I am designing a torsion spring like in the attached file. The inner diameter is 9φ, the arm length is 50mm and 110mm, and the spring angle is 100°. The 50mm arm is fixed, a plate of about 4kg is hung on the 110mm hook. The plate can be pushed in by hand and the spring will be opened up to 180 degrees with a force of about 6 to 10 kgf. This process can be repeated.
Under these conditions, could you please tell me the wire diameter and number of turns that are suitable for the spring design?
Thank you for writing to us, Kengo!
Although it is only a calculation result, we will propose the following dimensional specifications!
◆ Design proposal
Material: SWP-B
Dimensions: Wire diameter φ2.3 x Coil mean diameter 11.3 x Free height 40 x Number of active coils 14.45 (Inner diameter: 9.0 mm Outer diameter: 13.6 mm)
Spring constant: 8.44 N ・ mm / deg
Spring’s arm at an angle of 100° → 440N ・ mm (Load at this point: 4kgf)
At 180° → 1100N ・ mm (Load at this point: 6kgf)
* This is a design proposal based on calculated values. (The fulcrum point is at 110 mm)
Thank you very much. Designing springs is difficult, isn’t it?
I would like to know more about the design you have given me.
1. The spring constant when I calculated was 501.231Nmm/rad, and when I converted it to deg, it became 8.744Nmm/deg. I used the formula for when the arm lengths of the torsion coil springs are long, was it correct? By the way, the circumference ratio was 3.14.
2. If the free height is 40, does this mean that the coils are not in close contact and are slightly open? Does that mean anything?
3. “At arm angle 100 ° → 440N ・ mm (Load at this point: 4kgf) 180 ° → 1100N ・ mm (Load at this point: 6kgf)”
I don’t understand this part. 4kgf is about 40N when converted to N, isn’t it? Or is it 440???
Dear Kengo,
I’m very sorry, I misunderstood kgf as N and therefore made a mistake in the calculation <(_ _)>. I calculated again and, unfortunately, it is not possible to design a product that is 10 times larger than the current specifications.
◆ Design proposal (torsion spring)
Material: SWP-B
Dimensions: Wire diameter φ5.0 x Center diameter 19 x Free height 115 x Effective number of turns 21.45 (Inner diameter: 14 mm, Outer diameter: 24 mm)
Spring constant: 81Nmm/deg (4641Nmm/rad)
When the arm angle is 100° → 4317N ・ mm (Load at this point: 4kgf)
At 180° → 10800N ・ mm (Load at this point: 6kgf)
* The load is indicated by torque. (The length of the arm is included)
The outer diameter and height are over.
