Using ride-on toy gearmotors like PowerWheels

Community General Discussions
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Gearmotor_for_ride-toy.JPG (9644Bytes)

I am working on a project where I was seeking some low-cost gearmotors. They will be attached to a winch system that would lift a fairly light load.  The system needs some position control, and I was hoping to use a simle multi-turn potentiometers.

I recently purchased some gearmotors intended for kid's ride-on toys.  Here is the link to them.

http://www.ebay.com/itm/12V-Kid-Ride-On-Electric-Car-Motor-Gear-Box-For-BMW-Audi-TT-Hummer-Rover-Jeep-US/182345707668?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

But, I really don't recommend that vendor. They indicate they are in California, but in reality they are in China, and like most of the electronics vendors on E-bay, they give you the run-around for any issue or question.  The motors are simply shipped in bags, and get damaged in shipping. They seem to just have an auto-responder that says, "We have sent the problem to the related department to have a check, but we did not receive the reply at the moment, could you please contact us tomorrow to remind us?"

Here are the specs for the system that I created by either personally measuring it, or info from the motor part#.

Motor: DL 550-C,   12v    12,000 RPM (measures 18,000 unloaded)

  Motor Torque: 70.55 Oz-In

  No Load Current: 1.40 A

  Stall Torque :  69.16 Oz-In

  Stall Current:  85 A

  Shaft Dia 3.175mm

 

 Output from gearbox: 119 RPM  Gear ratio 97.75:1

   Calcllated force at the output when stalled:  895 Oz-In, drawing a current of 69 A.


Anyway, I am trying to find a way to use this low-cost gearbox and add position control.  Is anyone aware of a similar project?

Maybe I should just take the motor out, and 3D print some timing belt pullies.  One pullie for the winch spool, and another for my multi-turn pot.

-Joe

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Motors

I have used these motors before and they are terribly inefficient as well as being very noisy. The stall current rating of 85A is a joke. The wiring as well as the motor would melt down long before you got to that point. What I did on the ones I had was to replace the motors with some good quality units and to pack the gearbox with some white lithium grease.

After going to all that trouble, what you end up with still isn’t all that great, you would be time & money ahead to get a good quality motor & gearbox in the first place.

Just my opinion.

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You might look into

You might look into automobile windshield wiper or widow up/down motors. 

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Thank you for the comments.

Thank you for the comments. I had hoped that this cheap version  would be OK since my requirements are low in terms of force.  And at $19, including shipping, the price is quite attractive. The noise will certainly be an issue, since I want to use this in a theatrical play.  Perhaps this can be my experimental version, and then upgrade to a better motor if a theater actually pays to use my device. It will be a motorized Tinkerbell puppet flying on two threads. It will operate in a way similar to the “art bots” that draw on a wall.

I can vary my RPM needs by changing the diameter of my spool.  I have an existing spool 4.25" Diameter. So, for that I need at least 242 RPM with a 1 pound load.  This gearmotor is only 119 RPM unloaded, so I would need to go to a 9" spool at 144 Oz-In force.

I wish I could somehow search the RobotShop gearmotors for parameters such as 12v, 160 to 200 RPM, 75 to 150 OzIn torque. But, the best you can do is sort by one non-technical criteria like price or popularity.  A while back I even asked if I could download their list of motors, so that I could get them into Excel, and then sort that way.  But, there was no response.

I just spent over an hour looking for something.  This Pololu at $25 + Shipping, which would be 2 1/2 times as expensive.
https://www.robotshop.com/en/pololu-12vdc-350rpm-29-1-metal-gearmotor.html
Product Code : RB-Pol-81, 12V, No Load RPM: 350, Stall Current: 5A, Stall Torque: 110 oz-in

Or, if I want the same motor with a motor encoder, this Pololu one is $40 + Shipping. (4.7 X my cheap one)
https://www.robotshop.com/en/pololu-12v-301-gear-motor-64-cpr-encoder.html
Product Code : RB-Pol-336 .  

I was hesitant to spend that kind of money, especially without getting to hear it run.  If it were as loud as the ride-toy cheap one, it woudl be a problem.

-Joe

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I did look at windshield

I did look at windshield wiper motors. But, the output was too slow.  I can’t find any info on the RPMs of the power window gearmotors.

But, thanks for replying.

-Joe

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If you have encoders you

If you have encoders you can:

1. Regulate the speed (assuming sufficient torque)
2. Calculate  distance traveled.

 

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Gearmotor with encoder

Do you have an idea of the torque and RPM you need? Other gear motors with encoders are not as expensive:

https://www.robotshop.com/en/gear-motors-with-back-shaft.html

Planetary gearing is more efficient than spur gearing and as such should be a bit more quiet, but not “whisper” quiet.

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Again, than you for the

Again, than you for the comments and recommendations.

As for torque and speed, I have some leeway with that, because I could change the diameter of the spool.  But, my current target with my existing spool gives me the need for 240 RPM at 119 Oz-In torque at my peak need.  Though, in reality, it will spend less than 95% of its time doing that.  The total performance would be perhaps 2 minutes max.

I didn’t realize that the sub-listing of motors with rear shafts also listed motors with encoders already installed.   That greatly reduced my list of motors to something much more managable to search.  Though, in reality, I don’t need the precision of a motor encoder.

To share a bit of my design debate for position sensing;

My current decision was to use a multi-turn potentiometer on my output shaft.  It would give me absolute position. The arduino’s analog reading precision is good enough for the +/- 1" position tolerance I have.  And this way, I would not need to mess with homing.

I also can see the benefit of going purely with motor encoders.   I need about 37 revolutions of my spool, and I would need to gear this down to avoid over-turning my 10-turn potentiometer.   So, using a motor encoder alone has its benefits as well.  I can just put the spool onto the gear motor.

In the end, I am still somewhat on the fence.  The cost of timing belt sprockets and belt, plus the task of mounting them, would probably be comparible to the cost of the encoder. Though against that, is the task of homing.  I don’t really have a solid plan for that, since my Tinkerbell puppet is on thread, I don’t really have a good hard place to detect a “hit” when it homes.

Talking about it again now, has started me to shift back to the motor encoder version. Especially, since it is looking like the cheap ride-on toy version is looking less viable.

As for noise, I don’t have to be totally silent.  But, I do suspect that I will need to enclose the assembly in a box to reduce noise. I realize I will also need a fan to circulate air and cool the motor.

-Joe

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Limit Switches

Placing a limit switch near the spool would give you a “zero” position. Adding a second would tell you when you reached the end. You can use the return string to keep both switches near the motor.

 

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Limit Switches

As I mentioned before, I was concerned about how I would install limit switches. I was conscerned because my puppet had protruding things like hair and especailly wings.  If the thread went through her head or body, there migh tbe interference, or the potential to get caught up on the switches. But, I think I have a solution now. 

If my puppet is hanging from a T-shaped wire, that would allow the puppet to turn (via a servo inside her body) and also give me something firmer to detect a “hit” with my limit switch.  The hair and wings woudl be well away from the limit switchs.

-Joe