Ball compression shooting bot

FIRST General Forum
1

We are building a demo bot this summer that will shot 8.5 inch foam dodge balls. I was wondering what type of compression teams used in rebound rumble or stronghold that worked for them. We will be using a 4 inch wheeled shooter

2

In 2016, I believe we compressed the ball roughly 75%, which for stronghold (10" ball) was 2.5". It had pretty good results, if we had a better system for feeding the ball, we could’ve shot from the outerworks better.

3

I’d encourage you to prototype and find what’s best for your application rather than building one to a specification that another team used. You indicated that this was for an offseason project, so maybe a prototype that allows you to adjust the compression on the flywheel would be beneficial.

When prototyping a single wheel hooded shooter, remember to keep all but one of these variables consistent, if possible:

  1. Ball feeding speed and position
  2. Amount of wrap on the wheel (more is almost always better)
  3. Shooter RPM (Velocity PID is a good way to keep this consistent)
  4. Wheel type and size (different wheel durometers wear and behave differently)
  5. Motor & gearbox/belt reduction specifications
  6. Counterweight mass
  7. Shooting position relative to your target

A quick and easy way to prototype a shooter is to laser cut two side plates out of plywood and standoff them together. Be sure to consider adjustability in your design, such that additional prototypes aren’t necessary.

4

Make a curved back. Then just add layers of soft foam to build it up. Remember to keep one new ball and use the other to test so you get a ton of shots (100 or more). Get the olds ball dirty etc. Then shoot the new ball and add compression until the new and old ball trajectories converge. Then you’ll have a consistent shot assuming your velocity control is decent.

5

Let us know when you’ve built your demo bot. We’ve been looking at updating our Stronghold bot to make it a demo bot.

Maybe we can coordinate a community outreach day together.

6

This is what we did on 111 in 2016. If I remember correctly, we ended up at around 2.25". Playing with the exact material of the strips on our hood had a lot of impact on the shot characteristics.

Is this a single 4" wheeled shooter, or one on either side of the ball? I think you guys did the single wheel back in 2016, so you probably have a good amount of source material for that design. If you’re doing the mirrored wheels, the two designs I’d look at are 971 2016 and the Niagra triplets (1114/1503/1680) from 2006.

Hope that helps.

7

That sounds great we can do something like that. We are hoping to be done before the end of summer

Thanks for all the feedback everyone. We did some testing with 6 different compression and found that for the 2012 basketballs 2 inches of compression is the best for distance and accuracy. If you would like to see are data i will post an image of it bellow

[Album] Imgur

8