Best Practices for 2020 Shooters

From having heard about all the different ways teams improved their shooting with damaged balls and their inner goal accuracy (from the giant shooter wheel of 2481 to the additional flywheel on the ends of 4414 & others hoods) - what did your team find to be helpful in:

  1. Mitigating the effects of damaged balls?
  2. Increasing accuracy in the inner port?

These could be complex, like the methods mentioned above, or simpler, like choosing to shoot from closer up because you found you made a greater % of your shots in the inner goal that way.

Data, pictures of shooters, and video of it functioning would be excellent!


More shooter wrap tends to mean more consistency

Top wheel that is usually half the size (or less) of the bottom main wheel = still get some backspin but more linear force

Bigger wheels have sometimes shown to be more consistent, but I’m not all to sure about that one.

This is common knowledge, but bigger wheel means higher feet per second when in comparison to smaller wheels at the same rom

Taller bots have a better release point for the WoF shot.

Adding foam to your hood may help.

Using 2 motors with some sort of conservative upduction is common and should help.

Increasing compression along the path of the ball is good.

^^Those were just my general thoughts and tips I have learned from robots this year and when designing our shooters.


Do you mean this as just a general “compress the ball more” or a design similar to 3940’s, where the compression starts at some value and ends at some higher value?

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In terms of compression, I’ve seen successful shooters with 1-2.5 inches of compression. 1.5inches is my favorite. when i say increasing compression over time is just increasing the compression of the ball over the path, like from storage all the way to the end of the shot.

Something for us that decreased accuracy of any sort was larger shooter wheel - 6" was less accurate in early testing than 4" (at the same RPM) at the cost of less height and range.

Something I forgot here is that you want as rigid of a shooter as you can get. You don’t want things bending around, vibrating excessively, etc.


I really want to get back in the shop and get real data.
Interim, models are cool and my model says:

If you want to decrease exit velocity sensitivity to ball stiffness or grip, the objective is to make the ball stop slipping; the ball needs to reach a steady-state velocity before it exits. You can accomplish this with

  • more grip (both of the wheel, and the hood, though the hood is usually sufficient)
  • more travel distance
  • more compression (but it doesn’t do as much as I expected)
  • increase wheel diameter (even if you maintain the same surface speed… the increased diameter means less centripetal force that lifts the ball off of the flywheel. Wacky, right?)
  • reduce wheel RPM (this may decrease your shot power if you’re in the “slip zone”, but it should increase accuracy)

If you want to decrease exit velocity sensitivity to mass

  • increase wheel momentum
  • decrease wheel RPM (again, may negatively impact shot power)

From a rough analysis we understood most of this (even if we couldn’t put numbers to it) so we built accordingly with some pretty substantial travel distance and wheel diameter. Things were looking grim by the end of GSD though so we started looking for better wheels to increase grip, and we think we found the right set… ah, what could have been (what will be?).

Other miscellanea beyond “make shooter go thunk thunk”

  • Mount it rigid otherwise its worthless
  • Have a non-rocking drivebase otherwise its worthless (this is what motivated us to run a 2+2… you could definitely do a 6wd drop center with the weight biased properly)
  • Level your turret, if you have one. We noticed that we would shoot completely different forwards than backwards until we shimmed the ring. Granted, we’re not CNC-ing everything, but even then, tolerance stacks can be enough to warrant adjustment.
  • (more of a hunch than anything) Also for turrets, feed the balls dead center, with no asymmetry, with as minimal compression as possible, and straight up (no rolling). (Minimize the input variation as a function of turret angle).

Dual wheel shooters are weirder to understand.

Hopefully when we get back to the shop we can correlate test data to a model :slight_smile:


Increasing the contact distance between the shooter wheel and balls.
If you want to keep your shooter smaller, you can try to add a pre-accelerator wheel. (For accelerating the ball nicely)

Don’t use the compliant wheels because the ball is already plenty compliant on its own. You can lose a lot of energy because of compliant wheels friction.

Getting flywheel speed control down for potential speed losses while shooting multiple balls.

Interesting. We actually had our shooter geared up by about 1::2. We had 3 Neos with an adjustable hood. We found our accuracy to be better with higher RPM. We actually shot at about 10,000RPM. At that speed we found the flatter arc of the shot made things much more repeatable even with balls of varying quality.

This also gets at something true: your arc also matters. All of my previous points have to do with creating a consistent ball state after the shooter- how your trajectory is shaped impacts how the error in ball state gets magnified.

  • The straighter the arc the less sensitive you’ll be to variations in exit velocity.
  • The more perpendicular your trajectory intersects the goal (e.g. your trajectory ‘apexes’ when it hits the goal), the less sensitive you’ll be to variations in distance from target.
  • The more of a ‘lob’ you have, the less power required to make the shot (so the laser shot comes at a price… which you know already :slight_smile: ).

Try for yourself

If you have any gears in your shooter (not gearboxes. Gears.), make sure that the power cells have absolutely no way to get in contact with them. Otherwise, this happens.

We tried 4in orange bane bots wheels and Colsons and found that the bane bot wheels ended up in a further and more consistent shot and they also help with the power cell longevity

Our test results resulted in us picking an 8" wheel. Very happy with the accuracy.