"West Coast" drive?
 

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?

Re: "West Coast" drive?
 

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.

Re: "West Coast" drive?
 

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.

Re: "West Coast" drive?
 

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

Re: "West Coast" drive?
 

"West Coast" is used to refer to drive bases, most commonly 6wd, that have the wheels cantilevered outside the frame, usually with live axles and the center wheel directly driven by the transmission output shaft. The term is loosely used, but a definitive example of a west coast drive would be those built by team 254 or team 60. There are several advantages to a west coast drive system, mainly ease of maintenance and the light weight. Possible drawbacks include dangers to the wheels, which can be negated with bumper use or some sort of wheel guards, and manufacturing difficulties, which vary with your abilities and experience.

Re: "West Coast" drive?
 

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

Re: "West Coast" drive?
 

GUI nailed it.

254 can hardly take credit for the design though. It was Glenn Thoroughman's (60) baby from the start. We may have popularized it over the years (along with 968 and others), but Glenn should get all credit for the original design.

Re: "West Coast" drive?
 

West Coast Style

The Universal Chassis is a "West Coast Style" clone. Thanks to all those teams that helped perfect this gold standard of FIRST.

Re: "West Coast" drive?
 

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.

Re: "West Coast" drive?
 

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.

Re: "West Coast" drive?
 

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.

Re: "West Coast" drive?
 

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.

Re: "West Coast" drive?
 

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.

Re: "West Coast" drive?
 

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.

Re: "West Coast" drive?
 

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.

Re: "West Coast" drive?
 

Great! lets get going on them...

Re: "West Coast" drive?
 

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).

Re: "West Coast" drive?
 

Mine is very similar to that although with shorter frame rails and all the bearings are mounted in laser cut 1/4" thick aluminum brackets since I'm worried about the bearing holes enlarging in the wood.

Re: "West Coast" drive?
 

I think with a hardwood, the bearing holes might be ok. This is something that would need to be tested, of course! also thin plywood might be better for the "belly pan", as it's easier to buy locally, and to cut to size, and to attach firmly (glued and screwed).

oops! we sure hijacked this thread

Re: "West Coast" drive?
 

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.

Re: "West Coast" drive?
 

I know this isn't exactly rookie friendly but I am throwing around the idea of making a west coast style drivetrain from laser cut pieces of 1/2" thick meranti or baltic birch plywood. For all cross members and side rails, I would epoxy 2 pieces together to form a 1" thick piece, and then the base plate would just be the 1/2" thick material. The base plate would provide a huge amount of stiffness with a relatively low amount of weight since its wood. Also if it's not strong enough we could always lay up one layer of fiberglass. I would think that epoxying 2 pieces of plywood together with a few screws would be super strong. I will try to post up a cad rendition I have in a little bit.

Re: "West Coast" drive?
 

254/968's iteration is the simplest West Coast Drives I've ever seen. They took some liberties and cut a lot of weight by increasing the machining complexity, but they have the resources to do it. A CNC doesn't care if it's cutting a curve or a straight line. They could very easily scale back the design to be "easier" to make and it would still be the simplest West Coast Drive.

Also, separate issue; a West Coast Drive is center wheel direct driven, cantilevered wheels in 2x1 extrusion, #25 chain from gearbox to outer wheels on the inside of the frame. Any similar bases are just similar, not West Coast Drives.

Re: "West Coast" drive?
 

You need to get one of those little circles with an R in it after the phrase West Coast Drive :)

Re: "West Coast" drive?
 

All the files for the Universal Chassis are open source and downloadable from my website. www.team221.com

We took the major concepts from 254/968 and team 60 and made them production friendly. All components are made from stock sizes, they have no complex machining and every part is bolt together.

I made the first production batches in my home shop with a standard Bridgeport. A band saw, belt sander, scroll saw and drill press would suffice.

Re: "West Coast" drive?
 

Cory,
Its time for a post with a history lesson on teams 60, 254 and 968. We definitely remember Glenn and his contributions to many teams today with that drivetrain. ;)
What's more impressive is that all of you from teams 100, 115, etc. are now the new engineering "crew" continuing the traditional West Coast dominance.:yikes:

Re: "West Coast" drive?
 

Yes, I agree. The history behind this would be great. I think that it is was a development between design leaders Glenn Thoroughmann (60) and Steve Kyramarios (254), with their teams' help, but I am not sure.

Andy B.

Re: "West Coast" drive?
 

Team 60/Glenn had the directly driven cantilevered wheel way back in 2000 (in 99 they actually ran belts!). The cantilevered/directly driven idea is what I have always felt was the heart of the system, and what made it unique, elegant and ahead of its time.

The 6wd iteration used in 2004 was just the expected evolution of an already proven and well developed concept.


And as far as complexity is concerned, you are correct to a point. There can be much simpler ways of doing this same concept, but the way it is done now eliminates a lot of parts, increases reliability, eases in maintainability and has far fewer frictional losses than doing it pretty much any other way. Since we do have the resources to manufacture these parts, these other benefits I just mentioned create an advantage (in our eyes) over alternative methods and "simpler" designs.

Re: "West Coast" drive?
 

Oh dear, look at what I've gotten myself into now -- I should stay in programming where I belong. :P

In all seriousness though, thanks a bunch guys, this clears things up quite a bit.

Just to verify my understanding: the term "cantilevered" has come up quite a few times in reference to wheels; that just means that the shaft that the wheel is on isn't supported on the end, right?

My apologies for replying so late; I was out sick from school for almost a whole week and subsequently quite swamped.

Re: "West Coast" drive?
 

Correct; it can be used for almost anything where only one end is supported and the other end has a load on it. In this specific instance, the wheel is on the cantilevered end.

Re: "West Coast" drive?
 

Thanks. Is the only advantage of such a setup easy maintenance / wheel swapping, or are there others?

Re: "West Coast" drive?
 

The frame can be smaller and lighter. Also it's easier to make a live axle (axle turns with the wheel) robot with cantilevered axles.

Re: "West Coast" drive?
 

Quick & easy wheel swapping sure is nice, but there are also other benefits, as Travis outlined in his post.

Re: "West Coast" drive?
 

Ah, I missed that somehow, thanks for pointing it out.