Looking for an inexpensive High Torque DC Motor

[robot321]

Hello All, 

Looking for an an inexpensive, High Torque, Low mA, DC Motor. RPMs are not too important (Not less than 3)
This is for a mobile robotic arm project. ( I require no bells in whistles,  Just a motor and maybe a gear box..  I will handle speed,home sensors,position,feedback in-house)

Looking for something powerful enough to lift a gallon of milk. 8.5-8.8 lbs (3855g-3991g).

Also where can I find standalone really high gear ratio boxes?  4000+

Thanks so much in advance....

[Admin]

try these:

http://www.npcrobotics.com/products/index.asp

http://www.robotmarketplace.com/marketplace_motors.html

[robot321]

Thank you so much for the quick reply.  These sites do offer some nice choices. 
But I'm on a budget,  while I do not want to sacrifice performance.  I would like to find a happy medium.

The prices seem... bloated. No?  I mean I could buy a drill BNIB (Brand New In Box) take it apart as save way more right?  And if I bough a used tool.  If would go down way more.

These online stores maybe do not see the volume others may do hence higher prices?  Or consider themselves a niche repository?

But since I'm new to the game of pricing motors in particular I may be way off base.

Is motor/gearbox with nice torque/mA numbers in the <$35 a pipe dream?  Otherwise the cost of my project will spin quickly out of control.

BTW:  I found this site about 2 weeks ago.  GREAT SITE!! Lots of info.

[Nyx]

I agree that the prices seem bloated (160$ for a motor-gearbox-wheel kit? A single wheel that is?). I too am on a budget, and I found something very nice the other day.... A windshield wiper motor:

http://cgi.ebay.ca/2000-2001-Saturn-L-Series-Wiper-Motor-NEW-Wholesale_W0QQitemZ160081958589QQihZ006QQcategoryZ2594QQrdZ1QQcmdZViewItem

They sell it for $13. I already have one of those at home. Bought a second one. They can do ~100 RPM at 12V, 4A, or 41 RPM with 0.91A. I will use two of these to power the wheels of my robot. I can tell you that they are fairly powerful. Grabbing the lever and trying to stop it is quite difficult.

[robot321]

That's outstanding.  That's much more in the direction I'm looking for. 

Maybe not quite powerful enough. But I could use it for something else. Nice find. I'll need to check ebay more.  Its just shipping is usually out of proportion to what it should cost.

Nyx: How much does the battery weigh you are using?  Gel or Lead-acid based?

[annoyin_kid]

why not use a servo. and if u need continous rotation modify the servo so it does that.

[robot321]

"why not use a servo."

Price.. Maybe I'm wrong.   Show me some numbers.

[Admin]

Is motor/gearbox with nice torque/mA numbers in the <$35 a pipe dream?

Its a pipe dream if you want to buy a high quality new motor. Its definitely doable if you spend weeks/months bargain hunting for used scrap parts and are willing to settle for less . . .

Most of those motors in the links I gave are overkill for what you want, but are only slightly overpriced. The lowest reasonable price you will ever get for a motor you describe would be $80+.

What torque is your absolute minimum required?
(if you are not sure how to calculate it, go here: http://www.societyofrobots.com/robot_arm_tutorial.shtml#joint_force)

You might also want to consider using a worm gear . . . its slow, but allows you to buy a cheaper motor.

"why not use a servo."

Price.. Maybe I'm wrong.   Show me some numbers.

As for servos, if they can handle the torque, use them. For what you get, they are very affordable. Dont forget they include the price of feedback control, motor control circuitry, encoders/pots, and everything else you would otherwise need to pay for with a regular DC motor.

[annoyin_kid]

"why not use a servo."

Price.. Maybe I'm wrong.   Show me some numbers.

yea wot admin said

[robot321]

What Nyx suggested has a worm gear drive.

feedback control, motor control circuitry, encoders/pots can be implemented with a few dollars on parts.

I guess its time invested vs. money.

Or a guess I could get a really strong motor pay extra money and use it to drive multiple pathways.  TOMY was great @ implementing this back in the day. I just hate having 1 point of failure.  And it complicates design.

Thank you all for your input.

[annoyin_kid]

so wot u gonna use?

[Nyx]

That's outstanding.  That's much more in the direction I'm looking for. 

Maybe not quite powerful enough. But I could use it for something else. Nice find. I'll need to check ebay more.  Its just shipping is usually out of proportion to what it should cost.

Nyx: How much does the battery weigh you are using?  Gel or Lead-acid based?

I'm planning to go with a gel battery (deep cycle), around 30-40 Ah. It should weight about 30 pounds. I might also go with two seadoo batteries (19ah), depending on the availability. It's my understanding that deep cycle batteries are much more tolerant and easy to charge/handle than SLA batteries.

[robot321]

so wot u gonna use?

Not sure yet.  Much more research is needed. Few more days of thinking about it in the shower and other obscure places. lol. This discussion was needed to get my butt in gear and really start thinking about it.  And I thank you all for it.

For some stupid reason I take pride in saying how much the prototypes costs without time as a factor 

Nyx: If your are going gel..  IMHO Optima are awesome batteries.  May be overkill for your project though. And are on the high end of the cost spectrum.

[Admin]

For some stupid reason I take pride in saying how much the prototypes costs without time as a factor

I think we were all like that at some point, because I definitely was for like the first 3 years I built robots . . . when I was a poor college student, I had much more free time than free money (sorry, bad pun . . .)

[annoyin_kid]

so wot u gonna use?

Not sure yet.  Much more research is needed. Few more days of thinking about it in the shower and other obscure places. lol. This discussion was needed to get my butt in gear and really start thinking about it.  And I thank you all for it.

For some stupid reason I take pride in saying how much the prototypes costs without time as a factor 

Nyx: If your are going gel..  IMHO Optima are awesome batteries.  May be overkill for your project though. And are on the high end of the cost spectrum.

ahhh... no place like the shower is there robot321