Grasshoppers 2018 Offseason Activity

We’re working on a number of things this off-season to prepare for 2019.

First and perhaps foremost is that we are making the switch on OnShape after hearing about 319’s wild success and trialing it for a few weeks. The low startup cost, ability to help students in real-time, and collaborative nature have been great so far.

While we love using CANBus in general, the daisy-chain approach we have employed in wiring has been irritating at times. Losing one device or connection and having everything downstream go out is not as robust we would like. So, we wired our practice chassis with a branched CANBus. The old folks like me might recognize the distribution blocks. It worked first try with no programming changes and has survived several demos and practice sessions without any issues. While not at all up to our normal wiring standards, it proves the concept. We’re looking for the right piece-parts to implement it more cleanly.

Our battery cart got some color.

We learned how to do loop splices in woven synthetic line. This particular segment is for pulling axles out of cars/trucks/SUVs, but the same technique applies to smaller line.

IIRC this was a Brummel splice:

Our programming team is working on learning Pathfinder and Pathfiner-like auto navigation routines. Slow and inconsistent auto movement was one of our weakest areas last year, so we’re working to address that.

Finally, there is progress on future endmill giveaways! My employer is finalizing details related to a continuing giveaway, I hope it will be rolling soon.

We have official clearance to continue collecting and distributing end mills to any teams that want them.

We’re going to sort out a more sustainable distribution model for the mills. When that’s decided I’ll post back here.

Our pre-season activities have been pretty mellow so far. From a student/build skills perspective we’ve been building proficiency with OnShape and prototyping mechanisms for old games (2016 specifically). Our programmers have been bringing new students up to speed and are starting to learn path finder related techniques.

An area we struggled with last year was translating details from CAD to the builders. For our team it feels prohibitively time-consuming to detail in every fastener, wire tie-down, and other important yet unimportant part. To address wiring layout we are going to start using wire duct, it is quick to model in, provides a clear place to route wiring, and helps establish a sane component layout. OnShape’s built-in generic fastener tools should help with modeling in bolts and other fasteners.

From a broader organizational perspective we have been dividing up responsibilities among coaches that used to fall to the head coach (me) and my assistant coach. It has been difficult for me to keep up with as many team-related responsibilities now that I have two kids. I was pleasantly surprised at the willingness of the other coaches to take on additional work. This will help to prevent my burning-out I am sure.

For the endmill giveaway - there are some aggravating rules related to money handling between our school sponsor, the club, and any reasonable interface to other teams. For now I will accept paypal for shipping costs ($8 even to deal with paypal fees) plus any donation people care to make to the Grasshoppers. I will send out sets of 4 mills on a first-come first-serve basis. Please PM me for my email address and to get an idea of what the mill stock currently looks like.

Pro tip - OnShape gets a bit laggy on a 4k screen. Dropping the monitor to ~2k improves performance noticeably.

Our programmers are working with a robot battle simulator called Robocode in order to get new students up to speed. It’s straight-forward, engaging, and demonstrates the basics of antonymous robot programming well. There are several pre-programmed robots, so the learning curve is pretty easy. So far our new programming students have enjoyed it immensely.

It’s available here:

Now that our pre-season is largely wrapped up, here is a linkto the modest (and slightly cleaned up) workspace we were using in Onshape. It shows our general sheet metal construction approach that we’ve been refining for a few seasons. We generally do not detail out absolutely everything in CAD, but rather go for about 80%. It seems like that last 20% takes too much time for a very small value-add.

We also bench-marked our batteries last night and discovered that all of them have internal resistances over 30mΩ. Bummer. We’re going to be ordering a pile of new batteries (that’s 8, in metric) for this year. We generally stop using batteries for competition once they get over 21 or 22mΩ of internal resistance. Most of these batteries were 15-19mΩ at the start of the 2018 season (we sharpie internal resistance on the battery every year to track them). Our 2018 robot was power-hungry, had aggressive gearing, and we (tried) to drive the wheels off of it every match. It was not uncommon take batteries out of Keppler at 8-10V. We think these deep discharges degraded all of our batteries, but will be auditing our battery control process to make sure we didn’t miss anything.

Endmills will be shipping out soon!