Motors for larger robot

LMac

I'm working on a fairly large robot that will use a PC for the main processing and a cluster of stamps with serial communications to handle specific tasks like servos, compass readings, bumper sensors, sonar (with PING), and robot movement.· I want to use two HB-25 Motor Controller's to control 2 DC motors (differential drive steering) but I'm having trouble finding reasonablly priced motors.· Does anyone know of a good source?· The robot will be indoors and should finish out at between 50 and 100 pounds and I plan to use a 12VDC 21AH battery.

Paul Baker

Stores specializing in surplus equipment·is typically your best bet, heres a link that has many of the online surplus houses:
http://www.markscheeff.com/etc/links.html

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Post Edited (Paul Baker) : 4/21/2006 2:31:38 PM GMT

LoopyByteloose

Prices are far more reasonable if you can go to an actual surplus store in your area.· Most of· these are untidy places in the industrial section of town and expect people to bargain for whatever is sitting around.

Shopping by internet may or may not be as good.

I lived in San Francisco and had to specifically go to Oakland to locate things. At other times it was necessary to go down to Silicon Valley.·

There was next to nothing in San Francisco proper and driving one to two hours really did save money.

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Paul Baker

Local surplus is really hit or miss depending on your location. CA is the best, TX is OK, here in greater DC Ive only been able to find 1 outfit and they sell used military electronics. Great, but impossible to find spec sheets for.

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Jim Richey

I can recommend wheelchair motors,if they aren't too big for you.They are always available on Ebay.A nice set of 2 should run around $100.Try to get Invacare motors,they are rugged and dependable,plus they work great on 12 volts.They also use surprising little current.

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Thanks, Parallax!

Catharsis

http://banebots.com/osc/index.php?cPath=36_63

bulkhead

If you can get an electric wheel chair, it sounds like it would make a solid platform. If you want a cheaper solution than wheel chair motors, check out windshield wiper motors. This one www.allelectronics.com/cgi-bin/item/DCM-171/search/12VDC_GEARHEAD_MOTOR_.html has many good reviews, and it's cheap. I think it draws around 12 or so amps at stall, so you could run 2 per HB-25 for more power.

If you scroll down, one of the reviewers has tutorials on how to use the motors (create mounting brackets, linkages, etc): www.scary-terry.com/wipmtr/wipmtr.htm

LMac

Wow, you guys came through better than expected.· On my way home last night, I began to think that I have a 12VDC drill/driver that can deliver 225 in-lbs of torque so I started to consider getting a couple of replacement motors with gears to try ($38+ each).·· 225 in-lbs would be·3600 oz-in.

The RS-545 motor with 100:1 gear ratio looks good but I calculate it would deliver·3800 oz-in minus friction loss (please point out any errors in logic). I could get that in a 256:1 ratio for 9728 oz-in.

The windshield wiper motor sounds great for the price.· I can't do any calculations for it but I see a review that says it moved a bot that was near 200 lbs.

It also looks like I could use one Motor Mind C ($55) instead of·two HB-25 (~$99)·controllers.

I guess now I'll have to pick some wheels and do some speed calculations to see what suits my bot best.· Also, the wiper motor sounds great but the RS-545 has more specs I can work with.· I looked for wheel chair motors but couldn't find anything as good as these 2 motors.

Decisions, decisions.

Thanks for your help guys.

LMac

I settled on the windshield wiper motors recommended by bulkhead.· Of course, since I'm planning on using PWM and need the reverse movement, I planned on removing the case ground and I had some instructions from another forum.· Now that I see the motor, I'm not sure exactly what to do.· I've attached a photo of the brush that I think is tied to ground and I've labled some points (A - E) to help discussion.· Point E just marks a bare wire that comes above the board.· All of these points check as ground with an ohm meter.

I believe I need to clip the braided wire connected to the lug at point C but I'm not sure.· I know I need another wire (probable black) to go to the motor controller but I'm not sure where to attach it in the motor.· Also, is it likely that I could lift this board out if I removed the brushes?· Any help anyone can offer will be appreciated.

LMac

Got it.· Thanks bulkhead.· These are great little drive motors, and cheap!

deno

I find the following company has a very large selection of DC gearmotors.

http://www.surpluscenter.com/sort.asp?numrec=59&sort=1&search=dc%20gearmotor&UID=2005040807153250

I used 4 of the windshield wiper motors rated at 24 volts, but I am operating them on 12 volts.

My robot "Robochild" weighs in at about 50 pounds (pictured at left)

Deno

bulkhead

I'm glad those motors worked out for you, I've been considering them for a while now. How many motors did you get, and for how large of a platform? If you have the chance, could you make a post about your project in the projects forums when you are done? Some time in the future I will attempt to build a large robot and will probably go the same route, those windshield wiper motors and HB-25's.

LMac

I bought 2 of the motors for less than the price of·most single motors.· I was a little insecure about the mode to allow reverse movement but I shouldn't have been.· Unfortunately, I've had other things come up that will delay getting the controllers and actually building them into the robot.· However, I can tell that they are goings to provide good gearing so I should have plenty of power and speeds that are good for an indoor roaming bot that needs to navigate close quarters.· If I had a torque wrench, I'd try to measure the stall torque but I suspect it would exceed the range of most wrenches.· If I get any experimental measurements of the power, I'll post something.

LMac

OK, a kind of test.· Using the motor as it comes, with the bar and ball joint that would drive the wiper assembly, I added a rope between the ball joint and the ceiling of my garage.· With the motor running, and with the best grip I could arrange, I put as much of my 195 lbs as possible on the motor.· That would require the motor to lift about 2 inches.· With a 7 AH battery, and the motor on slow speed, I could slow the motor but I could not stall it.

Then I used the same arrangement with a 48 lb box of books and the motor lifted it off the ground with no indication of stall.· I'm sure 2 of these will move my 70 lb robot with no problem.· In fact, they should be able to lift it off the ground.