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A friend and I are working on a combat robot that uses a special drive. This drive requires a spring with a large wire diameter (over 3mm), a large outer diameter (40-70mm), and a large pitch (60-90mm). Since this is for combat robotics, we don't want to 3D print the spring since the plastic could fracture in a fight. In essence, our goal is to have a hard, impact resilient spiral. We aren't looking for a spring based on its spring rate, or compressed length. We are looking for a spring based on its helical shape to drive a wave-like mechanism.

We've reached out to vendors like AcxessSpring and LeeSpring but they haven't yet replied to our inquiries. We also looked at McMaster's custom spring options, but they are too expensive for our project. We've also considered making our own spring, but we're worried that bending music wire over 3mm in diameter is dangerous and virtually impossible to do by hand.

Could someone explain to me how you can make a spring with these specifications? What vendors are there that supply these types of springs?

Thank you for your responses!

Daniel T. Simpson
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  • Century Spring is a good resource. https://www.mwcomponents.com/locations/century-spring?gclid=Cj0KCQjwxveXBhDDARIsAI0Q0x09GPPuq3Zlnl2VxIw2wDiSFs9PrByck6aM4b0Pa0awSGwjPvLFiuMaAtA6EALw_wcB – Eric S Aug 18 '22 at 23:48
  • Unfortunately custom is expensive. You wouldn't make any of this by hand. Hand tools maybe. Most big spring manufacturers like Lee won't make unless for an extremely large qty ($!) order. Have you looked at repurposing trampoline or mattress springs? If all you need is shape, it is very safe to bend mild carbon steel wire or rods by comparison. It doesn't spring back. – Abel Aug 19 '22 at 00:19
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    I’m voting to close this question because it is a shopping question. – Solar Mike Aug 19 '22 at 06:02
  • But see www.eurosprings.co.uk But 3mm is not a large wire diameter... – Solar Mike Aug 19 '22 at 08:01
  • @EricS Thanks for the link! They look like a reliable vendor. – Daniel T. Simpson Aug 19 '22 at 14:58
  • @Abel We actually never thought of trampoline or mattress springs! That could be useful to look into. Thanks! I think since this is for a combat bot we can't use easy-to-bend material since an opponent may be the one bending us, haha. – Daniel T. Simpson Aug 19 '22 at 15:01
  • @SolarMike Thanks for the link! I'm sorry this isn't the best question, but I couldn't find much online on a quick method for bending springs so I figured I'd ask here. Just so I don't ask a shopping question in the future, should I have rephrased the question to: "Could someone explain to me how you can make a precisely dimensioned spring with wire greater than 3mm?" – Daniel T. Simpson Aug 19 '22 at 15:03
  • @DanielT.Simpson I used Century to wind some custom springs and they were very reasonable. The surprise was that 100 springs were only slightly more expensive than 10 springs. Set up is most of the cost. – Eric S Aug 20 '22 at 01:25

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