Request For Information (Stingray Experimenters)
Hey everyone,
Some of you, at some point were trying motors (I think erco was involved) trying to find one that was an ideal solution for the Stingray. Our motor supplier at the time went dark on us and we were unable to get better motors for you all. We recently got back in touch with the company and are interested in getting some better motors. This won't bring the Stingray back, per se, however it will provide motors for the motor mounting bracket kit we have. The thing is, since we have to wait for samples, we'd like to get the gear ration correct and I know some of you did empirical testing and found something that worked well with the wheels we have. Looking for the results of your findings. Anyone want to share? :thumb:
Some of you, at some point were trying motors (I think erco was involved) trying to find one that was an ideal solution for the Stingray. Our motor supplier at the time went dark on us and we were unable to get better motors for you all. We recently got back in touch with the company and are interested in getting some better motors. This won't bring the Stingray back, per se, however it will provide motors for the motor mounting bracket kit we have. The thing is, since we have to wait for samples, we'd like to get the gear ration correct and I know some of you did empirical testing and found something that worked well with the wheels we have. Looking for the results of your findings. Anyone want to share? :thumb:
Comments
100:1 Metal Gearmotor 37Dx57L mm with 64 CPR Encoder
The integrated quadrature encoder provides a resolution of 64 counts per revolution of the motor shaft, which corresponds to 6533 counts per revolution of the gearbox’s output shaft.
It is really nice to have the quadrature encoders built into the motor !!!
You simply mount the motor including the encoder with 3 screws. You don't need to worry about seperating mounting the encoders.
I am powering them from a 9.6Vdc NiMH battery that actually charges to a measured voltage of 10.7 Vdc.
The mounting holes in the motors match the Stingray perfectly, however the motor shafts are shorter then the original Stingray motors.
General specifications
Gear ratio: 100:1
Free-run speed @ 6V: 50 rpm1
Free-run current @ 6V: 250 mA1
Stall current @ 6V: 2500 mA1
Stall torque @ 6V: 110 oz·in1
Free-run speed @ 12V: 100 rpm
Free-run current @ 12V: 300 mA
Stall current @ 12V: 5000 mA
Stall torque @ 12V: 220 oz·in
Lead length: 11 in
Notes:
1
This motor will run at 6 V but is intended for operation at 12 V.
Sorry I don't have any video yet.
The motor’s rated speed is 100 RPM at 12 V which equates to a robot speed of approximately 2.1 feet/sec (0.65 m/s) or 1.45 mph or 1531.5 inches / minute. The encoders will generate 426.587 pulses per inch of travel or 5119 pulses per foot of travel. This is using the Stingray's wheels.
These speeds seem great for an indoor robot. If you have a 20 x 20 foot room you can get across the room in about 10 seconds.
Remember, since the motors are geared slower, you get more torque, so the robot can be heavier.
Also most motors can output more Torque when operating below their maximum speed, you need to look at the manufactures data sheet / graph.
Here is erco's video on the subject...
On the YouTube page erco says"A visibly lower RPM/higher torque motor for a Parallax Stingray robot to obtain finer low speed motor control. ~$10 Ebay China, called a "DC Gear Motor 12V 70rpm 37mm High Torque 8kg.cm" Bolts right in, almost identical size/weight, an easy swap.
An eBay search for the above will find - http://www.ebay.com/itm/DC-Gear-Motor-12V-70rpm-37mm-High-Torque-8kg-cm-Micro-DC-Gear-Box-Motor-/150990875645?pt=LH_DefaultDomain_0&hash=item2327c1ebfd
I ordered some of these, but have not installed them yet. Will probably try them at 7.2 volts first...
There are more videos and pics in this thread: http://forums.parallax.com/showthread.php/131522-Homemade-StingRay
Ron, I know you listed the ratio (50:1), but do you happen to know the RPM@V rating with that gear ratio?
Here are the specs http://www.pololu.com/catalog/product/1444/specs
I realize 80 RPM might be a little slow for some folks, but my critters seldom operate in the wide open spaces and speed isn't much of an issue. Also the torque is much better. Installing the motors in my tracked chassis, I find it can climb an approximate 45 degree slope... (with a decent surface, that is).
Just my two cents.
Amanda
I had similar thoughts and considered swapping out the 50:1 for 100:1.
That speaks volumes, Ron, especially considering the amazing accuracy you've achieved & documented already!
Just wanted to double check...these are marked 6V...is 12V a safe voltage for them?
Good question, I think so but I will ask. I do know that you can get them in 12 or 24V versions as well.
I think so. hard to decipher their answers sometimes. Here is what I asked...
... and their answer.