Advantages/Disadvantages of West Coast Drive

[EricH]

Originally Posted by RoboChair

Here is my only question for you, has 254 ever not done a WCD?

As a matter of fact, yes, I believe they have.

BEFORE the WCD was developed (2002-2004 timeframe), of course, but seeing as 254 is one of the developers of the WCD...

The WCD was officially unleashed in late 2003/2004 season, the result of a collaboration between 254 and 60. There are photos in CD-Media from 2001 showing both teams running elements of what is now known as a WCD, though 254 for some reason ran their chains outside their frame from a central gearbox that year (either one of which would, under the traditional definition, disqualify the drive as being WCD), and neither had more than 4 wheels on the ground (also disqualifying as a WCD under the traditional definition, which requires 6 (or more, depending just how traditional you want to get)).

So, more detailed answer: yes, but it's been quite a while and they were developing WCD when they did.


And now back to your regularly-scheduled discussion of the pros and cons of the WCD.

[Andrew Schreiber]

Originally Posted by RoboChair

Here is my only question for you, has 254 ever not done a WCD?

I'd bet $100 that 254 does a WCD next year, and another $100 that that is what we settle on as well.

It is quick, easy, and robust. Most of the design drawbacks for a particular game can be designed around with WCD without much effort, this year it was wheel spacing.

Here is my only question for you, why does "254 does it" make something a good design decision for a team without 254's resources?

[dirtbikerxz]

Originally Posted by Andrew Schreiber

Here is my only question for you, why does "254 does it" make something a good design decision for a team without 254's resources?

Because it does not take many resources to do a WCD, and by 254 doing it, they are proving that it is a good solution. Which means that is a good solution for not much resources. (Man my grammar was bad in that sentence.)

We are a low resource team, like really low resource, yet we do WCD with success.

[Billfred]

Originally Posted by Andrew Schreiber

Here is my only question for you, why does "254 does it" make something a good design decision for a team without 254's resources?

Originally Posted by dirtbikerxz

Because it does not take many resources to do a WCD, and by 254 doing it, they are proving that it is a good solution. Which means that is a good solution for not much resources. (Man my grammar was bad in that sentence.)

I think our definitions of "not many resources" differ. I've been on teams where the build budget was maybe $1,000, the machining resources stopped at that of a disused wood shop, and the mentor expertise didn't really include machining. I would wager my dollars to your donuts that that situation describes More Than A Couple Teams. I would also say those teams are less likely to have an inspiring season if they reached for WCD without more of a grasp of the situation than "254 does it and does well".

[Andrew Schreiber]

Originally Posted by dirtbikerxz

Because it does not take many resources to do a WCD, and by 254 doing it, they are proving that it is a good solution. Which means that is a good solution for not much resources. (Man my grammar was bad in that sentence.)

Then that would have been a better argument than "254 does it".

I'd disagree with that argument since it's not a function of raw number of resources but more a function of what type of resources and the allocation of them. For teams with tight budgets and resources using the KoP or VP DIAD may be better uses of tight resources. I don't see how 254-copy describes advantages or disadvantages for the purposes of resource allocation.

[JesseK]

For me, it's either WCD or KOP. Either can be purchased and put together with nominal amounts of machining and programming work.

Presuming you use all-COTS for either drive train, these are IMO, of course:

• WCD is easier to customize around an overall robot design since the frame consists of only 5-6 basic parts.
• WCD maximizes robot stability by putting the wheels at the outer-most maximum dimensions
• WCD makes it far easier to experiment with and find the right wheels - and then maintain them throughout the season
• WCD makes dealing with chains super-easy. If a chain snaps (literally) because of a wonky new offseason defense (@Nate @Matt .... ) then a fix requires just a few parts of adjustment rather than removal of anything.

• WCD reduces flexibility when it comes to bumpers. There are ways to design bumper mounts to make them secure, and most of them over-complicate the frame design when compared to the simplicity of WCD itself.
• WCD can be done with rivets, but IMO it is far simpler to design and execute if a team has a welding sponsor. The middle cross rail usually drives me up the wall, unless we have a welding sponsor.
• If welded, WCD frames are less forgiving if not properly cooled. The reliability of chains presumes the side rails are perfectly straight.
• WCD setups have very few COTS "plug-and-play" options that are designed specifically for WCD. Most gearboxes used in FRC will require some sort of custom mount in order to direct-drive one of the wheels in WCD. This isn't an insurmountable issue to fix for an individual team. Yet don't expect to go to the 3 major FRC gearbox suppliers to find anything that adapts non-WCD gearboxes to a WCD setup.

[Bertman]

I find this discussion interesting from the standpoint of the definition of WCD, KOP, & traditional when related to past baseline definitions. They seem to vary with how long you have been around. These definitions are very fluid and I believe will continue to be so. Just a thought.

[MichaelBick]

Originally Posted by JesseK

• WCD setups have very few COTS "plug-and-play" options that are designed specifically for WCD. Most gearboxes used in FRC will require some sort of custom mount in order to direct-drive one of the wheels in WCD. This isn't an insurmountable issue to fix for an individual team. Yet don't expect to go to the 3 major FRC gearbox suppliers to find anything that adapts non-WCD gearboxes to a WCD setup.

Both Vex and WCP make pretty much COTS "plug-and-play" gearboxes for WCD.

[frcguy]

Originally Posted by MichaelBick

Both Vex and WCP make pretty much COTS "plug-and-play" gearboxes for WCD.

Example of said WCP gearbox with integrated sprockets and bearing block. If we go WCD next year, we'll probably be using these.

[Billfred]

Originally Posted by MichaelBick

Both Vex and WCP make pretty much COTS "plug-and-play" gearboxes for WCD.

