Thinking about Rotoflex

[popeye]

Hello to all of you,

I am still thinking about the rotoflex conversion again for my old siwng spring car ... wich will be rebuild as a fast Car for track days

- Rotoflex seems to handle better but are heavy (twice the weight of SS)
- Rotoflex are expensive to maintain or refurbish: where is it possible to buy genuine Metalastik donuts?

- SS: An old set up from the Competition Departement back in the 60's
- SS: can be lowered easily
- SS: Maintenance is easy
- SS: I have heard about driver with half broken shafts, bearings .... ( the same is heard about the rotoflex and LOTUS ...) :-/ :-/

May someone could explain to me how it can be possible to lower the rear of a car fitted with Rotoflex ?

What is usually prefer on race cars in UK ?

Many thanks !!

[RedRooster]

Start here then have a think,

http://www.wolfitt.com/

RR

[Bradley1500]

Could do a CV conversion at the same time.

[tiggrr1]

I thought you meant our colonial cousin  ;)

[Nick Jones]

Swing spring, especially with wider wheels or the longer half shafts does give pretty decent handling and doesn't really suffer from the "tuck-under" of the original swing axle suspension.  It is simple, cheap and light.  However it does give alot of camber and track change on bumpy surfaces which can make the rear-end very "lively".  Not tail-happy as such, just an unsettled feeling on bumpy surfaces.  The other major hazards for this type is the universal joint, which takes all the cornering side-loads and the shaft itself, which breaks, just outboard of the wheel bearing allowing the wheel and brake drum to depart the car........ :o.  Not really an issue on relatively standard road going cars but definitely a real risk for high powered track cars with sticky tyres.

The Rotoflex rear, reduces the camber change and track change (though still pretty poor by modern standards) and allows a more settled feeling rear.  It is relatively complex, heavy and expensive.  These days there are several CV conversions available which allow you to have the roto-rear without the rotoflex doughnut itself.  You can also get alloy vertical links and wishbones to reduce the weight - at a price.  There are quite a few variants on the theme.

Personally I'd say rotoflex with a CV conversion - but I am biased  :)

Nick

[Tim Bancroft]

Def. agree with Nick's comments.

Swing spring is ok and is cheap, however I do not like the slightly detached feeling one gets with that system, it sometimes feels like the rear axles are deflected when one hits a bump. Not enough location.

I'd say go for the CV system coupled with Rotoflex vertical links and lower wishbones.

Also, spend money on quality rear shock absorbers.

[JohnD]

To add other reasons to go for CVs:
It is very difficult and expensive to find proper Rotaflex donuts, and chnaging them needs the hub to be dismantled, including the famous 110 ft-lb hub nut (feels a LOT more to take off!), so doing so reghulalry to compensate for poor quality donuts isn't on.
If you want to push the car - "track days" you said - the swing spring half shaft has a basic design fault,  ahard shoulder where it narrows for the hub.   Stress is exaggerated there and the wheel falls off.

Search here and on Sideways for several accounts of diffent versions.  The lastest is to use "monoball" joints, that replace either bushes or spherical joints - think beefed-up track-rod end, and see Sidewall.
John

[popeye]

Many many thanks to every body !!

On the SS The fact that the shafts could break is the problem: here is another question, why the shafts aren't hardened thanks to heat treatment like those done for cranks ?

I have no experience about the rotoflex rebuild and how tricky it could be ... shims .... The CV conversion is the solution: it seems there is several conversions possible (Canley, MGF bearings ...) and not cheap too. Of course, the brake lines need to be change, brackets welded on the healboard panel, brackets welded on the chassis...

Actually the car is fitted with progessive short front springs: so the front is 2cm lower than the rear (and it handles very very well). If Rotoflex are fitted, here are the questions:
- How to low the rear about 2cm?
- What about the rear spring, dampers?

[JohnD]

Lowering the rear cannot be simpler, in theory.
A block between the diff.housing and the spring, raises the spring, lowers the car.
Available from Jigsaw, and no doubt others, in various sizes.  IMHO 1", 2.54cms, is what you want, but ensure that the rear spring is stiff enough so that the car will not ground or the wheels foul the arches on max bump.

What? About dampers?

John

[popeye]

Thanks John,
I don't know who to low a rotoflex car as we do with the SS(extra holes on vertical links to avoid the spacer on the diff): is it the holes on the chassis brackets that will allow to do this?

[GT6MK3]

I've decided to go from swing spring to roto, albeit with the Nick Jones CV conversion kit.

the axles, CV kit and uprights are all sitting in the garage on the shelf.

