Drive Train Choices

[tuXguy15]

Our team wants to experiment with different drive trains and was wondering which would be the best to play with. What are the advantages and disadvantages of them?

[KrazyCarl92]

Originally Posted by tuXguy15

Our team wants to experiment with different drive trains and was wondering which would be the best to play with. What are the advantages and disadvantages of them?

What does your team have experience with? What are your manufacturing resources? Where do you have/lack experience (CAD, programming, machining, sensors, etc.)? Are you looking to work on systems you are inexperienced in or perfect ones that you already have a bit of experience with? Are you looking to work mainly with the kit frame and just improving upon it, or going after a custom construction?

An example of how these questions matter: a team with significant sheet metal sponsors and access to water jet cutting and a sheet metal break will likely design something differently from a team with mills, lathes, and experience using box tube aluminum. Heck, 1714 makes the majority of their robot out of lexan because they have a big sponsor that specializes in acrylics and other plastics!

[bbradf44]

My team is currently looking into octocanum. All the maneuverability of mecanum plus the traction of tank without the time and price of swerve

[MichaelBick]

Originally Posted by tuXguy15

Our team wants to experiment with different drive trains and was wondering which would be the best to play with. What are the advantages and disadvantages of them?

I highly reccomend perfecting your 6wd before you look any further into special drivetrains. A good 6wd will carry your team for many years. Once you have a solid drive, you can expand from there, based on what your team wants.

While mecanum, swerve, octocanum, and nona(and many others) are known to provide extra "manuverability", I personally find that this manuverability is often not used correctly, and better performance will usually come from more driver practice instead. I think it would be more worthwhile your time to look into a drivetrain that uses less resources or improve your current drivetrain(reduce resources too).

One promising drivetrain is butterfly. Butterfly can be built using very little resources. In addition, it offers performance increases over typical 6wds like getting out of t bones, straighter tracking for auton, and being unturnable(also butterfly can be built to have two different speeds).

There are many additions you can do to a 6wd too. We personally have added motors, used wider wheels, reduced resources to build our 6wd(primarily using new COTs parts), and reduced weight. Other notable additions that we are testing during the offseason are belts and drop down omnis/ball casters to get out of tbones.

[nicholsjj]

I believe the best advice I ever read on drive trains was a quote in a paper by team 33 that said ~"the best drive train in robotics is the one that gets you to the spot on the field where you want to be as quickly and as reliable as possible."

The Simbots have a terrific resource on the different drive train types including a general weighted table. http://www.simbotics.org/resources/m...rain-selection

The only addition to the ones mentioned on that page would be the octo./butterfly drive which had been mentioned earlier in the thread.
For butterfly I would start looking here http://www.teamneutrino.org/seasons/...bot/butterfly/ on team Neutrino's page.

This site has terrific pictures/caddings on the different drive types. http://www.frc-designs.com/drives.html

[BJC]

Originally Posted by nicholsjj

I believe the best advice I ever read on drive trains was a quote in a paper by team 33 that said ~"the best drive train in robotics is the one that gets you to the spot on the field where you want to be as quickly and as reliable as possible."
...

I think you are talking about this thread Post #24. Our best two seasons are arguably 2011 and 2013. In both of these seasons we used a chassis that we prototyped in the offseason. The 2011 one was had articulating back wheels and the 2013 one was just a normal 8wd. The benefit from the articulating wheels was marginal in hindsight but the fact that we already had a drivetrain solution we knew would work was invaluable in terms of speeding up the design and build process.

Attempting to follow the 2011 and 2013 success trends we are prototyping the second iteration of our 2013 drivetrain this summer/fall. I only recommend that once you pick a drive type you stick with it over the course of a couple seasons and refine it each offseason. It's pretty hard to go wrong with this tactic no matter what you choose.

Regards, Bryan

[Koko Ed]

Originally Posted by BJC

I think you are talking about this thread Post #24. Our best two seasons are arguably 2011 and 2013. In both of these seasons we used a chassis that we prototyped in the offseason. The 2011 one was had articulating back wheels and the 2013 one was just a normal 8wd. The benefit from the articulating wheels was marginal in hindsight but the fact that we already had a drivetrain solution we knew would work was invaluable in terms of speeding up the design and build process.

