"West Coast" drive?

[pogenwurst]

I've heard references to "West Coast"-style drivetrains a few times now on CD, and am puzzled as to what that means.

The only real information I've been able to dig up is:

Originally Posted by lukevanoort

Unless you are mounting your wheels directly on the transmission output shaft (West Coast Drive style)

Is that it, or does a West Coast drive entail more than that?

Also, what are the performance implications (positive or negative) of the use of such a drivetrain?

[RyanN]

I've also heard of this, but cannot define it for you exactly as there is no real definition for it.

I believe it just means they have a shaft driving the wheels directly from the transmission instead of running wheels from a chain and sprocket without any real physical connection to the wheel. There are obvious advantages, as a live axle wheel has little to no chance of losing power. If all your chains fall off, the robot will likely still have mobility. It also can reduce weight since you eliminate chain and sprockets.

[EricH]

Originally Posted by pogenwurst

I've heard references to "West Coast"-style drivetrains a few times now on CD, and am puzzled as to what that means.

The only real information I've been able to dig up is:



Is that it, or does a West Coast drive entail more than that?

Also, what are the performance implications (positive or negative) of the use of such a drivetrain?

6WD, drop center wheel directly driven from the gearbox. A modified version is to do a chain to the center as well as the rest.

6WD "drop" drive has a pile of implications that are out here.

[Lowfategg]

It also seems to me that west coast drives don't have outer chassis rails with bearing supports.

[Joe G.]

Direct center wheel power, live axles, 6WD drop center, cantilevered shafts, and wheel slide tensioners are all generally bundled into the term "West Coast Drive"

A classic example is the drivetrains of 254 and 968

http://www.chiefdelphi.com/media/photos/25814

[roboticWanderor]

But really, any "West Coast" style drivetrain might as well be named "(Team # Who Built It) Coast" because it has not only spread in popularity, but in variations of the design. I know my design (pictured above) has been tagged "West Coast" but it still lacks direct center wheel power, multi-motor transmissions, and wheel slide tensioners.

[sdcantrell56]

I just saw that you are from Duluth High School. I am a mentor at North Gwinnett. It's good to see you on here.

As has already been said, "west coast" has taken on many meanings, but it seems to have become synonymous with wheels cantilevered outside of the frame. Teams have designed many different variations of it with sliding tensioners, live and dead axles, directly driven center wheels, and many other variations.

The main performance benefits are slightly increased stability due to a larger track width, and much quicker wheel/tread changes.

The downside is that the wheels are unprotected, and many versions such as the awesome 254/968 iteration are very machining intensive.

If you guys need any help with drivetrains just send me a pm or something and I'd be glad to share with you the designs I've been working on and our previous drivetrain.

[AdamHeard]

Originally Posted by sdcantrell56

I just saw that you are from Duluth High School. I am a mentor at North Gwinnett. It's good to see you on here.

As has already been said, "west coast" has taken on many meanings, but it seems to have become synonymous with wheels cantilevered outside of the frame. Teams have designed many different variations of it with sliding tensioners, live and dead axles, directly driven center wheels, and many other variations.

The main performance benefits are slightly increased stability due to a larger track width, and much quicker wheel/tread changes.

The downside is that the wheels are unprotected, and many versions such as the awesome 254/968 iteration are very machining intensive.

If you guys need any help with drivetrains just send me a pm or something and I'd be glad to share with you the designs I've been working on and our previous drivetrain.

I would say that being machining intensive is not a downside of a West Coast Drive. Sure, a super efficient and lightweight design can be made with all custom parts, but you can also do a decent west coast without. Last year on 973, we just machined the siderails, two bearing blocks per side (just a block the size of the inner portion of the extrusion), the wheel shafts and the wheels. With COTs gearboxes and wheels, minimal machining is required. If your team can't get enough machining resources to get that made, your team is just not trying at all.

[sdcantrell56]

I was simply saying that a lot of the machining necessary for a west coast drivetrain requires at least a mill, and a cnc mill would be even better. I do agree with you that any team should be able to ask around and find someone willing to machine a few parts for them. A lot of companies are very eager to help with FIRST since the robots are a lot "cooler" than the parts they normally make. One of the things I have been doing is trying to design a west coast drive that i feel will be reliable and easy enough to make using mostly sheet metal tools since our main sponsor is a sheet metal shop. There are many different ways to do a "west coast" drivetrain and it's really up to the team to decide how much machining they put into it.

[GUI]

It is actually quite possible to build a west coast style drive system without anything beyond basic sawing and drilling. Our design last year could easily be converted to use live axles and direct drive on the center wheel by using commercially available pillowblocks and AM supershifters. Granted, certain parts would preferrably be different or customized slightly, but it would be reliable, easy, and cheap.

[MrForbes]

Time to get that wood OS chassis design started...it could be a "poor team's west coast drive", in one of the many possible variations.

[sdcantrell56]

Originally Posted by squirrel

Time to get that wood OS chassis design started...it could be a "poor team's west coast drive", in one of the many possible variations.

I have actually been working on a couple different wooden west coast designs although I don't know if I'd say they would be easy to do without a cnc mill or laser, or really just a mill. Of course it could be adapted to work with just a drill although it certainly wouldn't be as robust.

[MrForbes]

Great! lets get going on them...

[GUI]

My plan (once i get a model done, I'll post in on the open source chassis thread) is basically this in 6wd form with a supershifter directly driving the center wheel. All that would be needed to make it would be a saw, a drill, and tin snips (though the sheet metal shear makes that part much easier).

[roboticWanderor]

Team 418's "Wood Coast" drive train was a basic west coast style created using nothing more than common woodworking tools. It is achievable to make these designs using nothing more than a saw and drill press. going down from sliding bearing blocks, multi-speed transmissions, and direct axle drive can really simplify a design, and rid your team of the need for a mill, or other machine work. I hate to say this, but the "west coast" drive trains used by team's such as 254 are overly complex, and require a lot of machining compared to equivalent designs. Many teams (who win a lot too) go without expensive options such as direct drive gearboxes, such as 1114, or 330.


PS: sorry for ragging on your robots guys, i just wanted to make the point that these types of designs are possible without the use of expensive machines or parts.