Designing Rehabilitation Equipment for an Upper Limb (arm)

[SilverJW]

Before I ask my question, here's a little introduction of myself. I am a college student studying in Bioengineering, so I've been tasked to create an equipment to help rehabilitation for upper limb (any point of the upper limb, doesn't have to be the entire upper limb).

So I have this initial Idea that I'd be creating a device that hugs onto your forearm and biceps, allowing for rotation at the Antecubital area (The opposite side of the elbow). Therefore allowing the user to do bicep curls, however I'm facing a problem, I need to give the device adjustable resistance.

Here's what I came up with
1 - Inserting a huge torsion spring the middle of the equipment, using a sliding mechanism on the forearm & bicep pieces to adjust the active length of the torsion spring to adjust resistance
2 - Using cables or elastics to adjust resistance the pieces can give
3 - Scrap the idea of resistance and just give a piece that rotates for exercise

Any advice on calculations, design ideas or insights into this would be appreciated. Thanks in advance.

 

[Tom.G]

Think safety. I suggest you not use elastics, they are unreliable. Their frequent sudden failure can cause injuries, up to and including broken bones.

If you must use elastics, keep them enclosed and use many parallel elements for redundancy. Think about doing curls with the weight not held in your hand, but instead lifted via an elastic band that you are holding. When the band fails, where is all that stored energy dissipated... in your face, in your groin?

 

[SilverJW]

Think safety. I suggest you not use elastics, they are unreliable. Their frequent sudden failure can cause injuries, up to and including broken bones.

If you must use elastics, keep them enclosed and use many parallel elements for redundancy. Think about doing curls with the weight not held in your hand, but instead lifted via an elastic band that you are holding. When the band fails, where is all that stored energy dissipated... in your face, in your groin?

Though it won't really pose much danger being that my equipment is a "Bicep curler", still, thanks for the advice. I think it is important that equipment not fail on you while at work.

Anyway, is there any mechanically adjustable equipment out there? I thought of a torsion spring, but my lecturer told me that no matter where you press on the spring part that are sticking out, it will always be the same resistance.