Increasing cable draw speed... 1

[rcwalters]

In a project that I'm designing....

... there will be a cable drawn a certain length. However, to complete the function it is designed for, the length of cable drawn is not enough to provide the pull distance required. I'm not quite sure how to word this.... Is there a simple way to drawn a great length of cable by drawing a shorter length?

I've only come up with one concept so far, and I drew that for reference. Perhaps it will help explain what I'm asking...

http://www.pinnah.com/rc3/images/contra.jpg

(blue is pulled a short distance. a larger quantity of red is drawn as a result.)

Basicly, it's a torque creating function for a stronger pull except I need it in reverse.

Also, if this function has a name or has been discussed somewhere else on these forums, I'll go read that instead. I hope I didn't create a thread about something already discussed.

Thanks.
*says the newbie rcwalters*

 

[GregLocock]

The concept is step up ratio or lever ratio. There are about 7643 different ways of doing it. Is this homework?

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[rcwalters]

Thank you very much GregLocock. I'll scoure the net and these boards for those terms and try to learn all I can about them.
No, this isn't homework. After rereading my post, I see how it can sound like that. The use of all the unspecified functions and generic terminology was merely the result of my poor attempts at explaining what I wanted without just describing the entirety of my project. It's not like I'm fearing concept theives (though granted that would be horrible) but I'd just rather keep the details to myself. If I went on to describle the full function of my project, it would spring quite a lot of other discussion. Discussion I'm sure would have many tips and help for my project, blah blah blah.... but there's just too many complications. I hope that's ok with you.

My question still though, is, is there a very compact way to do this. A very linear design. I don't have much space to put this, and weight is an important issue so it has to be small or light. I'd rather not have to use a gearing assembly like I drew as those take lots of wear and to acheive the 'stepping up' I need, the gear spool would have to have a large diameter. But thank you for those terms, they'll be quite helpful.

- rcwalters

 

[handleman]

How about something like this?

Pull on blue and red travels twice as far.

 

[unclesyd]

Taking handleman's idea a little further add a few more sheaves and pull the blue harder

 

[rcwalters]

Actually, that works quite well. Thank you handleman.

This is still all just research in the various components that will be needed. Thus I don't know for fact wether anyone one design will be perfect. But I doo like to allocate a lot of designs or opinions for consideration.

Again, thank you handleman. That design really expresses what I'm thinking.

- rcwalters