Spooled wire device with adjustable tension?
Spooled wire device with adjustable tension?
(OP)
We're working on a museum exhibit where the user input device is a sliding block mounted on a guide rail. The position of the carriage is sensed via a wire-draw encoder mounted at the left end of the rail with the wire fastened to the left side of the carriage. Here is the specific encoder:
http:// www.sikopr oducts.com /viewProdu ct.cfm?pro ductID=SGI
At the moment, the slidable block when released gets accelerated left by virtue of the tension in the wire. We'd like to balance this with a pull on the right so that the block, left untouched, remains in position. The above encoder isn't overly cheap, and more importantly, doesn't have a tension adjustment, so duplicating this on the right-side is not a good option.
Question then: does anyone know of a spooled wire device with adjustable tension? Need 0-4m of travel, probably around 20N of force.
As always, any help is much appreciated.
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At the moment, the slidable block when released gets accelerated left by virtue of the tension in the wire. We'd like to balance this with a pull on the right so that the block, left untouched, remains in position. The above encoder isn't overly cheap, and more importantly, doesn't have a tension adjustment, so duplicating this on the right-side is not a good option.
Question then: does anyone know of a spooled wire device with adjustable tension? Need 0-4m of travel, probably around 20N of force.
As always, any help is much appreciated.





RE: Spooled wire device with adjustable tension?
Spring counterbalance from http://www.mcmaster.com/
RE: Spooled wire device with adjustable tension?
it sounds like the "user" positions the block on the wire, and the wire is drawn thru the encoder to tell the user where the block was. why not make the wire a loop ?
RE: Spooled wire device with adjustable tension?
@rb1957, suggest taking a look at the above link. The encoder is inside the sealed unit. The end of the wire gets fixed to the movable carriage. We need to counterbalance the natural tendency of the wire to retract into its housing.
RE: Spooled wire device with adjustable tension?
RE: Spooled wire device with adjustable tension?
RE: Spooled wire device with adjustable tension?
In the UK, "Tensator" type springs are produced by George Emmott (Pawsons) Ltd and are known as Constant Force Springs.
http://www.emmottsprings.co.uk/
Hope this helps.
Trevor Clarke. (R & D) Scientific Instruments.Somerset. UK
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RE: Spooled wire device with adjustable tension?
http
You could get one these and remove the pawl and get constant tension.
http://lubeq.com/categories/64
Additional areas of thought.
Are you may be able to find a retractable large dog leash that would have your length.
Bungee cord and few pulleys.
RE: Spooled wire device with adjustable tension?
http://www.reelcraft.com/whatsnew.htm#spring
RE: Spooled wire device with adjustable tension?
RE: Spooled wire device with adjustable tension?
Depending on the OD of your guiderail you may be able to get home/fence gate springs from the local hardware store that are 0.6 m long - cut or stretch(beyond yield strength)as desired.