Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: CalamariDudeMan on September 12, 2010, 04:04:33 PM
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Are there any guidelines on how much weight a servo can take? I don't mean before it stalls, rather, how much downward force can there be before bad things happen to the gears/motor/case/mounting hardware?
I'm going to be using some lead acids batts, a laptop, sensor accouterments, and a three-tier lexan/aluminum chassis, which seems to me like its going to have some significant weight. My servos will hopefully be four HS-625MG 's from servocity.
Bottom line is, will they be fine with omniwheels directly mounted to the horns, or will an axle and bearing be necessary?
Thanks
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For that much weight, I would recommend gearmotors instead of servos. Sure, using axle/gears with the servo is fine, but with the weight you are planning, the servos will struggle to move everything.
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Hi,
Servos are made in various build qualities. Some have a ball bearing (and some have two) on the axle at the business end and they can take a good bit more than those with just a brass (or even plastic) bushing of course, but most come in a plastic house, so even with bearings, there is a limit to what it will stand.
I don't think there's any guides about that, since it's an unconventional use of a servo, but if you know all the data (about bearing/bushing and housing), it can be calculated, but I guess it will be really hard to come by the needed data.
Lead/acid batteries comes in a lot of different sizes as well, so instead of us guessing, tell us the total maximum weight.
Even without knowing the precise weight, I think it sounds like you'd be destroying your servos (if they can drag all that weight around at all).
When lead/acid is involved, a DC motor and axles of (at least ~6mm) in diameter sounds more useable.
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I haven't actually started building anything yet, but my plan is to have two of the small batteries from UPS's. I apologize for being pretty theoretical, but I need to come up with $600 first >.<
The robot will be indoors only on level carpeting, so there won't be a need for insane amounts of torque scaling an incline.
I used the SoR servo calculator and by its measurements I should be fine with a 25 kg cm servo. On that note, does anyone know if the Tower Pro 9805MG is modable for continuous rotation? Otherwise I'll bite the bullet and get the $40 Hitec 805 from servocity </off topic>
Would it be better to not spend as much on servos and buy a different type of battery? I freecycled the lead acid ones which is why I would like to use them.
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Hi,
Well, don't take our word for it then. Buy servos and learn from your mistake instead ;)
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you really should just use geared brushed motors rather than a servo, as far as im aware some motor drivers let you control the motors with PWN similar to a servo if you'd wish. i honestly doubt a servo will be able to hold that much weight without eventually breaking