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[JamesCH95]

@MisterGrapfruit

So, for something like a shooter plate, it might make sense to pocket a thicker material, since the design in most cases would necessitate a large gap in standoffs for the ball to pass through.

Enh… if you ensure the plate is loaded in tension you can use pretty thin material. In our 2022 build thread you can find our shooter made from pocketed/trussed 0.09in aluminum. The elements in bending - the spacers and shooter wheel shaft - are pretty rigid in bending while they compress the ball, and the side plates are nominally just loaded in tension and thus are fine being relatively thin.

FRC95 2022 Build Thread

Time for another Grasshoppers build thread! Here are some important links: Youtube Imgur OnShape Open Alliance for 2022 We are beyond excited for the number of teams joining the Open Alliance. I specifically want to thank @Ty_Tremblay for leading the rowdy group of OA teams and making things official. Officialish anyway 95 did not meeting in person from March 2020 through August 2021. We have a lot of rust to knock off still, but with a handful of new students and four new FRC alum…

@MisterGrapfruit

But, for something like an exposed intake, pocketing a thicker material would probably hurt more than it helps because it would reduce the flexibility?

Generally, yes. Check out this post where we recorded HSV of slamming intakes into a wall:

FRC 95 The Grasshoppers 2023 Build Thread

Let’s talk about intake compliance! Over the years we have been known to publish ‘intake smash test’ videos every season. It’s kind of a brag (if I’m being honest) to be able to smash your intake off of a wall and have it still work. It’s also a good thing to understand about your robot so your drivers can drive appropriately. But what is actually going on? What design parameters are meaningful? How can we all build more robust intakes? To help answer these questions we took some HSV of our…

Extremely rigid intakes can work too if their deploying mechanisms are compliant.

FRC 95 The Grasshoppers 2024 Build Thread

A small follow-up on intake compliance testing. We added mockup carbon fiber intake bars onto Clarke and smashed them. The first time the drive mechanism worked as intended and back-drove. The second time the frangible mounts failed, but all of the principle components of the intake remained intact. Now the rookies have a good repair project for next week’s preseason meeting at least. [2023 FRC 95 The Grasshoppers Carbon Fiber Intake Compliance]

@MisterGrapfruit

Would any of this apply to material selection?

Absolutely. Stiffness is proportional to the material’s elastic modulus, but does not depend on material strength. Thus as a designer you should pick a material and form that matches the stiffness and strength requirements of a particular device. Some examples would be:

Strong and stiff (chassis, gearbox) - aluminum and steel tubing, composite tubing
Strong and compliant (end effectors that smash into things) - PC/polymer sheet, composite rods, coil or leaf springs

There are a number of cases where an intentionally weak part (frangible part) is desired, but that’s a whole other ball of wax we can go into detail later if there is interest.