>I have a few books that address Spitfire & GT6 history but thought I'd ask
>the forum that question....."Why did Triumph use rotoflex in lieu of perhaps
>a sway bar/swing axle Spit suspension or even an IRS setup?"
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Let's clear up one item first. . .both the Spitfire and the GT6 have true
IRS rear suspensions, just different types. IRS simply stands for
independent rear suspension, and both these vehicles have each rear wheel
independently sprung. One is a swing axle while the other (GT6+ and early
MK3) are via lower control arms/upper spring acting like a control arm and
also serving as the spring. As a side note, the early MK1 and very late
MK3 GT6 were swing axles just like their counterparts in the Spitfire.
With a swing axle car like the Spitfire, it is more desirable to REDUCE
roll stiffness in the rear, not increase it so adding a roll bar to the
rear of a Spitfire isn't really the way to improve the handling with this
type of suspension because it increases roll stiffness - The Swing spring
addressed this problem by reducing roll stiffness, and probably wasn't much
more expensive to produce, and manufacture than the existing setup - which
I'm sure played a big roll in its being adopted for production. It did
improve the handling characteristics in certain conditions, while not
costing much if any more to produce. A true win-win situation.
As far as using rubber doughnuts in the GT6, I suspect it was a cost
factor. However they offer several advantages. They do absorb drive line
shock, also provide the lateral deflection that would otherwise have to be
accomplished using some sort of spline arraignment, and provide the flexing
that a "regular" type u-joint provides, all in one package! Their
drawbacks are that they are relatively bulky, are limited in their power
handling capacity and probably angular displacement, plus are much more
labor intensive to replace (at least in this application) than a regular
type u-joint. But in the GT6 application, it was perfectly suited and
worked quite well and allowed Triumph to produce a really nice, better
controlled, and relatively inexpensive IRS in their slightly upscale Grand
Touring car!
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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