# Need help calculating torsion spring force for swing arms

Okay, I was hoping I could do this myself but I’m stumped. I’ve decided to take a crack at designing a swing-arm truck, ideally keeping it as simple as possible and, most importantly, making it easily mountable to most conventional decks. Here’s what I have so far:

The distance where the arms meet the baseplate is 218mm, and the arms add 56mm each, making for a total 330mm wide. This should hopefully make it wide and stable enough for mountainboard use. The arms will be held on the baseplate with M8 shoulder-screws, around which will also be placed a pair of torsion springs (and spacers if necessary) to help with shock absorption and returning the truck to center when not actively steering. Using the trampa springs as a guideline, I want to choose torsion springs of similar tensile strength. I calculated months ago- I forget exactly how- that one trampa spring requires about 57kg of force to fully compress. Even assuming that’s correct, I haven’t been able to figure out how to convert that into radial force. I’ve been using this site’s calculator: https://www.acxesspring.com/calculating-constant-force-on-a-coil-compression-spring.html But every combination of parameters I put in either seems to come out too high, or doesn’t have enough degrees of travel. Can anyone help me with this please?

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I would love to help test out your design. Have you tried just getting trampa springs and testing it with that?

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Not yet, I have another set that’s a bit bigger with a wider diameter that I want to try first. The problem is that there’s a lot of guesswork here, I suspect that the force on a trampa spring used as a torsion one will be bit too much. That is, it’ll be a little too soft and springy. I’ll start with what I have and if it’s too strong I’ll try trampa springs. I’m trying to get this as right as possible on the first try since I don’t have a lot of money for extra cnc work. The idea is that I can put on pretty much any torsion spring I want within reason, so I can fine tune it just from that.