I believe the claw lifts the front, and the rear is lifted by two pneumatic cylinders.
The most the angle can be off by is about 20°.
When the operator is holding their hatch intake button and the driver is holding the vision targeting button the swerve drive will actually PID the field oriented angle of the robot to 0° to ensure proper alignment to the loading station. This happens simultaneously as the robot centers itself left to right using vision and the driver controls the movement of the robot towards the loading station.
I don’t think it is shown in the CAD, but we put limit switches on the hatch mechanism so it would automatically grab the hatch.
Super cool, thanks for sharing. Lots of great design here.
How are the bevel gears attached to the drive wheels made?
I think they use a Tormach P440 Mill
This is honestly one of the most efficient robot designs I have seen this year.
Just a few questions:
- I see that you guys have a ground hatch pickup, however, I don’t recall seeing it much in action (if ever). Was this ever used, and if not, why?
- Did you guys switch to the wheel hatch intake at Houston?
- How are the bumpers mounted?
Once again, thanks for posting this!
Alright, 2910 fanboy here I think I can answer 2 of them.
not sure but not many teams used the intake. 1323 has some close calls and they were able to save it with the hatch pick up. It’s more of a just in case for most teams. I don’t know why 2910 didn’t pick it up
the had a wheel intake but switched to a finger intake like that of 148 at Houston.
We would tend to use the ground hatch pick up only a handful of times per event. It was kind of particular about initially intaking the hatch. We usually felt it was faster to go back to the loading station except when they were already both occupied.
We changed away from the wheeled intake shown in the reveal video before our first event. In all of the events we competed, we used a variation of our 2nd generation hatch mechanism. Shout out to 5803 for the inspiration on our 2nd gen hatch mechanism.
Great question. Our bumpers have a 1 X 1 versa chassis frame bolted to the wood near the top. We mount the bumpers to the robot chassis with 1/4-20 screws. The screws are partially threaded. Inside of the 1 X 1 bumper frame a lock nut is threaded all the way up to the unthreaded portion of the bolt. A spacer is below the lock nut. When the bolt is tightened from the top, the nut clamps the spacer and lower wall of the 1 X 1 to the threaded standoff that is mounted on the robot chassis. The nut can’t go any higher on the bolt because it is up against the unthreaded portion. The bumper bolts also never get lost because with the lock nut on them, they are captured in the bumper frame. At competition we have a couple drills with 3/16" ball hex bits for fast bumper changes. The drills’ torque clutch tightens the bolts to a reasonable torque. We have never had an issue with bumpers falling off using this method and bumper swaps are still pretty quick.
do you have a good video of their ground hatch pickup in action
They have a clip of it in their reveal video start at 0:56.
This is a great match to watch to see the hatch floor pick up in action. Definitely not our best match. Very solid defense being played by 2928.
Hey, sorry if its a dumb question, but what do you guys use to pivot your cargo mechanism? Are those just very large bolts?
The arm pivots on two FR8ZZ bearings. One long, 1/2" diameter shoulder bolt goes through the center of the bearings and connects the arm to the side plates.
Were there any major (or minor, I’d love to hear about those too) design decisions the team wishes would’ve been made differently? If given the chance to run the season over knowing what you do now, would you have built the same robot?
Why the bearings on the shoulder bolt? Wouldn’t it be fine without anything as a dead axle?
Isn’t it already considered a dead axle? (The axle(bolt) is not transmitting any torque.) Perhaps you were questioning the use of bearings instead of something like a bushing?
Missed a couple of essential words there…
Not OP, but raw aluminum isn’t great as a wear surface, and 1/2" rod is a pretty small load-bearing area for thin wall tubing. It’ll gall up and/or oval out over time and impact, which risks controllability problems late in the season.
Putting a bearing on it is good design practice, because it creates a good rolling interface to reduce friction, spreads out pressure to a wider bearing area, and manages your impact loads onto hard surfaces.
And if it wears out you just replace the bearing.
You could probably get away without it on a joint that operated 2-3x per match at low load - a “Harbor Freight” joint - but I’d rather just teach my students good design practice and have them make it nice the first time.
(Even if you don’t have OD for a “standard” 1-1/8" bearing, say you want 1x1 tubing, a brass bushing pressed into the tube will still decrease your friction and distribute shock loads)
So in the reveal video it looks like the cargo intake arms are lexan. I’m guessing this was the practice bot because it looks like your game bot had aluminum arms. Was there a problem with the lexan or was it just easier to mfg?
I think that was our comp bot in the video, we later switched both bots to aluminum arm plates. Yeah, so because polycarb is obviously pretty flexible, when climbing the driven side of the arm, the right, would push down much harder than the left side of the arm. This would make our robot slightly lean to the right when climbing, and the pneumatics would occasionally bind. We had lots of extra weight so it was an easy decision to switch to aluminum plates, and I think it’s more than possible that there were situations later in the year where our arm would have broken if it had still been polycarb. (As operator I totally didn’t slightly break another team’s practice bot by bringing the arm down at the wrong time… sorry 3663)