West Coast Drive, WCD

[CidTeach]

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?
thanks

[Chris is me]

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.

[thefro526]

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-te...OS_frc1429.JPG

Also here are some good examples:

http://www.chiefdelphi.com/media/photos/27537
http://www.chiefdelphi.com/media/photos/24654
http://www.chiefdelphi.com/media/photos/31597
http://www.chiefdelphi.com/media/photos/30564

[Andrew Schreiber]

http://www.chiefdelphi.com/forums/sh...st+Coast+Drive Should help you.

[Hawiian Cadder]

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.

2) 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.

[CidTeach]

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.

[Chris is me]

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.

[ajlapp]

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.

[pwnageNick]

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...

[thefro526]

Originally Posted by pwnageNick

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)

[Chris is me]

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.

[R.C.]

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:

http://team254.com/media/photos/2010-frc-build-season

254 does a great job showcasing the WCD.

-RC

[pwnageNick]

Maybe that's why my mentor had me write "Midwest Drive" on our post this year http://www.chiefdelphi.com/forums/sh...ghlight=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/..._newrobot.html

[thefro526]

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

[sdcantrell56]

Originally Posted by ajlapp

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.

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.