WCD vs Standard

[Gray Adams]

Don't weld or weld near bearings. The grease has a bad habit of lighting on fire.

Originally Posted by LedLover96

So you do want to put your smaller wheels farther to the outside, to widen your wheelbase? Putting them in the same spot you would put an 8in wheel would be pointless, I am assuming, because the wheel base would be the same, but you wouldn't get better speed?

And what is "press fitting"? Could you elaborate.

You need less gearing for 4" wheels though, and they have a lower mass (and therefore moment), so it can save you weight even if you don't put them further out on the frame.

Press fitting refers to having a hole that's just slightly smaller than the diameter of the bearing, so when you press it in, it doesn't come out. It's kind of tough to figure out what size hole to make and then make it accurately (within a few tenths).

[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.

[Walter Deitzler]

Originally Posted by Gregor

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.

So you do want to put your smaller wheels farther to the outside, to widen your wheelbase? Putting them in the same spot you would put an 8in wheel would be pointless, I am assuming, because the wheel base would be the same, but you wouldn't get better speed?

And what is "press fitting"? Could you elaborate.

[Garret]

And what is "press fitting"? Could you elaborate.

Press fitting usually means (at least how I have interpreted it in FRC) the hole is slightly undersized such that the bearing needs to be pressed in quite hard, this will result in a tight fit that will hold the bearing in place.

[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.