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Author Topic: Wheelchair motor is overkill.... looking for something cheaper, need help.  (Read 3443 times)

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Offline kiritTopic starter

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Hi, Im looking for a motor that is less powerful and less expansive than a wheel chair motor. I used the motor calculator page to get an RMF of 25. (40lbs robot, 5mph max, flat grass terrain 800-1000feet course). Does anyone have any cheaper suggestions? Im looking at using a simple 2 powered wheel design, but didnt want to go overboard with a wheelchair motor. Thanks for any and all suggestions. :)

kirit

Offline Trumpkin

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Maybe windshield wiper motors would do?
Robots are awesome!

Offline kiritTopic starter

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Maybe windshield wiper motors would do?
I was thinking something along those lines too. Only problem that the forum search turned up was that they are very inefficient and so that might bite me in the ass later and that getting documentation on it might be a pain in the butt.

Offline 4by4

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I used the Denso wiper-type motors that Parallax uses in their kit, but found that it's hard to attach them to wheels without a better equipped workshop than I have. Parallax apparently had a bunch of custom machined parts made to do the attachment, which I don't have the luxury of. So I then tried Power Wheels type motors and they work fine. I bought 4 from www.resunltd4u.com.

Offline kiritTopic starter

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So I then tried Power Wheels type motors and they work fine. I bought 4 from www.resunltd4u.com.

I tried looking for them but couldnt find it on that site. Any chance you can send me a link or pictures of the motor you bought? How are they working for you, are you getting all that you expect it?

thanks

Offline ArcMan

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I used windshield wiper motors on a robot a few years ago.  They were not mechanically designed to run in reverse - the worm gear did not mesh properly in reverse.  The robot was a failure.  Now, power window motors are a different story.  They are designed to run in both directions and would drive a 40 lb. robot nicely.  And they're cheap.

Offline 4by4

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Not sure why you had a problem with the link. Try getting there by googling Resources Un-Ltd. The part number is Product # CARDRIVE FP. You can also go to: www.modifiedpowerwheels.com There is lots of info there on how to work with these motors, and other sources for them. There are lots of different versions of this type of motor, but you shouldn't have to pay more than $15 for them. There is a different version of a kiddie car motor at Surplus Center. It looks smaller than the one I am using.

The motors work fine on my 4-wheel 35 lb vehicle with skid steering. The  vehicle has 10 inch tires, which gives about 4 mph speed. There is plenty of torque. I am using one motor per wheel, but there is enough torque if you only use two motors with two powered wheels and two caster wheels. After all, these thing are designed to carry kids weighing a lot more. The vehicle runs in deep grass and up hills w no problem. I am not using an ESC, just on-off controls.

The design of these motors makes attaching to wheels easier, since it has a flange with it. The only problem I had was my wheel didn't have a good place to bolt the flange to, so I had to design a work-around. 

About "wiper motors": I used this term too loosely. There are several similar types of motors - wiper motors, window motors, and seat motors. The Denso motors I referred to are actually seat motors, I think. They have plenty of power for a 40 lb robot, and they cost about $15 each. They are good motors, my only problem was I have limited capability for building a wheel attachment for them.

Offline kiritTopic starter

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Not sure why you had a problem with the link. Try getting there by googling Resources Un-Ltd. The part number is Product # CARDRIVE FP. You can also go to: www.modifiedpowerwheels.com There is lots of info there on how to work with these motors, and other sources for them. There are lots of different versions of this type of motor, but you shouldn't have to pay more than $15 for them. There is a different version of a kiddie car motor at Surplus Center. It looks smaller than the one I am using.
Oops, I must be a complete idiot. I didnt see it at all on their website. I did find it and they are going for 2 for $35 bucks. Not a bad deal.
Quote

The motors work fine on my 4-wheel 35 lb vehicle with skid steering. The  vehicle has 10 inch tires, which gives about 4 mph speed. There is plenty of torque. I am using one motor per wheel, but there is enough torque if you only use two motors with two powered wheels and two caster wheels. After all, these thing are designed to carry kids weighing a lot more. The vehicle runs in deep grass and up hills w no problem. I am not using an ESC, just on-off controls.
ESC?
Quote

The design of these motors makes attaching to wheels easier, since it has a flange with it. The only problem I had was my wheel didn't have a good place to bolt the flange to, so I had to design a work-around. 


