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Good Tires/Wheels or Good Motors?

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New ( offline )
Posts: 9
Posted: 2009-03-15 01:05 
I am making an all terrain vehicle of sorts, and have come to a crucial design decision. This robot will see offroad use and will most likely have to lug around some substantial weight. A very sturdy chassis, and arm. large batteries, etc. Which ever way I go, It will use a 4 motor, maybe even 6 motor, chassis. I have found two motors I like particularly well.
A) The ML-50 from the Robot Market Place
This motor is not as powerful, or as power hungry as the BB, or as easy to mount. However it does have a 6mm shaft with a flat spot, seemingly the most versatile of all output shafts in the hobby robotics industry. This will allow me to use some tires that are really geared towards what I need, aka the offroad tires from LM, and I also can get by with the much cheaper (and maybe even higher quality) motor controller, the Sabertooth.

B) The other primary contender is a 2 stage RS-540 motor by bane bots.
This has 3 times the stall torque, but a stall current of 45A :shock: It is also a fair bit easier to incorporate into my design. However this motor is an absolute pig when it comes to current, and it uses a 3/8" shaft, and all I can find that fits that directly is the banebots wheel system, which seems to be geared to smooth, indoor/sumo/battlebot conditions, not exactly All Terrain. These motors would also force me to purchase much more heavy duty electronics, some monstrous batteries, and just all in all more expensive, at the loss of traction. But they are some crazy powerful motors.

C) The other option, is both. I can use the BB motor with a pair of sprockets to alter the shaft size. However this substantially increases the cost and makes it relatively complicated.

So, which option would you pick?
Any help or suggestions are welcome.

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Rookie ( offline )
Posts: 10
Posted: 2009-04-07 18:28 
I have the 36:1 540 BB gearmotors and as you said these things are ridiculously powerful and use tons of juice. I have two of them powering a 25lb robot on tracks at 8mph with no problem.


Tracks are not efficient and make alot of friction. Granted, I'm using the 36:1 gearbox and not the 25:1 but your bot is going to be on wheels.

My bot uses the hubs for a 6mm shaft [ HUB-02 ] but was honed to 3/8" ID

Remember too that if a hub uses a 6mm shaft, it was probably meant to take only the torque a motor with a 6mm shaft can produce.

IMO, if you plan on using 4-6 motors on the robot, use the smaller ones.
Six 25:1 540 gearboxes would be overkill on a 75lb robot!!!

Cheers, Rob

Program it like you stole it


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