rubber bushings.
tim
08-28-2001, 04:39 PM
#2
Race Director
Nope, heat-treating doesn't change a metal's stiffness (you really mean rigidity), just it's strength. A metal sample's stiffness is intrinsic in its base alloy (iron/steel) and cannot be changed through heat-treatment. Next the object's rigidity is based upon the 3-dimensional shape used(length of moment arm).
Its strength (yield and ultimate) CAN be changed through alloying and heat-treatment. This is where the sample takes a permanent set or breaks completely. But all along the way, it will bend and have the same displacement as all other samples of similar alloys.
So you can take two identical steel objects, like a swaybar. One has been heat-treated and one not. Then you twist both of them. For the same applied force, they both will give and flex the EXACT same amount. However, the un-treated sample may break at a 25-degree twist while the heat-treated sample may go til 45-degrees before it breaks. But they both still have the same stiffness and rigidity.
Yep, common practice in race cars to replace the bushing with solid metal bearings.
Its strength (yield and ultimate) CAN be changed through alloying and heat-treatment. This is where the sample takes a permanent set or breaks completely. But all along the way, it will bend and have the same displacement as all other samples of similar alloys.
So you can take two identical steel objects, like a swaybar. One has been heat-treated and one not. Then you twist both of them. For the same applied force, they both will give and flex the EXACT same amount. However, the un-treated sample may break at a 25-degree twist while the heat-treated sample may go til 45-degrees before it breaks. But they both still have the same stiffness and rigidity.
On a 993, would replacing the anti-roll bar bushings with something stiffer and keping the bar the same make the bar more efficient?
