WCD vs Standard

[Walter Deitzler]

What is the advantage of a WCD over a standard drive? Why would you choose to do a WCD 8 wheeled or WCD 6 wheeled over a standard 8 or 6 wheeled drive?

[Akash Rastogi]

Hey Walter,

There are several threads that discuss the pros and cons of each style of drive. I search should yield you the results you are looking for.

Let us know if you can't find them.

-Akash

[Walter Deitzler]

I tried finding them, but only found WCD vs. Swerve and many pictures of a WCD.

Some things I've found on my way asking the same questions you do:
http://www.chiefdelphi.com/forums/sh...&highlight=WCD
http://www.chiefdelphi.com/forums/sh...&highlight=WCD
http://www.chiefdelphi.com/forums/sh...&highlight=WCD
http://www.chiefdelphi.com/forums/sh...&highlight=WCD
http://www.chiefdelphi.com/forums/sh...&highlight=WCD
http://www.chiefdelphi.com/forums/sh...&highlight=WCD
http://www.chiefdelphi.com/forums/sh...&highlight=WCD

All in all, WCDs are lighter, allow for direct drive (more efficient), and the wheels a bit farther out for better turning. 6WD vs. 8WD is mainly based off of whether or not the robot has to traverse an object (climbing over the bumps in '12 and '10). 8WD also allows a smaller wheelbase, so that a robot can be more maneuverable, but the turning difference is often nothing a 6WD can't do, and the extra weight isn't worth the little bit of turning help on a flat field.

[Walter Deitzler]

Thank for that Andrew, some of those links will be helpful, but as for the 6 vs 8 wd, I phrased the question poorly, that is not what I am looking for. The standard vs. WCD ones are useful though!

Thanks!

[avanboekel]

SuperNerd's last link is probably what you are looking for (If I am reading your question right, you want to know the pros and cons of a WCD vs a non WC 6WD, not 6wd vs 8wd).

http://www.chiefdelphi.com/forums/sh...&highlight=WCD

[MattC9]

Originally Posted by SuperNerd256

All in all, WCDs are lighter, allow for direct drive (more efficient), and the wheels a bit farther out for better turning. 6WD vs. 8WD is mainly based off of whether or not the robot has to traverse an object (climbing over the bumps in '12 and '10). 8WD also allows a smaller wheelbase, so that a robot can be more maneuverable, but the turning difference is often nothing a 6WD can't do, and the extra weight isn't worth the little bit of turning help on a flat field.

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

[Walter Deitzler]

Okay, so in the 4th link, I saw that WCD's use a live axle, vs. a Standard using a dead axle.
First off, could some elaborate on the difference between the two? I found the posts kind of confusing as to the difference (the live axle is spun by chain or gears or motor while dead axle is just sitting there, not powered?)

Next: Why would you choose a live axle over a dead axle, if the center wheel is lowered, thus making your robot rock between the front and back wheels? It seems that live axles (if I have their definition correct) would make the 6 wheeled work like a 4 wheeled when it turns, porblematic. But, when observing many WCD's, I do not see slick wheels or omniwheels to offset the traction/turning problems associated with a 4 wheeled.

[JosephC]

To my understanding, A live axle is one that supports part of the weight of a robot and drives the wheel(s) connected to it. A dead axle is one that carries part of the weight of a robot but does not drive the wheel(s). The wheel(s) rotate on the end of the dead axle.

[smistthegreat]

Originally Posted by LedLover96

Okay, so in the 4th link, I saw that WCD's use a live axle, vs. a Standard using a dead axle.
First off, could some elaborate on the difference between the two? I found the posts kind of confusing as to the difference (the live axle is spun by chain or gears or motor while dead axle is just sitting there, not powered?)

Next: Why would you choose a live axle over a dead axle, if the center wheel is lowered, thus making your robot rock between the front and back wheels? It seems that live axles (if I have their definition correct) would make the 6 wheeled work like a 4 wheeled when it turns, porblematic. But, when observing many WCD's, I do not see slick wheels or omniwheels to offset the traction/turning problems associated with a 4 wheeled.

All of your information is correct, but you make a couple of incorrect conclusions. Yes, live axle is when the axle itself is powered, and dead axle is when only the wheel is powered. Also, you are correct about the drop center making it turn like a 4 wheeled drive. However, this 4 wheeled drive now has a shorter wheelbase, making it easier to turn. The whole point of dropping the center wheel is to shorten the wheelbase enough to where it turns smoothly without adding slick or omniwheels

Originally Posted by MattC9

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

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).

[BrendanB]

WCD's are known to be lighter but they aren't always lighter.

[EricH]

Originally Posted by smistthegreat

All of your information is correct, but you make a couple of incorrect conclusions. Yes, live axle is when the axle itself is powered, and dead axle is when only the wheel is powered. Also, you are correct about the drop center making it turn like a 4 wheeled drive. However, this 4 wheeled drive now has a shorter wheelbase, making it easier to turn. The whole point of dropping the center wheel is to shorten the wheelbase enough to where it turns smoothly without adding slick or omniwheels

And the other implied conclusion--dead axles don't need a drop--is also an incorrect one. A 6WD, dead or live axle, without the drop will act almost exactly like a 4WD with all traction wheels (there are exceptions, like FRC25); so will an 8WD without any drop.

[Garret]

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).

How are you getting 86" I would think that you are only eliminating 74" of railing, though I have never built a WCD so I may be off. Also I have seen plenty of plain non-cantilevered 6WD robots with direct drive on the center wheels.

However I do know that with the WCD it allows for wheels to be removed much easier because the shafts do not need to be removed.

[Walter Deitzler]

Originally Posted by EricH

And the other implied conclusion--dead axles don't need a drop--is also an incorrect one. A 6WD, dead or live axle, without the drop will act almost exactly like a 4WD with all traction wheels (there are exceptions, like FRC25); so will an 8WD without any drop.

What does 25 do? why are they an exception?