Kris, Ross and friends,
I think You are both right. Leaf springs sucks - and they do
a nice, cheap and efficient job...
Kris asked:
> ...has anyone ever installed a set of coil-assisted shocks
> on the rear and eliminated the leaf springs altogether?
As far as I've heard nobody has done exactly what You are looking
for, not without re-designing the entire rear axle layout and
hacking out the car to find space... Unfortunately...
But, there is actually one rather simple (and yet wonderfully
high tech and amazingly engineering intensive) way to get rid
of the fact that the small chassis Triumphs of the '60s (and
some of them long into the '70s) [And! The Corvette still does!]
had to rely on a single (half elliptic) leaf spring pack. Some-
thing not even the old horse carriages did! (They used several!!)
The trick is to use two pneumatic bellows units, with adjustable
air pressure in them, supported downwards on the nr 1 and 2 leafs
(who act merely as the upper control arm) and upwards against a
T-girder (bolted to the rear axle housing). The girder has an
elliptical lower form against which the two remaining leafs can
lean/offload during bump movement. The (by far) main part of the
load is taken by the bellows. Air pressure in them is adjusted to
give a level ride according to the current load in the car.
With an extra set of valves it is even possible to correct for un-
even load left/right in the car...
The shockabsorbers must be set to a slightly harder setting, this
since the friction between the leafs are now gone.
Everything is reversable to the original setup should the need to
be original arise again...
A very nice design indeed!
Yours
Odd
> ---------------------------------------------------------
> Kris Kane wrote:
> My wife and I currently own only one Triumph - a 1979 Spitfire.
> We purchased it 2 years ago with aspirations of restoring/re-
> building it to drive and perform better than the condition it
> was in 1995. While this thread is going on about the rear
> suspension, is there anyone who just hates the rear suspension
> setup with the transverse leaf springs? I was told by a local
> shop, that could re-arch the springs if I wanted, that doing
> so would not guarantee the car sit straight. My only alterna-
> tive at the time was to buy a new leaf spring set. I hate leaf
> springs.
> My question is: has anyone ever installed a set of coil-
> assisted shocks on the rear and eliminated the leaf springs
> altogether?
> If this is a subject that has been covered already, and there
> exists FAQ's on it, could someone please guide me to them?
> /Kris
> ------------------------------------------------------
> Ross Vincenti wrote:
> Kris -
> The idea is good, unfortunately the amount of engineering in-
> volved would almost make it prohibitively costly. The spring
> acts as the upper control arm and the axle shaft acts as the
> lower control arm - that's why it is called a "swing axle"
> suspension.
> You'd need to design, fabricate and install some form of upper
> control link in lieu of the removed leaf spring. While it
> certainly "could" be done, I don't think it would be very easy,
> it would require a lot of trial and error set up, and would
> also be expensive unless you own a fabricating shop.
> You say you hate "leaf springs", but I am not clear why.
> Although not the "best" design for handling purposes (this is
> subject to debate for some folks - Corvettes use them and seem
> to handle great), a transverse leaf set up is effective, simple
> and cheap - which pretty much describes most LBCs of the 60s
> and 70s. Your's is a 79 Spit which has the "swing spring" rear
> suspension. I recently restored my 64 Spit and in hindsight,
> I should have probably swapped to the later swing spring design
> when it was all apart. The transverse leaf spring setup is a
> pretty sturdy, reliable system and unless you plan to autocross
> the car or race it in vintage races it should be just fine for
> the street. In fact, there are a LOT of Spitfire racers who have
> cars with the same suspension design that can run circles around
> more sophisticated set ups so long as you know how to adjust it
> properly. If you have camber problems, consider a "camber
> compensator" - typically a cable and pully arrangement that
> sounds "hokey" but works pretty damn good from what I've heard.
> Keep in mind, the sping set up is only PART of the entire handling
> equation. There are so many other things you can do to make it
> handle great I don't think the transverse leaf is a problem.
> My $.02 is that if you want a superb handling LBC buy a Lotus
> Elan or Lotus Europa - those babies are phenomenal when it comes
> to handling, just a little fragile and expensive. Sorry I couldn't
> offer more encouragement.
> /Ross
> ----------------------------------------------------------
--
Odd Hedberg
Pomonagatan 4 International liaison secretary,
S-74236 Östhammar Triumph Club of Sweden
Sweden '70 Spitfire Mk3 FD82497LO Signal Red
E-mail: odd@triumphclub.se
Club URL: http://www2.passagen.se/triumph/
Home Telephone: Int+ 46-1731 7131
Geographical Position: N 60deg15min E 18deg23min
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