[Robotgroup] bead chain gears

[brooksdesign]

  The best place around austin for bead chain is Breed&Company on W29th just west of Guadlupe. They have 5 or 6 differant sizes and the 1/8th inch in nickle or stainless(I suggest the stainless for the extra strength).
  For the sprockets I've been lucky enough to have a rotory table for my drill press and managed to get the settings close enough on the first run to get it right on the second pass. If you get a successful setting make a bunch as getting the setting right is the hardest part. If they don't have to be any larger than 4" I could turn some blanks for you on my mini lathe when I get back this weekend and I think the rotory table is still on the drill press so at worst case we could have the first one milled in an hour or 2. The new lathe can handle pieces up to 12" but I just got the estimate for the shipping and it looks as I will be scrambling to get some jobs going just to eat. 1 lathe, 1 bandsaw, one spotwelder=about 1700lbs + about 200lbs of aluminum and car sear gear motors = $1000 in shipping with lift gate delivery. I was hoping to add on an extra room just for the new machines but at this rate I'll just be packing things a little tighter in the main shop.
  I've also messed with molding them in epoxy by making a loop of the chain and used grease for the release but the first test was lobsided and warped but still worked just not at the higher speeds I wanted. Looking back I think draping the loop on a cone may have self-centered it better or maybe drawing a circle pattern on cardboard and using push pins to keep the loop tight and in place and one for the center pilot hole. Useing a composite mix of glass bead and/or graphite at least 1 part composite to 1 part epoxy.

-----Original Message-----
>From: Gray Mack <gray_mack at yahoo.com>
>Sent: Feb 19, 2008 6:28 PM
>To: The Robot Group Mailing List <robotgroup at puremagic.com>
>Subject: [Robotgroup] bead chain gears
>
>I still have not had any luck in making bead chain
>gears. I want to use bead chain to get linear movement
>from a pair of stepper motors in a frame.
>
>I tried PC-7 compound but it was too sticky to work
>with and I tried clay, but its hard to get a good
>round gear where the bead dimples align when you get
>around the circle. I guess I could try measuring,
>marking and hand cutting some plastic. Seems like I
>need some sort of protractor vice thingy, but ideally
>this would be a maker type project that wouldn't
>require a machine shop to complete.
>
>Also I was trying to work with the small 1/8" bead
>chain but I can get the larger bead as well. I went to
>several Goodwills but didn't find the kind of
>mini-blinds that have one. I guess I can press forward
>with some rubber pullys for now to proof the concept,
>I would just expect some amount of slip to occur over
>time with that system.
>Any suggestions?
>-Gray
>
>
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