On 7 Dec 2007 at 7:10, Chuck Arnold wrote:
> Seems to me that the more straight up and down the link is, the less
> lateral stress there is in the components
> On Dec 7, 2007 4:42 AM, Bob Danielson <75TR6@tr6.danielsonfamily.org> wrote:
> > Any opinions on which way provides better handling?
A few observations, besides the kudos already given. One more kudo
from me won't add much.
Check the angles through the range of suspension travel, not just at
ride height.
The thing is, the supposed need for the A-arm and sway bar to be
parallel is a simplification. The A-arm has a longitudinal swing
axis but the sway bar's swing axis is transverse (plus minimal
flexing of the bar itself). As the suspension moves up and down the
mounting point on the A-arm (the top of the link) moves in an arc as
viewed from the front, but the outer end of the swar bar (the bottom
of the link) moves vertically. At ride height the A-arm isn't quite
at its furthest out-most point, but at the suspension extremes it
will have moved inward. So the angle of the link as viewed from the
front won't stay at the pretty "vertical" in your picture. It will
sit like that most of the time but the sway bar isn't torqued unless
there is differential suspension travel between the wheels. Minor
suspension movement upward will move the link's upper end outward a
little. Major movement upward and any movement downward will move
the upper end inward. I'm guessing you still want the "flipped-over"
vertical arrangement, but it is worth checking. From a geometry
standpoint a big improvement is simply having a longer link, which
means less angle change as the suspension goes up and down, and less
flexing of the bushings too.
Also the transfer of movement from wheel to sway bar depends on the
geometry. The top of the link will move more if it is further out on
the A-arm. This means the bar will be torqued more, thus equivalent
to a stiffer bar. The geometry between upper and lower link ends
will change during the suspension travel and for the two different
mounting arrangements it will change differently. But it's hard to
say whether one is better or if the difference is even signficant.
A final observation is that all the vertical force on your link will
be born as flex on a planar surface. There is no vertical backing
edge to convert that flex to shear. Perhaps your bracket is robust
enough that it doesn't matter, but you should check it over time for
fatigue. Heaven forbid that in another 3000 miles you have to do all
this again.
--
Jim Muller
jimmuller@rcn.com
'80 Spitfire, '70 GT6+
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