319’s public Onshape document is now live here: https://cad.onshape.com/documents/78727dd9f8bc28f0060b8f7d/w/71602decb78b721b7a9c1c5b/e/f5e2cd10e186165292be7a11
You’ll notice that the top assembly is empty right now. In fact, everything is barely started, let alone finished. This year, we’re going to try and better document our journey / process in developing the CAD. Each week, we’ll try to post something in the cad that we think is neat, and/or something we’re struggling with.
Something we’re currently struggling with is the ability to go through the trench. I’ll make a case for both below.
A bot going through the trench has an advantage in cycling because it has a defense free area (TRENCH RUN) to travel through to get to the other side of the field. Conveniently, that area can also be used as a protected shooting location. The math seems to show that a short bot can still hit the 3pt shot from the TARGET ZONE, giving it another protected shot. A low bot will also have a low center of gravity, helping prevent tipping if the bot does have to zip through the rendezvous points.
The tough part here is that it’s a monster of a packaging problem. 319 is a competitive team, and wants to be able to do everything on the field if we can. Stuffing all the things that we want our robot to do into a bot that can fit under the trench will be a tough challenge.
A tall bot has a better angle at the 3pt goal from all shooting locations than low bots. It has more space to store and index POWER CELLS, more space to stuff a hanging mechanism in, and the CONTROL PANEL mechanism doesn’t have to be articulated. All this amounts to the fact that a tall robot can be an easier packaging solution. This obviously comes at the cost of not being able to go through the trench, which means full field cycles will take longer.
It’s possible that not all 3 robots can cycle through the trench run effectively in a match, meaning that a bot that can play effectively from one side of the trench or the other would be advantageous. Due to the previously mentioned better shooting angles, a tall bot might have an advantage over a short bot as a fullback or forward since it can place it’s shooter such that the shots are unblockable by a 45" tall robot.
We’ll be deciding this weekend if we’re going tall or short. Ultimately, it will come down to which 319 bot will be better. Would a 319 tall robot be better than a 319 short robot? Let me know what you think.
I haven’t designed a turret since 2012, so i figured I’d take a crack at it. We recently received a Markforged printer, so I decided to leverage printing a jumbo HTD pulley. I generated the pulley with the MKCAD pulley generator I posted a while back. The design was inspired by the Armabot Turret 240, and will eventually feature a similarly sectioned pulley. I just didn’t want to put in the effort in the event that 319 chooses not to use a turret.
The bearings for the turret started with the “bearing sandwich” approach, but I removed the bottom bread bearing of the sandwich and replaced it with a printed “bushing” that will ride on the aluminum plate. I tried to minimize the stack height as much as possible, and I’m happy to take suggestions on how to get it even shorter. The pulley is 160T 5mm HTD with an 8" hole blown through it. It’s all supported by a 3/16" AL plate.
I just slapped a 30:1 VP with a NEO 550 into the model to see how it’d look. The math says that this would rotate at around 247 deg/s.