Mechanics and Construction > Mechanics and Construction

Motor/Power/ Drive recomendation?

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minotaur:
Gang,

Can any of you get me a recomendation on the following. Thanks!

1) Need to build a small wheeled platform that traverses 95% of  flat indoor floorings. ( I presume this leaves out tracked vehicles.)
2) It needs to carry about 2.5 -3 lbs including its own weight.
3) I will visually be able to drive it remotely.
4) I plan to use a lead acid rechargable batt because I am guessing I will need a 2Ah battery (heavy..)

A) Is 4 wheel drive recomended?
B) DC motor, stepper motor, or servo?
C) Speed is not critical but what torque/ power would you guess is needed?

Thanks to all the experts here to set some initial criteria for my testing!

trigger:
http://www.societyofrobots.com/robot_tutorial.shtml

Somchaya:
A) You don't really need a 4 wheel drive. I'd recommend using a differential drive, since it's a lot easier to construct.

B) All 3 kinds would work actually, although a DC motor might be too fast (unless it's a geared motor or you gear it down) to control remotely properly.

C) Hmm.. I'm not very good with torque calculations.

So, I recently built a differential drive robot with a single castor, that carries around 3 lbs of weight. I used 2 standard servos originally, and the speed for that was ok, although torque was kind of low. However, I used really big wheels which reduces the torque. So, for a robot carrying 2.5 - 3 lbs, those standard servos should work fine, especially if you get decent sized wheels unlike me ;D

If you're intending to drive it remotely, it's probably better to go for a lower speed, unless you're really good with remote control cars :P Personally, I'm terrible at that so I have trouble controlling my robot even though it's not going very fast.

minotaur:
Trigger, not sure what you wanted me to see in the link, most of that information is pretty basic, so let me know if I missed something.

Somchaya,

Good info, this is helpful. What standard servos did you use? I agree on the difficulty driving remotely, especially since I have quite a bit of transport delay/ lag. Hitting a wall is bad, hitting a wall fast and far away is even worse...

Somchaya:
I used the Hitec HS-425BB (http://www.servocity.com/html/hs-425bb_super_sport_bb.html). It has a torque of 57 oz/in at 6V and can go at 62.5 rpm.

I ultimately upgraded the servos to higher-torque ones, but if you don't use huge wheels I think it should be sufficient  :)