Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

I actually do have another question :p For the articulating arm, why did you use a pair of gears to go from the gearbox to the arm itself? Is it necessary? Could you have gone from the Planetary directly into the arm?

Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

Could I get the measurements of your robot, please? Also, what defenses was this tested against?

Great design!

thanks,
popvideo
GRA-V mentor

Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

We were worried about putting any weird torques on the versa planetary. There is definitely a way to direct drive using the shaft (a hex to hex coupler...). Actually, if we had access to a hex to hex coupler that's probably what we would've done. The geometry also worked out nicely with the gears.

Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

I'm doing 18 credits right now and I'm also 200 miles away from the robot... if you could specify what dimensions you're looking for I'd be glad to get them. I was hoping to CAD the robot, but time is valuable when you're in college.

Our drivetrain was successfully tested against the rough terrain, low bar, and ramparts. The others might be possible, but we didn't want to damage our pathetically built drivetrain. I'd recommend 6 pneumatic wheels with a drop center if you have access to them.

Quick question regarding the shooter. Did you guys have an issue with the shooter back driving the cim that controlled the elevation of the shooter? Example would be you had shooter positioned at say 35* did the shooter want to drop ?

Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

The turret would begin to drop when the angle between the ground and the shooter approached ~45 degrees as an estimate. I think if you're debating whether or not to add a mechanical brake to the shooter, I would recommend it. The reason I say this other than the back driving, the shooter would rock while driving, and especially while traversing obstacles. Stabilizing that seems like a good idea.

On the other hand... you could just ignore the rocking and then stall the articulation motor. Up to you!

We came up with a design on kickoff day for the shooter that was almost identical to the one you made, only real difference is we are using 775 pros with a 3:1 versa planetary, and the original set up for the ball to roll in on and be supported was going to be aluminum tube, but once I saw the plastic tubes you used I started looking for similar material. I am thinking the plastic covers for fluorescent lights will be the ticket.

Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

We desperately wanted to throw some LEDs in the tubes, but time is a killer. Going back, if we had access to 775pro's that's exactly what I would've done. I'm not sure if I'd do 3:1 or 2:1 though... would've needed to do some testing!

On the tubes do you know what od you went with off hand?
On the 2:1 vs 3:1 we figured that a mini cim is spinning around 6000 rpm so a 775 at 3:1 is also about 6000 rpm so should work out pretty much the same as you guys ended up with. We are going to use the versa planetary encoder to measure and set the rpm using a talon srx.
And leds in the tubes are a given!

Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

I bought 1.5" OD with 1.125" ID. I actually bought the tubes because I thought they might have utility as a roller intake, plus we would be able to press fit a bearing into the tube. The rigidity was more than satisfactory and they weigh barely anything.

Awesome. Thanks for the tips.

Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

Did you work with 4" wheels on the shooter right from the start? If so, why did you go with this size? If you tried other sizes what were your findings?

Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

I can tell in the video that there is a device that induces the ball into the fly wheels. It looks like it might be that little gearmotor with the microcontroler, but its covered in tape and I cant tell. What is it and how did you get it to work ?

Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

Sorry for the delayed reply! I must've missed your post. We used 6" wheels right away and didn't like the profile of the shooter, it was much bigger than we wanted. So we tried 4" wheels and it got us a shot that we liked with a profile that would work. I could see a team shrinking the profile even more and running 3" or smaller wheels at a higher RPM.

Re: paper: [Ri3D] The GreenHorns 2016 Present: Rivvet
 

We actually used a rotary servo like this one from AndyMark. We mounted a 4" piece of aluminum to it that acted as the lever arm. Our setup was slightly underpowered, but that could easily be remedied by using a stronger servo, and/or a shorter lever arm. Just be sure to do the math. Your trigger should be able to reliably push the ball into your shooter when your shooter is at any angle.