pic: Stryke Force FRC2767 Variable Hood Angle Ball Shooter from 2017


#1




#2

How would you fabricate the ramp-pieces? I’m guessing 3D printing, maybe a markforged or similar?


#3

I’d imagine you could easily get away with just PETG for those parts; there’s not too much load and it’s spread over a decent area. We used similar prints in 2017 without an issue.


#4

Very cool! Would 2767 ever release the CAD of your 2017 bot?


#5

Enjoy. :male_detective:

https://grabcad.com/library/frc-2767-styke-force-2017-1


#6

I have looked at the swerve modules before, I was actually curious at looking at the gear mech in the CAD form :). It was magical to watch.


#7

I’ll see what we can do to get the CAD for it. In the mean time, here is a picture of it.

New photo by Cory Walters


#8

Sorry guys. I’m not fluent with the CD tools. My original intent with this was to contribute to the variable shooter thread started by Plato2000. I couldn’t attach a picture there (perhaps b/c I don’t have enough experience points?) so was exploring putting a picture on the image gallery that I could then reference. I actually didn’t think I had pressed the “submit” button on this…

At any rate, in 2017, StrykeForce pushed itself to have the ability to shoot anywhere from the floor using vision targeting. Because we wanted to have full control of the trajectory from any range (i.e. control of the angle at which we entered the target), we went with a continuously variable shooter. We had full continuous control on both launch angle and speed. The optimal speed/angle settings were determined emperically for several ranges and curve fitting was done on the data to define functions. Any time we made a tweak to the system (which was often), the data needed to be retaken. We were ultimately successful (~85-90% hit rate at 10balls/sec from close in to ~20feet out), but it was PAINFUL. We also had a mode where we could touch off against the boiler for a protected shooting position, but we had to reduce the firing rate because the balls would pile up on each other at the apex of the steep trajectory–causing a “starburst” effect with poor accuracy. I still maintain that Wiffle balls are somehow fundamentally evil. Something important that isn’t modeled in this image is the foam liner we put in the output of the ball raceway. We used some thin adhesive backed foam to give us some compliance/damping. The accuracy was HIGHLY dependent on the foam thickness, positioning, etc… This was a large part of the pain factor. We could get to ~60% accuracy easily, that next third was tough.

As far as construction: The tan parts were printed in PC/ABS on a commercial FDM printer owned by our primary sponsor. The bigger parts could have been broken down for printing on a desktop printer. The outer shell was a weldment made from aluminum. Another of our sponsors is a WJ company and did them for us. However, these particular parts could just as easily been fabricated using laser or CNC milling. The black part, essentially a large bushing the assembly rotated about, was milled from a block of Delrin.

On CAD: I’m not at all opposed to sharing the CAD, but I’ll have to work with someone else on the team who knows how best to do it. I’m also currently extremely busy at work and it may be a bit. Please have patience.


#9

I’ve uploaded the hopper/shooter assembly CAD from our 2017 robot to our GRABCAD site. I’ve also uploaded the gear handling assembly.