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Canley swing spring?

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Fend-la-bise Avatar
Fend-la-bise Bruce W
Mazamet, Tarn, France   FRA
Greeting all. I am newly arrived on Triumph Experience Car Forum and am looking for advice on a total rebuild of a Spitfire4 1964 that I am about to acquire in a totally deconstructed state. The car is stripped to the chassis and the carbs, gearbox & overdrive, differential, steering rack have been rebuilt. The rest is up to me and my son. I am not totally ignorant of classic cars having rebuilt with help from the MG Experience Forum my MGB 1966. It seems to me that one of the first questions to address is that of the rear suspension. Is the original setup really as unstable on hard cornering as some would have you believe? Is the Canley swing spring a definite improvement? Drive safely!

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stage3 Avatar
stage3 Christian P
Saarbr├╝cken, Saarland, Germany   DEU
Hi Bruce

I am a long-term owner and driver of a Spitfire MK3 and my experience is: the swing-spring is an improvement to the orginal fixed-spring set-up, no doubt. And it is much nicer to work on as it has less tension than the original MKI-III spring. But on the other hand it is not a must-have. The early cars are far from the death-traps described by many people (most of whom have never driven one). So my advice would be: if you have to buy a new spring anyway, go for the swing-spring conversion. If you have a good original spring, just keep it.

Christian

clshore Carter Shore
Beverly Hills, Florida, USA   USA
In reply to # 1491496 by stage3 Hi Bruce

I am a long-term owner and driver of a Spitfire MK3 and my experience is: the swing-spring is an improvement to the orginal fixed-spring set-up, no doubt. And it is much nicer to work on as it has less tension than the original MKI-III spring. But on the other hand it is not a must-have. The early cars are far from the death-traps described by many people (most of whom have never driven one). So my advice would be: if you have to buy a new spring anyway, go for the swing-spring conversion. If you have a good original spring, just keep it.

Christian

I've owned, driven, and raced Spitfires since 1968, from Mk I to 1500.

A fixed spring Spitfire needs a Camber Compensator.

Under normal conditions it exhibits safe and stable behavior.
But when pushed to the cornering limits, rear jacking will occur, especially if you are braking and cornering at the same time.
An driver experienced with the car and this behavior can usually anticipate and compensate for this, avoiding loss of control or a crash.
Now some will argue that they drive carefully, and so don't need to worry.
But the problem is, the need for emergency manouvers or accident avoidance arises suddenly and without warning.
We tend to react by reflex with violent and sudden steering and braking actions, creating exactly the conditions where jacking occurs.
So what might have been a simple scare or fender bender becomes a loss of control, collision with a fixed object (fence, tree, power pole, barrier, etc.),
or overturned upside down Spitfire.

The Swing Spring setup eliminates this hazard, but so does a Camber Compensator, and also yields better handing.

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, British Columbia, Canada   CAN
I have driven Spitfires, Heralds and Bond equipes for many years with the standard swing axel suspension and in my oppinion it is it is not as bad as it's reputation, BUT it is something thing you need to be aware of.

I can only think of a couple of times I was cought. One was entering a Motorway on a Cloverleaf (going too fast) only to find traffic was backed up due to an accident. I had no choice other than to hit the brakes on the bend, and I felt the rear end jack-up and swing sideways.
Nothing bad resulted other than the car ending up sideways. But it was a sobering experience.

Swing spring (and stiffer front roll bar) or Camber compensator would be something I would add to the car, if only for that 'once in a blue moon' occasion when it could save you.

I suspect the swing spring might give a more comfortable (soft) ride if that is an issue.

