WCD vs straight up 6 wheel

[lemiant]

What is there to choose between West coast Drive or regular 6wd like that of the 1114?

[lemiant]

I figure I'll start with my very uninformed opinion. It seems that WCD has two [small] drawbacks: It is cantilevered resulting in less rigidity, and it uses live shafts resulting in more complexity.

[sgreco]

Originally Posted by lemiant

I figure I'll start with my very uninformed opinion. It seems that WCD has two [small] drawbacks: It is cantilevered resulting in less rigidity, and it uses live shafts resulting in more complexity.

Having live axles doesn't necessarily add complexity; it depends on implementation. In the case of 254's drivetrain, the live axles provide them with ease of maintenance that probably wouldn't be possible with dead axles. (There chain is easy to access, and switching wheels out takes about a minute).

I think the primary idea behind a west coast drive (or at least a very important one) is the widened drive base. A WCD, due to its nature, optimizes the 38x28 box by allowing the wheels to be as far apart as possible. This is helpful for maneuverability and control for the driver.

This would be easier to discuss if you define "straight up 6 wheel".

[Chris is me]

Originally Posted by sgreco

Having live axles doesn't necessarily add complexity; it depends on implementation. In the case of 254's drivetrain, the live axles provide them with ease of maintenance that probably wouldn't be possible with dead axles. (There chain is easy to access, and switching wheels out takes about a minute).

It's less complex to maintain, but it's easily more complex to design. Their bearing block recipe and implementation along with the direct drive gearbox are not nearly as simple as a kit drivetrain with a chained gearbox.

[lemiant]

Originally Posted by sgreco

This would be easier to discuss if you define "straight up 6 wheel".

Something like this: http://www.chiefdelphi.com/media/photos/36931

[Hawiian Cadder]

There are too many varieties of both drive styles to really make a good comparison. Really when people ask this I think the main thing to discus is cantilevered vs non cantilevered wheels. When people say that supporting the axle on both sides makes the frame stronger I tend to disagree: Usualy the outer support is not attached by much (at least not near the middle wheel, where most of the weight is supported), and 80% of the weight of the robot is on the inner support. So unless your frame is really, really rigid, I don't think its any stronger to support a wheel on both sides. Cantilevered wheel systems are usually lighter, because there are only 2 wheel supporting members as opposed to 4. Because there isn't something in the way, the wheels can be moved farther apart, resulting in a more stable robot that turns with more force. The last and one of the best cases is ease of repair. A well laid out WCD can have all of the components removed without moving any of the axles. This makes repairs much faster, and require fewer tools. Every part can be replaced with nothing but needle nose pliers and an Alan wrench.

[EricH]

6WD variations
-Live Axle
-Dead Axle

-Drop Center
-Corner Omni
-Force it (no drop, no omni--see Team 25)

-Cantilever
-Non-Cantilever

-Direct Drive
-Chain/Belt/Gear Only

-Shifting
-Non-Shifting

Now, which of those options go into a "straight up" 6WD?

Spoiler for Rhetorical question answer:

All of them. It just depends which team you're asking.

The classic WCD is a live axle, drop center, cantilever, direct drive/chain combination, shifting drivetrain. Different teams have different tweaks to that drivetrain.

[lemiant]

Originally Posted by EricH

6WD variations
-Live Axle
-Dead Axle

-Drop Center
-Corner Omni
-Force it (no drop, no omni--see Team 25)

-Cantilever
-Non-Cantilever

-Direct Drive
-Chain/Belt/Gear Only

-Shifting
-Non-Shifting

Now, which of those options go into a "straight up" 6WD?

Spoiler for Rhetorical question answer:

All of them. It just depends which team you're asking.

The classic WCD is a live axle, drop center, cantilever, direct drive/chain combination, shifting drivetrain. Different teams have different tweaks to that drivetrain.

The same as WCD except that it is not cantilevered and the outer axles are dead (like 1114 does).

[Jeff 801]

Originally Posted by sgreco

I think the primary idea behind a west coast drive (or at least a very important one) is the widened drive base. A WCD, due to its nature, optimizes the 38x28 box by allowing the wheels to be as far apart as possible. This is helpful for maneuverability and control for the driver.

I am just going to throw this out there is that you can do other types of drive system other than a "west coast" that are just as rigid and keep the wheels very close to the outside edge of the frame perimeter. To further explain as seen here in this picture of 254 from this past year (254's 2011 robot) the wheels are set in the range of .5" to .75" and in the attached picture you can see with this drive system the wheels are just about as close to the outside of the frame perimeter.

[Travis Covington]

Originally Posted by Jeff 801

I am just going to throw this out there is that you can do other types of drive system other than a "west coast" that are just as rigid and keep the wheels very close to the outside edge of the frame perimeter. To further explain as seen here in this picture of 254 from this past year (254's 2011 robot) the wheels are set in the range of .5" to .75" and in the attached picture you can see with this drive system the wheels are just about as close to the outside of the frame perimeter.

Our wheels were set in that far to allow us to increase the wheel width if we determined it was required later in the season. We never saw the need, but it was comforting to have the capability. In previous years, however, we pushed the wheels to within an 1/8" or so of the frame/bumpers.

[jwfoss]

Honest Answer: The best option is to choose something that your team can build within their means, and maintain thoughout the season. Spend some time looking around the CD-Media gallery, do a search for drivetrains or chassis.

In the end, if all your team can afford to do is put together a strong 6wd kitbot with drop center and appropriate gearing you'll still be ahead of at least 25% of the other teams running.

[Chris is me]

Originally Posted by jwfoss

In the end, if all your team can afford to do is put together a strong 6wd kitbot with drop center and appropriate gearing you'll still be ahead of at least 25% of the other teams running.

I'd say that's closer to 75% of the other teams running. There are a LOT of bad custom drivetrains, mecanum drives, and whatnot at competition.