My friend and I are working on a project requiring for us to propel a syringe forward in a small container with significant force. We are debating whether to use an elastic band wrapped around the syringe (in the form of a small hand slingshot) or a flat piece of spring steel that upon activation will revert into its original, curved shape, pushing out on the syringe.

Is there such a type of spring steel that will be able to do this effectively and with a large force? If so, are there any downsides to using it as opposed to an elastic band? The goal is to make a product viable on the market for long-term, one-shot use.

  • This is very geometry dependent. What about coil springs? – Eric Shain Jul 22 '17 at 17:13

The down side of rubber/elastic is that it can degrade over time from oxygen, oil, and uv exposure. If you go this route make sure to use silicone rubber with uv inhibitors. Shielding from the environment also helps.

The down side of spring steel is the increased cost, and additional structure to hold all the pieces in place.

Have you considered a coil spring; it seems like the geometry would work out better. You could put the entire assembly in a capped tube. They make all different shapes and sizes, many of which publishing force coefficients. Use Hooke's Law to calculate your force at a displacement.

McMasterCarr Spring Catalog

I don't know your application, but do some more searching for "spring syringe". You may find a solution for sale or at the very least some design ideas.

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Stanford University image article

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