Re: FRC 2012 Ball Launcher by iR3
 

After making seeing that shooter the dimensions of the robot are starting to look a lot smaller! Hopefully it can be successfully compacted.

Re: FRC 2012 Ball Launcher by iR3
 

Absolutely, I agree! There is plenty of room for optimization in this prototype using these components. I think a great place to start is the packaging, smaller wheels may help the overall size as well.

Though this setup could theoretically serve as a final design, the point of the shooter was to help answer the practical questions while designing the final solution. Questions like what trajectories work best for long rage shots at the top goal. We tested that in a recent video seen here: http://www.youtube.com/watch?v=l8U9u2iqMEs&sns=em

On the other hand, our final design will definitely include room for modularity and adjustability so that we can continue to iterate and improve on the design.

Re: FRC 2012 Ball Launcher by iR3
 

This is very similar to the shooter we got up and running last night. We designed for all the same adjustability, but not having the Modulox components to make that trivial it took several hours. However it works similarly well. We are unable at the moment to get the speed up to what we would like due to gearing constraints (again where Modulox would be awesome), but are VERY pleased with consistency and should be able to get the speed we need just by gearing down less (the torque seemed more than sufficient). No video yet, but soon.

Re: FRC 2012 Ball Launcher by iR3
 

nice job! good music, too.

would you be willing to do some controlled tests to compare it against my trajectory spreadsheet and post the results?

Mostly, I'd like to see you use your fixture to estimate launch velocity based on range. Mount that sucker to a desk to make it the right height and lock down the angle on it. Feed the balls as nicely as possible and check the distance traveled against numbers from my sheet. It will go a long way to helping us figure out what the drag effect will look like.

Re: FRC 2012 Ball Launcher by iR3
 

I like your idea! We did some trajectory testing in the second video I posted but nothing to the extent you're talking. I think the hard thing will be calculating launch velocity to compare it with theoretical. If I'm thinking correctly wouldnt you need both for drag?

We could calculate wheel speed rather simply but it may be difficult to determine the balls acceleration through the shooter. Right now my only thought is high speed camera or some sort of photo gate.

Am I over complicating this? Any thoughts?

Re: FRC 2012 Ball Launcher by iR3
 

Could you give us an indication of what kind of rpm you were spinning those wheels at for the various ranges?

Re: FRC 2012 Ball Launcher by iR3
 

High speed camera=good investment. Buy a Casio exilim for 100$ and spraypaint a scale behind it.

Re: FRC 2012 Ball Launcher by iR3
 

We are actually doing our best to track down a tachometer but theoretically CIM motors free speed around ~5310 rpm.

We currently have it configured as a 1 stage reduction 14 CIM Gear to 40 Tooth Gear. So a gear reduction of roughly 2.85:1.

5310/2.85 = 1863.15 RPM

Taking into account the mass moment of the wheels and some inefficiencies maybe like 1400 rpm @ around 75% efficiency?

Re: FRC 2012 Ball Launcher by iR3
 

Thanks! We did the math on a half-court shot and the surface speed of a 6" wheel is in that order.

Re: FRC 2012 Ball Launcher by iR3
 

That sounds about right. In our trajectory testing video we were hitting some shots around 23'3". That is just about half court so it sounds like your calculations were pretty close!

Re: FRC 2012 Ball Launcher by iR3
 

Hi there.

We actually considered using that concept, but then we accounted for the inaccuracies. Still we keep it as a backup plan. I saw a video using that launcher to launch a ball 80-feet! It was really neat!

On my team, using a gyroscope to center the robot according to the location of itself to the drive station, and having two sonar sensors built right on to the robot, we used last year's robot and gave it the ability to utilize holonomic mech wheels to freely rotate and speed the robot which way the driver would like in a perfectly accurate direction.

Please check out the video at
http://www.bit.ly/team871gyrotest

Please post all comments!
Thanks so much. :)

http://www.westisliprobotics.com