Fend-la-bise Avatar
Fend-la-bise Bruce W
Mazamet, Tarn, France   FRA
Christain, Carter & Tony, many thanks for your imput. It looks as though that is the way to go when doing a total rebuild. Might as well get it right first time! Drive safely. Bruce

Yellowhawk Valley Avatar
walla walla, washington, USA   USA
1969 Triumph Spitfire "Walla Walla"
1969 Triumph Spitfire "Portland"
1972 Triumph Spitfire MkIV "Spokane"
1975 Triumph Spitfire 1500 "Dayton"    & more
I have to go along with the majority here and suggest you do need to do something with the stock setup. Based on my experiences with both solid spring (I did take part in the Spitfire dance one time) and swing spring cars I will suggest that either way is ok to go. The best deciding factor may be cost. The CC is probably less expensive, of you can get one, and much easier to install. The swing spring is more work to install but is not noticeable at all once installed. In your situation where the car is disassembled, the work/time factor is not likely to be as important. So, it boils down to primarily being a cost and visual issue.

If you go with the swing spring, then you have to ask the question and get into the discussion as to which spring to use, short or long axle. There will be opinions for both.
Dan

spitlist Avatar
spitlist Joe Curry
Sahuarita, Sahuarita, AZ, USA   USA
A bit of history:

After I restored my first Mk1 in 1995, I realized the shortcomings of the swing-axles so I went looking for a solution. Despite much research, I did not find anyone who was still making the camber compensator. So I installed a swing-spring. It did improve the situation but I was not entirely happy with the performance.

In 2000, I started making camber compensators patterned after the ones Kas Kastner was using in the 60's but with s couple of upgrades to improve the cost of manufacturing as well as the life of the product. After installing one in place of the swing-spring, I noticed immediate improvement in the handling of the car.

Apparently, Triumph also saw the same thing since their original swing-spring was installed on the same shorter axles as were used on the round tail cars. Their engineers apparently were not satisfied with the results since midway through MkIV production, they changed over to the longer axles that were installed on all subsequent Spitfires. This induced more negative camber which goes a long way toward reducing the potential for wheel tuck even without any other camber compensation hardware.

My conclusion is that if you were to switch over to a swing-spring, you should also change to the long axles and a larger front swaybar if you want to get the full effect of the swing-spring. If you do this, you will end up spending a lot more money than if you just add a camber compensator to the stock suspension.

Joe

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billspit Bill Kea
Moore, Spartanburg, SC, USA   USA
^^ I would buy one of Joe's camber compensator and be done with it. Having said that, years ago I bought a Mk IV to get the OD transmission for my 64 and ended up swapping over the differential, rear spring, axles and front roll bar for nothing. I'm pretty happy with the way it handles and these are probably the short axles. Getting all the parts for "free" helped with my decision.

tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
Tuck-in' is inherent in the swing axle design, that the Spitfire shared with other cars, for instance the Mercedes 200 SL gull-wing. Do you hear stories about that being a death trap?

No! Youth can ignore it, u less you like to drive badly, like braking, or lifting suddenly at the apex of a corner. Which is what motoring journalists did at the launch of the car, advertised as the first with IRS .

A useful mod is to lower the car, by a spacer between the spring and diff. This will put the suspension in a different part of its arc, further away from a 'jack-up' and 'tuck-in' position.
John

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TinDrum Herald Ma
cologne, NRW, Germany   DEU
The Mercedes SL300 had no usual swing axle, but a special one with deep roll center!
No comparison with the Herald/Spitfire one.

Herald



Edited 1 time(s). Last edit at 2017-10-12 04:27 PM by TinDrum.

clshore Carter Shore
Beverly Hills, Florida, USA   USA
In reply to # 1491591 by tapkaJohnD Tuck-in' is inherent in the swing axle design, that the Spitfire shared with other cars, for instance the Mercedes 200 SL gull-wing. Do you hear stories about that being a death trap?

No! Youth can ignore it, u less you like to drive badly, like braking, or lifting suddenly at the apex of a corner. Which is what motoring journalists did at the launch of the car, advertised as the first with IRS .

A useful mod is to lower the car, by a spacer between the spring and diff. This will put the suspension in a different part of its arc, further away from a 'jack-up' and 'tuck-in' position.
John

https://en.wikipedia.org/wiki/Mercedes-Benz_300_SL

... However, the rear swing axle, jointed only at the differential, not at the wheels themselves, could be treacherous at high speeds or on imperfect roads due to extreme changes in camber. The enormous fuel tank capacity also caused a considerable difference in handling depending on the quantity of fuel on board.

