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| Need some help from the auto-rotating monitor experts... |
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| DNA Dan:
On a shaft that small I would use the timing pulleys if you can fashion one on the motor to mate it up with. http://www.robotmarketplace.com/products/timing_pulleys_main.html You're going to be hard pressed to couple those two. If you have a drill press you could drill out the 1/2" shaft and either slip or thread the 8mm shaft. |
| kahlid74:
--- Quote from: DNA Dan on March 20, 2012, 01:06:53 pm ---On a shaft that small I would use the timing pulleys if you can fashion one on the motor to mate it up with. http://www.robotmarketplace.com/products/timing_pulleys_main.html You're going to be hard pressed to couple those two. If you have a drill press you could drill out the 1/2" shaft and either slip or thread the 8mm shaft. --- End quote --- The problem with timing belts is you can't adjust the size. So literally I'll have to create the mechanism the size of the belt and then get a tension-er. With the V-Belt I've found an adjustable V-Belt that can do what I want. - http://www.amazon.com/Powertwist-Power-Twist-V-Belt/dp/B001BQDS8I/ref=sr_1_1?ie=UTF8&qid=1332267529&sr=8-1 Perhaps then I should use gears. Also, trying to find a Floor Flange/Die Cast hub with a 3/4" bore is quite challenging. |
| DNA Dan:
I think the belts with the teeth on them would be okay as long as the motor was able to be adjusted once the belt is worn in. Beyond that, there should be very little slack that develops in the belt with the speeds we are talking about. The rotation isn't a super fast RPM, it's more of a properly geared/torque issue. I am going to attempt the feedback motor for positioning, so I want something that has no possibility of slippage, which would be a sprocket. I just hope there isn't too much slack from the teeth once they are in the chain. I don't know whether this is better than the toothed belts in this regard. Although a toothed belt can slip, as long as there is some tension on the belt I think they are pretty solid and perhaps just as good as a chain drive. The drawback to the belt is the size is fixed like you say. You should however be able to find one in the size you need to meet the mechanic design. In the long run, this may be an issue if the belt is no longer made. So maybe the old chain/sprocket stuff is more likely to be around in 10 years?I dunno, both designs seem to be industry standards that aren't going away. For your 3/4" flange, I would buy the 5/8" one and drill it out. You only need to gain 1/8" |
| TopJimmyCooks:
--- Quote from: kahlid74 on March 20, 2012, 10:31:31 am ---My stepper motor has an 8mm shaft, but I can't find any pulley's with that bore. Any of you have any ideas? --- End quote --- 8mm drill. can't get it at Home Depot but Grainger, McMaster, any real hardware store, even stateside. --- Quote from: kahlid74 on March 20, 2012, 10:31:31 am --- "enlarge" the shaft on the motor from 5/16" to 1/2"? Are there metal collars somewhere I can use? --- End quote --- It would be called a bushing. That would be hard to find in that ID/OD - probably fastest to have one cut for you at a machine shop out of brass or aluminum. --- Quote from: kahlid74 on March 20, 2012, 02:19:13 pm --- The problem with timing belts is you can't adjust the size. So literally I'll have to create the mechanism the size of the belt and then get a tension-er. With the V-Belt I've found an adjustable V-Belt --- End quote --- Tensioning is best achieved by having an adjustment to the motor's distance from the axle rather than trying to have an exact belt length. A powertwist usually goes on a 3/8" sheave/pully for woodworking equipment use. They're designed to slip a little rather than positive grab all the time. not recommended. --- Quote from: kahlid74 on March 20, 2012, 02:19:13 pm ---Also, trying to find a Floor Flange/Die Cast hub with a 3/4" bore is quite challenging. --- End quote --- It's a standard NPT size, not a Home depot item but a real plumbing/gas supplier would have a bin of them. It would be for 3/4" ID pipe, not od, though. 3/4" OD not sure there is such a thing if that's what you meant. (like a 3/4" rod used as an axle.) --- Quote from: DNA Dan on March 20, 2012, 03:07:08 pm ---I think the belts with the teeth on them would be okay --- End quote --- Those are usually called gilmer belts. They are hard to spec gears for but if you have any old inkjet printers they often have small ones, perhaps could be doubled up. For this application you can shorten one by cutting 45 degrees on each end (aligning the teeth) and taping it back together. Don't know the tape used but many of them are made with tape splices from the factory. EditAll tape would work if you can find some. |
| DNA Dan:
--- Quote from: TopJimmyCooks on March 20, 2012, 03:37:18 pm --- Those are usually called gilmer belts. They are hard to spec gears for but if you have any old inkjet printers they often have small ones, perhaps could be doubled up. For this application you can shorten one by cutting 45 degrees on each end (aligning the teeth) and taping it back together. Don't know the tape used but many of them are made with tape splices from the factory. EditAll tape would work if you can find some. --- End quote --- The belts are nice, but the gears for them are pricey and don't come in the size I want. I will be using the geared pololu motor maybe 100:1 with feedback so the chain system I need can just be 1:1 or slightly better. I think my cab now has the higher gear ratio with the friction setup and it's a little overkill. |
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