Small leaf spring design

[ThinkSnow247]

I am looking for information on designing small leaf springs. The design needs to incorperate attachment points and the spring all into one piece without any bending to form it. The plan is to cut the spring out of sheet material in a dog bone shape. The flex would occur in the plane of the material. I am wondering what material would be best to make this out of and what sort of heat treatments would be needed?

 

[amorrison]

How small is small?

A mechanical windup wristwatch spring ?
A mechanical alarm clock wakeup alarm spring ?
A lawnmower motor starting rope return spring ?

 

[ThinkSnow247]

Sorry, small can definately mean a lot of things. I was trying to eliminate car leaf springs. It would be abour 1.25"

 

[NickE]

The best material that I have found for flat springs is Sandvik Hi-Flex Stainless Swedish Flapper valve Steel. It is hardened and pre-tempered when you buy it in coil form. Then you can stamp the material and finish to provide good fatigue life.

Some helpful sites:

http://www.smt.sandvik.com/

Nick
I love materials science!

 

[MintJulep]

Something like this perhaps?

http://www.smallparts.com/products/descriptions/fs.cfm

 

[ThinkSnow247]

MintJulep- The flex needs to occur in the same plane as the attachment holes. Without a picture the best description I can give is a dogbone shape. Two broad attachment points connected by a thinner section that acts as the spring.

 

[ccw]

Hi ThinkSnow247,
Other flat strip spring stock materials are spring steel SAE1074, clock steel SAE1095, brass, phosphor-bronze, beryllium copper, various stainless steels, and nickel alloys. The 1074 and 1095 are not as corrosion resistant. The non-ferrous and stainless alloys are relatively corrosion resistant. Stamping out your final form from prehardened stock is preferred. However, if for some reason the material needs to be formed in a softer state, there are some materials that can be precipitate hardened or hardened and tempered after forming. 17-7 PH stainless, beryllium copper, 1074 and 1095.

 

[MintJulep]

As a general rule, leaf springs prefer not to bend the "hard way". They will twist, buckle or do other things undesirable in an attempt to bend the "easy way".

 

[ThinkSnow247]

The the thickness of the cross section in the middle of the dogbone will be material thickness or less, making it the easy way.