NonLinear Springs

[flim]

Would be glad if someone can provide me information (or URLs) of places where I can buy nonlinear compression springs. It can be those 'not consistent' wound springs or even rubber tubings ... Many Thanks

 

[butelja]

Nearly all elastomer isolator mounts are nonlinear. There are many companies that manufacture these items. One that I am familiar with is Tech Products Corporation. Their web address is

http://www.tpcdayton.com

. If you use an elastomer mount on an application that will experience a wide operating temperature range, then you will need to beware that elastomer properties are highly temperature dependant.

 

[Brakeman]

What if i am trying to design a spring to fit a target non-linear load deflcetion curve. (My only constraint being the volume). If I go in a for a rubbber spring what aerthe parameters I can change . Foreg can I play aroundwith different shapes?
Also what about fatigue properties of rubber. can I model these theoretically?

 

[MikeyP]

Not sure how you could make a wound spring non-linear (unless the material was viscoelastic) but a leaf spring clamped at both ends gives a hardening cubic stiffness non-linearity. Bear in mind that viscoelasic materials will be non-linear in both stiffness and damping.

M

 

[Tmoose]

A coil spring with uneven coil spacing can be non-linear if the travel is great enough to cause some of the coils to go into coil bind during operation, thus reducing the number of "working" coils. That method is Used on lots of motorcycles and cars but spring compression must be many mm.

 

[GregLocock]

Tmoose - yes, we do that all the time. You can also taper the wire, and/or the diameter. We do all three.

Brakeman, if you look over a car you will find many non linear rubber springs. Assuming you want an axial compression spring then you can use snubbers, which are typically truncated pyramids or cones of rubber that gradually come into contact with a metal part, or you can use things like jounce bumpers, which are long polyurethane foam cylinders that you see on the shaft of a shock absorber.

http://www.shockwarehouse.com/cgi-bin/shocks/misc

Alternatively use rubber in shear, like an engine mount.

Cheers

Greg Locock

 

[GregLocock]

Here's the curve for a jounce bumper, about 100 mm long by 50 mm diameter
mm,N
0,0
30,400
50,1070
60,2320
68,9500


Cheers

Greg Locock