We are deciding whether to build a “west coast” chassis and drive train this season. We have also launched an all female FRC team. We are deciding whether or not to standardize chassis design for both teams to standardize parts purchases, ease of cross training/repairs, and the ability to share parts during a competition without a lot of drama.
I’m looking for pros and cons on a West Coast system (probably pre drilled by Vex since we don’t have onsite machine shop. Should we just use the KoP chassis for the rookie team or build a standard?
Has anyone else done this other than for a practice robot to use during “bag it time”?
Did you opt in / out for the AndyMark voucher? If you’re receiving an AndyMark drive in the kit of parts, that decision becomes easier.
I’d stick with the kit of parts drive base for this next season for both teams, especially since you’re familiar with it. Building a west coast drive isn’t going to improve your performance much more but focusing on what goes on top of your drivetrain will.
If you’re still wanting to try a west coast drive, I’d recommend doing it in the off-season in 2019. Build one and do all of your learning then. You could probably do one here in the next month but it will be rushed, especially if you haven’t designed one before.
What tools do you have? Any team can put together a competitive West Coast Drive using the COTS Versachassis system with a hand drill and a hacksaw (though a bandsaw / chop saw would be preferred).
The primary advantage of the kitbot is the fact that you get it on day 1 and don’t really need to think about it. You just assemble and go. For most brand new, unsupported teams, the kitbot is probably the best way to go because they don’t need to think about it, they just throw together parts and can focus on what goes on top of it (because that’s what typically scores more points).
Teams do get to a point, however, when they have the support and competition experience that the competitive advantage in the variability and ease of maintenance in a WCD becomes more valuable than the ease of the kitbot. Typically by the time such teams reach a point where they are held back by the kitbot, they are also at a place where they can make a WCD with very little cost.
So where does this put your rookie team? That depends - how much support do they have? If they have an experienced team working with them they may be able to start off with the versachassis system and not sink time into making a drivetrain. If they’re more or less on their own, I would recommend kitbot for sure. At the end of the day what matters is the team weighing their capabilities and goals and seeing if the versachassis makes sense for them. The argument shouldn’t be why you use the versachassis, but why shouldn’t you use the kitbot. I would argue most teams would not have enough compelling reasons not to use the kitbot, but the only way you’ll find out is by doing that analysis.
Agreed. We’ve been around since 2010. We were wanting to jump up in rigor. That’s why we were kicking around versachassis for both teams. We’ve got a load of handtools, powertools, chop and band saws (wood and metal). Guess we’ll make some decisions tonight. Thanks for the information. I’ll use it to spice up thinking this evening.
When we priced it out in 2017, the Vex Versachassis kit (including hubs, wheels, sprockets, shafts, chain and gearboxes) was a bit cheaper than the AM14U3 kit. Vex raised their prices significantly this year though, so that may no longer be the case. If you are already getting a frame kit in the KOP, then sticking with that will be cheapest of course.
The Versachassis is just as easy to put together IMO as the AM14U3. The parts that require a bit more thought are the gearbox mounts (if you aren’t using a vex ballshifter) and the bumper mounts. Both aren’t that difficult with a bit of thought.
WCD cantilevered axles have the great advantage of making wheel changes quick and easy, and you are likely to have to change wheels at least once per season in my experience.
[edit] All that being said, the AM14U3 is perfectly good, and lots of competitive teams have built awesome robots with it.
The instructions to build a westcoast drive are easier to follow than the kitbot, and there is no reason that someone should be dissuaded from building a WCD.
If you ask many people that have built them year after year you will see how much simpler that the WCD will make your life.
Ask my rookie team last year that spent the practice day at district champs desperately trying to replace the worn wheels and repair their toughbox, losing them all the possible matches they could have had.
Do you know how much time the team will need to design and manufacture a custom WCD chassis and how much time they would need to assemble a KoP chassis?
The team I am mentoring this year has only a few returning team members and no returning mentors and teachers so we are essentially a rookie team again. Over 10 two hour meetings, the team almost finished assembling and wiring an older KoP chassis they had as a training exercise. They had done custom chassis for the last several years but will be reverting to a KoP chassis for the 2019 season. It is unlikely that we could design and manufacture a custom chassis that performs better and could be manufactured in less time than the KoP chassis.
Same amount of time, assuming that you are not using ballshifters.
With ballshifters, especially being the first time you assemble them, there will be some difficulties with the pancake cylinder and the encoder stage that will slow you down.
If you use the single speed WCP gearbox fits together no problem. All you really need is a steady hand and a step bit.
And you get the freedom of building it in whatever dimensions you need/want and are not limited in any ways.
We did WCD for the first time last year. Before doing it, however, we spent some significant time in the fall prototyping. We used the VersaChassis system with a WCP DS gearbox, and got everything set up to let us test one side of a drive, including chain tensioning and bumper standoffs. It worked alright, so we went with it in season. I would not have done that without spending the time prototyping in the fall.
In season, it went ok as well. There were some things we didn’t like, so don’t assume that making the switch is going to be all unicorns and fairy dust. We’re iterating on our design this year to fix the things we didn’t like - we’ll see how it goes, I’m optimistic!
My team had a similar experience to yours at our first regional. We had to take out and put back in all 6 wheels of our KOP chassis on practice day… it took us about 10 minutes. Furthermore, we took out both of our Toughboxes, replaced a gear or two, and had them back in pretty quick (probably 30-45 minutes)
My point is this: because my team knows the KOP chassis inside and out, the repairs we made were easy for us. If your team is not intimately familiar with the workings of a WCD, then repairing it might be as difficult as repairing a KOP chassis.
I can see this being true if you have a bunch of team members and mentors who are experienced in the manufacturing processes. Is this true for the OP’s rookie team?
I have seen this become a trap for some teams as they iterate the design of their chassis over and over to make it just a bit better when it was already good enough or they design in some “clever features” that they discover is not manufacturable with the processes and equipment they have available to them. The end result is that they end up with a chassis that is not really any better than a KoP chassis but have drastically reduced the time they have available to implement their scoring mechanisms and to practice.
This idea is valid, but I think the wording implies a bit of an exaggeration of how long it takes to design and build a WCD. You can download CAD files from Vex of a VersaChassis using ballshifters that has everything already designed except the bumper mounts. That design isn’t vastly more difficult to build than the kit frame. I agree that doing it in the offseason first is best.
Apart from the ability to change wheels easily (my favorite advantage), I like having the wheels all the way to the robot’s sides for better turning and stability instead of having an inch of frame between the wheel and the outside.
All of that depends on how you designed the rest of your robot, however. Accessibility is key - having something in the way that impedes access to your gearboxes, for example, could dramatically increase the time needed. It’s not just a question of “knowing the kop chassis”.
Unfortunately my primary team took precedence for me, but they had attached mechanisms to the outside rail of the Kitbot, as soon as you do that it becomes an absolute nightmare to take the rails off.
After learning that fact at worlds I took a look at countless kitbots, and my rookies were not the only team that had done that.
I had not built a kitbot since 2013 unfortunately so I unaware of this when on week 3 they asked if their design was going to be fine.
Had they built a WCD, they would have avoided this trap.
We had a competition west coast for last season, but that was only on the table because we made one in the offseason. As many people already pointed out in this thread, you should do what you know. Because you have already built a kit bot, it would make more sense to do that.
As for standardizing your drivetrain between the two teams, that is a fantastic idea. It makes much more sense to just standardize the engineering on the drivetrain so that you can have more time to experiment with other mechanisms. Having not enough prototyping was a problem for us in the past, so I would steer towards spending the most amount of time on that