It has been a while since our last update, but we have been slowly making progress through the weather and issues for our robot concept this season. Some of our sponsors and mentors have of course been affected by the pandemic and this has slowed progress on a few fronts (including a funeral that delayed this update). Through our network many have stepped us the help and keep us on track.
So how are we doing at the end of week 3 going into week 4?
Overall design concept:
Yeti has been prototyping and updating our concept through testing using Stumpy. We have recorded a few videos of our progress on this prototype, and from this we believe we are on track to have a robot that can do a multi-ball auto and do at the bare minimum a high bar climb with a stretch goal of a traverse. We completed the gearbox and main climber mechanism with a custom gearbox. This is actually our first fully metal custom gearbox worth mention for the team and we learned a lot on this design!
We have driven our prototype robot Stumpy around with different roller materials and shapes to try to get a performance that we are happy with between the intake and tower that leads to our shooter.
We have also worked heavily on using this prototype to get a lot of our programming done prior to completion of the robot.
We feel we are falling behind on some goals but through strategic prioritization on base line competitiveness we feel we are in a good place to be successful this season.
Drive system:
As of 1/29 during our last in person meeting, we had a huge amount of progress. We have completed our drive system on the ground with temporary wheels while we wait for back ordered items and the weather to get our parts in.
We decided to go with a different method of construction this year because we lost our sheet metal sponsor through the pandemic but gained some other sponsors that can machine components for us. This means we decided to deviate from our 2018-2020 design for our bumper system.
We took heavy inspiration from the new tube plugs from WCP and Team 78 when they posted this idea on Chief: Team 78 Offseason WCD Mule Chassis CAD
Our take on the method is virtually the same because even our 2021 robot used the same snap latches to get the job done. We went ahead and ordered our reversible bumpers and are waiting for the bumper plates to get machined at a sponsor to have our drive base 100% done.
The ratio discussion on FIRST Updates Now got us rethinking our sprint distance and after we finally got additional game pieces we ran a quick mock match and saw that our sprint distance is going to be much much lower. We tweaked our ratios a bit but ordered two gear sets for us to play with. Rolling the dice on our best performance we have this ratio currently installed:
Overall, the frame and drive system was designed and cut out by rookies with the help of our Ultimate West Coast Guide and some mentors who could teach the students to use the Bridgeport Mill so we think this was a success!
Turret and Shooter Subsystem:
The shooter from our 2021 robot was modified in our last update. The only difference here is that we completed the design 1/28 out of metal and printed a solid hood that has an integrated limelight mount instead of the churros we had on the prototype.
We also decided to test out the WCP flywheels since they don’t expand too much at the ratio we are running, and this resulted in a similar performance to the Colsons with a quick way to also increase mass of the flywheel.
The turret gear was fully 3D printed like last year, but we made some modifications to it the raise the shooter up off the gear a bit more. This was to allow for more clearance between the turret gear mesh and the bottom swing of the shooter.
We decided that we wanted to go with an absolute encoder so we are going to use the integrated encoder from the versa planetary gearbox and bypass all of the complicated work we did in 2021 to zero the turret each time we started the robot.
I am mildly concerned with backlash and drift for this one but if we need to swap it we are prepared to use a Rev Through bore encoder with a 3D printed holster between the gearbox and turret plate as a backup plan.
The turret is driven by a BAG with Talon SRX instead of a Neo550 from 2021 since we cant use the mag encoder with the SparkMax. The turret plate was cut from .250 aluminum and we were using the same bearings as last year for our bearing stack. ( part numbers WCP-0041 and 217-3489 for the curious)
Tower:
We have been playing with the compression and location of the rollers to center the ball and power the ball consistently through the turret ring above it to get repeatable shots. As a test, we wrote some code using the Rev beam break sensors that runs our tower until a ball is present.
We can still run the intake separately and keep a ball lined up inside our robot to shoot. This should prove invaluable to us on the field as we run the robot blindly on the far side of the field. We will of course plan to use a camera for the driver to see where the balls are, but once inside the tower things will be hard to see from afar.
Here is a shot of what we expect to be a quick cycle if we get this right.
We decided to try belts on this design for the majority of the drive shafts so that we can transmit power at all times on the game piece and have no dead zones whatsoever. Through layout and experimentation, we know that these two lexan plates will probably change a few times until we are happy with the performance of the final tower.
I think they were tired and not happy about this last tower.
Climber
This subsystem is the most complicated by far and we are still developing it. We have iterated on the hook shapes about 10 times by now to try and satisfy the geometry that will let us high climb and traverse too.
We felt confident in the structure and ease of construction for the moving part of the climber since we had experience with the 2020/2021 version, so we decided to go ahead and make the gearbox out of pocketed aluminum sheet and use the first version to power us on and get us off the ground for further testing.
There are still some parts to machine and our final hook shapes are still in flux, but we have made great progress getting the first stage complete with gearbox and most of the second stage installed for testing.
If we wanted to just go for the high climb and ignore the traverse we think we have a geometry that will let us simply do that now. The traverse is the prize that will ultimately be the thing we either tweak a lot of things until we get it right, or we simply cut bait and stay with our stable high climb with less risk. Trust me, if we get that traverse climb we will be happy to post that victory without a blurry robot!
Intake
Ah yes, this thing. I don’t know why, but our team is never satisfied with our intakes.
Probably because they get stuck into the design last and we always but less experienced members on them? Either way, we have iterated on this intake so many times I have lost count already. If I had to guess I think our team has made about 15-20 shapes of this thing between cad and prototyping.
We are floating between two types of design that we like and running things over with Stumpy to see how they go. Every team should focus more on their intake this year because it will make or break those cycle times.
Some laughable times on this last one, this would have won champs in 2010 for juggling a ball:
For us, we want to be able to run our intake into a wall, and possibly even trap a ball against the wall and still be able to suck the ball in while other robots are hitting us. Currently we have plenty of room for our intake and we have reduced from three rollers down to two with a single strut running across.
This year looks like the year of the 4 bar linkage as most teams are trying to compact their intakes into tiny spaces, us included since we left about 4” of space for our own intake. We have a shape that works and if we went to competition with it, it would probably do ok. But we want speed! We have invested in the roller wheels that have the 1.125 inch hole in them so that we can put our intake wheels into a versa roller tube. That should allow us to plow into a wall and not bend those thunder hex rods into bananas.
Hopefully our next update wont take so long! We want to have the mechanical robot done this week for first testing and hand it over to the programmers while we optimize our shapes. The rest happens when we power on the robot and go drive into the field.
As always, if you have questions on our ratios or cad we can provide more information in the thread or on the Open Alliance Discord!
