West Coast Drive Custom 6WD

Our team has recently decided, per my last few posts, that in the fall preseason we would build a custom West Coast Drive. I am putting together a presentation to go over more background for this Drivetrain. What are some ideas, tips, experiences or facts we should know when looking into the Drivetrain.

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We did one this season for the first time and the best thing is the vex bearing blocks and the wcp cam for tensioning buy lots of 1x2 tubing and find machining sponsors in your community willing to fabricate parts for you

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We did this for the 2018 preseason and used it last year and this year. We’re using the vex bearing blocks which are an absolute godsend for WCD and the vexpro gearboxes go with them nicely. We have cad from last year on our website - we did a 6w drive base on Bonus Level for 2018. The preseason project is up there as well.

https://www.team2655.org/mechanical/

Think of the little things:

  • How are you tensioning the chains/belts?
  • How are you mounting encoders?
  • How are you mounting the gearbox to the drive rails?
  • How are you mounting bumpers?
  • How are you meeting the rules regarding bumper supports?
  • What size rivets/bolts are you using?

WCD is a highly configurable drive system that can work with virtually any gear ratio, any quantity of wheels, any wheel size, and any frame dimensions. With the introduction of various COTS parts (WCP gearboxes, VexPro bearing blocks, etc) it’s also quite possible to build without any advanced machining.

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Totally agree but machining and materials sponsors can really help with the cost and since wcd is so simple it can really build to a better relationship with machining sponsors

How are you going to service the parts that @Lil_Lavery listed in his post? How are you going to replace the wheels?

@philso @Lil_Lavery We plan on building this out of 80/20 and 1/8” sheet metal, unfortunately we do not have a sponsor that will machine any parts for us, maybe next year we will. My mentor however regarding the wheels thought it’d be a great idea to have easy slap on/off wheels, I do have an idea that we could possibly put collars of some sorts on the very ends of the rods to secure the wheels on, this way we could swap wheels easily. Also the bolts likely to be used would be 80/20 Button Head Screws and 1/4-20, 10/32 screws when need be (Machinery screws) I do have the feeling any drivetrain structural screws will need to be loctited. I am not so much concerned with motors or driving functions. We are thinking about using a chain.

What you’re describing doesn’t sound much like a West Coast Drive.

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@Lil_Lavery we do not plan on this being a season robot due to it being against the rules, we will start from scratch and figure out details as in bumpers for the season robot. To us, Bumpers are not a concern when we are building a practice robot, we will add them if need be

This would be a similar concept to it, the one we are building we are using parts from the Versachassis to build it in 6WD

More/Less it’s pretty much a custom chassis of a West Coast drive

What about it makes it sound not like a west coast drive?

What is your team’s objective? To build something to get more experience building something? To learn to build a 6WD WCD chassis so your team will have the experience for next season? If it is the later, then why would you not try out different ways of attaching the bumpers considering that so many teams do this so poorly?

We want to build a custom drivetrain to improve our performance and also step out of our comfort zone, get experience/do trial and error before the season. The reason we are doing it preseason without bumpers is because it will never face defense and bumpers aren’t something we should spend time on due to our limited preseason time. If need be, we can duct tape pool noodles on like in the past.

We have, in regard to bumpers found an awesome approach to bumpers by using the KoP attachments for bumpers

The 80/20 and 1/8" sheet metal attached together with button head screws.

A “west coast drive” typically means a drivetrain modelled after the drivetrains pioneered by teams like 60, 22, and 254 in the early/mid-2000s. The defining characteristics of a “WCD” are that one wheel per side is direct driven by the gearbox output shaft, the wheels are cantilevered outside the drive rails on live axles, and the frame is constructed from aluminum box tubing. Here are some prior threads discussing WCDs (pictures and links may not be broken).

Some pictures to better describe the concepts:


(Notice the center wheel directly driven by the gearbox, the cantilevered wheels outside the tubes, and the welded tube construction).

(Notice the rudimentary bumper mounts to provide support consistent with the 2007 bumper rules).

(Notice the use of gussets instead of welding on the drive rails)

The OP describing the desire to use 80/20 and 1/8" plate for construction seems to fly in the face of the standard aluminum tubing construction, which makes me question if their intent is really to build a WCD or a different style of custom drivebase.

@Ryan_Brown_6032 the reason bumper mounts are so important to plan for in a WCD is because the wheels are cantilevered. Unlike the KoP chassis, where the wheels are inside the frame and the frame can be used to support the full length of the bumpers, you need to plan for how you will meet the support requirements for the bumpers. The KoP attachments can work for physically hooking/unhooking the bumpers (although there are better ways), but aren’t sufficient for meeting the support requirements.

There are some good videos on YouTube that talk about designing and building WCDs.
My team has videos onlaying out and assembling VersaChassis without precision machining.
2363 has awhole series on building their variety of a WCD.

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I’d recommend watching the 2363 video series, then watching the old 973Ramp 2 part video and then watching the 2363 video. Cannot recommend these two resources enough.

Ok, I can see why for bumpers now, here’s an image of the drivetrain we are looking to build out of 80/20, the sheet metal is simply an electronics panel to act as part of the structural integrityVersaChassis-6WD

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The best drivetrain design is very very dependent on a teams situation. What are your machining resources? How much access do you really have to these machines (especially early on in the season)?

If you don’t have the resources to machine aluminum box tubing, then a custom “west coast” drivetrain probably isn’t for you. The kit drivetrain is a very very good drivetrain. My team could have used a kit drivetrain this year and I think we would have achieved just as much as we did.

That being said, building a custom drivetrain can still be a great offseason project to learn from, even if you opt to stick with the kitbot during build season.

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We have the machining to get by with aluminum box tubing, not a welder but enough to get by. One of the reasons we looked into using 80/20 instead other than it’s strength. But yes I agree with your views. @Cog