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# Spiral spring design

## Spiral spring design

(OP)
Hello everybody,
I have to integrate a spring in an actuator, and I was thinking about a round wire spiral spring. Unfortunately I have no experience in the design of such spring.
first question: does the torque versus angle formula is linear or what is the calculation formula?
2nd: what is the maximum angular stroke I can have with such spring.
The torque values for my application are arround 25 to 100 mNm and the Spring OD would be about 38mm.

Does it exist a simple software to design it?
bye

Electro-mechanical designer

### RE: Spiral spring design

The formula is linear. A spiral (a clock spring) can have up to 3 full revolutions. Above it it will buckle in the spring rotation axis direction.

http://www.webspawner.com/users/israelkk/

### RE: Spiral spring design

Can you be more specific about the torque and deflection? You ahould give the desired torque at two deflection points. Is it for cyclic or static use?

http://www.webspawner.com/users/israelkk/

### RE: Spiral spring design

(OP)
Hello Israelkk,
the actuator will run for a million cycles, and I would like to have about 15 mNm preload torque and after aa angle stroke of 70° the spring torque would not exceed 40 mNm.
The OD of the spring will be about 38mm and I assum that the ID will be arround 20mm. I made a rought calculation and I found a spiral spring with 2.5 turns and a stiffness of 0.31 mNm/° But I'm really not sure of my calculation.
Bye

Electro-mechanical designer

### RE: Spiral spring design

jamesXIII

The software you refer to does not deal with spiral springs made of round wire but only spiral springs (hair and brush springs) made of rectangular strip wire. For spiral spring made of round wire I use a custom made other software for my personal use as a consultant.

http://www.webspawner.com/users/israelkk/

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