Some Projects that I would like an opinion on

Hey y’all over the summer I created a set of three spreadsheets just to see if I could. The first spreadsheet (Shooter Calculator) uses the motor curve data and such to fairly accurately calculate things like:

  • Spin up time
  • Highest possible feed speed
  • Shot accuracy as balls are being fired and rpm varies
  • etc.

The second spreadsheet is a drivetrain calculator that given a motor curve and such can calculate:

  • Ideal Gearbox Ratio for a given sprint distance
  • Top speed
  • Time to get to top speed
  • Time per one way sprint

The third and last spreadsheet attempts to solve a problem I noticed mentoring last year with making design calculators. The only easily accessible and public motor curve tables is the one for the Falcon 500. I created a calculator that given some basic and usually public information it can calculate:

  • The Brushed DC motor curve data
  • The Brushless DC motor curve data

The beauty of this third spreadsheet is the motor curve data can then be plugged into other spreadsheets that use motor curves (like my first two).

I have crosschecked all of these spreadsheets with the team I mentored this past year and they seem to check out but I would like some second opinions to find bugs.

Drivetrain Calculator.xlsx (4.2 MB) Motor Curve Calculator.xlsx (93.0 KB) Shooter Calculator.xlsx (621.8 KB)

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Do you have anything detailing the methods / numbers to ensure you’re getting accurate or reasonable results? Would like to compare notes, you’re doing a bit of what I’ve done.

This is wrong:

(It looks like the wrongness is the only difference between brushed and brushless, or am I missing something? I don’t think there should be any difference between those curves…)

So after looking at some other motor curves for a brushed dc motor I noticed that the current has an opposite trend to what a brushless motor would have as shown in the falcon 500 motor.

Would love to find more information on it though!

The accuracy for the brushless motor curve sheet is based on comparing it directly to the falcon 500 motor data. For the brushed motor, I am going off a relationship i noticed between a graph in my textbook of a brushed dc motor and the falcon 500 motor data. I am attaching a picture of said brushed motor graph that is pretty close to the one in my textbook. image

The curves should have the same shape…

via VEXpro Motors - VEX Robotics


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Ok then I wonder if I am just interpreting the textbook graph wrong. Thanks for the help! I will update the change later tonight. Did you happen to find anything with the other two as well?

Look at the axis - the Vex curves measure with speed as the independent variable, the textbook uses torque. The graphs model the same information, just displayed differently.

Not sure if you don’t know about this or if it’s insufficient for some reason, but have you tried https://motors.vex.com? It has detailed data for all FRC legal motors (barring some of the more obscure automotive motors that almost no one uses). For example, NEO Motor - Other Motors - VEX Robotics

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Ahh i see now. So the vex site (unless i am blind and I probably am) doesnt have the torque and such at a rpm intervals. That was what I am after since using that you can get much more accurate calculations.

“Click to Expand Motor Curve Data” - big red button near the bottom.
You can also download the data as a csv, linked right below the image of the curve.

Oh I am blind then. Thank you!