Wheel shooter gearing

[Ether]

Originally Posted by GW Kalrod

Your team wants to gear a 19,000 rpm motor up?

I'd get a basic FIRST concepts/Physics concepts PowerPoint rigged up for your team.

@Clark: would you please review your original post and clarify if that's what you meant? I assumed you meant you wanted to lower the speed (although as Nick says your wording suggests otherwise).

If your team is indeed pushing for increasing the speed up from 19300, there's no way you want to do that.

[Clark Pappas]

Sorry for the confusion everyone. I'll clarify (This is what i get for typing while i'm tired )

The team insisted we want to gear the 550s UP rather than DOWN, and that didn't sound right to even me, who has only taken a conceptual physics class I never paid attention in. I looked around CD, and need a little more information and help to prove to my team we want to gear down, and to get some sort of range of gearing ratios. Had our design not get changed again, the information in this thread would be ample to get us going.

However, the team says they now want to switch to a launch system drive by one side of wheels (underneath). So, now I'm lost completely in the physics (again), and stressing out about deadlines (again).

Any additional help would be appreciated. More gearbox recommendations would be appreciated as well; seeing as ship day is too close for us to get things ordered (Especially with the way our school processes orders), we will be having to add gearboxes at the competition. The plan is to bring it all as-is when shipped to the competition and add it there, since they could be considered a COTS part.

[Jon Stratis]

If you want to go with a single-wheel shooter with a hood, just think about what the ball is doing. In that case, it rolls between the hood and the shooter, which cuts its speed in half, when compared to a two-wheel shooter design. So, where my team has a 7:1 reduction for a two wheel shooter, we would want a 3.5:1 reduction for a single wheel shooter. That would double the speed of the shooter wheel, which would keep the speed of the ball the same as we have now.

[gurellia53]

Look at AndyMark gearboxes. They are made for FRC motors and they'll be the easiest to get working out of the box.

Also look at banebots gearboxes. The CIM-U-LATOR is a fairly decent gearbox for the job.

[JesseK]

Originally Posted by Ether

Does this agree with your numbers?

69.8 feet/sec wheel tangential velocity,

34.9 feet/sec ball exit velocity,

38.1 feet theoretical* max range

* no drag, no magnus

Ha, I screwed up. When we cut the launch angle in the guide I measured it from the normal plane rather than the parallel plane. So it's inverted with a flatter trajectory than we want. Theoretical distance is the same, yet we need the extra height for the high goal. We also comepletely re-fabbed the shooter shaft since there was a slight wobble, and relocated one of its bearing blocks since it was slightly out of alignment. All told, I think we're back up to 30 feet-ish (ball barely peaked before it hit the wall at 15 feet) with the flat trajectory. Once we finish sensor wiring tonight I'll know more.

There would be significant magnus effect if the ball's trajectory went further or higher -- we hit the wall at probably > 70 degrees angle of incidence (20 degrees from parallel with the floor) and the ball came almost straight down due to the backspin. May make for some interesting layup shots.

[DjMaddius]

What kind of RPM's is everyone else using for their shooters?

Ours is just over 2k rpm, 1 wheel for bottom, 2 for top. Spin the top very slightly slower to get backspin on the ball so it falls in easier of course.