Re: Subject: [alfa] torsion bar mathematics?

[bearbvd@xxxxxxxxxxxxxx (Greg Hermann)]

At 11:53 PM 8/1/04, Richard Welty wrote:
>i should have been clearer in my original posting.
>
>the relationship between a coil spring and a torsion bar is not
>a particular mystery.
>
>what is an issue is the math describing the behavior of a spring
>where it is inserted into a complex of control arms, and the
>effective spring rate is different depending on where it appears
>in the system. in an alfetta, a torsion bar which is coaxial with
>the inner pivot of the lower control arm is in a very different
>place from, say, a coilover attached to the lower control arm
>that passes through a hole in the upper control arm and then
>attaches to the body.
>
>this is the math i'm after.

For a coil spring--

if you have the spring rate in lbs/in.--take that times the ratio of the
distance from the pivot of the control arm on which the spring acts to the
distance from the pivot of the same control arm to the center of the
contact patch times the sine of the angle of the centerline of the spring
to the line from the pivot of the control arm to the center of that arm's
ball joint times the cosine of the angle between a line from the pivot of
the control arm and the center of the contact patch and a horizontal
line---THIS will get you the effective spring rate at the contact patch.

for a torsion bar--

if you have the rate of the bar in ft-lbs per degree--divide this by  2 pi
times the length of a line from the axis of the torsion bar to the center
of the contact patch (in FEET) and multiply by the cosine of the angle of
that line to a horizontal line and divide by 30 (which is 360/12)--THIS
will get you the effective spring rate in pounds per inch at the contact
patch.


Greg
>
>somewhere buried in my inbox i have something Douglas
>Milliken sent me on the subject back when my interest was
>more theoretical and less practical. it may take me a while
>to dig that up, i think it may have been back when i was
>running w2k on this laptop, so digging that out of my old
>eudora inbox may be a bit of a challenge. this is assuming
>that i can find that inbox and that i'm guessing right about
>which one it's in.
>
>richard
>--
>Richard Welty                                         rwelty@domain.elided
>Averill Park Networking                                         518-573-7592
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