FRC 95 The Grasshoppers 2020 Build Thread

Welcome one and all to The Grasshopper’s Build Thread, presented by #openalliance :wink:

This is our 7th build thread and we are ecstatic to be participating with the other open build teams. It has been one of the most rewarding projects that our team has undertaken thanks to you all who provide kind words, helpful advice, and copy/borrow/are inspired by what we post. It means the world to us!

We have been toying with a change in chassis design during the off-season that we might want to use during the season, so before kickoff even, here is our OnShape directory for 2020:

Grasshoppers 2020 OnShape Directory

This is a living document. Expect things to change on a routine basis. It may be messy and disorganized at times. Most of the time. It’ll be a train wreck probably until week 3 or 4.

Anyway, our objective was to make a WCD-sort of chassis using sheet metal instead of tubing.

Why?
-We have an awesome sheet metal sponsor, Progressive Mfg
-We want to more-easily service wheels, which was a big point of pain last year
-We need a stronger chassis, NE defense is famous for a reason

Other objectives for this year include (but are not limited to):
-Use more rivets
-Scope the robot’s capabilities to our team’s size (we’ve over-stepped a bit the last few years)
-Be better at scouting
-Win an award we haven’t won before

We are pumped for 2020. Good luck everyone!

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One of my favorite threads every year. Can’t wait.

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Piggybacking onto the build thread, here’s our codebase for 2020:


It’s the 2019 codebase with some modifications made during preseason.

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Wow! What a great response so far! I hope we can live up to your expectations this year.

OnShape pro tip - I have had a great time using a Chrome extension called Night Eye to make OnShape ‘dark.’ I really like it, although it is a paid extension. OnShape looks like this for me now:

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How do the sketches look with Night Eye on?

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The amount of detail and time that goes into this thread is amazing! Keep it up! Looking forward to seeing this threat develop this year. Even after graduating, I still appreciate all the details you give out!

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Dark, but on a nicer monitor it’s usable. I haven’t tried to optimize any of the Night Eye settings for it.

Awesome!

Carefully consider what the value proposition of higher-end production is for your team and your objective. We (very intentionally) have a low production value on all of our content. It lets us get things out more quickly and reduces the burden on us during the already-strained build season. This is not the only option, of course, but it’s the right choice for us!

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After the game reveal we started with a rules and strategy discussion, then brainstormed some robot archetypes and used a weighted decision matrix to rank some initial ideas.

I’m not sure that everyone is appreciating the lower point ceiling of only scoring in the lower power port. We’re going to continue this discussion and perhaps do some sort of offensive power analysis.

This initial work will guide our prototyping in the next week or two.

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Before we get too far into the thread, just wanna say our team got a ton of useful information from this thread last year. We didn’t have the resources to make effective prototypes (and I am ECSTATIC to say we definitely do now), and threads/blogs like this were so helpful for us.

We had a fantastic 2019 due in some part to teams sharing their work and ideas, so this is awesome. 6574 will be making efforts to start a build blog this year to pay it forward.

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Your robot archetypes are kind of opaque in the chart, heading to your blog to see if I can understand them better. Tha KS for doing all this so publicly

Try zooming in on the image or downloading them. I screen shot them from a 4k monitor, so they might be a little hi rez.

If your team has a mechanism or method for forcibly balancing the switch, and you don’t call it the skywalker or anakin, you are a fool of the highest caliber.

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I don’t mean opaque as in, I can’t read them. Just trying to understand the meaning of some of the names, lol

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Gotcha. The first image is basically a check list of capabilities for each type.

:laughing:

Suggested reading and video review:

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First post-kickoff meeting update:

We’re meeting less frequently than in the past. In part to reduce mentor burnout (people are having kids and buying houses and stuff) and in part to take a deep breath and make sure we’re heading down the right path. We’re also doing robotics work outside of meetings, which is somewhat more relaxing.

We made some initial decisions to guide our initial prototyping and design work.

We distilled some of our archetypes down to simpler descriptions. We settled on ‘fire support.’

We also did what we have termed a DPS analysis (you gaming nerds will get it) to look at what the more efficient operations might be for scoring. Note - tailor the difficulty and difficulty rating to your teams abilities if you choose to do this.

Some subtle tweaks to our chassis model. It’s coming along nicely. We are planning on using 4xneos in 2-motor ball shifters geared at 7/15ft/s with automatic shifting again. This sort of combination has worked well for us since 2018.

The AM performance wheels are sold out, so we’ll be looking at other options.

Prototyping is coming along, but nothing worth a picture or write-up yet.

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Robot, you are the chosen one, destined to bring balance to the switch!

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I would strongly encourage every team to run some sort of simulation on their drivetrain every year. The ubiquitous JVN Design Calculator is a great way to start, especially if you’re using an OTS gearbox. I don’t think it has BLDC motors yet, but it’s good enough to scope out your drive options (and other mechanisms).

For the next level there are a few options. I gave @JesseK’s ILITE DTS a go this year. It provides some wonderful insights and data. It’s a simulation - so don’t take it to the bank. But it can help you make a better drivetrain gearing choice, and it supports BLDCs.

We’re dropping on the side of ‘geared a little slower than optimal’ which is a nice place to be to have some extra margin on your drivetrain. Especially if you intend to defend or anticipate being defended.

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