This is 95E’s early season reveal for Change Up! I’ve put more details in the drop downs below!
Motor Specs
4x 200 rpm Drive Motors
2x 200 rpm Intake Motors
1x 600 rpm Indexer Motor
1x 600 rpm Top Roller Motor (Chained 2:1 1200RPM)
As we believe cycling out goals to be more important, and to occur more often, than fielding this season, we opted with 200rpm front intakes in order to have more torque to easily descore from goals.
We opted for a 1200RPM top roller in order to consistantly lob the balls into goals, without putting too much stress on the motor. In our testing, a 3:1 1800RPM ratio was overkill - too fast and the motor burned out much faster than a 1200RPM ratio. The standard 600RPM was not fast enough to consistently lob the balls, as they would clip on the side of the goal on occasion.
The 600RPM indexer was the safe bet, as it does not burn out quickly and moves the balls at a reasonable pace. The indexer could be faster, however, and we plan on speeding it up in the future.
Capacity vs Speed
When we started building this robot, we centered the design around having a large capacity, while not sacrificing too much speed. The robot, as shown, has a 5 ball capacity, and a cycle time of about 1.8 seconds. Going into the future, we plan on shifting that in the other direction, as we believe that speed will continue to gain prominence as the season goes on, not to say that it’s not important right now. To put it frankly, a 5 ball capacity isn’t super necessary, and a smaller capacity will increase cycle speed drastically. We are definitely proud of the robot we revealed, but we plan on having a much smaller capacity in the coming months.
Thanks to SCA for helping me tackle some issues I’ve had along the way, and for being a general sounding board! Hope you enjoy the reveal, if you have any questions, feel free to ask!
Yes - we use encoders on the two tracking wheels on the bot, which we use for PID. We plan on adding a third tracking wheel, as well as implementing odometry, in a later rebuild.
its a gear ratio; a change in MA. causes the intakes to have more speed at a proportional sacrifice in torque
(also i’m p sure that’s a 60t and 36t but i could be wrong. concept still applies either way)
@markmark If you would like a better explanation on the concept of gear ratios and Mechanical Advantage (of MA as this weirdo @Ethan5956F calls it) check out this epic reply to a different topic by me! (totally not for clout, I promise)
It looks to me like the intake has no gears, but there are 24T sprockets in front and 18T sprockets on the back. And chain connects on all 18Ts between front and back.
If you watch the first second at x0.25 speed, you will see how the ball starts faster, but then slows down where it needs to be pushed between the rings on the goal with more force. So it makes sense to have smaller diameter intakes there, but torque is the same because both have 18T, I guess.
Also, worth watching at 1:04 where it intakes from the center goal.
Those are sprockets. Specifically, sprockets with chain linked around them, which are then wrapped with rubber bands to make compression intakes.
These two quotes summarize how the intakes work pretty well. There aren’t any gear/sprocket ratios on the intakes, meaning everything is 1:1. Below all of the sprockets with rubber bands, you’ll see 18T sprockets that are chained together, which is how the back compression sprockets are powered. The larger compression sprocket in the front, however, has a higher speed than the back compression sprocket due to the larger radius.
oh interesting. mb then @weilin
most people have done their compliance wheels with gears rather than sprockets cuz you don’t need the extra chain for it so i assumed that what y’all did. on my phone too so it being blurry also didn’t help
