2 wheel Hooded Shooters

[pandamonium]

Can someone help me out and give me the rundown on this. I have seen many robots that have a hooded shooter with an adjustable hood. I have seen a few robots with what looks to be a new variation, an addition of a second flywheel on the top. This looks so cool and I would like to do some research and learn more about these. What advantages does this get and how did this come about? Any insight prototypes or tips from a team who made this? I dont even know what they are called?

[alex.richards48]

@pandamonium

Whats advantages does this get and how did this come about?

I can’t speak for them exactly since my team hasn’t made one, but having 2 wheels on a shooter lets you get a flatter/straighter show that won’t arc much. This is good for long distance shots which were common in 2020/2013. I assume putting a 2nd wheel on the hood came from wanting both the long distance flat shot while having close range shooting. Maybe someone from 1678 or 4414 can speak more on them, I know they used them to good success at LA North.

[troy_dietz]

@alex.richards48

lets you get a flatter/straighter shot that won’t arc much

I believe the scientific term is frickin laser beam shots.

[AdamHeard]

These were popular in 2006.

I reccomend checking out 217 and 1114.

[ThaddeusMaximus]

@alex.richards48

lets you get a flatter/straighter show that won’t arc much.

Assuming fixed wheel RPM (and surface speed being the limiting factor on ball speed), this is true insofar as the ball will be travelling at a much higher velocity (as the ‘upper’ part of the ball has a nonzero velocity). Lower time of flight = less time to drop = flatter shot.

However the decreased backspin means decreased magnus effect, which will tend to make a shot more flat (as the magnus effect generates lift counteracting gravity). Think of a glider versus a missile.

So if RPM is the limiting factor, you could achieve the best of both worlds (increased exit speed, and increased magnus effect) by… well… spinning faster.

All of this is in theory. Practice throws many, many wrenches in this (the most obvious being “grip is probably a limiting factor”).

A neat exercise would be to take a dual-wheel hooded shooter and lock the upper wheel in place, then adjust the lower wheel to have a higher RPM in order to achieve the same exit velocity (either theoretical or experimental… I’d be interested in both results!). This might help track down the exact source of the benefits because there are so many variables that can change between any two different shooter implementations.

Alternative theory would be you get flatter shots by virtue of higher exit velocity while the mechanism for producing the flatter shots isn’t dependent on aerodynamic effects which could vary significantly from ball to ball. If there’s inherent benefit from such a design, this is what I’d hunch it is.

[Ari_2412]

@alex.richards48

I can’t speak for them exactly since my team hasn’t made one, but having 2 wheels on a shooter lets you get a flatter/straighter show that won’t arc much. This is good for long distance shots which were common in 2020/2013

My first season was 2019 so I can’t speak exactly for what happened in 2013, but I play on an ultimate frisbee team. When we throw, we need to get a lot of spin on the disc to be able to control where the disc goes. Now I realize robots throw the frisbee differently from humans, but I don’t believe the whole principle of getting a disc to be thrown through the air is going to be different. If a robot had a duel flywheel shooter, the only way I could see a disc getting spin and for the disc to be able to accurately leave the shooter (without a separate component) is for the flywheels to be set to different speeds. I’m probably overthinking things

[The3]

The common idea is this:
2 wheeled shooter (with the same size wheel): Since you have no spin, you have a chance of hitting a knuckle ball. However, you get a lot of linear force, meaning that you throw far but very inaccurate.

1 wheeled shooter: all back spin, so you have a more consistent shot, but since you have less force being put on the ball, you have a good chance of having a weaker shot.

What some teams did in 2020 was use a 4in Fairlane wheel on the bottom and a 2in Fairlane wheel on the top powered off of the same belt (meaning 1:1). The top wheel has lower surface wheel (smaller wheel == lower surface speed, bigger wheel == higher surface speed), meaning that you get the best of both worlds, backspin and a good amount of force on the ball. However, you can still get high power/distance using a single wheeled shooter. Add more compression, and a bigger wheel, add an inertia disk, add an upduction, add more wheel wrap (see 2481) or just add more motors. You need to find a good balance for all of those, but you end up with a very strong shot using only one wheel. Both solutions work, its just various approaches to one problem. I have a very rudimentary knowledge and would love from someone from a team who used this style (and has a real understanding in physics!) to explain.