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(...) Travis, I've had a reasonable amount of success building sumo robots, and I always try to use 2 motors per port. (some rules don't allow that) It's my understanding that the motors draw ~250 milliamp when stalled (that's when they draw the (...) (21 years ago, 4-Nov-03, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) ...I love understatment. sigh... (...) OK, in trying to implement this I've come to an interesting impasse. Calculations suggest that for a 4 lb sumobot with reasonable tires would "benefit" from six motors, three on each side (differential (...) (21 years ago, 25-Nov-03, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) Well, I've never actually tried running six motors directly from the RCX. However, I have used three motors to drive a sumo robot. And I've also used four motors (two on each side) to drive six wheels (two on the right, two on the left, and (...) (21 years ago, 25-Nov-03, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) I'm just thinking out loud here, but it seems that the problem with the two middle motors is that they are wired together. So even if the RCX is told to float the motor output, both motors will want to turn together. If one turns, it will act (...) (21 years ago, 25-Nov-03, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) Yes, that was the problem Brian was having. And, because the LEGO motors are so efficent, they work really well as generators. So, if you hook two together, and try to turn 1 and stop the other, you will have problems. I'm not sure I explained (...) (21 years ago, 25-Nov-03, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) Yes, thank you - you explained it very well. The day after posting the question, I realized a differential would solve the problem... but you stated the solution far more clearly than I had thought of it. Now, of course, I'm trying to think (...) (21 years ago, 26-Nov-03, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) (URL) such a mechanism I built in my latest sumobot... (sorry, bad photograph) Two gear shifts are activated at the same time, one for right wheels, the other for left wheels. The gearshift is activated by a motor controlled by RCX, gearing (...) (21 years ago, 26-Nov-03, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) So, how well did it work? How did the robot do? (21 years ago, 26-Nov-03, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) Rather well... (...) ...but it was beaten by a simpler but slightly heavier 'bot! And it sometimes committed suicide too :-(( Philo (21 years ago, 27-Nov-03, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) hmm. see rule #1: (URL) my BIGGEST piece of advice for your sumo robot: make SURE it does not leave the sumo area on it's own." :) Steve (21 years ago, 27-Nov-03, to lugnet.robotics.rcx)
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| | Re: multiple motors
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In lugnet.robotics.rcx, Steve Hassenplug wrote: <SNIP> (...) </SNIP> So Steve (or Brian or anyone else reading this), have you actually built the drive train you describe? And if so, can you share the specifics of the gearing and configuration of (...) (21 years ago, 15-Feb-04, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) ... (...) Jona, Take a look at Fingers from Sumo-bot 4 (on YOUR web site :) :) (URL) a pretty good picture from the bottom. (URL) robot uses 4 motors (two RCX outputs) to drive 6 wheels. That's kind of the opposite of what you want, but it may (...) (21 years ago, 15-Feb-04, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) Now that is conveinient! ;) (...) I am messing around with this idea hoping to get the gear ratio I want (2:5). I currently have 16t on the motors driving 40t on the drive axle. I haven't come up with a good way to incorporate the differential (...) (21 years ago, 15-Feb-04, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) Okay I've done it. I have the drive train all figured out with the exact gearing I wanted. Now the question to answer before I totally tear down and rebuild a complete robot is; will adding an additional 2 motors to help in forward and reverse (...) (21 years ago, 16-Feb-04, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) It's been my experience that a robot with 6 motors will push harder than a robot with 4 motors. (...) If you're concerned about spending money on batteries, your best bet is to go with a 2 motor robot. If you want to build a really strong sumo (...) (21 years ago, 16-Feb-04, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) Great. My method was to combine the motor outputs down to two axles (left & right) and then do the gearing down/up. I also played with running the "boost" motors at a different gear ratio than the other four, but wasn't sure it would help (...) (21 years ago, 16-Feb-04, to lugnet.robotics.rcx)
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(...) My main concern isn't spending money on batteries, that's just something that popped in my head when I was listing our questions I had about the 6 motor solution. My main concern is getting half-way through the tear-down/rebuild process only (...) (21 years ago, 16-Feb-04, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) Thanks Brian, I doubt I will attempt your suggested test of driving into a wall (this scares me very much!) but I hear what you are saying. Based on Steve's reply, I have decided that 6 motors pushing is better than 4. Since I have already (...) (21 years ago, 16-Feb-04, to lugnet.robotics.rcx)
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| | Re: multiple motors
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(...) Actually, I think what he's suggesting is a pretty good idea. I usually test most of my sumo robots this way. Place the robot next to a wall. If you don't want to damage a wall with a big, powerful robot, :) use a book held against the floor (...) (21 years ago, 16-Feb-04, to lugnet.robotics.rcx)
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