Is there such a thing as a wooden constant force sping?

[Rod]

I am looking to keep a project all natural and instead of using a metal conical compression spring I was musing if it was possible to make a similar spring from wood.

I may be on a wild goose chase but with all the knowledge here someone may know something of help. I presume that it may be possible from bentwood techniques. The range would have to be over about 4 inches lifting a weight of about 1/2 lb.

Any ideas appreciated.

With Thanks

Rod

[Mitch Berkson]

I'm not sure why wood is more "natural" than metal. But, from wood, you could make a pulley and counterweight. Or you could use a beam spring made from wood and transmit the force via a cam which would offset the kx force.

Mitch Berkson

[J. Clarke]

Not sure how wooden Belleville washers would hold up. There's another design for a constant-force spring that has more range but less force capability--it's basically just a coil of spring steel that's fastened at one end and the uncoiling of the other end provides the resistance. I suspect that laminating one of those up might work if you could keep the radius large enough. There's some description of the metal version at .

Alternatively, as Mitch suggested, a pulley and counterweight will if the geometry you need allows it probably be an easier solution.

[Rod]

Didn't express myself very well. Ultimately I want this unit to be biodegradable; stainless steel components will eventually oxidize but...you get the picture.

beam spring made from wood and transmit the force via a cam which would offset the kx force.

Clever idea -thanks Mitch

Rod

[Rod]

Thanks, I may experiment with the laminating but without any known precursors it may be a long road.

Thanks again.

Rod

[Jim Wilson]

Depending on external geometric constraints, such a spring seems theoretically reasonable. It should be possible to minimize variances in the initial properties of the spring by using multiple "fibers" of a suitable wood.

Property variance over time is another issue, especially as the spring bio-degrades. Its characteristics will certainly be changed by that, so the desired working lifetime is an important factor in the design, as is the target rate of decay.

Property changes due to moisture fluctuations in the service environment should be considered, as well. These can probably be controlled somewhat by finishing, but anything you do to limit moisture content will impact the decay rate.

Cheers!

Jim

[Rod]

Thanks Jim, a wax finish seems the go.

Regards