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Author Topic: Double checking RMF math before purchasing.  (Read 697 times)

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Offline EithmanTopic starter

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Double checking RMF math before purchasing.
« on: April 28, 2012, 12:48:44 PM »
Hello everyone. This is my first time on this forum but I really like the layout of the site. Very easy to use and helpful. My question is regarding whether or not my RMF math is correct before I go ahead and buy this motor. I read through the statics and dynamics tutorials. Using that knowledge I checked online and found this motor http://www.robotshop.com/solarbotics-gm2-gear-motor-2-offset.html. I plan on buying two of these to be the front wheels on the base of a robot I am building. I will use regular wheels for the back. Here is what I came up with when calculating.

https://docs.google.com/document/d/1_BfaLPuMPeYCOFPSX-UcX8mNfMZ36hYB7RN_iL7Rg0Q/edit

So it would seem that I should be fine and even have a little extra, correct? Does anyone see any problems or should I go ahead with the buy? Thanks for the help!

Offline Soeren

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Re: Double checking RMF math before purchasing.
« Reply #1 on: April 28, 2012, 08:18:12 PM »
Hi,

https://docs.google.com/document/d/1_BfaLPuMPeYCOFPSX-UcX8mNfMZ36hYB7RN_iL7Rg0Q/edit

So it would seem that I should be fine and even have a little extra, correct? Does anyone see any problems or should I go ahead with the buy?
Sorry, I'm still in a long aftermath of a Google redirect virus :( and even going by the IP number I cannot get through to your document, but anyway, if you want people to bother, it's better to post the file here, rather than on any other site. A .doc or whatever will do if your options are limited, but .pdf is the preferred cross platform format that is readable to all (just don't make it compatible with the newest edition only).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline EithmanTopic starter

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Re: Double checking RMF math before purchasing.
« Reply #2 on: April 29, 2012, 01:10:01 AM »
Sorry about that  :( For sake of ease, I will just type out the results as to avoid any other confusion.

Mass - 3 lbs
Desired Velocity - 0.5 ft/s
Desired Acceleration - 1 ft/s^2
Expected Efficiency - 90%
Incline Angle - 0 degrees
Wheel Diameter - 0.32 feet
# of Powered Wheels - 2 Wheels

RMF - 0.133 lb*ft*rps
RMF (zero incline) - 0.133 lb*ft*rps
Momentum - 1.5 lb*ft*s
Motor Rotation Speed - .497 rps
Energy/second - 0.00231 Watts

Torque - 0.036 kg*m
Speed - 0.63 rps
Motor RMF - 0.164

This is copied directly from the RMF calculator offered in the dynamics section. If there is any other information you need, please let me know. Thanks!

 


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