>As I understand it:
>The design of CV joints allows them to operate at high angles (over 40
>degrees) - enough to cope with suspension travel and some lateral movement,
>while providing a constant velocity to the axle regardless of the operating
>angle. The CV joint can be thought of as essentially two universal joints
>connected together at an angle. When lateral play is required, this angle
>increases or decreases.
>On an IRS TR rear axle, the standard u-joints do not allow sufficient
>suspension movement without binding. As the rear A-arm drops down vertically
>and the dif stays in place, the distance between the dif and the hub becomes
>greater - resulting in lateral stress.
>To solve this problem, the TR axle is splined to allow the two parts of the
>axle to slide back and forth, thus changing the effective length of the
>axle. If (or rather "when") the two parts of the axle lock together under
>hard cornering, suspension damage is the likely result - sometimes with
>catastrophic results. The CV axles do NOT need sliding spline axles.
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Well, your close and you have most of it correct. Just one minor
correction if I may. . .CV joints, by their design maintain a constant
rotation with respect to the input/output regardless of the angle (within
design limits of course).between the input and output shafts With
"regular" type joints, the output shaft, at any angle different than the
input shaft will, for a given rotation, fluctuate in it's output. That is
to say that for every revolution on the input shaft, the output shaft
speeds up/slows down in it's revolution. (this is the big difference
between the two types of joints) With two cardian joints, set in phase with
each other, and the critical part here, the input and output shaft axis
remain parallel to each other the joints will cancel out the fluctuations,
and you will have smooth rotation once again. With the suspension geometry
what it is, the distance between the hub, and the differential changes
within it's designed travel up/down and this changing dimension must be
accommodated for by some means. Regardless of the type of joint used, CV
joint or regular cardian joints, this changing dimension is accomplished by
a sliding member. In the case of stock TR shafts, the splines are in the
shafts themselves. With the CV type, it may also be in the shaft, or be in
one or both of the joints themselves where the shaft is inserted into the
joint assembly, but in either case, there is a spline of some kind to
accommodate the changing length of the shaft as required buy the suspension
geometry. The principle advantage of using CV joints, is the loads imposed
on the "intermediate" portion of the shaft is more constant, and as such it
and the joints, take less of a beating than simply using two standard
joints. But, the two "standard" joint axle is much cheaper to make- The
rotoflex joint setup used on many race cars and the GT6 as well as other
some other Triumphs accomplished this dimensional difference by simply
flexing-
Barry Schwartz (San Diego) bschwart@pacbell.net
72 PI, V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire (long term project)
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