I can't find the motor speed of the Parallax Motor, Bracket & Wheel Kit ( Product ID 570-00080 )
Please help,
I can't provide a quantitative specification off hand, but let me try to describe it.
It moves about as fast as you walk, +/- just a bit. I guess you could also say this is "fast enough" in case your programming skills mean there's a potential of impact with a person or object - any faster could do some damage to whatever you run into. Or, how about this: It's fast enough that if you're using an ultrasonic sensor and headed to a wall at full speed, a quick "ramp down" will leave you five feet from the wall when the Ping))) makes the first detection at about 10 feet away.
Couple of other facts about this kit - it's really quiet and smooth. People are always surprised that they don't hear anything from the motors. Also, the encoders help it to go really straight. And, it'll run ActivityBot code (both Arlo and ActivityBot have 36/count/revolution encoders).
@markuster: RPM/speed will vary according the max drive voltage, which can range from 6-15 VDC. The torque specs below from the product PDF are helpful, but RPM specs are MIA. No-load RPM at 6 and 12VDC would be helpful in this post and added to the PDF. Matt G, can you assist?
Motor ratings
o 6–15 VDC (12 V Nominal)
o No-load current: 0.22 A @ 6V
o Stall current: 3.5 A @ 6 V (>5 A @ 12 V)
o Max motor torque: 24.78 lbf-in (0.285 kgf-m)
Dimensions
o Wheels: 4 7/8 inch (12.4 cm) diameter x 0.8 inch (2.03 cm) wide
o Mounting height: 3.86 inch (9.8 cm) from ground to mounting surface
I realized I've been replying in reference to the Motor Mount and Wheel Kit, but erco replied properly about the product mentioned by the original poster.
"After 1 hour burn-in, the motor wheel assemblies exhibit about 3/16" to 1/8" (extreme to extreme) of backlash.
Wheel diameter is still right at 6", just like the previous version.
The motors have approx. 85" lbs of torque.
We have eliminated all backlash in the attachment of our machined aluminum axles to the square drive shaft from the motor. It is a "tap on gently with a small hammer, interference fit".
Amps @12.0 VDC = 1.3
Amps @12.0 VDC = 1.5
Amps @12.0 VDC = 1.6
Amps @12.0 VDC = 1.7
...and Full LRA (Lock Rotor Amps - stall condition) is > 12 amps
RPM's @ 12.0 VDC = 93 (all under no load)
RPM's @ 12.6 VDC = 100
Actually I think Matt G is referring to the MMWK used in the Eddie/Arlo platforms. The Gear Motors with the Hall Effect Encoders are rated from the manufacturer as 82 RPM @ 6V. I will try to get some more information, such as speed and RPM at varying voltages this week.
Hi,
It seems I made a mistake and lost my last post.
Any way, I don't understand why Matt wrotte samething about 85" lbs of torque because the Motor, Bracket & Wheel Kit ( Product ID 570-00080 ) has
less than 30 lb-in. I don't know if I am speaking about the same motor kit.
The specs below are for a different motor kit((#570-00070) ). Maybe you can use these motors as a reference to calculate the speed once you know the RPM:(~310 RPM equates to a speed of approximately 6.6 feet/second (2.0 m/s))
7.2 V Motor, Bracket and Wheel Kit (#570-00070)
Congratulations on purchasing the 7.2 V Motor, Bracket and Wheel Kit! This kit contains power, durability
and simplicity all in one box. This kit features lightweight and sturdy aluminum brackets which are
specifically designed to make mounting the included 7.2 Volt DC motors a breeze. Each bracket is
machined in-house at Parallax headquarters in Rocklin, CA. The brackets are machined from 6063
aluminum extrusion and anodized black for improved scratch resistance aesthetic appeal.
High quality 7.2 Volt DC motors feature durable
construction and 100% all-metal gears that
stand up boldly to rough terrain and abuse. The
motors’ top speed of ~310 RPM equates to a
speed of approximately 6.6 feet/second (2.0
m/s) which is perfect for most medium- to
small- size robotic projects. The included
machined aluminum hubs solidly engage the 4
7/8 inch (12.4 cm) diameter wheels. The tread
is molded directly onto the wheel and offers
excellent traction on most common surfaces.
But I am asking about an other motor from Parallax. It is the Product ID 570-00080 .
