WCD vs Standard

[EricH]

Originally Posted by LedLover96

What does 25 do? why are they an exception?

6WD flat. I don't know how they do it, but they don't bounce when turning, even with high-traction wheels. I think it has something to do with how they groove their tread, but I'm not sure.

At least, they used to do that. I'm not sure if they still do or not.

[MichaelBick]

For weight it honestly depends: if you are running tube then WCD is a pretty good choice to save weight. If you are running sheet there is really no need to run a WCD. However wether you run sheet or tube you always should drop the center wheels and should direct drive the center wheel.

[Walter Deitzler]

And I am assuming that the standard KOP C-Channel will not work for a WCD, or, at least, that C-Channel is not a good choice? I have never heard of a C-Channel WCD.

[MichaelBick]

The KOP is not made for running a WCD. WCD is overall a better drivetrain, but for teams that don't have the capabilities to build a WCD the KOP is a find alternative. I believe they even make supershifter mounts for the KOP

[Walter Deitzler]

Originally Posted by MICHAELABICK

The KOP is not made for running a WCD. WCD is overall a better drivetrain, but for teams that don't have the capabilities to build a WCD the KOP is a find alternative. I believe they even make supershifter mounts for the KOP

Why can you not run a WCD on a KoP chassis?

[MichaelBick]

The definition of WCD usually means that you are running a cantilevered, live axle, direct driven a dropped center drivetrain. While the KOP is drop center, it is not any of the other things. The C Channel of the KOP is definitely not strong enough to cantilever something off of it. because you are not cantilevering you might as well run a dead axle set up.

[Walter Deitzler]

Originally Posted by MICHAELABICK

The definition of WCD usually means that you are running a cantilevered, live axle, direct driven a dropped center drivetrain. While the KOP is drop center, it is not any of the other things. The C Channel of the KOP is definitely not strong enough to cantilever something off of it. because you are not cantilevering you might as well run a dead axle set up.

That makes sense, thanks.

[BrendanB]

Originally Posted by LedLover96

Why can you not run a WCD on a KoP chassis?

Technically you can make a WCD using the KOP but it isn't the most efficient way. The team who made it escapes me but I know there is a photo here on CD.

How they did it was they took the outer most rails in the standard KOP frame and moved them inward so they ran flush with the inside rails. This meant all they had to do was put their KOP bolts through the holes with chain and sprockets and they had a WCD. Cantilevered in all.

This method could make for a great fall project for any team that doesn't want to spend money yet still wants to work towards custom drivebases. Who knows, we might do it this fall just as a learning experience!

[R.C.]

Originally Posted by MattC9

Do you have solid proof that WCD are lighter than any other drive?

Matt,

I can't think of another drive that would be lighter than a WCD other than a super pocketed sheet drive. I'm curious to see the weight comparison and sheet drive.

But WCD is decently light due to the fact:

-No outer Railing
-Minimal amount of parts.
-Smaller parts: Wheels/Sprockets/Gearboxes etc....

We switched over to WCD in the fall of 2010. Never looked back (thanks 973!), its such a nice system that 254/968 has perfected over the years.

-RC

[sdcantrell56]

While not the traditional wcd, doing one with fixed wheels and belts would without a doubt result in the lightest drivesystem in FIRST.

That said there is really no right or wrong answer. Do what works best for you. If your main manufacturing resources are sheetmetal then WCD might not be the best choice. It is possible and we have actually run a sheet WCD before but it's not the best use of resources.

[Kristian Calhoun]

Originally Posted by LedLover96

What does 25 do? why are they an exception?

Originally Posted by EricH

6WD flat. I don't know how they do it, but they don't bounce when turning, even with high-traction wheels. I think it has something to do with how they groove their tread, but I'm not sure.

At least, they used to do that. I'm not sure if they still do or not.

Jared from 341 made a really good post about our drive train about two years ago: http://www.chiefdelphi.com/forums/sh...5&postcount=31.

[Tom Line]

Originally Posted by SuperNerd256

No outer framing. Basically eliminates about 86" of outer railing (assuming a 37" long by 27" wide bot). Center wheel is direct drive, so less chain (6 chains per average 6WD, 4 for your average 6WD WCD).

Could you show the mathematics for that? West coast drives have to carry the same amount of force that a standard chassis chassis does. Keeping in mind that both have the same load requirements, I see no reason that one can't be engineered to the same weight as the other. West coast style introduces a rotational component that needs to be accounted for that astandard chassis does not require.

Nothing stops a team from direct driving on a standard chassis, and a standard chassis does not require bearing blocks.

[Walter Deitzler]

Okay, new questions to ask.

In my WCD design I have designed the wheels to be far enough from the outside to allow for interchangeable wheel sizes of 4in, 6in, and 8in. Is this a good idea? I have read somewhere that you use 4in wheels to save weight, go faster, and keep your wheels as far to the outside as possible. Is this true? Should I design my WCD to use one type of wheel?

Also, can you weld the AM Flanged bearings to standard aluminum wall? (6061 I think).

Thanks!

[Mk.32]

Generally speaking the bearings are pressed into the alum, or sometimes held in place with super glue if needed.

[Gregor]

Originally Posted by LedLover96

I have read somewhere that you use 4in wheels to save weight, go faster, and keep your wheels as far to the outside as possible. Is this true? Should I design my WCD to use one type of wheel?

Also, can you weld the AM Flanged bearings to standard aluminum wall? (6061 I think).

Thanks!

Smaller wheels will in fact make the robot go slower at the same gear ratio. Wheel size shouldn't be considered in terms of speed, as you should be adjusting your gear ratio to account for the wheel size. However the 4" wheels will save weight and widen your wheelbase, as opposed to 6" and 8" wheels.

Typically, teams press fit bearing, as opposed to welding them.