During the course of the 2017 FRC season the Robowranglers went through a significant amount of development on our intake subsystem.
Very early on the team decided it would be advantageous to be able to pickup a gear off the ground. We believed that teams would drop gears during normal match play and that being able to pick these up would save us significant time when running "gear cycles".
In addition, our team originally wanted to pickup balls off the floor. We decided there would be some benefit to an intake which could pickup both balls and gears, without violating any of the possession rules. The functional requirement we set for ourselves was to "drive full speed through a pile of balls + gears, and come out the other side with all the balls and one of the gears."
Below you can see the progression of our development!
This is the Mark 1 intake. It uses the lexan + sheetmetal construction style we experimented with at the end of the 2016 season with our Championship revision intake. The Mark 1 was fully built during week 1 of the build season. It did not have a functioning shoulder joint (the gears are shown in the CAD for reference only). It utilizes the WCP Spiral Flex-wheels (http://www.wcproducts.net/versarollers) as rollers mounted on 1/2" Thunderhex.
We mounted the Mark 1 intake onto a furniture dolly and did initial testing this way.
The geometry was very frustrating - to get the intake to package in such a way that the balls go up, the gears go down, and everything fits into a reasonably sized package which still pivots into scoring position. One of the variables we experimented with was how far into the intake the gear could be pulled while still going into scoring position when tilted up - we also had to make sure that this gear position did not interfere with the ball intake.
The Mark 2 intake was a revision designed for "final" production. This version included the shoulder-joint design in which the large gear is mounted to the robot chassis and the actuator motor is mounted to the intake. As the motor turns it "rolls" around the stationary gear and moves the intake.
The Mk2 motors shifted. Now the ball roller and gear roller motors would mount in the same set of holes which were spaced such that a timing belt could run to either roller from that location. This made the side plates smaller, and identical.
The Mk2 had all the detail work done for the "side" ball intakes. The Mk1 only had ball pickup in between the primary lexan plates, but the Mk2 had the two outer sections to maximize pickup width.
The Mk2 also incorporated a major new feature - a CAM mechanism built into the back of the gear intake which allows the gear to fully enter the intake while the intake is down, but as the intake tilts up would push the gear outward 2-inches so it is in a better scoring position.
This cam driven gear-pushing mechanism is one of my favorite features to ever appear on a Robowrangler robot. It was so totally CUTE. It was totally invisible, and most people never even noticed it... but I giggled every time it worked.
The Mark 3 intake built as an extension of the Mark 2 by replacing some key components (the primary lexan side-plates) and adding new parts.
The Mk3 intake was created to integrate with the newly designed articulating hopper. The hopper would be spring loaded outwards and the intake would push it in as it actuated up. The sliding hopper had a bearing which would ride along a cam-track on the top of the intake. This cam track was designed such that the intake and hopper would actuate through the same space without hitting each other.
The Mark 4 intake was another "extension" of the Mark 3. This was the intake used in the 148 2017 "Rogue" Unveiling Video, and would be the intake used at the Dallas FRC regional. This revision incorporated lessons learned from testing the Mk3 on the competition, and practice robots. (148 built three almost identical robots in 2017).
The major changes to this revision were in the cam-track which actuated the hopper. We tweaked how that mechanism worked. Instead of the hopper being always spring-loaded out, we attached springs onto the intake itself. As the intake actuated down it would pull the hopper out. As it lifted up, the springs would de-tension (leaving the hopper to freely move) until the follower-bearings hit the cam track and it began to lift. At the top of the motion, the springs would pull over-center and would actually HOLD the hopper in its upper position. Building these "not physically constrained, only held by spring tension" sections into the top and bottom of the motion made the entire mechanism more reliable.
If you re-watch the unveil video... can you spot the Mk 1, 2, and 4 intakes? (Even I couldn't spot any Mk3s in there).
After adjusting our strategy for the Dallas regional, and rethinking how we wanted out season to go - we decided to eliminate the ball pickup and "double down" on making one of the best gear intakes in the world.
The Mark 5 was an experimental design which utilized 1 MiniCIM to power top and bottom gear rollers, and a front leading-edge ball "sweeper" roller. It would never be constructed beyond a few quick prototypes.
The Mark 6 was the first in the final "series" of intakes. This design utilized similar scoring geometry to the Mk1 - Mk4 intakes, but since the intake no longer needed to pickup balls, we did not need to worry about pulling it in so far. This means "no more super-cute-cam-driven-gear-pusher-linkage-mechanism". JVN sad.
This intake also used a very different gear ratio for the pivot joint. Now that it isn't lifting as much we greatly reduced the gear ratio.
Since this design only uses 2 motors (1 for the roller, 1 for the shoulder) we were able to use the "mount them on the same hole pattern" trick to reduce the size of the plates even further.
Many teams struggled to pickup gears from the midst of balls. Our Mk1 - Mk4 intakes never had this issue, since... the ball intake just pulled up any balls in the way. (We were spoiled!) The team was concerned that by eliminating our ball pickup we would suck at pickup up gears.
We added a ball "sweeper" roller to the Mk6 intake. This roller is mounted high enough that it never contacts the gear, and spins in reverse at high speed to push away any balls from the front of the robot. It worked GREAT!
Mark 7... so apparently there is a rule which says "don't shoot or hit balls" when you're on the opponents side of the field. We decided to remove our super awesome reverse sweeper roller even though it was super awesome, because MAYBE it was illegal. (Other teams had these rollers, but whatever.)
The Mk7 also added more lexan cross-plates to help with the backstop for the gear and to help funnel the gear into position. The Mk6 was TOO good at pulling the gear in, so the Mk7 had to better brace against it.
Instead of the reverse roller the Mk7 had a free-spinning roller at the leading-edge. (VEXpro spacers running on a 1/2" OD tube axle).
Mark 8 - small changes to the geometry of the backstop, upper roof/funnel and lower blade. This one worked GREAT. Until the drivers ran it full-speed into the wall while holding a gear.
JVN says: "Don't run it full speed into the wall while holding a gear!"
Drivers say: "Ok, we won't do that."
Tonthat says: "You could totally make it durable enough to handle that if you tried. If you don't, I'll do it." (This response may only ave occurred in JVN's head).
JVN says: "Sigh." and goes back to work.
ALL lexan construction. Very durable. Takes a licking and keeps on ticking.
Integrated top / bottom hard-stops. Reinforced "skids" and leading edges. New "double" lower blade.
Yes... it can ram into a wall full-speed and suffer no damage.
This intake would be used at the Houston regional, Las Vegas Regional, StL Championship... and one of the spare Mk9 intakes would end up on the X016 prototype robot (which would become Bolt!)
It's kind of weird for me to look back at this development. I think of developing the 9 intakes over he course of the season... but really we did 4 of them before bag day, and another 5 in the time between the Dallas and Houston regionals.
We still joke about the mythical "Mark 10 intake". Maybe the CAD exists... maybe if the Mk9 ever fails someone will show up with a Mk10 intake fully built! No one knows for sure...
You can find the CAD for our "Championship config" 2017 robot Rogue, and the "Bolt" X016 prototype here: http://www.robowranglers148.com/resources.html
Both CAD models include the Mk9 intake.