Motor specs

Competition Off-Season Events
1

As a novice team, we’re trying to learn about the motors used in this contest. Also, we need to run a few more calculations.

First off, could you please verify that the motor specs in the CDI App Notes are correct? What I’m hearing via the grapevine from other people WRT “which is the better motor for <this> or <that> purpose” does NOT appear to agree with the specs I see there. Also, some of the specs don’t agree with the white paper’s “Motorpower.PDF” file. For example, the latter says Globe motors are 50-63W (not 23W), and Keyangs are 40W (not 31W), which reverses which may be considered the stronger motor at their respective optimum power points. I’m SO confused!

Also, can you please simply ID the motors by original vendor part number, and point me to the three websites that contain the FULL performance curves for each of the three motors? The curves in the “FIRST Motors Etc” Power Point file are tiny and illegible, and I need to see the full curves for each motor for some calculations.

Thanks!

  • Keith McClary, Huron High Team 830
2

I will try to anwer your motor questions, but they are not “official” responses. The globe motors and the keyang motors used in this competition are slightly different than the ones used the FIRST competition. The drill motor is in no way anything like the one used for the FIRST motors. What you are probably hearing is that the globe motors are better for drive train. That is a gray area. The Keyang motor actually has more HP, but has a couple of negatives: (1) Has an internal temp sensor which effectively brings the motor to 0 torque if overheated, (2) a gear ratio of approximately 9:1 is needed to bring the output torque to an acceptable level. The globe motor is the choice of several teams, because of its output torque (although at 180 in-lbs it is higher than the trantorques are rated) and its ease of packaging. For our team this year, I advised the students to use the Keyang, because of horsepower, but they decided to use the globes for the advantages I discussed above. If you design the drive train correctly, either motor will work fine.

If you have any other technical questions, please feel free to contact me.

-Paul
Team 217, The Thunderchickens

3

Nice job Paul,
The information in the white pages applies to the FIRST motors. I think Joe J. had the motor information included in the Application manual that went out with the rules. I’ll contact Joe J. and ask him to respond as well.

4

Below is the typical information given in the Application Notes (that are part of the RULES by the way – please read them!):

Application Note: Globe Motor
Specs:

  1. Stall torque at 12 Volts: 180 in-lbs
  2. Stall current at 12 Volts: 20 Amps
  3. Free Speed at 12 Volts: 45 RPM
  4. Peak Power at 12 Volts: 23 Watts (mechanical power, not electrical power)

With the data given, you can generate the motor curves you are interested in. Use the spread sheet in the whitepapers section of this web site if you need help generating the plots (my motor calc spread sheet would like to have free current as well as stall current, but for our purposes you can get away with entering zero or 0.5 or some other estimate with little ill effect).

I hope this helps.

Joe J.

5

Thank you very much, but unfortunately it requires the Excel application to run it and I’m not a Microsoft Office tool user. Now I’ve got the READERS for Microsoft tools like Excel, DOC, and Powerpoint files, but the Excel reader won’t let you enter numbers nor run spreadsheet calculations.

Could someone here with Excel please run the formulae on the three motors and either post the output, or email the various output curve & tables to me? In addition to text I can READ virtually ANY image format, HTML, PDF, and Microsoft DOC files. (No PostScript, please.)

Thanks!

  • Keith McClary, Huron High Team 830