Amen. I did a lot of work to my front suspension to get the roll centers
right--or at least in the ballpark--not easy with a Triumph. The
difference is amazing. Frankly I think it's a lot more worthwhile
modification than changing the steering actuation method.
You really need to have adjustable camber, and the bump steer with a
stock front suspension is just scary. Unless you're going to run tall,
skinny tires and soft springs the steering will be very darty, turning
in radically in high speed sweepers.
I considered rack & pinion steering, and modeled the result on a CAD
system. I didn't try shortened housings, but it was obvious that the TR4
rack was just not going to work well (unless I made a mistake in the
measurements). The toe in varies by several degrees over even a small
amount of differential suspension travel (ie--one wheel rebounds while
the other doesn't). Looks like a lot of work to get it all right.
> From: Chip Bond [SMTP:spirals@esinet.net]
> Sent: Thursday, April 16, 1998 4:33
> To: 'Angelo Graham'; 'Alexander Joseph H'; 'Amici Triumphi'
> Subject: RE: TR3A rack and pinion conversion.
>
> As the upper and lower "A" arms go thru their respective arcs, the
> spindle
> and hub will gain and loose camber. When the steering arm and the
> inner tie
> rod end are located properly (usually close to the horizonal
> centerline of
> wheel at ride height) the rod end will approximate the movement
> generated
> by the wheel-hub with mimimal change in toe. And the length of the tie
> rod
> must be correct to decribe this arc. The problem is, the arc at the
> wheel
> and hub, because the upper and lower "A" arms are unequal length, may
> not
> be a smooth curve, but, rather an ellipse. So toe change must occur
> since
> the outboard end of the tie rod can only describe a true arc.
>
> I guess what I meant was that the steering geometry should be
> developed
> based on the existing (or desired) suspension movement.
>
> The sprite rack had to be modified to get the inner pivots in the
> correct
> location. I'm sorry to say that I don't recall exactly what was done,
> but ,
> I think, the case was shortened, rack ends cut and pivots reinstalled
> on
> the shorter rack. This change (whatever it was) was actually quite
> easy
> given the design of the Sprite unit.
>
> After the mod, the car was much more precise at speed with
> significantly
> harder slow speed steering. It was more darty, which has yet to be
> sorted.....
>
> Sadly she sits in the back building awaiting the ministrations
> lavished on
> the race car.
>
> (more projects than I care to think about....)
>
> Chip
>
>
> ----------
> From: Alexander Joseph
> H[SMTP:AlexanderJosephH@Waterloo.deere.com]
> Sent: Thursday, April 16, 1998 3:41 PM
> To: 'Angelo Graham'; 'Amici Triumphi'
> Subject: RE: TR3A rack and pinion conversion.
>
> Chip.. why is camber an issue here, since it is fixed?
>
>
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