I’ve seen a lot of references to a this but have no clue what it is. Searching didn’t help either, so if somebody could explain what makes this different from a normal tank drive I’d appreciate it a lot.
my understanding is that a WCD has cantilevered wheels on the outside of the main frame (like a car) where there are supports between the wheels to hold up the bumpers. WCD also often has 8 smaller diameter wheels.
the “Traditional” tank drive has the wheels inside the chassis.
In Ascii (W = wheel, | = frame):
WCD:
W|------|W
W|------|W
W|------|W
W|------|W
Trad:
|W|-----|W|
| |-----| |
|W|-----|W|
| |-----| |
|W|-----|W|
Here is my best description. Someone please correct me if I’m wrong.
The primary defining characteristic of a West Coast Drive is the cantilevered wheels, with one wheel directly driven by a gearbox. The “WCD” is largely derived from designs by 60 and then 254 in the early 2000’s. Other common (but not required) components include 6 wheels, adjustable bearing blocks, and the minimal possible wheel size. Variants may run the chain through tubing or use belts instead. It does not refer to just any 6WD, and does not require that there are only 6 wheels on the robot.
West Coast Drive is a tank drive with cantilevered wheels on live axles with one of the center wheels directly driven by the gearbox, with an aluminum tubing chassis.
This is wrong. The West Coast Drive dates back to the early 2000’s. Here’s a thread from 2008 that briefly discusses the origins and characteristics of the west coast drive. FRC 60 originated it, 254 perfected it.
It doesn’t have to be the center wheel that directly driven, but otherwise this is spot on.
Here are some pictures to illustrate:
Is the consensus that WCDs must have all wheels be live-axle, or does that not matter*? I know most WCD designs are live-axle for various reasons, but I’ve seen some that would otherwise be WCDs except they use dead-axle wheels**. The second example Sean posted has dead axles for all of the wheels except the direct-driven one. Personally, I’m fine calling dead-axle drives WCDs, but I’m interested in hearing other people’s opinion on the distinction.
*There’s no “official” definition that I know of, so consensus is really all that matters.
**Or unpowered wheels
Since bumpers have become standard required equipt. we (Team 60), don’t actually even use it as much anymore. You pretty much need to mount your bumpers to something outside the wheels, and they need to be backed by frame.
Not saying we won’t, just saying lately we have not as much.
Live axles are what I consider one of the few certainties about WCD. Dead axle WCD style drives don’t sound like a great idea.
I see sprockets and chains on all 4 of the images Sean posted above save the 1st image that is the 8 wheel drive chassi that has yet to have the chains installed on the installed sprockets yet. No dead wheels there, all are intended to be powered and driven by the drive motors it appears via chains and sprockets.
Cantilevered wheels, at least 2 wheels (1 on each side), directly driven by the gearboxes, so no matter the loss of other wheels, chains or sprockets, the robot would maintain mobility, chain or now belt adjusting pillow blocks, and drop center axles it was easily explained to me by those that helped in dreaming it up. I was not around in Glen’s day, but George Williams was and still is.
It received a tag of WCD Tank drive by others. Some are directly driven 1 wheel on each side directly off the gearbox shaft, but many use a sprocket and short chain to drive the center wheels sprockets. They may also have chains or belts and sprockets you never would see in a photo, as they are assembled inside the chassi frame tubes. And then 2 speed and 3 speed transmissions are also added if there is lots of real open running room onfield for pushing and banging your friends, or pulling and climbing.
Thank’s for the history thread link. Think I’ve taken that stroll before.
BtW, you were correct, pic 2 has dead axles only because no gearbox has yet to be mounted on the chassi.