A spring with variable k.

Not necessarily a spring, I was looking forwards towards an arrangement so as to provide constant force regardless of the distance by which the thing has been pushed...just like a spring with variable k so as to maintain so as to maintain a constant force regardless of the distance it has deviated from it's mean position (commonly called as x) (of course up till a limit).

Now, there should be no additional input energy involved (apart from the force which's acting on the spring/arrangement)...for e.g. a motor (which's active but not rotating will provide a constant force) is not the solution...it should be a conservative system.
I'm sure there are many ways to [over]design something like that, but http://www.vulcanspring.com/conforce.html" [Broken] might be what you're looking for.
Last edited by a moderator:


A really long spring will have an almost constant force...
These rolled ribbon springs, what exactly are their limitations...I mean, what's the maximum force after which the deflection becomes considerable?

Can they provide 2 or 3 tons with variation of like....0.2 tons at most with a distance of 10 ft?

If so how much space will they require?

An opposite case...can they provide like 4-6 lbs with at most 0.5 lbs deflection with a distance of 1ft?

Can they be used as gym weight replacements (not the bars and dumbbells of course...other stuff)?

Finally, can they expand instead of applying force through contraction.
Last edited:
I'm not sure about the specifics. You'll have to check the specs from the retailers. The link I gave before let you spec one out I think. As far as expanding rather than contracting, I would guess no, but that's just my guess.

I did checkout various manufactures but they only make the thing on order...so they don't have any "predefined" limitations.


The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving