Newsgroups: comp.robotics
Path: brunix!sgiblab!spool.mu.edu!agate!tcsi.tcs.com!iat.holonet.net!bsmall
From: bsmall@iat.holonet.net (Brad Smallridge)
Subject: Re: Constant Force Mechanisms, Counter Balance Mechanisms
Message-ID: <CDqsp0.8FH@iat.holonet.net>
Organization: HoloNet National Internet Access System: 510-704-1058/modem
 
References: <27nq2i$dqm@scarecrow.asel.udel.edu>
Date: Wed, 22 Sep 1993 06:29:20 GMT
Lines: 20

Constant force is a real problem. I struggle with this almost every day.
The constant force springs are too expensive. I usually try to design some
long dimensions into my robot hand or arm so that I can put some very long
springs in it. The springs are stretched 50% of maximum length or so and
the long length means that their delta x is small percentage wise and
therefore the force doesn't change too much.

Wow, if any one can say what I just wrote better I'd appreciate it.
Then I usually try, on the hinged joints, to provide for a small
radius such that the delta x is small in comparison to the spring length.

By the way, I have found that using latex hose (or is it viton?) makes a 
great spring. I pass a needle and string through the ends and tie the 
hose wherever I want. The string usually doesn't ripout of the hose.
Saves a lot of time and money to get just the right amount of force.

Brad Smallridge
bsmall@holonet.net


