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Suggest a suitable Spring

Suggest a suitable Spring

(OP)
Dear all,

I'm looking for a spring with torque 0.5~0.8 lb in for oscillatory motion like for oscillating rotary table. Please suggest as I read torsion springs cannot be used in both wind and its opposite direction.
Any suggestions highly appreciated :)

RE: Suggest a suitable Spring

Torque is not enough, how much deflection angle is allowed?
Torsion springs can be used in winding and unwinding too. Just take into account that the stress correction factor is different for unwinding.
You can also use a round torsion bar if you have the space.

RE: Suggest a suitable Spring

Look up the Associated Spring SPEC catalog.

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RE: Suggest a suitable Spring

stealthbingo,

For back and forth motion, the spring must be continually loaded. In other words, you cannot go from compressed to extended, or vice versa. If your torsion spring is continually loaded, I see no problems with it.

It sounds to me like you are designing a mechanism. Torsion springs work. Levers and coil springs work. Lay out the mechanism in CAD. Look for a suitable spring. Do your calculations in a spreadsheet or in MathCAD. Probably, you will have to try several layouts. This is what design is all about.

--
JHG

RE: Suggest a suitable Spring

Good Morning:

One needs to determine the Torsional Yield Strength of the material that is specified.

If you are 'close', you will see 'unloading' as the spring is 'yielded'.

Unless the quantity of springs is ordered is sufficient to coil on a automatic spring coiler,

you will see variability in the hand wound springs. It is difficult to hand wind with the 'same'

back pressure of the coiled wire to the coiling area. REMEMBER, that as one coils, the wire wants

to 'rotate' because of the torsion applied during this process. I have seen 'grown men' buckle

under this back pressure!! 30+ years in the Spring Industry

RE: Suggest a suitable Spring

Quote (HJBittner7)

One needs to determine the Torsional Yield Strength of the material that is specified.

I assume this is in reference to the round torsion bar mentioned by israelkk.

The torsion strength of the material doesn't play a significant role in the strength of a coiled 'torsion' spring. Perhaps ironically, the load that the wire sees is mostly bending.

RE: Suggest a suitable Spring

Be aware that a bidirectional torsion spring will have zero restoring torque at zero deflection, and near-zero restoring torque near zero deflection, which means that there will be some hysteresis/uncertainty of position when 'centered'.
That may not be what you want.
You can provide mechanical centering of such a device by using two compression or two extension springs preloaded against each other. ... or two torsion springs preloaded against each other, at the expense of some complexity at the interface.
Consider also a drum with strings (see 'dial cord') acting against springs or weights.


Mike Halloran
Pembroke Pines, FL, USA

RE: Suggest a suitable Spring

MikeHalloran,

I have designed all sorts of spring loaded mechanisms. The basic problem is that you cannot transition from a tension load to a compression load. If your mechanism rotates ±40°, your spring must engage somewhere outside the angle range. The spring can engage perhaps at +50°, and stretch out as the mechanism rotates to -40°. The extension or compression of the spring must be within its limits. The force must be acceptable throughout the range of travel.

All of this means laying something out, selecting a spring, analyzing it, and trying out different springs and geometries until you get something that works.

--
JHG

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