 A quick video about torsion bar springs or torsion springs. Torsion springs are relatively simple. It's basically a bar or piece of round stock that you twist in order to store energy in the deflection of the material and, you know, then recover that, you know, like you do with a spring. And springs in general are elastic energy storage devices so we're storing energy in the rotational deflection of that spring. Torsion bar springs can be found in things like automotive suspension or like, you know, small doors or little doors that have a hinge that you want to automatically return closed because, you know, since it's just a bar, it's easy to just slide the spring into the hinge and, you know, it's relatively small, doesn't take up a lot of space. So just very briefly, basic principle of what we're talking about, we would have, as an example, a long piece of material, long and thin. One end here is fixed and this is just like a bent piece of material, another bent at this end and this end is, you know, the load is applied to it so it's twisted and it causes a twisting rotation around the long axis of that shaft and it's pretty straightforward then based on some of the stuff that we've already seen in that we can analyze it as a torsional stress, a shear stress. We can calculate torsional deflection using the standard equation and we can get a spring constant which is related to our geometric properties and our material properties using that. So again, stress, deflection and spring constant which, you know, typically is going to have Newton meters or foot pounds or inch pounds as units might also be called spring rate sometimes but that gives us a measure of how much force, you know, we can apply to get a certain amount of deflection out of it. So not too bad for analyzing, relatively simple, just a straight cylindrical rod that we twist, can look at the stresses in it.