Apart from general inertia, the thing currently holding me up is

(a) trying to figure a way to keep the Koni's from my swing spring set-up,  I'm hoping I can find a bracket somewhere that will let me keep them.

and (b) trying to figure out what to do about a rear spring.  If I could find a roto-spring here in Aus, the next problem will be that the diff housing is only a 4 bolt hole job, and the roto spring needs 6.  Do I ship out a spring and diff housing from old Bilighty, or do I try to work the swing spring itself with the roto/CV hubs.

Any thoughts appreciated!

C.

[Gt6s]

1248 wrote:

or do I try to work the swing spring itself with the roto/CV hubs.

You can make a swing spring over rotoflex work very well indeed.

I use this arangement. You will need to build a hybrid spring tho, a swing spring with roto main leaf, too much neg camber otherwise. Also if using rotoflex coupleings you will also need to remove the outer clamp brackets.

And as far as I know you can use your Konis with the Bowler Jones Conversion. Though I do remember being wrong once before.


Laurence

[Nick Jones]

Gt6s wrote:

You can make a swing spring over rotoflex work very well indeed.

I use this arangement. You will need to build a hybrid spring tho, a swing spring with roto main leaf, too much neg camber otherwise. Also if using rotoflex coupleings you will also need to remove the outer clamp brackets.

And as far as I know you can use your Konis with the Bowler Jones Conversion. Though I do remember being wrong once before.


Laurence

I think you are right about the Konis  ;) - though some have reported fore-aft misalignment between the chassis bracket and roto VL damper mount.  This seems to vary between cars and isn't usually a big problem.

Nick

[JohnD]

popeye wrote:

Thanks John,
I don't know who to low a rotoflex car as we do with the SS(extra holes on vertical links to avoid the spacer on the diff): is it the holes on the chassis brackets that will allow to do this?

Popeye,
Did you read my post?
Block under spring.

There are mods to do to the chassis wishbone brackets.  An engineer called Eikhoff wrote anm artilce in the 80s in Courier where he showed that two mods could acheive the least cmaber chnage and the least 'plunge' on the donut, but IMHO neither were practically useful.   The 'racing' mod is to take the chassis bracket hole down 25mm and out 5mm,  With a 1" (25mm) block, this achieves negative camber from neutral to bump, which I think is the most useful set up.

John

[junkuser]

"and the roto spring needs 6.  Do I ship out a spring and diff housing from old Bilighty,"

     Have no idea if the early Spitfire 4, 6 stud housings are the same as you are after or where you are in Australia but I have one you are welcome to, if suitable, and the freight should be cheaper than from the UK.

I'm just south of Newcastle NSW.

[popeye]

Hello John,

I just read your messages: Many thanks !!!

I understand a spacer block is needed on rotoflex whereas it could be avoid on SS (extra holes on the vertical link). I was pretty sure some adjustment could be done on the chassis brackets but i didn't know about the "out" setting : thanks a lot !

The genuine metalastik couplings are hard to find nowadays: how long is their lifespan?
What are the differences between the different CV conversions?

Many thanks again for sharing with me your knowledge  ;)

[Clive]

1248 wrote:

I've decided to go from swing spring to roto, albeit with the Nick Jones CV conversion kit.

the axles, CV kit and uprights are all sitting in the garage on the shelf.

Apart from general inertia, the thing currently holding me up is

(a) trying to figure a way to keep the Koni's from my swing spring set-up,  I'm hoping I can find a bracket somewhere that will let me keep them.

and (b) trying to figure out what to do about a rear spring.  If I could find a roto-spring here in Aus, the next problem will be that the diff housing is only a 4 bolt hole job, and the roto spring needs 6.  Do I ship out a spring and diff housing from old Bilighty, or do I try to work the swing spring itself with the roto/CV hubs.

Any thoughts appreciated!

C.

It is very easy to drill/tap the extra holes in the housing. The top plate is just that on a roto setup, a bit of plate with 5 holes. So no need to import a diff housing.
Spring may be trickier, but no reason a decent spring maker couldn't make one for you. Or tray the "hybrid" idea so you only need 1 leaf making.

BTW I have a cv setup on my spit chassis, and I am only using 4 studs for the spring (secondhand but good GT6 roto spring). Need to get a 1" spacer though.

[JohnD]

popeye wrote:

The genuine metalastik couplings are hard to find nowadays: how long is their lifespan?  

Popey,
You really aren't reading my posts, are you?
Go back and read what I had to say about chnaging donuts.

And why fixate on redrilling the uprights, when you can just fit longer studs in the diff and a block?  If you don't like one size of block you can change that.  You can't drill an upright twice, ther's no room.
John

[popeye]

Thanks John,
I understand couplings maintenance isn't easy and expensive: that is the reason why CV are a better option.

Ok for the spacer : I thought it could change (less) the movement of the suspension. It is easy too to install and test ;)