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Originally Posted by Tytus Gerrish
i just tested whe vandoor motor with a 1.5" spool on it. with no power i just leand back with the cable in hand and iot was backdriving
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When I started thinking about how I was going to pick up the robot this year, I also thaught winch, and at first I thaught van door motor, but yes, that darn backdriving thing killed that, So, I looked at some of the other motors in the kit, and I decided on using the globe motors, now each globe produces 150 in-lbs of torque, not too shabby, but cant have a side load, not a real big issue, as long as you have good bearings, and a tight assembly with little slop. it runs at about 100 rpm's no load, and that gets cut by a little more than half when there is this much load on it. now, you could get away with just one globe motor, and say a 2 inch dia. spool, would give you 150 lbs of lifting force, but it would be slow, you could increase the spool size, but then you loose force, again it would be slow, and one thing is, you don't want to sacrifice twenty seconds to just lifting the bot. so, like everything I've designed this year, im using two motors, and a drum, which will provide over 300 lbs of lifting force, and I can tell you it will take less than 5 seconds to live the robot two feet off the ground.
example:
torque(in-lbs)=force(lbs)*radius(in)
300in-lbs = 300lbs * 1in.
power(hp) = force(lbs) * radius(in) * rpm / 63025
If we know the hp rating of the globes, which we do, and it is just over .2hp, (.21hp), you can find out the rpms of the motor under a specific load.
yes, it really is that easy. but if you do use the globes, make sure whatever your turning is supported right, and with bearings, so that the motor dosnt see any side load, because no good can from that.