Leaf springs

[ada]

I'm after some leaf springs with a suitable spring constant and size
for a 10kg vehicle. I can't seem to find any in this size.

[Kris]

Is it possible to take two 5kg load springs and run then together (I'm not suggesting you do this just wondering if that's how it works)
I've often noticed leaf springs are always stacked on one another and I'm assuming it's to make a non linear response to the load when it hits a bump.

ada <a...@panda2.net> wrote:

I'm after some leaf springs with a suitable spring constant and size
for a 10kg vehicle.  I can't seem to find any in this size.

--
Sent from my Android phone with K-9 Mail. Please excuse my brevity.

[ada]

On May 7, 3:33 pm, Kris <k...@sleepingplanet.com> wrote:
> Is it possible to take two 5kg load springs and run then together (I'm not suggesting you do this just wondering if that's how it works)

Yes. The mechanical-electrical analogy says that this is like running
two capacitors together.

(I can't find any leaf springs in this size range.)

> I've often noticed leaf springs are always stacked on one another and I'm assuming it's to make a non linear response to the load when it hits a bump.

A linear combination of linear elements results in a linear element.

[Iain Chalmers]

They have this trick with leaf springs - see the 2nd and 4th spring stacks in the image on this page:

http://www.puresuzuki.com/leaf_springs.htm

They both have that "floating" leaf, which doesn't "combine with the other linear elements" until the other springs are all compressed enough forint to start touching them.

It's a "stepped" rather than a curved nonlinear response, but it is non linear.

(there's a similar trick with coil springs, where you wind them with some of the coils very close together, so they bump into each other and effectively shorten the spring - the call them "progressive rate springs". They are difficult to damp properly…)

Big

[Kris]

But it wouldn't be a linear combination would it? The leaf springs are of different lengths and stacked on top of each other. The deflection from the bottom causing the least deflection in the top of the stack. The amount of force increasing exponentially to cause the same deflection in the top leaf vs the amount of force required in the bottom leaf to cause the same deflection. This would result in a non linear curve of force vs (average) deflection.
I see what you are saying, the characteristic of each leaf is linear, apply x force, get y deflection. But if they behaved like that grouped why bother with many springs, just use one thick one.
Hmmm metal fatigue maybe?

[Kris]

Ah, thanks, wished I'd read your response before posting.

[Andrew]

What about using piano wire? K&S wire is available in sizes up to 1/8" from
hobby shops.

If you use multiple wires held together with form blocks - strip of material
with 1/8" holes through it for the wires.

See attached 1000-words worth of picture.

This arrangement makes it easy to adjust the length and strength of the
spring.

One drawback is that the product may be subject to more twisting than a
single flat leaf spring.

--
You received this message because you are subscribed to the Google Groups
"Robots & Dinosaurs" group.
To unsubscribe from this group and stop receiving emails from it, send an
email to sydney-hackspa...@googlegroups.com.
To post to this group, send email to sydney-h...@googlegroups.com.
Visit this group at http://groups.google.com/group/sydney-hackspace?hl=en.
For more options, visit https://groups.google.com/groups/opt_out.

[Tim]

With a live axle twisting wouldn't be an issue!

I love that idea... I'm going to get a nice phat piano wire and rest it's springyness now... 

(for crossbows though, not tiny cars)

Tim.

[Andrew]

Only for use in states other than NSW, right?

[Tim]

Only in Max's state,  New South Addresses :)

[Kris]

Perhaps max has a legally recognised archery club?
(and a permit)

[Max Nippard]

What will you do after it is sufficiently rested, Tim?

[Tim]

Ask it nicely to go and get me a crossbow :)

[ada]

On May 8, 9:27 am, "Andrew" <andr...@arcadius.com.au> wrote:
> One drawback is that the product may be subject to more twisting than a
> single flat leaf spring.

also, it has an isotropic response (at least in two dimensions) and
thus does not self-locate.

(the reason for using a leaf spring over a coil spring is that they
have a markedly higher spring constant in the cross-planes and so
essentially constrain movement to being in a single plane. this is in
comparison to coil springs which have a much _lower_ spring constant
in the cross planes and so need a linkage system to constrain them to
uniplanar movement.)

-a

[Andrew]

Had another thought for you, Ada.

You could possibly use a power hacksaw blade as a leaf spring. When I was a
kid, I knew a local engineering company had one of these machines and were
always throwing out broken or blunt blades that were useful for all sorts of
things.

Andrew