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Nick
Experienced Roboteer
Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW
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Sewersnake's design is a classic, I have been looking at a lifter more like Pipe Wench for some time. Those magnum motors might be physically tough enough, but the gearing is probably too high.
Here is my reasoning:
* The lifter arm needs to travel much less than 360 Deg. for a lift; I picked 90 degrees for the total arm motion.
* The lifter arm doesn't need to move all that fast, I figured .25 sec end to end was fast enough and a convenient number to work with.
* 0.25 sec for 90 degrees of movement works out to 1 rps or 60 rpm (I did say it was a convenient number! )
* The Magnum gearboxes have an output speed of 900 rpm @18v, so they would give you 15 rps or a lift time of .017 seconds; too fast IMHO.
* Now you need to look at the torque the gearboxes develop, a theoretical 17.6Nm - lets round it down to 15Nm (30Nm for two motors) after friction losses and over enthusiastic manufacturer specs. The bot needs to lift the opponent and assuming even weight distribution and that the other side of the bot is still on the ground, the lifter needs to to get 15 Lb moved a distance defined by the length of the lifter arm in a time defined by the gearbox speed.
This is where my engineering knowledge fails; I am not sure what formulas to use to use to combine the rpm, arm length etc into a torque value for the gearbox - if anyone who actually took an engineering course would like to step in here, that would be appreciated!
What I was looking at was a single Banebots P90 gearbox with a 4 stage reduction and an extra 2:1 reduction coupling to the lifter arm. I never picked a motor due to the problem with the maths - too big a motor wastes weight and too small a motor won't perform.
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Sat Oct 08, 2011 11:09 am |
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