Talk:Torsion spring

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Wrong equation[edit]

The differential equation in the section Damped pendulum is incorrect. It is the equation of an ordinary gravity pendulum (Mathieu's equation), not a torsion pendulum. The nonlinear term -g \sin\theta only applies to the gravity pendulum, nor should the acceleration of gravity g or length \ell appear. The correct equation is:

I \frac{d^2\theta}{dt^2} + \gamma \frac{d\theta}{dt} + K \theta = 0

--Chetvorno 19:41, 16 July 2007 (UTC)

Completely rewrote Damped pendulum and Oscillatory motion of torsion pendulums sections to correct this error and present more useful information. --Chetvorno 19:10, 12 August 2007 (UTC)

Better terms?[edit]

I think the term torsion catapult clock in the 2nd paragraph is not used. I googled the term and didn't find a single reference to it. I think torsion pendulum clock is the term you want. --Chetvorno 20:18, 16 July 2007 (UTC)


Is the tortion spring this one?

Yes, those are torsion springs. That would be a great picture to add to the article. Can you get permission to use it? --Chetvorno 23:59, 29 July 2007 (UTC)

Use in firearms[edit]

Best I can tell, the springs inside most firearms to add resistance to the trigger are torsion springs. Can anybody confirm this? Is it worth adding to the article under Uses? --Asriel (talk) 19:46, 2 April 2008 (UTC)

Error in torsional harmonic oscillators[edit]

An IP noted that "there is a mathematical error in at least one of" the equations in this section. I pulled out my vibrations book and found the equation but it's laid out completely different. Moreover, it's been a long time since I've dealt with vibrations, and it isn't coming back quickly. If anyone else has a better source or knowledge it would be appreciated. Wizard191 (talk) 22:35, 16 April 2009 (UTC)

Wrong Units[edit]

If the first equation

 \tau = -\kappa\theta\,

has correct units, then the units of \kappa must be [\kappa] = N/m because the units of Torque are [\tau]=N/m (so that F=R \times \tau) and \theta has no units. The equation for the energy then is wrong, because it also gives the units N/m, again because \theta or \theta^2 has no units. Have in mind that Joules are [U]=N \times m —Preceding unsigned comment added by Kakila (talkcontribs) 19:28, 30 April 2009 (UTC)

I believe you used the wrong units for torque. Torque is defined as: \tau = F \times r. So the units of torque are [\tau] = N\,m = kg\,m^2\,s^{-2} , the same as the units of energy . With this correction, the units in the equations mentioned work out correctly. --ChetvornoTALK 20:39, 30 April 2009 (UTC)

Yes, you are right. A moment of confusion, I guess. Thx

The torque is defined as \tau = r \times F


Classical torsion springs don't seem to fit into either of the 'two types' listed.[edit]

I'm thinking of the torsion springs used in later Greek and Roman artillery. But I'm sure there are other examples. (talk) 19:25, 27 April 2012 (UTC)

As in a mangonel, you mean, where an arm throws a missile powered by a torsion spring consisting of twisted fibers (ropes)? A similar example is those toy airplanes with propellers powered by a twisted rubber band. I think that would come under the heading of a "torsion fiber". --ChetvornoTALK 20:11, 27 April 2012 (UTC)

Wrong Link to French Site[edit]

The current link to the French language site points to an article about a Torsion Balance. The correct article can be found at this URL: - but I am not smart enough to figure out how to change the link.

Incidentally, the English link on the French page correctly points back to this page. — Preceding unsigned comment added by DazedAndConfused (talkcontribs) 15:42, 27 August 2013 (UTC)