We are proud to present Nagini, our all-new robot for offseason events this year. Reveal video here!
Nagini is the first robot we’ve built out of our new campus/shop. This was a fun build over the last three weeks, one that gave our all new student leadership valuable time to engage with our newer members.
Specs
Overall dimensions:
22" cube
75lb with batteries and bumpers
Drivetrain
4WD WCD - Parallel omnis / 0+4
50:12 gear ratio through custom 3D printed gearboxes
3.25" Vex Pro Omni wheels, Theoretical 17 ft/sec
Intake/Gear Eject
558/4481/2200 style intake
Gear eject inspired by 558 and 180
7:1 775Pro driving 2" rollers
Printed on a Stratasys UPrintSE. Motor mount plate, standoffs, and frame mounting plate were printed in High Density infill. Gearbox housing was printed in low density. Material is ABS.
We’ll post some pictures of the gearboxes and internals after Chezy Champs to show how they fared.
As a warning, I have 3d printed CIM gearboxes using the Stratasys UPrint and know from experience that they can fail very easily if not designed properly.
Make sure you have bolts that extend all the way from the front mounting plate to the back plate of the gear box to reduce the pressure on the plastic, especially along layer lines.
It looks like your design might be okay, but I can’t quite tell from the photos. At least your gearboxes don’t need to stand up to the stronghold defenses.
This is a beautiful bot and I am envious of your teams huge success in such little time!! Also, kudos to your driver for being able to fly around on those omnis, that task is difficult to master.
Do you think you’ll run into problems for strategic possession of two gears? (I can’t recall the exact rule ATM and I’m too lazy to look it up) In your video you show a couple times driving up a peg with a gear sitting in front of it, placing a gear, sucking up the one in front, and then placing that one too. It seems like it would be pretty easy to intake too fast and have two gears in your bot.
Don’t get me wrong I think it’s super cool. I just wanted to ask about it.
Figured it’d be a fun maneuver to practice. One advantage to this style intake is we don’t have to waste time moving fallen gears out of the way before we can score. Obviously, we’re going to make it clear we are not controlling more than one simultaneously.
After playing defense for a good part of our season matches this year, we feel we gained a pretty good understanding of the mechanics of defensive robot interactions. We figured a fast 2+2 configuration or a 0+4 would allow us to slip through the typical defensive maneuvers - T-Bones, pins, etc. We ordered the wheels for both configurations with the plan to decide between the two based on driver feel. After testing both configurations, we felt that the all-omni option would complement the play style we wanted a little better. Obviously that means we can’t play traditional contact defense, but it’s definitely a fun thing to investigate.
The bottom wall of the gearbox that was shielding the 50t gear seemed to have clipped something and strafing across the field seemed to have chipped off the rest. This only occurred to the right side gearbox, left had no damage. This wall was already pretty thin to start - about 1/16".
This damage doesn’t seem to affect functionality at all. The gearboxes seem to be running smoother than ever.
The parallel omni drive probably helped quite a bit for longevity of the gearboxes.
Looks like we have one more event to go with this robot. Will report back with any issues.
Drum dia was 1.375". 2x 775pros. ~40:1(might have been up to 49:1) overall reduction. We basically took our ~2.1s season climber and upped the drum diameter a bit. YMMV. This combination of drum dia, motors, and gearing only worked because we knew the robot wasn’t going to weigh more than 80lb fully loaded. It’s quite a narrow safety factor, but we have 3 different stages of reduction that we could have tweaked to make it safer.
The climber speed was WAY overkill, but it was fun to watch and probably saved us in more than one match.
Can someone go into further detail as to what this was, why it was necessary, and how it was accomplished?[/quote]
Our gear eject fingers were 3D printed going into the event. Actually didn’t get our CNC router fully installed and in a metal cutting capacity until the Wednesday after the event :P.
They lasted all throughout quals, but after the constant hammering by 5026 in semis, they ended up breaking off at the base of the “finger”. Without this finger, we could not reliably score gears. If the same part broke on both sides(as it inevitably did!), we could not score gears at all.
Thanks to the combined pit crew of 5012, 1671, 4990, and 4904, we were able to come up with a quick fix that involved zip-ties, hand drilled and tin-snipped polycarb, and a length of bent 1/4-20 threaded rod. I tend to get in the way during intense pit repairs like this, but by the time I came back to check on the robot, the repairs were done, tested, and ready to go all within the timeout that we called in semis. We’re thankful to our partners for assisting us in this repair, and I’m personally impressed by my all-new pit crew for their quick thinking and fast execution. Probably one of the greatest moments of the event for me.
This is the best picture I have. Unfortunately, we didn’t take too many robot-specific pictures between end of quals and when we ended up CNCing a replacement. Area of interest is towards the end of the horizontal 2x1s. https://i.imgur.com/5nXmUlK.png #fueldoesn’tmatter
gear ratio through custom 3D printed gearboxes
