Torsion Spring Number of Active Coils
Torsion Spring Number of Active Coils
(OP)
I am trying to come up with a torsion spring, but not knowing much about torsion springs I do not know if my results are very valid. I am trying to figure what diameter of wire is needed as well as how many turns are needed.
Design parameters:
k = 9314 in*lb/turn
D_m = maximum of 3 in.
The spring will turn 1/4 of a turn therefore M = 2328.5 in*lb
so far I have been using two equations to try and design the torsion spring.
1. k = (E*d^4)/(10.8*D_m*N_a)
2. S = (32*M)/(pi*d^3)
where
k = spring rate (in*lb/turn)
E = Modulus of Elasticity (psi)
d = wire diameter (in.)
D_m = mean diameter coils (in.)
N_a = number of active coils
S = stress (psi)
M = Torque (in*lb)
To begin my calculation I selected ASTM A228 as my material.
E = 30500 ksi
Yield strength = 231000 psi
Using equation 2 I solved for the diameter of wire I would need to use which worked out to be 0.4682 inches
Then using equation 1 with the parameters stated above solving for N_a I am getting around 4.9 coils.
Do these value seem valid?
I am wondering if there are any restrictions on the equations that I have used which may give invalid results.
Lastly is there any material that would be more suitable for a torsion spring such as the one I have described?
Design parameters:
k = 9314 in*lb/turn
D_m = maximum of 3 in.
The spring will turn 1/4 of a turn therefore M = 2328.5 in*lb
so far I have been using two equations to try and design the torsion spring.
1. k = (E*d^4)/(10.8*D_m*N_a)
2. S = (32*M)/(pi*d^3)
where
k = spring rate (in*lb/turn)
E = Modulus of Elasticity (psi)
d = wire diameter (in.)
D_m = mean diameter coils (in.)
N_a = number of active coils
S = stress (psi)
M = Torque (in*lb)
To begin my calculation I selected ASTM A228 as my material.
E = 30500 ksi
Yield strength = 231000 psi
Using equation 2 I solved for the diameter of wire I would need to use which worked out to be 0.4682 inches
Then using equation 1 with the parameters stated above solving for N_a I am getting around 4.9 coils.
Do these value seem valid?
I am wondering if there are any restrictions on the equations that I have used which may give invalid results.
Lastly is there any material that would be more suitable for a torsion spring such as the one I have described?





RE: Torsion Spring Number of Active Coils
RE: Torsion Spring Number of Active Coils
I knew music wire generally had a smaller radius I just didn't know how small, looks like I will have to use a different material and rework the calculations.
Any suggestions on a material generally used for springs that has a maximum wire diameter of about 0.5" ???
RE: Torsion Spring Number of Active Coils
It is not clear from your post how many cycles the spring has to live the 1/4 turn and if it always to one direction or both directions? From a quick check, for cyclic operation you may not be able to find simple solution without some secondary operations on the spring that will make it much more expensive and will be only a proper for a spring that deflects to one direction only.
RE: Torsion Spring Number of Active Coils
The spring has to be able to have a 1/4 turn in both directions. The spring should live for around 10000 cycles.
Do you know of any sources that can help me determine how this spring should be designed?
RE: Torsion Spring Number of Active Coils
https://sites.google.com/site/israelkk/home
RE: Torsion Spring Number of Active Coils
As far as weather conditions go it would be mounted on the outside of a car, it would have some type of covering to protect it from things such as rain.
From reading a rather lengthy article about torsion springs it appears that the all the conditions are accounted for by safety factors and the equations I stated above are still valid..???
I think if we decide to go this route with the project it would be a great idea to have an expert design such a hinge, however I was hoping to do some preliminary calculations to see if this would even be possible before hiring and paying an expert to tell me that it is not.
RE: Torsion Spring Number of Active Coils
I have noticed from your last post that this is not just a torsion spring but you also use it as a compression and/or tension spring which is a whole new game am I correct?
Usually torsion spring coils are touching each other and the spring's length changes as a result of the torsional deflection, at the same time the outside diameter decreases or increases too.
RE: Torsion Spring Number of Active Coils
Sorry for the confusion but I was talk about putting the torsion spring in tension or compression, not sure if those are the correct terms but basically the different directions you can go with a torsion spring.
From reading some posts it seems as though torsional spring are much better for only one direction, if you are going both it complicates the spring quite a bit?
RE: Torsion Spring Number of Active Coils