Off Panhard bar

[Greg Hermann]

>
>>Or go scrounging in a boneyard that has some old Alfas. They used an upper
>>triangle, with two pivot points on the chassis, and a BALL joint attached
>>just to the left side of the pumpkin, plus two lower trailing arms.
>>Particularly if you replaced the chassis pivots of the triangle (rubber
>>stock) with bronze on steel, also if you replaced the lower rod ends with
>>real rod ends, they were as NICE a live rear axle setup as you could want.
>
>(Lurk mode off)
>
>It's nice to have something to say !
>
>I disagree.

Well--If I still had a 101 Alfa set up the way the one I had was, plus
modern wheels & tires, I doubt that you could come up with anything that
would touch it for handling, let alone with a live axle, It went to the 1 g
ballpark with E-70 x14 Goodrich's on 14x6 Borrani Mags about 28 years ago.

The pumpkin was pretty narrow, as it was an aluminium center section, and
came apart the way the old Timken truck axles do--with a big flange on one
of the inner end of one of the axle tubes. The center point of the ball
joint was only mebbe 3 --4 inches above the centerline of the axle shafts,
and mebbe only 3 inches off the centerline of the car--not perfect, but not
bad.

The later , 105 series,  Alfas had a much wider base for the triangle, with
the ends out to about where "frame rails" were, but a rubber bush replaced
the ball joint.  A racing option for the 105 cars did exactly what you are
pushing for--had a sliding block that ran up and down in a slot in a truss
behind the rear axle , and pivoted on a pin which was located dead center,
side to side, and near the bottom of the pumpkin. Lowered the rear roll
center about 6 or 8 inches from the standard set-up. Which was the deal
that allowed the pictures of Horst Kwech in his Trans-Am GTA lifting his
inside FRONT wheel on a LOT of corners.
>
>Any assymmetry of the linkage will cause the car to react differently in
>right hand turns than it does in left hand turns. Secondly, because the
>A-arm is above the axle, and it determines the roll center heighth, the roll
>center is high. In addition, since the a-arm components must absorb all
>cornering forces they are subjected to extreme stress, hence the ball
>joint.

All true, but I am here to tell you, barely noticeable in practice! And,
the high stress on the two front bushings of the narrower base triangle is
why it did so much good to replace them with bronze on steel pivots. And,
the ball joint was the same part that Alfa used for the lower arm front
ball joints--it came apart, you could set the clearance in it with steel
shims, and it was BIGGER than the lower joint ball in a late '60's 3/4 Ton
Chebby! On a 2100 lb car, needless to say, they did NOT wear out--in fact
all the suspension joints on those cars were stout to the point that they
were more likely to seize than wear if you did not keep them greased!!!

Not only that, I think that you would get nearly unanimous opinion from
people who KNOW live axle sports car handling, that Alfa had it as right as
it ever got had! The low unsprung weight at the CENTE of the housing, due
to the use of aluminium had a LOT to do with how well they did on rough
surfaces, of course. And this comment doesn't even touch on the
sensitivities of the rice-boys who would prolly still hate to admit that
SCCA did favors for Datsun just as NASCAR has done favors for Ford--after
all the Datsun Trans-Am cars were IRS!
>
>>Another very nice set-up was the old Rover 2000 Di Dion setup--instead of a
>>lateral link, they used half shafts with no slip joint, upper and lower
>>arms on each side, and a slip joint in the Di Dion tube.
>
>Huh?
>
>Am I missing something here? I've read this three times and it still doesn't
>make sense.

YES, you are--BUT--here's what---

--the upper AND lower arms on each side were both longitudinal, not
lateral! I thought that this would be obvious, but I shall try to write
more carefully in the future. The (non-plunging) half shafts were the ONLY
lateral locating element to the Rover 2000 suspension--and , yes, the slip
joint in the Di Dion tube was free to twist as well as to slide in and out!
And, yes, there was anti-squat/anti jack built into the geometry of the
longitudinal arms on each side.

>of articles for National Dragster named Pitside with (you guessed it) Dave
>Morgan and at least one book titled Doorslammers IIRC. Lots of illustrations
>of instant center, anti-squat, center of gravity, etc. calculations. Written
>for the drag racer, but applicable to a road car also.

I think I would rather stick to one of my old texts on the kinematics of
machinery  than something dumbed down enough to be intelligible to
economically significant quantities of drag racers!

Regards, Greg