Theoretically, if we modify the top plate to mount a second drive motor whose pinion engages with the large drive gear, and choose a higher drive gear ratio, then we can accelerate faster and have faster top speed increasing number of cycles in any match. Are there limits to top speed allowed? Any input? anything I haven’t thought of… please critique…
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Throwing more motors at a problem has diminishing returns. You need to take into account any traction limits, and more importantly driver skill. A fast accelerating and fast moving robot is trickier to control on human scale time, so requires more practice in order to drive well.
This is also assuming that everything in your drivetrain/module can handle the additional torque.
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I think FRC has pushed our 18 AH lead-acid batteries as far as they can go. Many of these batteries that on paper will deliver 100-200 charge cycles are toast at less than 50.
You would, frankly, be better off utilizing the increase in performance that CTRE FOC provides rather than adding more motors.
You only have so much electrical current you can pull at a time. 4 falcons/Neos gets reasonably close to that limit.
Seems there are a few teams that are doing this successful this year, but they know what they are doing.
Id imagine you would get a bigger bang for your buck by making your robot lighter and making it have a really low CoM before you would get benefits from an 8 motors drive.
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I’m not certain of Hightide’s reasoning for doing that but one reason could be that they want to keep their motors cooler throughout the match.
The constant current graph shows that if you are trying to get the maximum output of the motor for the whole match it will overheat before the match ends. However, I don’t believe that you would really hit those limits under typical circumstances, but more motors could help for pushing matches.
They talk about it in their reveal thread
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My son used to race race go-karts competitively, there is an old adage in motor racing, “slow is fast”. Making the drive system faster may make it harder to drive. We have the older SDS Mk3 system. Our programmer worked with the driver to make the chassis easier to drive. We then tested it on our obstacle course and the drive was faster.
Again in motor racing, making the chassis “drivable” can make up for lack of HP.
Something to think about.
Mark
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Good point - Does anyone know battery limit in AMP Draw?
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Im not sure… Center of Gravity? 30 pound belly pan made from steel ensures very low center of mass. yes we do need to worry about “wheelies” if top heavy… and acceleration limits would be part of PID
Edit: refer to Upgrade Swerve MK4i Increase acceleration and speed w 2X drive motors - #17 by electroken
If you are acceleration limiting a 1 traction motor swerve, there’s no need for a 2 traction motor Swerve
During our first regional (Central Illinois Regional) we ran with 2 falcons with custom top plates on each module. We struggled to have enough battery to finish the match and brownouts were always happening. For Seven Rivers and Worlds we were running a single falcon per module with much better results. I don’t recall the gearing we were using but I can find out if someone wants to know.
See all important motor characteristics on this post… and a working 4414 robot using dual drive motors… SICK !!!
yep - thanks… mee too
From the MK Battery ES17-12 data sheet:
What if only 2 of the modules have 2 drive motors, would the other 2 modules with only one drive motor drag the other down?
yes; it won’t be too noticeable but it will happen
But you will still have more speed (with the proper config) than using only one drive motor per module, right?