I realize that and as I stated" The specs below are for a different motor kit((#570-00070)" I put it there as a reference to this statement from the spec sheet The motors’ top speed of ~310 RPM equates to a speed of approximately 6.6 feet/second (2.0 m/s) which is perfect for most medium- to small- size robotic projects "
in response to Ken's statement about speed calculation." I still haven't checked this, but I think they're 120 RPM at 12V with a 6.25" diameter wheel. Somebody smarter can do the speed calculation. "
====================================================================================
Once someone provides you the RPM for your motors, the example above should provide the ratio to calculate the speed.
I have a home-brew platform with the new 570-00080 kit installed along with our caster wheel. I've been meaning to get speed information for some time now, but each time I go to take it outside it rains lately (like today). When I get back to my home office tomorrow I will rig up something on my bench. I've got two tests in mind and I will post my results on both the product page and here.
I still haven't checked this, but I think they're 120 RPM at 12V with a 6.25" diameter wheel.
Somebody smarter can do the speed calculation.
Ken Gracey
From math theory when a wheel with diameter 6.25” makes 1 rotation then will travell a distance s=3.14 * 6.25”=19,625” i(nch) . If this wheel rotated by a motor with 120 RPM, in 1 minute will make 120 rotations and a distance equal 120*19,625”=2355” (inch). So the speed of the robot will be 2355 inch/min=2355*0.0254 /60 m/sec=0,99695 m/sec
so is we could give a formula that will calculate the speed m/sec in conjunction with RPM and wheel diameter will have the following:
Speed= (wheel_diameter * 3.14* RPM)/6000 m/sec
(Give the wheel's diameter in cm)
All the above are right in theory without frictions etc.....
The easiest way to do this calculation is to take the RPM, and divide by 60 to get RPS (no one thinks of robot travel over a full minute). So 120 RPM is 2 RPS. Remember just the RPS value; the RPM is no longer needed.
You then multiply by the circumference of the wheel, which as Nikos shows is diameter * pi. A 6" wheel has a circumference of 6 * 3.14, or 18.784 inches. To calculate travel speed in one second it's 18.784 * 2, or 37.68.
Obviously you can do the same in metric by substituting the metric diameter of the wheel.
All sweet, except most manufacturers rate the speed of their motors under no load, or a specific load that has absolutely no bearing on the design of your robot. The loaded speed can easily be 30-50% less than no-load. The ONLY way to calculate loaded speed of your robot is to actually measure it in action. This would then account for the load (weight) of the robot, friction of the wheels, affect of the surface you're traveling over, deformation of pneumatic tires, actual running voltage of the motors, etc.
Comments
I can't provide a quantitative specification off hand, but let me try to describe it.
It moves about as fast as you walk, +/- just a bit. I guess you could also say this is "fast enough" in case your programming skills mean there's a potential of impact with a person or object - any faster could do some damage to whatever you run into. Or, how about this: It's fast enough that if you're using an ultrasonic sensor and headed to a wall at full speed, a quick "ramp down" will leave you five feet from the wall when the Ping))) makes the first detection at about 10 feet away.
Couple of other facts about this kit - it's really quiet and smooth. People are always surprised that they don't hear anything from the motors. Also, the encoders help it to go really straight. And, it'll run ActivityBot code (both Arlo and ActivityBot have 36/count/revolution encoders).
Does this help?
Ken Gracey
Motor ratings
o 6–15 VDC (12 V Nominal)
o No-load current: 0.22 A @ 6V
o Stall current: 3.5 A @ 6 V (>5 A @ 12 V)
o Max motor torque: 24.78 lbf-in (0.285 kgf-m)
Dimensions
o Wheels: 4 7/8 inch (12.4 cm) diameter x 0.8 inch (2.03 cm) wide
o Mounting height: 3.86 inch (9.8 cm) from ground to mounting surface
Somebody smarter can do the speed calculation.
Ken Gracey
Ken Gracey
"After 1 hour burn-in, the motor wheel assemblies exhibit about 3/16" to 1/8" (extreme to extreme) of backlash.
Wheel diameter is still right at 6", just like the previous version.
The motors have approx. 85" lbs of torque.
We have eliminated all backlash in the attachment of our machined aluminum axles to the square drive shaft from the motor. It is a "tap on gently with a small hammer, interference fit".
