FYI: Test fitting of Strano Hollow swaybars--done
11-25-2009, 07:25 PM
#51
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Black is the color... Shipping is not included, and is location dependent. Normally $20-30 to most of the US.
Not the cheapest bars, that wasn't the intent. Also not the most expensive (just charge a fair price for them). The pricing is based on what it cost to make what I wanted, not what I had to cut to make them meet a price point.
Not the cheapest bars, that wasn't the intent. Also not the most expensive (just charge a fair price for them). The pricing is based on what it cost to make what I wanted, not what I had to cut to make them meet a price point.
12-07-2009, 06:31 PM
#52
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If you regard a rear sta-bar as being the last tool in the box of hardware for fine-tuning the handling, it's the thing that ends up balancing what you can't (or don't want to) fix by other means. IOW, in many stick-axle cases you might be able to do without one if you could live with a higher rear geometric roll center and/or higher rear spring rates and shock damping. The classic approach outlined in Millikens' "Race Car Vehicle Dynamics" is to first choose the springs and then add bar(s) in order to hit some target roll stiffness. You'd probably choose a front spring for a particular ride frequency that suits the intended use of the car, and then choose a rear spring to match that front spring for "flat ride" properties over some given range of speeds. If you can hit your roll stiffness target by adding only a front bar and this does not drag too much of the roll stiffness to the front (there are some rules of thumb here), you're done. Some cars weren't even equipped with front sta-bars, as even that item wasn't needed in order to achieve the ride quality and roll stiffness targets (1964 Dodge 330 with the base V8, to name one that I have firsthand knowledge about).
It also depends somewhat on weight distribution, available power and tire size, etc., etc., etc., even driver preference.
On the other hand, many cars are delivered as OE with rear bars that have little effect (OE Fox Mustangs and my '79 Chevy Malibu only gain 45 lb/in or so from their OE LCA-mounted rear bars, compared to perhaps 500 or even 600 for the front bar). I have it on really good authority that this is frequently a function of customer expectations of a rear bar being present, so a rear bar is provided. But it's left at being only slightly stiffer than cooked spaghetti so that its presence won't upset the rest of the car's tuning.
Norm
It also depends somewhat on weight distribution, available power and tire size, etc., etc., etc., even driver preference.
On the other hand, many cars are delivered as OE with rear bars that have little effect (OE Fox Mustangs and my '79 Chevy Malibu only gain 45 lb/in or so from their OE LCA-mounted rear bars, compared to perhaps 500 or even 600 for the front bar). I have it on really good authority that this is frequently a function of customer expectations of a rear bar being present, so a rear bar is provided. But it's left at being only slightly stiffer than cooked spaghetti so that its presence won't upset the rest of the car's tuning.
Norm
I understand with a panhard bar, there's a decent amount of roll cnter migration, and with a watts link, the rear roll center is right at the center pivot location. How would a sway bar affect roll center location?
12-08-2009, 05:59 AM
#53
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In the pure kinematic (geometric construction) sense, they don't.
But they actually can have a secondary effect on RC height once you start considering suspension bushing compliances. In the case of the GM & Fox Mustang converging 4-link suspensions with the rear bar fixed only to the LCAs, the rear bar improves the effectiveness of the LCAs at resisting lateral loads. This effect isn't a huge one, but by making the LCAs more effective while leaving the UCAs alone you end up lowering the RC a very slight amount in this particular example. Sort of like moving the convergence point of the skewed lowers rearward a bit.
Roll stiffness is different from roll center height and the roll moment that is developed from the sprung mass CG being at a different height, as roll stiffness per se is not a geometric effect (even when the details of applying it can be). Maybe think of roll stiffness as being the next link in the chain, where after you have determined the total roll moment (which is based on front and rear RC heights and the sprung mass CG height) you're trying to find out how the resistance to this moment is distributed.
Approximately (but not exactly), Total Lateral Load Transfer Distribution is the sum of RC height effects plus roll stiffness effects plus the effects of the unsprung masses, summed up separately for the front and rear axles. And it's the TLLTD that determines the overall load transfer effect on steady-state handling balance. BTW, lateral load transfer is not the only effect that matters.
Norm
But they actually can have a secondary effect on RC height once you start considering suspension bushing compliances. In the case of the GM & Fox Mustang converging 4-link suspensions with the rear bar fixed only to the LCAs, the rear bar improves the effectiveness of the LCAs at resisting lateral loads. This effect isn't a huge one, but by making the LCAs more effective while leaving the UCAs alone you end up lowering the RC a very slight amount in this particular example. Sort of like moving the convergence point of the skewed lowers rearward a bit.
Roll stiffness is different from roll center height and the roll moment that is developed from the sprung mass CG being at a different height, as roll stiffness per se is not a geometric effect (even when the details of applying it can be). Maybe think of roll stiffness as being the next link in the chain, where after you have determined the total roll moment (which is based on front and rear RC heights and the sprung mass CG height) you're trying to find out how the resistance to this moment is distributed.
Approximately (but not exactly), Total Lateral Load Transfer Distribution is the sum of RC height effects plus roll stiffness effects plus the effects of the unsprung masses, summed up separately for the front and rear axles. And it's the TLLTD that determines the overall load transfer effect on steady-state handling balance. BTW, lateral load transfer is not the only effect that matters.
Norm
Last edited by Norm Peterson; 12-08-2009 at 10:42 AM.
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