This is our early season bit that went to the first US competition of the year. We are proud to reveal JarJar. The robot was very capable early season but after decided to rebuild for much desired improvements we wanted to share this bot with the community.
Motor specs
-4m 200rpm base
-2m 200rpm intakes
-1m 333rpm uptakes
-1m 600 rpm flywheel
This bot was inspired by several earlier reveals such as Ynots and 99999Vs, we did our best to take our own spin on it and are excited for the next even better bot.
The bot looks really awesome, I love how compact it is and how nicely it folds up to fit within 18". The lowered chassis so that the bot is even more smol is pretty unique.
We had one at 280 but we had to switch quickly switch before competition due to burning out in the gear box, planning on something between those two on the next one
You can consider using a 257 rpm drive (3:7 600) as it has multiple advantages
Good speed, it is slightly faster than 200 but not too fast that its uncontrollable
Lower slop, the slop from the motor will be lowered by 7 / 3 since the drive is geared up
Small size, the length it takes to fit the gears is smaller than a 7 : 5 since the gears used are smaller
Also, I want to ask about what make you choose to go with a 333 / 600 rpm rollers rather than 600 / 600 - 1200 rpm rollers which most teams seem to use.
It’s not inherently bad but as Ethan says the numbers are kinda meaningless without output diameters. 257 rpm drive on 2.75" wheels is ridonkulously slow while on 4" wheels is relatively quick. Same with discussing uptake rollers, giving random rpm numbers is not good for comparing speeds when you may have different sized rollers. Someone could run 600 on 18t sprockets, but maybe have some trouble running the same speed on 30t because it’s so much faster. It’s just meaningless numbers by the way in which it has been discussed thus far in this thread.
Also I am pretty sure this is not correct. Yes, the drive is geared up, and theoretically lowers slop, however, the 600 rpm motors have less ticks per revolution than 200rpm , which also has less than 100rpm, so the slop still higher than with 200 rpm motors that are direct driven.
In addition to 600 rpm cartridges having more “slop” than other lower rpm cartridges, so whatever apparent advantage you may get in the external gearing in terms of slop, you have already lost it in the higher rpm cartridge.
the 600 rpm carts are actually just a single stage reduction. they have less slop than the other cartridges because the others are multi stage (with that said, the ratio impacts how slop is transmitted across gears, and i dont remember which way a smaller reduction or larger reduction multiplies)
edit: MA greater than 1 decreases previous slop, so the logic follows that a 36:1 ratio (red cartridge) has less slop than a 6:1 ratio (blue cartridge) because the 36:1 has higher mechanical advantage. this is however, not taking into account the fact that the 6:1 is single reduction while the 36:1 has 2 stages (2 or 3, don’t remember). it could honestly go either way; just depends on whether or not the additional stage adds more slop than the ratio diminishes.
Shouldn’t it just be based off the number of ticks? This is from VEX:
1800 ticks/rev with 36:1 gears
900 ticks/rev with 18:1 gears
300 ticks/rev with 6:1 gears
Based off this, wouldn’t it really just be the faster the diameter output, the more the slop/lower the resolution? I believe it would just be a constant linear relationship
Yeah that makes sense for the most part. But why does the number of stages for reductions have any impact on the slop, independently of the ticks? I don’t understand why the number of ticks/rev isn’t the only major factor influencing slop, but that may be because I don’t know a ton about this topic