Amps @12.0 VDC = 1.3
Amps @12.0 VDC = 1.5
Amps @12.0 VDC = 1.6
Amps @12.0 VDC = 1.7
...and Full LRA (Lock Rotor Amps - stall condition) is > 12 amps
RPM's @ 12.0 VDC = 93 (all under no load)
RPM's @ 12.6 VDC = 100
RPM's @ 13.0 VDC = 102
RPM's @ 13.8 VDC = 106
I'll see if I can dig out more...
-MattG
It seems I made a mistake and lost my last post.
Any way, I don't understand why Matt wrotte samething about 85" lbs of torque because the Motor, Bracket & Wheel Kit ( Product ID 570-00080 ) has
less than 30 lb-in. I don't know if I am speaking about the same motor kit.
Couls you confirm please ?
Regards,
Nevermind the replies from MattG and myself - we're both a bit crazy and discussing a different product.
Chris is the guy to pay attention to and it sounds like he'll collect a few more specs on the product you're asking about.
Thanks for your patience. We didn't mean to throw so much confusion towards you along the way.
Ken Gracey
7.2 V Motor, Bracket and Wheel Kit (#570-00070)
Congratulations on purchasing the 7.2 V Motor, Bracket and Wheel Kit! This kit contains power, durability
and simplicity all in one box. This kit features lightweight and sturdy aluminum brackets which are
specifically designed to make mounting the included 7.2 Volt DC motors a breeze. Each bracket is
machined in-house at Parallax headquarters in Rocklin, CA. The brackets are machined from 6063
aluminum extrusion and anodized black for improved scratch resistance aesthetic appeal.
High quality 7.2 Volt DC motors feature durable
construction and 100% all-metal gears that
stand up boldly to rough terrain and abuse. The
motors’ top speed of ~310 RPM equates to a
speed of approximately 6.6 feet/second (2.0
m/s) which is perfect for most medium- to
small- size robotic projects. The included
machined aluminum hubs solidly engage the 4
7/8 inch (12.4 cm) diameter wheels. The tread
is molded directly onto the wheel and offers
excellent traction on most common surfaces.
Giving your robot mobility has never been
easier!
http://www.parallax.com/sites/default/files/downloads/570-00070-7.2v-Motor-Bracket-and-Wheel-Kit-Documentation-v1.1.pdf
But I am asking about an other motor from Parallax. It is the
Product ID 570-00080 .
Regards,
-MattG
I realize that and as I stated" The specs below are for a different motor kit((#570-00070)" I put it there as a reference to this statement from the spec sheet
The
motors’ top speed of ~310 RPM equates to a
speed of approximately 6.6 feet/second (2.0
m/s) which is perfect for most medium- to
small- size robotic projects "
in response to Ken's statement about speed calculation." I still haven't checked this, but I think they're 120 RPM at 12V with a 6.25" diameter wheel. Somebody smarter can do the speed calculation. "
====================================================================================
Once someone provides you the RPM for your motors, the example above should provide the ratio to calculate the speed.
From math theory when a wheel with diameter 6.25” makes 1 rotation then will travell a distance s=3.14 * 6.25”=19,625” i(nch) . If this wheel rotated by a motor with 120 RPM, in 1 minute will make 120 rotations and a distance equal 120*19,625”=2355” (inch). So the speed of the robot will be 2355 inch/min=2355*0.0254 /60 m/sec=0,99695 m/sec
so is we could give a formula that will calculate the speed m/sec in conjunction with RPM and wheel diameter will have the following:
Speed= (wheel_diameter * 3.14* RPM)/6000 m/sec
(Give the wheel's diameter in cm)
All the above are right in theory without frictions etc.....
You then multiply by the circumference of the wheel, which as Nikos shows is diameter * pi. A 6" wheel has a circumference of 6 * 3.14, or 18.784 inches. To calculate travel speed in one second it's 18.784 * 2, or 37.68.
Obviously you can do the same in metric by substituting the metric diameter of the wheel.
All sweet, except most manufacturers rate the speed of their motors under no load, or a specific load that has absolutely no bearing on the design of your robot. The loaded speed can easily be 30-50% less than no-load. The ONLY way to calculate loaded speed of your robot is to actually measure it in action. This would then account for the load (weight) of the robot, friction of the wheels, affect of the surface you're traveling over, deformation of pneumatic tires, actual running voltage of the motors, etc.