Im thinking of attaching a pair of bicycle wheels to it. Just a simple 2 wheel robot with no caster wheels. I figure if most of the weight is under the axle, I should be fine. Any thoughts? Im trying to keep this as simple and cheap as possible. A platform to learn as i get my EE degree. :)

Offline Trumpkin

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Quote
ESC?
Electronic Speed Controller
Robots are awesome!

Offline 4by4

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You're going to need more than two wheels unless you're building a segway. Usually in a design with 2 powered wheels and differential steering, there are one or two caster wheels for supporting the other end of the vehicle. As far as bicycle wheels, keep in mind that with a larger diameter wheel such as an adult's bike wheel you will be getting a much faster speed, maybe too fast for a robot. A kid's bike wheel, say 12 inches dia., might be better. Off hand I'm not sure how I would attach the flange of the kiddie car motor to a bicycle wheel. The flange is designed to bolt to a flat surface.

Offline chelmi

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You're going to need more than two wheels unless you're building a segway.


Or something like:


Offline kiritTopic starter

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You can also go to: www.modifiedpowerwheels.com There is lots of info there on how to work with these motors, and other sources for them.

OMG, this is a great website. Im reading lots of good info, not finding everything, but ive just scratched the surface. Any chance you (or others)have similarly great sites bookmarked?

as to using a 2 wheeled robot. I wanted something that could basically turn on a dime. I was under the impression that if I kept most of the weight under the axle that I wouldnt have too much problem with it. Basically something that looks like chelmi's pic. I got the idea from this pic:

Im not going for something that cool looking.

On attaching the bike wheels to the motor. I hadnt put too much thinking into it.  ;D Im hoping for some inspiration as the projects moves forward.

Offline airman00

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Or something like:



I have a feeling that the part on the axle sways around a lot.
Check out the Roboduino, Arduino-compatible board!


Link: http://curiousinventor.com/kits/roboduino

www.Narobo.com

Offline 4by4

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I see what you're saying about two wheels only. There's also a "throwbot" developed on DARPA money that only has two wheels, and it drags a stiff tail-like thingy out the back to prevent the body from rotating in the opposite direction in reaction to the motor torque.

http://blog.wired.com/defense/2007/05/the_amazing_tos.html

Offline jamort

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www.maximumrobotics.com had some electric scooter motors for $25 a piece... I'm prety sure the'd do it
my english teacher once said, "dont talk about what you dont know in public...."

so I replied the truth, " Exactly why I dont ever talk about English."

Offline Razor Concepts

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Or something like:



I have a feeling that the part on the axle sways around a lot.


If you see videos of it, it flips around all over the place making it harder to turn off

Offline kiritTopic starter

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Sorry for not replying for the last couple of days. Had a mid-term exam, few quizzes and life in general to deal with the last few days. Anyways, back to this. I like the idea of a scooter motor. While looking for info, it turns out that there was a great motor called EV warrior 24v, but I guess they dont make that one anymore.

The more I look into it, the more I like the idea of the modified power wheel motor. Im thinking that 2 of those motors, a scooter ESC and some way to control the motor via a laptop will be a winner for me. Now I just need to research how best (more importantly economically) to control the motor through a laptop.

kirit

Offline jamort

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do you mean to control it manually via joint stick or it be autonomous?
my english teacher once said, "dont talk about what you dont know in public...."

so I replied the truth, " Exactly why I dont ever talk about English."

Offline kiritTopic starter

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do you mean to control it manually via joint stick or it be autonomous?
Autonomously. I plan on getting a couple of usb cams and a few other sensors as it progresses along. Initially I want to have it navigate a course, where it needs to stay between the lines, and eventually avoid objects in its way.

 


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