Actually, the Mercedes 300 SL design used a low pivot variant of swing axles that lowered the effective roll center and virtually eliminated jacking.
The design is actually a semi-swing axle, where the left and right sides pivot in the middle, and are coupled by a small coilover device that limits the angle.
This yielded the good single wheel compliance of an independent suspension over small irregularities, but similar camber behavior to a live axle in corners, braking, acceleration.

Having driven our cars in anger over every variation of road surface you can imagine for nearly 50 years, so I'm far from an alarmist.
I can attest from personal experience that tuck under truly exists, and it can and does occur even in seemingly benign conditions, even when you are driving carefully.

Ignore it if you wish, just be sure to fit a roll bar, to prevent being crushed when you flip over.

John is correct that running lower and with more rear camber helps.
Better is a 50% (or more) stiffer rear spring, which allows you to run tire friendly rear camber.

claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
Awww Carter,

You are bringing out my inner car nerd.

The gullwing 300SL had a swing axle (and drum brakes)

The later convertible 300SL had the low pivot swing you describe, and moved to disc brakes at some point in its production.

The early car was allegedly quicker and more responsive, the later car foolproof. I have never driven one so I can not tell, but there was a later one in for some love at HVR a couple of weeks ago.



Edited 1 time(s). Last edit at 2017-10-12 04:59 PM by claytoncnc.


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Tgt6 Avatar
Tgt6 Joao Simoes
Ann Arbor, Michigan, USA   USA
1973 Triumph GT6 MkIII "GT6 Cabriolet"
1973 Triumph GT6+ (MkII)
Speaking of roll bars, any recommendation of a nice roll bar that's is streetable, not for racing but safe in a rollover.



A penny for your thoughts but everyone gives their 2 cents' worth...somebody is making a penny.

Joao

197? GT6 Convertible
1965 Volkswagen Karmann Ghia Coupe
1950 Dodge Meadowbrook

claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
In reply to # 1491644 by Tgt6 Speaking of roll bars, any recommendation of a nice roll bar that's is streetable, not for racing but safe in a rollover.

Any bar is better than nothing, but a streetable item that fits under the top will likely be unbraced.

Mine has (rather ugly) gussets for strength and was engineered and approved for the seat belt mount.
I designed it, and it was made by an engineering company who certified the welding to satisfy the registration authorities.

It is too low and unbraced, but it just fits under both hard and soft tops, and would be of use if I invert the vehicle, but would not stand up to high speed or high impact loads.

It is also useful for carrying a shelter to a club meeting


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tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
Marcus,
In the Uk, the experts on what makes a roll-over bar (Roll Over Protection System - ROPS) are the Motor Sports Association, the ASN that regulates sport under the FIA.
That organisation's writ barely runs in the US, so I refer you to the regulations of the SCCA, which are effectively the same, quote, "Main hoop shall include a diagonal brace" (https://dk1xgl0d43mu1.cloudfront.net/user_files/scca/downloads/000/018/970/GCR-_Updated_January_2017_ver4.pdf?1484605640 Page 110) The brace is irrelevant on getting the hoop under a fabric roof, it's the height that matters.

Moreover, the MSA regs include that a line from the top of such a braced hoop to "a substantial structure forward of the driver" must pass above the top of the drivers helmet. The SCCA regs iunclude exactly the same provision, page 109. Despite your picture, where the windscreen surround holds up some luggage, it would fold like paper in a roll over. A length of string tied to your hoop might show if it satisfies this criterion.

I'm sorry if my post seems like destructive criticism, but the question was, recommendatuions for a roll over bar that is "safe in a roll over". Clearly, by the recommenedations of national and international experts, a low, unbraced ROPS is not.

John

PS When my son first car was a Spitfire, we fitted a rollover hoop, with a brace. His main complaint was on how difficult it made erecting the soft top, but he accepted that no ROPS, no car. Niot this one, anyway.
He was voted to have the "Coolest Car in the School Car Park"!

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