Haven’t seen a lot of 2 wheel shooters on here so have ours. Traditionally our team has been hush hush but the open alliance inspired us to change our thinking.
It has a consistency of 8/10 (1 miss being hitting the inter goal edge and bouncing out) in the outer goal from 48’ 10”
Some tech specs
Angle of the shooter ~19 deg
6” vex traction wheels (3 treads thick)
With a distance between them being 3.5” so 3.5” of compression
1 neo per wheel at 1:1
Top wheel is spinning at 1740 rpm or 33% max motor speed
Bottom wheel is spinning at 3285 or 62% max motor speed
It takes 1/5th a sec for the wheels to get back to speed after shooting a ball I.e. ~1 sec to shoot all the balls
We are adding a guide and tuning the pid better to hopefully bring it to 9/10 or 10/10 tomorrow.
Lmk if you have any questions about it.
Intake:
Current design is a four bar system to extend our roller bar outside our frame.
The roller bar consists of 8 4” mecanum wheels (4 on each side) and 2 4” green compliant wheels in the center. I don’t have any good pictures of this mech right now.
Team that inspired this: 971 in 2016 and 2019 ps we love you guys
Why not use smaller wheels and increase the power on the NEOs? I did some basic math and the surface speed with direct drive at max power and smaller wheels would be faster. Plus, it would be easier to package.
True, but the lead acid batteries we use charge higher than 12v. Motor RPM is directly related to battery voltage. So if you design to run the motor at 12v then even if your battery drops from its fully charged state (13.2v I think), it would still have plenty of power.
4’ wheels were tested but we would have to add flywheels in addition we never like to have a mech that only works at full power especially one that will be run as often as a shooter. This way we keep our draw on the battery lower.
This may seem a little counter-intuitive, but from what I understand you generally want to design so the desired flywheel speed is achieved at about 6V-8V, which gives more overhead for a PID controller to restore the flywheel velocity post-shot. If your pre-shot flywheel speed is already at 12V and you lose some speed from a shot, you can’t increase your voltage any higher than that 12V and are trapped on the tail end of the motor’s power output curve. If, however, the shot drops you down to your motor’s 6V free speed, you can crank up the input to 12V and suddenly your motor is at peak power, which adds energy back to the system much faster.
Fantasic and simple KISS shooter for this game, great breakdown and specs, really nice prototyping, great shot. Just 1 question, what model are those gearboxes please? Thanks in advance. Keep up the good work, we will be watching the build thread.
What levels of compression did you guys test and have you guys tested multiple wheels stacked next to each other as a shooter roller instead of shooter wheels?
We’ve tested at .5” increments this was chosen because it had one of the best distance and accuracy combo.
Edit: and also we have tried 2 separate wheels on top and bottom but that had problems when the ball would contact one set first then the ball would have nasty spin and miss.
