ok, I found some stuff out!
First, I found an easy formula on a web page to calculate swaybar rates:
Rate = 793.5 * (Bar OD^4 - Bar ID^4) / (BarLength * LeverLength^2) = kg / mm
So, I take the numbers above from the kit car. I measured the bar length from end to end, not just the straight part but from hole to hole since I think that total length is important. Total length = 99.5cm = 39.17". Arm lengths I measured 20.5cm-21.5cm, it's not very accurate. That's 8.07"-8.46".
Now:
Rate = 793.5 * (0.9"*2.54*10 (to get mm))^4 / 995mm*205mm^2 = 5.18 kg/mm = 290 lbs/inch! Pretty close to the 295 number!
Same with 1.125" :
Rate = 12.65 kg/mm = 708.5 lbs/inch!
that's the Formula!
When I take it to measure my swaybar, but I take now 21.5cm, not 20.5cm (a little bit longer than the kit car) and the diameter I measured was 22.4mm (0.881"):
Rate = 4.34 kg/mm = 243 lbs/inch.
I measured with my woodblock on scale test about 210-260lbs/inch. It was every time a little bit different, not very accurate, but that's about what I calculate.
So the Firmfeel 1 1/4" front b-body swaybar will have a rating of about 982 lbs/inch!
The 11/8 about 644 lbs/inch, a little bit less than the kit car because of the slight longer arm length I took.
But what I still think that Mike Martin got wrong in his book:
You can't just add front swaybar rate and torsion bar wheel rates together on the front and same on the rear. The swaybar rate needs to be calculated with the motion ratio since it's attached some distance after the pivot point! In my opinion you need to calculate the real wheel rate of the swaybar and then add THIS to the Tbar and leafspring wheel rate.
The swaybar is attached 15.5cm (6.1") after the pivot, the LCA length is 41.5cm (16.3"). This gives a motion ratio of 0.373.
Wheel rate of swaybar: 0.373^2 * swaybar rate.
This would give for the 11/4" FF swaybar: 982 * 0.373^2 = 136 lbs/inch! A MUCH lower value!
Also it is really small compaired to the Tbar value since it's motion ratio is always 1!
Am I thinking right here or is it wrong?
By the way, I called FF, the rear b-body swaybar goes from perch to perch, they got the 44" ones and the 47.3" wide ones I would need (71-74 b-body).
It's 3/4" thick and the arm length he tld me is about 11" so the rate is about: 62 lbs/inch with the same motion ratio as the leafspring I got.