And before I even thought about working at AndyMark, we made a Toughbox Mini work for a chain-in-tube-with-coulda-been-cantilevered-wheels (but weren't cantilevered because this game is brutal) by getting the flat front plate, using the long output shaft cut to length, and pressing a bearing into the tube. Done.

[RoboChair]

Originally Posted by Billfred

I think our definitions of "not many resources" differ. I've been on teams where the build budget was maybe $1,000, the machining resources stopped at that of a disused wood shop, and the mentor expertise didn't really include machining. I would wager my dollars to your donuts that that situation describes More Than A Couple Teams. I would also say those teams are less likely to have an inspiring season if they reached for WCD without more of a grasp of the situation than "254 does it and does well".

You can make a WCD these days with a hack saw, a hand drill, and some aluminum tube. The gear box and bearing block options from Vex make producing a WCD a trivial task these days as long as you can drill some straight holes. This is how 5458 made their drivetrain this last season. You can make a 6 wheel drive for around $450 depending on your choice of gearboxes(~$150 and up) and motors.

[JesseK]

Originally Posted by MichaelBick

Both Vex and WCP make pretty much COTS "plug-and-play" gearboxes for WCD.

To an extent. I wouldn't call what we have a plethora of options that are specifically designed with WCD in mind. For a given drive train design we have 1 great product and a few other adaptable choices. If a team can't make an adapter plate of some sort, there's really only 1 SS and 1 DS product.

AM - practically non-existent because the mount points interfere with the chain runs

WCP - yes! We've used these for 2 years now and love both the single and double-speed options. WCP-WCD-DS lasted through 85 matches in 2016 during the preseason, competition season and post-season with zero issues. Zero. None. We snapped quite a bit of chain (broken links), but the gearbox kept on chugging.

VEXPro -
Single Speed: The single-speed double-reduction looks like it will work for WCD as-is, yet I have some reservations about longevity. There are effectively about 5.5 lbs cantilevered off of 2 mount points through plastic housing. I'd trust such a setup for a single competition. Yet I have reservations for so many matches between March 1 and November 31 in a game like 2016 (with considerations for transporting the robot so many times). It would require additional support somewhere, either from adapter plates or a super structure. So IMO it's not quite plug-and-play in WCD. My team could easily get it done, but I'm not sure for a typical team.

There also seemed to be a very large sensitivity to assembly tolerances on the VP Ball Shifter. I heard of multiple teams who had gear teeth sheer on the 3rd stage due to slight misalignments, and one such team was our alliance partner in the Finals at their 2nd event. It was something manageable, but I know my team would have to consider how rough the game is on drive trains before purchasing ball shifters.

These are, of course, my perspective based upon what I know about my teams strengths and weaknesses.

[dirtbikerxz]

Originally Posted by JesseK

VEXPro -
Single Speed: The single-speed double-reduction looks like it will work for WCD as-is, yet I have some reservations about longevity. There are effectively about 5.5 lbs cantilevered off of 2 mount points through plastic housing. I'd trust such a setup for a single competition. Yet I have reservations for so many matches between March 1 and November 31 in a game like 2016 (with considerations for transporting the robot so many times). It would require additional support somewhere, either from adapter plates or a super structure. So IMO it's not quite plug-and-play in WCD. My team could easily get it done, but I'm not sure for a typical team.

There also seemed to be a very large sensitivity to assembly tolerances on the VP Ball Shifter. I heard of multiple teams who had gear teeth sheer on the 3rd stage due to slight misalignments, and one such team was our alliance partner in the Finals at their 2nd event. It was something manageable, but I know my team would have to consider how rough the game is on drive trains before purchasing ball shifters.

These are, of course, my perspective based upon what I know about my teams strengths and weaknesses.

We've used VEXpro for 3 years now, and it relatively pretty easy to do WCD. We use bearing blocks, and all you have to do is turn the middle one upside down to get the required drop. This year we used this system, and the triple cim ball shifter and it worked like a charm. We supported the gearboxes by having a crossbar over the gearboxes and screwing into the mounting points on top of the plastic housing. Never snapped a chain, and just generally never had problems with the drivetrain at all this year. And we were definitely one of the more "violent" bots while crossing defenses.

[GeeTwo]

Originally Posted by Billfred

And before I even thought about working at AndyMark, we made a Toughbox Mini work for a chain-in-tube-with-coulda-been-cantilevered-wheels (but weren't cantilevered because this game is brutal) by getting the flat front plate, using the long output shaft cut to length, and pressing a bearing into the tube. Done.

While not canonical WCD, I bet that a couple of TB Micros with long hex shafts at each end of the drive train would interface with rectangular tubing even easier. I find myself liking the idea of using six TB micros and six CIMS on six wheels, with chains inside a 3"x1" tube to transfer torque among the wheels on each side as needed. Not really cheap, but much less than swerve, and eminently functional in case of chain failure. If I get to call the name, make it Gulf Coast Drive.

Originally Posted by roboruler

Sounds really heavy.

Yes. I wouldn't want to use it every year, but it might have been worth it to play Stronghold with a drive train that works almost as well even if you lose a chain. We could have spared the extra few pounds this year.

[roboruler]

Originally Posted by GeeTwo

While not canonical WCD, I bet that a couple of TB Micros with long hex shafts at each end of the drive train would interface with rectangular tubing even easier. I find myself liking the idea of using six TB micros and six CIMS on six wheels, with chains inside a 3"x1" tube to transfer torque among the wheels on each side as needed. Not really cheap, but much less than swerve, and eminently functional in case of chain failure. If I get to call the name, make it Gulf Coast Drive.

Sounds really heavy.