West Coast Drive, WCD

Hello teams,
Can anyone shed some light on west coast drive? Our team has been reading about it and seeing these types of robot chassis/frames. what are the specifics?
I have been through cd-media, too many “this is not wcd” pics. Is there a white paper or somekind of criteria teams follow?

A “west coast drive” is generally a term referring to a drive similar to 254’s drivetrain. IMO these things need to be present for it to be a “West Coast Drive”:

  • Six / eight wheel drive, with the center wheel dropped
  • All wheels cantilevered
  • One wheel directly driven, rest chained to that wheel.

Once you have these three things, you have something resembling a “West Coast Drive”.

There are many different variations of even this drive, though. Some teams, like 27 and 118, cantilever the wheels on dead axles and tie the wheels together using chain and sprockets bolted to the wheels. Other teams like 254 and 973 use live axles and run their chains on the inside of their drivetrain, cantilevered off the back of the axle.

Tensioning is another system where differences occur. Many teams use sliding bearing blocks that move each wheel in order to tension drive chain. Some teams tension in other ways.

My team’s (2791) west coast drive is really different enough that I’m not sure I’d even use the name. We cantilever our wheels on live axles, but we run timing belt instead of chain. Because timing belt does not stretch, we can run systems with basic idlers instead of tensioners and never need to adjust the belting after we get it right. In addition, for added security and to save space, we run the timing belt on the inside of our drive’s welded tubing. This results in a very clean and simple drivetrain that has been remarkably reliable for us.

The West Coast Drive is the Drivetrain traditionally used by many West Coast Teams including 60, 254 968, 1323 and 1538.

In it’s purest form, it’s a 6 Wheel Drive with cantilevered wheels (Only supported on the inboard side) that are all driven via live axle (usually hex) from a central transmission. Most WCD’s use either 4 or 6 inch wheels to keep weight down and to simplify the transmissions. If done correctly a WCD should be lighter than an equivalent “Standard” drive train.

Here’s a picture of a WCD based on Team 221’s Super Light Chassis System: http://www.team221.com/upload/594-team%20KAOS_frc1429.JPG

Also here are some good examples:


http://www.chiefdelphi.com/forums/showthread.php?t=70334&highlight=West+Coast+Drive Should help you.

west coast drive is a drive-train where the axles are canteleverd (unsupported on one side, like a car. typically 6-8 wheels, but i have seen a team (dont know name or number) that had a 20 wheel west coast drive (roller blade wheels) the reasons for doing this are;

1)weight, there is no frame outside the wheels, so fame weight is drastically less.

  1. wider stance. moving the wheels out 1.25-1.5 inches on either side allows for a wider wheelbase, which makes the robot more stable, as well as aids in turning.

3)ease of repair. it is easier to repair a WCD quickly. because the wheels can be taken off without moving the axles. changing tread, or replacing an axle, takes much less time.

Thanks guys, this helps a bit.
One thought though, if the wheels are cantilevered and there is no plate on the outer perimeter of the robot would there just be some sort of pegs or standoffs to mount bumpers too? I thought bumpers had to be rigidly mounted to frame/chassis with minimal “openings” or voids behind the plywood.

Thanks again.

This year’s rule allow for up to 8 inches between “openings”. To rectify this on modern robots, it’s pretty simple to add brackets to mount bumpers with.

Here’s 2791’s “west coast” chassis showing our simple bumper mounts.

For what it’s worth, I’ve never been more satisfied with a drive base than this one. Other than the axles, which were made with the wrong aluminium alloy, I’ve never been more satisfied with a drive base.

Here’s an early shot of FRC27, Team RUSH, using our Super Light Chassis kit.

FRC 27 on Super Light Chassis

You can clearly see the cantilevered wheels and the bumper standoffs.

I think everyone has said it right. ALthough two things, the middle wheel doesn’t have to be directly driven, and there can be framing on the outside if desired. Our team uses belts and is not directly driving the middle wheel, and we have a sheet metal plate on the inside and outside of the wheel. This is still west coast I believe right? Unless our drive train isn’t considered west coast…

For it to be a “True” West Coast Drive, one of the wheels should be direct driven, and the wheels should be cantilevered.

If your drive isn’t cantilevered - if it has supports on the outside basically - then it’s probably not a WCD. (Unless the support is superficial or for bumper mounting)

Not every single six wheel drop center drivetrain is “West Coast”.

However, not every non - “West Coast” drive is bad, by any means. If I used sheetmetal instead of welded tube to build robots, I probably wouldn’t cantilever the wheels, because it doesn’t really save much material weight.

As others have stated, West Coast Drive System was created by Glen on Team 60 and has been popularized by FRC 254/968/973/1538 etc…

But the best pics of the system:


254 does a great job showcasing the WCD.


Maybe that’s why my mentor had me write “Midwest Drive” on our post this year http://www.chiefdelphi.com/forums/showthread.php?t=93061&highlight=pwnage

And we made the decision to have sheetmetal plates on the inside and outside for strength, because last year our wheels got bent, and then we made plates for IRI last year with great results. http://pwnage.foxvalleyrobotics.com/gallery/pwnage_gallery_newrobot.html

Nick, from what I can see, that looks like a standard drive train to me.

That’s a great looking and clean chassis! Only thing I don’t totally understand is why you go dead axle instead of live with the chain on the opposite side? Not really a critique just wondering what the decision making process was.

Hello All!
After following this thread, I was curious about what the advadntages of WCD are, and when is the optimal situations to employ such a system. I am curious because we are about to begin working on offseason training which might entail building various drive chassis and systems to get some offseason design experience. Thanks!

The advantages that lead us to a west coast-ish style drive were:

  1. ease of maintenance
  2. wider track width
  3. less weight
  4. protected belts

We were already planning on direct driving a wheel no matter what frame style we chose and also leaning heavily towards a live axle system since for us it is easier to fabricate the components so a west coast inspired drive fit in perfectly with what we were already leaning towards.

That’s a great looking and clean chassis! Only thing I don’t totally understand is why you go dead axle instead of live with the chain on the opposite side? Not really a critique just wondering what the decision making process was.

Some of the reasons:

-standard axles. we use chromoly tube to form the dead axles…simply cut to length. this reduces machining.
-we use AM standard wheels. the plaction variety is cheaper than the performance wheel…so using a dead axle saves us having to add AM hex or key hubs back into the wheel, thus increasing the cost.
-we can service the wheels just as easy as any live axle setup i’ve seen. when the chain is tensioned properly it slides off the axle with the wheel as part of the assembly…no issues.
-dead axle blocks are slightly easier to manufacture…just ream an undersized hole for the axle. no precise bearing fit.
-chain on the outside of the frame rail doesn’t interfere with any assembly on the inside…this makes life easier when we have to add something unplanned inside the perimeter
-we can adjust the rocker by swapping out different end blocks. live axle blocks don’t allow this because there isn’t enough material to machine away in the vertical direction.
-we used to use custom Dewalt planetary drive transmission…they wouldn’t have worked well with a double sprocket on the inside of the chassis rail.

Note that the Super Light Chassis product can be used in either variety. The standard version is “dead” axle, but “live” axle blocks can be dropped into the outer wheel positions.

WCD sounds like it has a lot of benefits, but how do you mount a standard gearbox to the rail?

Normally if your going to all the trouble of making a custom drivetrain, you’ll be making your own gearboxes as well. The only place that currently sells gearboxes integrated for a WCD is Team 221 Robotics.

But 973 Back in 08 used a shifter shifter in a WCD setup: