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

Thanks Jim, a wax finish seems the go.

Regards

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

Rod wrote...

> 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.

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

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

Thanks again.

Rod

<snip>> I'm not sure why wood is more "natural" than metal.

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.


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

Clever idea -thanks Mitch

Rod

Rod wrote:

> 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.

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
<http://pergatory.mit.edu/2.007/kit/springs/kp_cnstspring.html>.

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

--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)