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Wire rope pulley?

  1. Jun 16, 2008 #1
    Hi, I have this pulley that is intended to drive a short length of steel cable back and forth.

    A picture of the pulley should be attached to this post.
    Alternatively, you may view it at photobucket here [​IMG]

    In this capacity, it had the cable attached to the pulley in the middle of the height of the pulley (bottom of the slot), and then had one side wrapped with cable, and the other side not. When it would rotate one way, it would unwind the cable that it had, and wind cable on the other side.

    I believe this is called a "wire rope pulley". After 20s of variations of that, a week on the calendar, and a couple of hours in front of the monitor, and various combinations with other words that I thought would be near to it, I did not turn up any relevant results in google.

    I've tried grainger, mcmastercarr, jlindustrial, smallparts, sdp-si, and a number of others that I found with google, and none of them seem to have what I'm looking for. Even a pseudo exhaustive inspection of all products listed on sdp-si's website did not turn up anything relevant.

    I called a number of places local to me, and most knew what I was talking about, one even told me the name as being "wire rope pulley", but none had what I was looking for, and the one that did have something close, it was somewhat larger than I was looking for (2"+ OD).

    This is not a conventional drive product (it cannot transfer single direction power continuously, where something such as a timing/cog pulley and belt can). I fear that these sorts of pulleys are all custom produced in large numbers and not available in standard configurations like cog pulleys and belts are. I suppose this is more of a motion control product, which, from what I can tell, is in short supply.

    For reference, the pulley is Aluminum, but I also have one like it that appears to be made out of GRP. It is probably metric, but using "inch" measure the bore is around 3/8", and the OD is maybe 3/2". What I am looking for is a pulley; Alum, GRP, or the like, that has an OD of around 1", and a bore of exactly 1/4" or 3/8".

    Any info or help that anyone can provide about this topic would be greatly appreciated.

    Thanks.
     

    Attached Files:

  2. jcsd
  3. Jun 18, 2008 #2
    That's a Chinese windless.
     
  4. Jun 18, 2008 #3
    I should say windlass. It will exert a tremendous amount of force with small turn.
    Why would one want such an odd little device?
     
  5. Jun 19, 2008 #4
    I intend to mount it on a stepper motor and use it to drive a load along a linear rail.

    A similar result could be effected by using cog pulleys and a cog belt. However, I am trying to price compress this project, and if I can get such a pulley for ~5-10USD it will noticeably reduce the cost of the drive system (over cog pulley/belt). Furthermore, a belt would need to be the exact length, where as I can simply pull the cable tight and use a bolt/washer/nut to clamp the cable ends together. Attaching the load to the cable is easier also; just use a bolt. Attaching to the belt is tricky so as not to damage it and cause premature failure.

    The pulley pictured was removed (by me) from a Knoica photo copier of vintage circa 1990. It was used to drive the lamp/reflector carriage back and forth under the platen glass. The mechanism has a similar pulley on the other side, only that one is made out of GRP rather than Alum. I have another similar such pulley that I pulled off of a different photo copier. That one was probably vintage 1980.

    After what was apparently 34 google searches for such parts, I was only able to find one other example of a stepper using such a pulley. (See: http://www.motors.wrobots.com/BH200575019.php) So, at least the set isn't empty. I know they're out there. I'm just having a bit of trouble finding them.

    I reinstalled the pulley on the copier and took pictures of the pulley with the cable on it at both the CW and CCW extremes (please see attached).

    Thank you.
     

    Attached Files:

    Last edited: Jun 19, 2008
  6. Jun 19, 2008 #5
    No, it's not a windlass. Such a hard thing to find. I can only keep my eyes open for a source. Very sorry. Good luck...
     
  7. Jun 19, 2008 #6

    Q_Goest

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    Hi razer,
    I've had things made like this before. They're not expensive, and you can be pretty sure they aren't 'off the shelf'. There are a few companies that come to mind that make stuff like this (ex: Berg), but this particular piece is something that is custom made for a given application.

    Depending on quantity, you can have these made very inexpensively. The part you have is die cast aluminum, though I'm not as familiar with die cast as with sand cast. For sand casting, the molding cost will be on the order of a thousand $. For die cast, I suspect it will be 5 to 10 times more but you'll get a much better finish and lower overall cost for large quantities. From there, the cost is mostly on a per pound basis. Aluminum is cheap, so these things would cost less than 1$ once you have the mold made. Obviously, you'd need to order thousands to make up for the die cast mold.

    There are plenty of foundaries capable of doing this part for those kinds of costs. Start by doing a search on Thomas Net for aluminum casting.
     
  8. Jun 20, 2008 #7
    Ouch. Thank you both very much for the replies. I suppose the writing has been on the wall for a while now. I emailed sdp-si and mctcable. Neither responded. I suppose they mustn't have what I want.

    Q_Goest; thanks for the links; it's always nice to add to my parts suppliers list.

    -razer
     
  9. Jun 20, 2008 #8
    I can machine one for you for a very reasonable price. PM me if you are interested.
     
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