leaf spring design inspired by hot rods

[shoppingcartking]

Hello! Im new to the forum so please bare with me. I have a idea for a kart im currently building. I was inspired by the single horizontal leaf spring front suspension. I have a drawing I made up please take a look and give me your feedback. Will it work? If not why. Thanks! Names Anthony btw

 

[Scout]

You want to use a transverse leaf spring rather than a coil in an a-arm setup? You could go old school and run a beam front axle, transverse leaf spring, and hair pin links. that would probably look good in a rat rod kart.

AS long as you have the center of the spring mounted securely and shackles at each end I don't see why it wouldn't work.

 

[shoppingcartking]

Doin white walls too! And thanks for the reassurance I thought so too. After some parts shopping im going to make a post on the front end build

 

[Doc Sprocket]

Fantastic. Leaf spring builds fascinate me. You'll have to let us know what you surce the spring from, and whether it ends up too stiff or not.

 

[shoppingcartking]

Well this definitely isnt the performance route lol, ill be happy as long as It drives straight. Ill source one tomorrow and start a build page a little after, this is definitely form over function !

 

[OzFab]

AS long as you have the center of the spring mounted securely and shackles at each end I don't see why it wouldn't work.

There's the important bit; there's no centre mount in your sketch...

 

[landuse]

Does anyone remember this thread. It is a cool read

http://www.diygokarts.com/vb/showthread.php?t=2941

 

[OzFab]

Those are so cool!

 

[mckutzy]

Going the Corvette kinda route. That's cool.

Here's some more info if you already don't have it.
http://en.wikipedia.org/wiki/Corvette_leaf_spring

 

[itsid]

There's the important bit; there's no centre mount in your sketch...

That was my first thought too,
but I think it looks much cooler without;
AND I think you actually wont need a center mount.

You just need to prevent the A-arms from moving further down than this 'resting position' in the picture.
This way the spring will be under load all the time;
it'll just reduce the force a bit since the spring can move more or less freely, but a stiffer spring (than one for a center mounted layout) and it should indeed work

It'll be a pain to mount, and really dangerous if it breaks loose.. but good looking

'sid

 

[danssoslow]

That was my first thought too,
but I think it looks much cooler without;
AND I think you actually wont need a center mount.

You just need to prevent the A-arms from moving further down than this 'resting position' in the picture.
This way the spring will be under load all the time;
it'll just reduce the force a bit since the spring can move more or less freely, but a stiffer spring (than one for a center mounted layout) and it should indeed work

It'll be a pain to mount, and really dangerous if it breaks loose.. but good looking

'sid

Look at the pic again. Each side only has a single a-arm and thus a single hinge point on either side of the frame. If the spring wasn't centraly mounted, what would keep the front end of the frame from twisting when the weight shifts in a turn?

 

[itsid]

Look at the pic again. Each side only has a single a-arm and thus a single hinge point on either side of the frame. If the spring wasn't centraly mounted, what would keep the front end of the frame from twisting when the weight shifts in a turn?

the inside wheels A-arm since it wont be able to move 'downwards' thus compressing the spring.

single hinge is no problem, not at all

[EDIT]
lemme explain with a picture:


So dark blue is the frame, light blue the A-Arm with an arrestor attachment, red pivot point, green the spring, well you know;

So at this position neither of the wheels can travel downwards if you lift the kart,
just upwards to provide suspension.
And the same goes for cornering... should work indeed.

'sid

 

[danssoslow]

the inside wheels A-arm since it wont be able to move 'downwards' thus compressing the spring.

single hinge is no problem, not at all

'sid

Just so that I'm understanding you correctly; when you say "downwards", are you saying the HINGED side of the a arm can't go lower in a turn?

 

[itsid]

yeah the wheel cannot move downward.

See my edit above (I was just editing while you replied)

Still this is not ideal, since it'll require a really tough spring (with all it's downsides), but in theory ...

'sid

 

[danssoslow]

Here's the thing, all wheels tend to tilt, or tip, toward the outside of a corner. That's why cars are engineered with static negative camber.

Taking a look at the pic you made, let's imagine the picture turns toward the left. Knowing that both wheels will have a tendancy to tip toward the right, how are the wheels and body being controlled? How I'm seeing it, that spring is nothing more than a tie rod at this point; as it will simply move as a whole to the right of center.

 

[itsid]

No not both wheels, just ONE will have the tendancy to tip, the other simply can't.
since that'd require a downward motion of the wheel (prevented by said arrestor).

If one of the wheels in the picture has to move upward relative to the chassis
(because of a road bump or in a turn, doesn't matter)
the distance between the two spring mounts left and right on each of the A-arms
will decrease.
They can neither increase the distance further than on the picture nor can they be in the same distance if any of the wheels move relative to the chassis.
The only way the distance can decrease is under tension of the spring.


Let's add a road..
Basic set up


jumping kart: wheels up in the air, leaf spring can push neither of the wheels down.


landing is suspended, both wheels move up relative to the chassis,
well the chassis moves down relative to the street to be precise


road bump or rock, one wheel moves up, that's it.


tight turn, chassis tilts (exaggerated) even without load the other wheel might loose contact, but still be an anchor to the leaf spring.


(yes I know the wheels are straight which they wont be... thing is the a-arm and the wheel are two different objects in this picture, rotating both at the same pivot is a pain so I left that as an artists interpretation)

'sid

 

[danssoslow]

No not both wheels, just ONE will have the tendancy to tip, the other simply can't.
since that'd require a downward motion of the wheel (prevented by said arrestor).

If one of the wheels in the picture has to move upward relative to the chassis
(because of a road bump or in a turn, doesn't matter)
the distance between the two spring mounts left and right on each of the A-arms
will decrease.
They can neither increase the distance further than on the picture nor can they be in the same distance if any of the wheels move relative to the chassis.
The only way the distance can decrease is under tension of the spring.

'sid

I'm picking up what you're throwing down. I like this!

Here's something else I see. Understand, all I have ever seen of leaf springs were its usage with a centered load, basically on rear axle setups; never where the forces interact end to end.
As one begins to compress, as the other is stationary, wouldn't the spring simply bow, rather than fight, or dampen, the compression?
I think I'm stuck on this setup working like a anti- rollbar; one side counteracting the other.

 

[danssoslow]

You added those pics on me, didn't you? I don't remember seeing ghat before I replied.

 

[itsid]

while you replied, yes

Well, and you didn't see that because it's just plain stupid for a rear axle (since you unwillingly have a upper limit due to the car body, and not adding a center mount would just be nuts.
center mount IS better, no doubt.
But a completely floating leaf spring... how cool would THAT be?
this wouldn't work on a full size car I think, but on a kart I am pretty confident that you'd get away with it.
the spring has to be twice as hard as it had to be for a center mount set up (roughly)
but leaf springs are not compression based, it's a bow spring;
and allthough it looks like it (since most are prebend and go straighter with increased load) it's just a different set up for the same principle. okay this way a sandwiched leaf spring has to be completelrecalculated.. but who needs that on a kart anyways.
Single hefty spring.. and done.

'sid

 

[danssoslow]

I agree that it looks cooler, if for no other reason that it does perplex a lamen mind like myself.

And honestly, if it didn't work (not out of the question if a too light spring were purchased, making it hard to justify buying another, etc.), the center post could always be added in the future. The OP said this isn't going to be built for speed, so it couldn't be a life threatening danger to try it out. (insert IMHO for accountability purposes)