coil springs sideways motion

[arto]

Anybody have any info of the effect of sideway movement of an extension coil spring? Instead of being pin/hook connected on both ends, so that extension forces are along the axis of the spring, one end would be held fixed & the other hooked to an arm that sweeps through an arc. Kind of like using a spring as a cantilever beam.

Thanks!!
Arto

 

[GregPerry]

Why not use a beam spring? The theory is easily available and it would be doing what it is designed for.

 

[GregPerry]

Why not use a beam spring? The theory is easily available and it would be doing what it is designed for, as opposed to using a coil spring as a cantilever.

 

[arto]

?it's still gotta stretch like a coil spring - as the arm sweeps through it's arc.
{There's a picture of this in the old Maleev Machine Design Book [1946] p. 289: hook on one end, "threaded" plug screwed into the base end}
High Quality ArtoCAD:

o
[up ^ /
& | | arc of motion X [cL arm]
down]v \
o
Z [spring]
Z
Z
Z
___Z______
/////////

{I gotta figure out how to attach a picture }

 

[GregLocock]

I thought I had seen this in one of the books, all I can tell you now is that it wasn't in Roark or Timoshenko!

It might be worth doing an FE model of this, I doubt that any simple calculation will be accurate for such a strange geometry. You will need to go to a non linear large deflection code, if you want to only build one model.




Cheers

Greg Locock

 

[prex]

If I understand correctly your picture (you can include an image if you can post it at any publicly accessible URL, see Process TGML in the Reply window), the arc is half up and half down, so that the horizontal displacement should be quite small with respect to the vertical one: under such conditions I wouldn't care for this horizontal displacement: anyway, how much are these displacements and the spring length?
The lateral stiffness of a coil spring is normally negligible, so that you shouldn't worry for this: but if the coil elongation is also small with respect to coil length and the diameter to length ratio of the spring is also small (in other words: normal), then you have a further reason to not worry. prex
motori@xcalcsREMOVE.com

http://www.xcalcs.com

Online tools for structural design

 

[arto]

So far the active spring looks like ~19" long ~5" OD with 5/8" or 3/4" dia wire.

The extension motion is ~10" total [up & down] & the arm radius is ~33", so the sideways movement is ~0.4" total.

Thanks!
Arto

 

[GregLocock]

A liner solution would work for dimensions like that. It almost sounds like a roadspring for a suspension - we ignore the lateral thrust of the spring. Cheers

Greg Locock