On Wednesday 23 May 2018 06:24:24 andy pugh wrote: > On 23 May 2018 at 10:53, Gene Heskett <[email protected]> wrote: > > Any of that 'style' of encoder > > will last longer if a separately supported shaft is driven and can > > absorb the belt tension. > > The belt tension can be very low if driving only an encoder.
True Andy, but I haven't searched for teeny toothed belts to see whats available. The 10mm wide stuff I'm familiar with is so stiff that it takes 5 lbs of preload just to bend it around a 20 tooth pulley. I think I'd go to the hobby shops and get 2 identical gears big enough to get the separation distance needed, and set them for a slightly sloppy engagement. Buckets easier on the bearings in the encoder. And not subject to as much error as the belt when it goes slack on one side or the other as the motion is reversed. A plastic gear 2mm wide, fixed at both gears hubs, would last till a foreign object got jammed between them. Covering it by sandwiching it between two sheets of 24ga alu, and they should last till the rapture. I still like the idea of making a back shaft for the motor and direct driving the encoder with that. Thats what I did, with the encoders mounting holes big enough to let it move to self align and equiped with large washers to hide the big holes. It doesn't move in service, and I've had the motor cover off a couple times without having to loosen the bolts to re-align it. I just had it off again last week to replace the cable coming from the old optical encoder that broke the z conductor, with a stranded version of that same sized cable, and tied it down better to reduce the flexure at the point where it broke. And g33.1 works again. :) I am still taking the spindle index from the old encoder, and ignoring the z from the new encoder. But Jeremy knows better than I what he has to work with, and what will work best for him. If it can be found, a single strand of kevlar or dacron fishing line that has balls like a light switch pull chain molded to it, and a couple matching pulleys would work well without significant preload. But I've no clue whats available from the hobby robotics folks, so I'm just tossing the idea out there to see if it sticks. We do a lot of the "what if's" here while solving each others problems. :) Its a bit one sided, you've helped me a lot more than I've helped you. Thank you Andy. -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
