FRC 95 The Grasshoppers 2020 Build Thread

Here it is. Easily our favorite featurescript since we have access to a laser cutter!


Every day I’m more and more impressed with Onshape. Thank you very much for sharing! This is an incredible featurescript that can save hours and hours of time.


What made you guys decide to try topspin before a more traditional hooded shooter?

@Schmools to change the angle when it bounces off of the top of the outer port. I’m assuming you meant backspin.

I was more wondering why the ball path didnt wrap around the wheel but simply passed over the wheel from the top.

It’s designed to make a shot from the target zone, so a very steep angle. We had to tip it forward a lot to avoid just bouncing power cells off of the ceiling.


Why just the target zone? /are you planning on shooting from more areas? Looks like you have some good range with that shooter so I’m curious if you are planning on being able to shoot from non-target zone areas.

Good question.

We’re starting our design off with the somewhat modest goal of shooting from the target zone, but we are leaving in the room to add a hood extension to shoot from one or more additional locations. This will depend on how quickly we achieve our initial goal of a reliable target zone shooter.

Lots of prototyping progress today.

We tried a number of shooter configurations, including this monstrosity:

Best results were from this setup:

Shaved the crown off of two colson wheels and added an HDPE hood shield. Shot velocity increased from both changes and accuracy+precision were both good. Thanks to 971/EWCP crew for the pointers on that.

Our students wanted to an easy way to figure out where the balls were landing in successive shots. Well… they were remarkably creative. One of those ideas every year that blows my mind.

We drew serious inspiration from 6135 for a hopper protortpe. They had lots of power cells to test with, but we didn’t, so we used CARGO from last year to do scale testing.

The magic here is that you can vary speed and direction of each wheel. The result is that jams quickly clear, but the cargo were still pulled in fast. We are likely going to use this approach.

We borrowed heavily from 125’s 2017 collector for our latest collector prototype.

We loved the collapsible nature and large collection area of the 2017 125 collector, but added our own spin on it (HAH!). The second row of rollers is larger than the bottom, this creates a speed difference between the two, tending to pull the power cells in. The shots that look like they sail through the collector are actually being actively pulled in.

We can run a TON of pinch between the power cell and bumper, like 3-4 inches of pinch/gap. We are very happy with the results and will be looking to implement it. The drive motor and a single VP end stage are the pivots. There were only 4 laser-cut parts here. It was easy to put one of these together.

To bookend this post with another monstrosity: we are adapting our 2018 chain maw design into a control panel spinner.


What’s your source for the torsion spring on the intake?

Could you link to where you saw the 6135 hopper? I’m having trouble finding it and would really love to see it.

Sweet intake James. I’d be worried about the chains derailing if you’re intaking and the intake gets pushed sideways. Have you tried that?

Have you done any speed control on your shooter for testing, or is it all 12V open loop?

I think this is the source:

  • Sunny G.

@Phil_McJoe we bought a number of spring like this one, with varying rates and angle offsets, a few years ago. Couldn’t tell you the exact one we used, but this is the family.

@Log see @ttldomination’s post.

@Tom_Line thanks! We have bumped it a lot with no observed issues so far… the real one will likely have a 5:1 ratio instead of the 3:1 we had on hand to test with, and we have spots to install chain guides if needed.

@s_forbes all open loop. Closed loop starts on Tuesday.

That is a really cool intake. How does it fold up. Looks like 125 use a second pneumatic cylinder. Did you find away to passivelly extend it.


125 used two sets of gas springs to extend. It never retracted during a match, and never needed to.

We are discussing a second set of air cylinders to deploy the end section or releasing a spring/gas spring and leaving it out for the match.

It’s also not incredibly difficult to integrate a virtual 4-bar into this system either, which would prevent another actuation.

Correct! The other side of the collector is open for a comparable chain run to make a virtual 4bar.

Not really sure what a virtual 4 bar is. Do you have any examples

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