West Coast Drive Without Prior Experience

Didn’t want to be redundant by making another west coast drive post but my team was considering using a west coast drive this upcoming season but was unavailable to make one of these during the offseason. Is it still worth it to make this drivetrain without prior practice in doing so?

Did y’all order a KoP chassis for the 2020 season? If so, designing and building a WCD during build season is going to be much of a challenge, of course all of this depends on your teams capabilities, if you have high confidence that you can do it right and produce a correct custom drivetrain during build season, proceed with caution. If not, KoP is your best bet and you’re left with more time to work on other mechanisms.

My team is doing it too, we found a video series on YouTube by YETI Robotics, #3506. The videos a pretty clear and go from design considerations to cost to actually building it. The basics are simple, we chose to heavily modify their design but its up to you. We did it because we had a very specific issue last year. Be warned though, you may already have the AndyMark KoP drivetrain on the way if you didn’t opt out and the WCD tends to be more expensive, ours is about 2500 USD without motors.

@Shreykv I don’t know if we did or did not order a KoP chassis this year. I’ll check on that.

@RobotCapt yeah i’ve been watching those videos too to try and wrap my head around WCD.

I second this, if you haven’t already planned one out and don’t think you have the expertise to do it, it might be too much.

Came here to say this. I hope you didn’t opt out, and if you didn’t you’ll receive a competent drive system. Maybe heavier than you want or not configured to your perfect ideal, but always competent.

4901 built, effectively, a chain-in-tube WCD in 2016. We did support the other end of the wheel axles rather than cantilever them, but that was because it was 2016 and we were running fat 8" pneumatic wheels like most did and designing for full sends. Toughbox Mini gearboxes, 4 CIMs, 17T double sprockets. While I don’t have the BOM, there is no way we were $2500 into it.

(Coincidentally, Sandstorm III was a drivetrain we did without building a prototype…but we also had access to the University of South Carolina’s machine shop. I would likely not attempt that again without similar access.)


So the overall idea is to not do it unless you have done it in the offseason?

How on earth did you get all the way to $2500 for that?

Drivetrains usually aren’t that expensive, or at least they shouldn’t be.


I mean you can do it without doing it in the offseason but you might have issues that pop up so it’s generally better not to do it without prior experience. The other thing is, has your team done the KOP frame in the past? If so, you’re team likely ordered the KOP Frame again this year.


I really don’t understand what you bought in order to reach that number. Unless you’re making the frame out of titanium, which even then likely wouldn’t get you that high, I really have no idea how that is even possible. If you are spending $2500 on a drivetrain though, stick to the KOP Drivetrain.


@ProPain37 we have used the KoP chassis for the past couple of years so hopefully we did order it but I don’t know for sure. I will try to find out from our mentor though but our mentors did change this season due to our mentor from previous seasons retiring.

Between custom gearboxes and not having almost any of the basic required parts, it racked up. This was less of an issue because we had a very large grant that ended up being heavily restricted, our drivetrain and some spare lumber was about all we could get.

Custom gearboxes should not cost that much. If anything they should be a lot cheaper than that. Unless you’re counting the cost of machinery. What do you mean by basic required parts? Tools and machinery or actual parts? Can you give an example of a basic part?

We dont have any chain or the tools for it. We purposely over ordered some parts for spares but the chain alone wasnt terribly cheap. Then we had to get a ton of sprockets for our 8-wheel drive, those arent cheap either. We didnt have any aluminum left from last year, we also went witht the Versa Block Kits with WCP Cams.

We did our first one two years ago, cold. It’s not difficult and Vex gives some good instructions on their website. You do, however, need:

(1) the ability to cut decent-sized holes in aluminum – see posts on here for “Annular Cutter.” For this, you really need a drill press.
(2) the ability to drill holes with decent precision. (measure, use a scribe, drill a pilot first, use a drill press vise, etc…)
(3) A good way to cut aluminum to length
(4) Rivets of the proper size and a decent riveter.

Definitely use the Vex bearing blocks – don’t try to put bearing holes directly into your aluminum. Recognize, though that the bearing holes are slightly off-center from the center of the 2" side of the tubing. Get some Vex gussets.

And, don’t ignore the rules about supports holding up your bumpers – the drivetrains shown on the vex site DON’T take into the account that you have to have something holding the bumper on the sides.

Somebody said something about $2500. That’s a bit high, but once you add in the gearboxes, motors and motor controllers, you are definitely over $1000.

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Even if your team opted out (which took a mentor actively logging in and clicking the button), you’re not too hosed. The 2019 KoP drive base kit, the AM14U4, retails for $689.

If you opted out, you will have an AndyMark voucher for $450. If the 2020 drive base kit retails for the same amount, you’d only be out $239 plus shipping to catch up.

Assuming there is a 2020 equivalent to the AM14U4 Frame Only (they’ve always offered one in the past), you could go through your parts stash and only order the extra parts you truly need to save some money. Omitting the extra belts will save you some cash in particular (and was the secret to the success of the since-departed AM14U3 Square Deal Edition).

@Billfred thanks for that but from my info the KoP chassis is pretty heavy compared to custom drivetrains and with the new weight changes with bumpers and batteries now being included into the weight our team is a bit hesitant to use it this year because we have had issues with weight in the past.

No where does it say that bumpers and battery are part of the robot weight. As far as I know, they have never been a part of the robot weight. Bumpers can’t exceed 15 pounds per last years rules but this years rules on weight haven’t been released.

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Emphasis mine, but: Citation needed. They could still make it this way when they release R5 at Kickoff, but the Pre-Kickoff Game Manual Content does not declare this.

It was eminently possible to build a contending robot within the 2019 weight limit, even with heavier-than-stock-AM14U4 drivetrains (source: we added some weight with that third Mini CIM and using a 3CIM4U instead of a Toughbox Mini). It does require some design choices and planning though.