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This is a spreadsheet calculator that can be used to determine the optimal gear ratio for a mechanism with a given motor and load.
Using formulas from JVN's Mechanical Design Calculator, I have created a spreadsheet that automatically calculates the optimal gear ratio for a given motor and load. My team is using this spreadsheet this year to help calculate gear ratios and determine motor requirements for our manipulators. I thought I would share it with the FIRST community to help other teams with the process. If anyone finds any bugs or has any suggested improvements, please let me know and I will try to make those fixes.
The calculator is intended to work for any kind of manipulator, but not for drive trains[1]. It also has a feature for calculating the gear ratio needed given a maximum current input, since sometimes the optimal gear ratio will require a current above what is desired. Note that in this calculator, the calculations are done with wheel radius instead of diameter to support arms and wheels in the same calculations.
[1]It will work for drive trains, but you will need to do some more calculations by hand to figure out what the force of friction on the wheels will be.
Optimal Gear Ratio Calculator.xlsx
Optimal Gear Ratio Calculator.xlsx
17-01-2017 19:59
Ari423With an hour and a shower spent thinking of motor curves, I am prepared to release v1.5. The new spreadsheet is effectively the same, except these calculations are exact instead of guess and check. This makes the spreadsheet more efficient and slightly more accurate, but there is effectively no change in the output.
17-01-2017 21:37
jojoguy10This is amazing and very simple to use! Thanks!
18-01-2017 09:41
MonochronDo you have a good way to estimate load for a system? For instance, if you were building a flywheel for the Fuel, what is appropriate load? And would that load chance as you increase throughput?
And just to clarify, using the flywheel example, if you reduce voltage to a motor at this gear ratio to allow headroom to keep your flywheel speed steady, would this change the required gear ratio? Or are you still able to hit peak power with this given ratio at each voltage? My question is really, is the ratio needed for peak power at 12V the same ratio needed for peak power at 6V?
18-01-2017 10:41
Ari423|
Do you have a good way to estimate load for a system? For instance, if you were building a flywheel for the Fuel, what is appropriate load? And would that load chance as you increase throughput?
And just to clarify, using the flywheel example, if you reduce voltage to a motor at this gear ratio to allow headroom to keep your flywheel speed steady, would this change the required gear ratio? Or are you still able to hit peak power with this given ratio at each voltage? My question is really, is the ratio needed for peak power at 12V the same ratio needed for peak power at 6V? |
18-01-2017 11:46
Ether|
are you still able to hit peak power with this given ratio at each voltage? My question is really, is the ratio needed for peak power at 12V the same ratio needed for peak power at 6V?
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20-01-2017 11:07
Ari423I just uploaded version 1.6.
Change log:
20-01-2017 11:38
JesseKThis is a nifty calculator! Personally I appreciate quick updates based upon feedback. Release away!
I was apprehensive at first, since some of the other papers that come out which try to improve upon JVN's Calcuator often come at a price of complexity and/or mathematical results that don't match what JVN's models or what I've modeled/measured. Yet I put our 2017 climber setup into this spreadsheet and validated the 'optimum' and 'current-limited' gearing values match JVN's and also my own models.
So now that it's validated, it definitely saves a little bit of time when trying to figure out what gearing to aim for. Thanks for putting in the voltage changes - that helps when determining end-of-match characteristics.
20-01-2017 18:49
Ari423Wow two updates in one day! It was brought to my attention that one of my formulas was slightly off (only noticeable for very small radii). The problem has been fixed and version 1.7 is now available. Please let me know if you find any more bugs or have any more suggestions.