9 replies to this topic

[bugeye]

Would it be possible to use a transverse leaf spring or two in an open wheeled car? What I imagine would be using the spring as an integral structural part of the suspension arms, say replacing one of the lower or upper arms. My thought was that if you were able to use it in the lower suspension mounts you could lower the CG a bit. You'll have to forgive me as I really don't know much about suspension dynamics, but it would seem a good way to improve packaging, though not sure about how you would adjust the springs and obviously you'd still have to place the dampers somewhere...

What do you all think?


Dave

[Richard Border]

As much suspension travel as they use now you could bolt the axles to the body like a little kid's peddle car. From what I've seen the tire sidewall IS the suspension!

[Engineguy]

There are many examples of this 1930s-1960s. It is an enticing idea especially with a variable cross-section composite leaf, but the "effective" pivot point of the leaf in its suspension link role moves around as the leaf flexes. Any effort to force it to a stay where you want it compromises spring rate adjustability, etc. In short, it's a great way to reduce parts count for something like a concession race car (i.e. Malibu Grand Prix) but would be very difficult to get right in a serious racer. The fact that the current F1 carbon composite suspension links weigh next to nothing and are perfectly capable of obtaining and controlling any desired geometry make it pretty unlikely any other solutions will be sought. It does surprise me that springs/dampers are so blatantly mounted so high in so many cars though.

[Darren]

I don't know desmo. Maybe I should have been more literal in comments about Formula Edwardian. Side valves, leaf springs...

[Ray Bell]

1930s to 1960s?

The only cars running leaf springs in 1960s were out of date models or specials.

There were some in the 1900s through the 1920s as well, probably even the 1890s.

Leaf springs, from what I recall reading, are less responsive than torsion bars or coiled torsion bars, commonly known as coil springs.

Curiously, they have been tried for valve springs, just as torsion bars got a run in that department (1960s F2 Honda engines, for instance)... which brings up the other prospect....

how would hairpin springs go? These were used as valve springs on a number of engines, notably the Vanwall. They might form a suspension part fairly easily...

[Engineguy]

Originally posted by Ray Bell
1930s to 1960s?
The only cars running leaf springs in 1960s were out of date models or specials.
...
how would hairpin springs go? These were used as valve springs on a number of engines, notably the Vanwall. They might form a suspension part fairly easily...

Regarding the use of a leaf in dual role suggested...

The *new* in 1960(?) German Ford Taunus sedan used a transverse leaf in place of front upper arms, as did the *new* in 1963(?) Shelby Cobra (at least front, maybe rear). Early 60's Cooper F3 cars (and others?) also used this arrangement.

As for modern use of leaf springs purely as a spring, the *current* Corvette uses transverse composite monoleaf springs front and rear. I'm not sure if the racing version that just won Daytona 24hr outright had the leaf springs intact (although it was a stated goal of the program to maintain as many production parts as possible).

Aren't hairpin springs just a special case of a leaf spring (i.e. a pure bending action rather than the twist of a torsion bar or the combination of twist and bending in a coil)?

[desmo]

The hairpin springs I am familiar with have a coiled bit and would function mostly as a coil spring which as Ray pointed out is essentially a sort of torsion bar.

The Corvette C5-R as run at Le Mans this year runs standard coil-overs in back, those replacing the fiberglass leaf springs of the production car.

[Ray Bell]

Engineguy... most of the time around here we discuss open-wheelers, but I'll address your post as I can.

First, I would seriously doubt that 'early 60s Cooper F3 cars' had any leaf springs, nor the Formula Juniors, for that matter. I think you're about a decade out, for you will find this type of suspension on the Cooper F3s of the fifties. These were the cars that formed the thinking for the early F2 and then F1 Coopers, which continued with leaf springs until 1959.

Transverse leaf springs were commonplace in sedans. Skoda, Peugeot, Fiat, Studebaker and others using them as primary springing media as well as locating suspensions with them. Peugeot were still building this in the 403 well into the sixties, Skoda as well.

I would, however, hardly include the Cobra as a 'new' model in this context. The AC company had been building these cars with their own six-cylinder (and the Bristol 6) for many years before Shelby got a hold of them.

[bugeye]

Leaf vs. Coil would seem to come down to packaging efficiency vs. Flexibility. I think a modern f1 suspension has so little travel that any geometry problems would be minimal.

As to the fact that leafs are old technology, I don't really see how that's relevant, a technology either works in a given application or it doesn't. In my opinion there have been some great engineering minds in the past and plumbing the inventory of older inventions for modern applications is a sensible approach. Take lever shocks like my old MG had, sure they sucked, but with the development of more modern fluids and materials could they have an application? I dunno, but maybe, one thing is for sure, lever shocks were less of a pain to change than Macpherson struts. Or take the Wire wheels, made out of steel they are completely obsolete, but if one were to use graphite and titanium what would happen? Or take the example of wooden boats, obsolete? not really, in certain applications (SOME Sea Kayaks) wood is lighter and stronger than fiberglass, poly and rivals carbon (FWIW, I have a POLY kayak)

For the record, I am not a Luddite and I don't pine for the good old days or anything like that, I would no more want to commute in that MG than I would like to watch black and white TV.

Dave

[Ray Bell]

Oh, you learned how delicate those shocks on the MGB really were?

Of course you did.

But let's look at this issue of the damper type... you have picked the extremes here, with levers and struts mentioned.
You can readily see that the strut displaces a great deal more fluid in its travel than the lever's piston does. Just consider the forces going on within that lever shock's body!
A tiny piston running in (we'll stick with Armstrongs here, the ones that lingered longer) a die-cast cylinder, with leverage in the order of about 10:1... what chance did the components really have?

The physical attributes would make it impossible for them to benefit from any modern technology or improved materials. It was simply a matter of too much leverage on a component doing too important a job.

I would have loved them to have been better at the time - I owned a succession of 3-litre pommie Austin sedans at one time (tremendous towmasters for my race car!), but from freshly rebuilt with good bits to absolutely stuffed, the front end lasted a bare 9000 miles each time!