I doubt that next year will be a shooter game, but I can guarantee that some years down the road, there will be another year where a shooter is the de facto method of scoring. I hope this thread will be useful to teams when that year does roll around!
So what less than (or more than) obvious facts have you learned about shooter design this year? What problems did you run into that you weren’t expecting, and how did you fix them?
I’ll start off: Make a single axle shooter if you want backspin. And if you make one with two axles, make an easy way to adjust the squish and make it easy to take apart. Because you’ll be doing a lot of that.
1712 had no issue getting backspin using a dual-axle shooter. We had each axle controlled independently so we adjust the backspin, but you could also find the ideal ratio and gear them to it. We never really adjust our backspin, so that capability is not the most useful in the world.
One thing to keep in mind when prototyping is the amount balls squish change the distance they go (at least for this year/this type of ball), so to build a prototype which can quickly go from one distance to another can help see what you want to do. For us we had a top shield and bottom shield, with a space between the bottom shield and the shooter wheel to make contact with the ball and different amounts of spacers between the top and bottom shield to adjust the amount of space between the bottom shield and the wheel.
Not sure if that makes sense but hopefully it does.
Consistent feed and positioning of the ball as it enters the shooter is absolutely critical. Our initial design allowed the ball to move left and right in the lift ~1/2" each way, after adding guides (and inducing a slight amount of lateral compression in the ball) we noticed a large increase in our accuracy.
For reference our shooter is a hooded shooter, 2 6"x1.5" colson wheels ~1.5" apart, and between 1"-1.5" in compression.
Many teams using 2008/2010 KOP wheels on their shooters found it necessary to remove the crowns left on the wheels from the molding process, essentially breaking in the wheel before use.
Though, I know of a team using 2006 KOP Skyway wheels that ran into Issues with them wearing over the course of the season and losing grip.
We’re using this year’s kit wheels, right out of the box, with no problems with wear after 2 events. I guess it all depends on your set up. Prototype, prototype, prototype!
Consistent feed and positioning of the ball as it enters the shooter is absolutely critical. Our initial design allowed the ball to move left and right in the lift ~1/2" each way, after adding guides (and inducing a slight amount of lateral compression in the ball) we noticed a large increase in our accuracy.
^Truest statement I’ve ever heard.
Some balls lose their squish…and other balls just don’t like to be squished all that much.
If the game requires precision distance shooting, do us all a favor and get the design done so you can tune said design. Just ramping up the power does NOT equate to making a shot.
Oh, and if you’re using heavy, custom fab wheels, make sure the motors you pick have enough power to make them go…
Don’t solid-mount your gyro to your turret or other vibrating chassis components. Use a soft material that will damp vibrations. Note: we only learned this yesterday, when we took the time to do proper analysis on our gyro’s heading over time. Makes it hard to auto-aim straight if your gyro starts drifting about 1deg/sec when the shooter turns on.
Since I’m looking to mentor new teams next season, these are the things I’ll be bringing if a shooter game comes back up:
Lighter wheels - With lighter wheels, the wheel will be back up to speed faster. This is especially necessary if you’re using a motor with less torque and power to run the shooter wheel.
More time on programming - Shooters are almost definitely the best way to score this year, but a lot of shooters aren’t used to their full potential because the programming wasn’t up to par. Spending more time on the target tracking algorithm can allow a shooter to be very succesful.
Watch the weight distribution - Our robot this year is a bit top heavy. That’s being worked on and resolved for champs, but it hurt us at FLR. When designing a shooter in the future, I’d like to make sure the shooter doesn’t have an uneven weight distribution. This prevents disadvantages in game situations such as the bridge, and prevents the robot from rocking and potentially tipping as it moves.
Responsive, consistent turret - Part of the key to succesful shooting is having a quick, responsive turret to shoot at the proper angle to meet your target. With a turret that has the proper hardware and coding, shooting can be made greatly effective.
Make sure the ball enters the shooter quickly and consistently. We have a nasty habit of coming up with some unnecessarily complex storage-to-shooter designs. With some thought, I think there could be a quicker, more consistent way of getting the balls into the shooter.
Don’t let the balls enter the shooter at an angle - Without making sure of this, balls may enter (and come out) at an angle, or not get into the shooter at all.
These things aren’t NEEDED for a good/great shooting robot, but they are things I’m going to greatly consider next time there is a shooting game.
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Interesting… If our shop wasn’t getting knocked down next week (and rebuilt hopefully by September) we were going to add a bunch of weight flywheel-style to our shooter to see if that increases accuracy!
Also, this is just an anecdotal observation, but single-axle hood shooters seem to be much more reliable than double-axle shooters.
Yeah. We used a pretty heavy custom wheel for our shooter (modeled off our 2006 shooter). I noticed we really need to be careful of the timing we shoot at, or else the balls don’t go nearly far enough. Again, we’re working on it for later in the season, but it kind of hurt us at FLR. Especially before we got our shooting to be somewhat accurate.
1.) The amount of contact arc between a single-wheeled shooter and the ball doesn’t appear to matter much with respect to shot consistency, though this also makes the assumption that entry speed/position/angle is identical from shot to shot.
2.) Re-calibration of shooter distances is a non-stop thing to do. Expect to test calibration every few matches.
3.) There were two teams in DC that used back-EMF in unpowered motors to detect how fast the shooter was spinning. This seems like a much more elegant solution than an encoder or tachometer/light sensor since the Voltage across the analog sensor port is directly proportional to the SPEED of the shaft the motor is on. Both teams used KOP-legal motors (one was a window motor without its gearbox, the other was a RS-395).
4.) Flywheel vs no Flywheel, that was the question. I’ll post back after I talk to a few teams at championships about their shooter controls.
5.) A single 8"x1.5" IFI wheel with roughtop tread was a very good choice for a shooter wheel this year, and it is a choice we will revisit in the future.
Our shooter was designed in such a way that rotation was handled by the drivetrain, and distance by shooter rpm.
If using a CANjaguar, extremely repeatable results can be obtained by measuring the voltage instead of the rpm.
Shooting at a very high angle can be a lifesaver, because you can avoid shooting for the backboard, which makes shoots somewhat unreliable. Not to mention shots that are all net look pretty cool when you make them every time!
Make sure that you tighten bolts/other fasteners on your shooter whenever possible, because the vibration + excessive movement = inaccurate shots.
Recalibration is a must. During our regional, the balls would keep getting squishier and squishier at a rate which we did not expect. So between matches (when our robot wasn’t being repaired ), we would head down to the practice field and change constants in our program.
Our team made 2 diffrent shooters this year one was a wide belt design using really heavy pulleys and the other was a single axle shooter. Interia will only help you so much, you need the power to bring your wheel up to speed faster. Compression of the ball or object your shooting was a great variable as well but once again there is a limit on that as well. We ended up going with a custom wheel that was 3 seperate pieces and effectly built our fly wheel into the middle of the wheel powered by 3 rs 550’s. I think we determined that for us, at least for this game, a single wheel rather then double wheel is much more effective.
), we would head down to the practice field and change constants in our program.