Leaf Spring Suspension
Leaf Spring Suspension
(OP)
A friend and me are toying with ideas for a small, underpowered city car, and I'd try to do a cheap low-tech suspension (but hopefuly with adequate performances)... Seeing there are quite a few very knowledgeable members here, I'd be grateful for your opinions on the concept.
I was thinking of using a strut suspension, but seeing how coil springs are often not coaxially mounted on the strut, I thought of relieving struts of the task of providing the springing force (only guidance and damping) and replacing control arms with a leaf spring supporting left and right wheels. Should it need restrainig, I could use MacPherson type of restraint (with ARB linkage). Are there any obvious or inherent faults with this design that I'm missing?
I'm also a bit concerned that lateral loads on wheels might contribute, even significantly, to the deflection of the spring (seeing how spring will serve as control arm and hence support almost all lateral loads), and that it should be carefully modelled when designing the suspension (not that I know how, most of the stuff I've seen deals only with vertical loads*)... Am I correct in assuming so?
Thanks in advance.
* I should do some digging at my Uni, they're bound to have some good books on the subject of leaf springs there... but considering the manner in which we parted ways, I'd best use a proxy for that task
I was thinking of using a strut suspension, but seeing how coil springs are often not coaxially mounted on the strut, I thought of relieving struts of the task of providing the springing force (only guidance and damping) and replacing control arms with a leaf spring supporting left and right wheels. Should it need restrainig, I could use MacPherson type of restraint (with ARB linkage). Are there any obvious or inherent faults with this design that I'm missing?
I'm also a bit concerned that lateral loads on wheels might contribute, even significantly, to the deflection of the spring (seeing how spring will serve as control arm and hence support almost all lateral loads), and that it should be carefully modelled when designing the suspension (not that I know how, most of the stuff I've seen deals only with vertical loads*)... Am I correct in assuming so?
Thanks in advance.
* I should do some digging at my Uni, they're bound to have some good books on the subject of leaf springs there... but considering the manner in which we parted ways, I'd best use a proxy for that task





RE: Leaf Spring Suspension
http://www.spridgetguru.com/Autocar052958.html
Peugeot used a transverse leaf spring clamped in the center as a locating member for the IFS on 403.
AC/Cobra did the same for the front and rear suspensions for some models
RE: Leaf Spring Suspension
RE: Leaf Spring Suspension
http:/
the lower member there is a leaf spring.
Yes I think for a city car it should work. Packaging is the issue, your leaf spring is running through the diff gearbox or sump, I suspect.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Leaf Spring Suspension
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RE: Leaf Spring Suspension
Apart from the spring packaging that Greg mentions, a second concern with your idea to use a strut with such a spring will be the conical compliance of the spring end bushing. In the SLA the upper arm prevents undesireable rotation of the knuckle - but with the strut you'll lose that constraint.
RE: Leaf Spring Suspension
Yes, the packaging will be even more of an issue (the idea was mentioned about possibility of at least two drivetrain configurations- either individual drive by 2 PM flat pancake motors, or one motor, or mechanical KERS, driving both wheels through the diff).
GT6Racer2- actually, my initial idea was to bolt the ball joint to the spring rather than to use 'eyes' and bushings. In end-effect it wouldn't matter because the concern you express would be translated to torsion/twist of the spring itself... Speaking off top of my head, maybe both concerns could (perchance!) be aleviated by using two springs in paralel- to straddle the drivetrain/motors and provide good and stiff LCA.
RE: Leaf Spring Suspension
RE: Leaf Spring Suspension
You could use a king-pin design with MacPherson also, but the spring on its own probably won't give good enough anti-rotation of the strut. A strategically positioned radius rod could serve that purpose. Or, if you arrange it so that the pivot axis of the king-pin passes directly through the eye of the leaf spring dead center, anti-rotation of the strut won't matter so much because the various forces at the contact patch won't impose any moment arm that would cause it to rotate, and if it does rotate, it's on the same axis as the steering anyway, so it won't matter.
RE: Leaf Spring Suspension
they are exactly what you mention, a "small, underpowered city car"
RE: Leaf Spring Suspension
I'm new in this forum: my name is Calixto and I'm from Spain.
I race competition sopaboxes and we use a double leaf spring system that combines A-Arm and spring functions. It's simple, light and reliable, considering that our maximum total weight is 444lbs, max speeds around 80 mph and max lateral acceleration around 1,3G
This winter I'm working on the damping system, inspired on FSAE cars
You have more info ( in spanish ) at: http://www.zonagravedad.com
I hope it helps.
RE: Leaf Spring Suspension
1.3 gs? on those tires?
banked turns?
RE: Leaf Spring Suspension
We use these 12,5 x 2,25 on slow tracks with lots of hairpins ( lower moment of inertia for slightly faster acceleration). In fast tracks we use 16 x 4 tires ( as shown in this picture of myself in Spanish Championship )
Our Center of Gravity is lower than motorized single seaters. Suspension travel is just around 1 - 1,5 inches.