I would like to know some of the major reasons why your team builds a custom (non-kitbot) drivetrain (assuming the reader is on a team that does) instead of just using the kitbot. This is intended to be somewhat of a referendum on the kitbot’s features, but only in a secondary fashion. If your team uses a non-kitbot COTS drivetrain (e.g. versachassis), I would still call this “custom” for the purposes of this poll.
Please only select the options that you would consider a MAJOR deciding factor and try NOT to choose things that might factor in, but don’t really tip the scale in favor of a custom drivetrain.
See the reply below for a second poll for your top choice (which I think will be valuable data as well).
NOTE: West Coast Drive is not considered a “Unique Drive Type”. It is a tank drive and functionally equivalent to the kitbot (although it might have specific advantages which you can choose below, such as reduced weight or increased clearance between the wheel “pods”).
Dimensional Flexibility (length and width)
Dimensional Flexibility (height of top)
Increased Ground Clearance
Increased Clearance Between Wheel “Pods” (for electronics, mechanisms, etc.)
Custom Frame Shape e.g. w/ cutout)
Unique Drive Type (type of wheels/number of wheels)
Unique Drive Type (swerve, mecanum, h-drive, octocanum, butterfly, etc.)
This is a great poll, and I think it does a lot to elucidate the reasons behind this decision. I was a little surprised by how few selected Unique Drive Type. You may want to have an option for “Other, specify below,” though.
I think you might have missed what I would consider one of the most important reasons – ease of maintenance.
Having used the kit chassis (albeit with many upgrades/modifications including using non KoP shifting gearboxes) pretty much ever since it first existed as a team, we switched to WCD this season and won’t go back and ease of maintenance is very near the top of our list why.
“Ease of Integration” may be another reason, as you have much more flexibility with your mounting schemes for other subsystems with a custom drivetrain.
For us, we use an as close to COTS WCD as we can because we find it significantly easier to mount a superstructure frame using the design style we are most comfortable with than the current kitbot design.
The real underlying reason: With the various mount-to-2x1 hardware available, it’s not a huge step up in difficulty from the kitbot. Given the increase in flexibility of dimensions, parts choice, etc. makes it well worth it.
I would say that inertia is a major factor for my team. We’ve been building custom drivetrains for years (at least 6, maybe more), and now that we have the design experience, I’m not sure we’d ever go back. Despite making drivetrain design errors every year for the last 3 years, the benefits still outweigh the cons. We took our drivetrain completely apart twice during our competition this year, and if it weren’t for how easy it was to maintain, we would have performed a lot worse.
If you ask me to design a custom WCD, I can do it in a few hours with my eyes closed. I honestly wouldn’t know where to start building a KOP chassis. I’ve barely ever had my hands on one.
Exactly, I feel like this is the case for a lot of teams that exist since before the AndyMark KOP chassis, we’ve always built custom drive trains and it’s become so easy for us to whip up a Westcoast drive that there’s really no reason for us to use an off the shelf one(source: have designed, built and wired a basic drivetrain robot in one day)
Is it really that easy? I’m part of the team that does KitBot. Our custom isnt even custom- it’s the nanotube with fixed gear ratios (2017 & 2019 bots). But I’m someone who loves to build. Would i be able to make a WCD?
It’s never really been a question of being able to do it. WCD, especially a COTS Versachassis, is relatively straightforward. It is primarily about focusing your team’s effort during the season. Can your team design and build a WCD chassis in the first week? Mistakes in the drivetrain will kill your season. Is that risk worth it? The KOP chassis really is a great chassis. More than likely, time is better spent working on mechanisms. Don’t make this decision lightly.
Very easy just follow the instructions below and you’ll be driving in no time.
You can obviously get more fancy and many teams do, but are only marginal benefits you gain in a WCD by using you manual or CNC mill compared to just a step bit and a good drill.
I wish more teams took the plunge, it is a great learning tool for students. The students in my experience get to view a couple boxes of random metal and chains and in an afternoon have a robot. Although I have nothing really against the kit, I notice a number of students always take great pride in their “custom” drive train. Its an experience that I wish more of the students are able to get.
It’s an experience thing. We’ve been making custom drivetrains since 2008. It’s the only type of drivetrain we know how to make, so going to a KOP drive would be a lot of re-education for us. I don’t think that we’re doing anything with our drivetrain that a KOP drive couldn’t do, and if we had KOP drive experience, that’s what I’d do.
That’s pretty much it for us too. We’ve gotten very good at designing and manufacturing custom drivetrains. In fact, in the past week-and-a-half or so we’ve designed about 6 different WCD, mecanum, and H-drive chassis and built three of them to help out our local hospital. At this point there are really very few downsides to making custom over using the KoP chassis for us. The advantages aren’t huge: tighter control over dimensions, wheel spacing, mounting points, gear ratios, etc; but they certainly outweigh the negligible disadvantages.
That being said, this is only true for our team which has fairly good machining resources, mentorship, and rookie training. I wouldn’t recommend that just any team use a custom drivetrain over the KoP chassis because the disadvantages are a lot bigger if you don’t have the same resources and experience. My high school team, for example, spent (and still spends) a lot of their resources every year to make a custom chassis, almost always to the detriment of the rest of the robot. They would probably be a lot better off using the KoP chassis and spending their limited machining resources elsewhere on the robot.