Attempting to follow the 2011 and 2013 success trends we are prototyping the second iteration of our 2013 drivetrain this summer/fall. I only recommend that once you pick a drive type you stick with it over the course of a couple seasons and refine it each offseason. It's pretty hard to go wrong with this tactic no matter what you choose.

Regards, Bryan

Our operator is obsessed with creating a version of your 2013 drive train for our team (we used Mechanums last year. It was good for qualifications but cost us in the elims. We got put out by strong defense @ FLR and I beleive it cost us from being considered as a viable pick at the championships in spite of performing well. People just don't like Mechanums).

[Racer26]

Building a test bot with mecanums can be a valuable learning experience.

Put it up against your 6wd kitbot, and you'll see quite quickly why most teams refuse to use them. You lose every time in a pushing match, if you've got mecanums, and they're a tank.

IMO, the only "omnidirectional" drivetrain worth building for a competition bot is a swerve. The problem, is that the mechanical and coding complexity of swerve drives tends to make them unreliable, AND it makes building one eat a significant portion of your build season.

During my 9 competition seasons with 1075, we built:

2003: Steered track unit, unpowered trailing wheels. A bit like a snowmobile in reverse, steering the track. Allowed turning at full speed to reach the top of the ramp first.

2004: 14" bike tired 4wd, the trailing wheels articulated vertically with the arm, so that hanging from the bar was primarily a "lift the wheels, rather than the bot" motion.

2005: Didnt compete

2006: 2+2 Coaxial Swerve, All 4 wheels driven from same gearbox, using 1 turn pots for position feedback. I couldn't tell you how many pots we snapped with this robot. It was awful. For the offseason, we built the first iteration of our belted drives.

2007: Belted drives (motors inside the belts driving a shaft running the length of the unit, through the guts of a supershifter, a bevel gear, then chain to the drive cog). I believe we competed with the 3rd iteration of this drive. 4th iteration in the offseason. We kept having problems with belt breakage, many of the iterations added deflection (sometimes variable) to the bottom surface of the track.

2008: 5th iteration of the belted drives. Partway through the offseason, we switched to a more standard 6wd drop center, and walked away with BE7.

2009: 2+2 Swerve again, only this time, with encoders, and independent motors for each wheel. MUCH better than 2006.

2010: 2+2 Double Sided Swerve. Essentially the same design as 2009, only with an extra set of wheels on top, in case we flipped going over the bumps.

2011: Another iteration of the 2+2 Swerve.

2012: Another iteration of the 2+2 swerve.

Then I left 1075 to go work with 4343.

2013: 1075 built a 4wd, front two omni drive, and 4343 built the kitbot drive.

Each year 1075 did the swerve? The drivetrain ate up so much of their season, that they were scrambling to get the end effectors working properly.

Working with 4343 in 2013 using the kitbot drive? That made life SO much easier.

[tuXguy15]

Hey guys by drive train i mean different wheels like mecanum wheels, swerve wheels, etc. Any kind but the standard FIRST KOP wheels

[Akash Rastogi]

Originally Posted by tuXguy15

Hey guys by drive train i mean different wheels like mecanum wheels, swerve wheels, etc. Any kind but the standard FIRST KOP wheels

There are omni wheels (90 degree rollers) and there are mecanum (45 degree rollers) but there are no specific wheels a swerve needs.

The AM Hi-Grip wheels in the kit are great, and they are making improvements to them for 2014 to prevent failures that some teams saw this year. You can try out AM Plaction wheels which are pretty sweet and affordable. VEXPro also offers a variety of wheels to try. Then there's Colson wheels which 11 and many others use, but they require a hub that can be purchased at WCProducts.net

PM me if you want some specific suggestions for your team in particular.

[BJC]

Originally Posted by Koko Ed

Our operator is obsessed with creating a version of your 2013 drive train for our team (we used Mechanums last year. It was good for qualifications but cost us in the elims. We got put out by strong defense @ FLR and I beleive it cost us from being considered as a viable pick at the championships in spite of performing well. People just don't like Mecanums).

I'm glad that we could serve as inspiration. That's really what this program is all about.

In my own experience Mecanums are definetly looked at as inferior and will drop a robot on the pick list if not straight off of it. Especially when looking for a second pick, alliances are generally looking for robots that can play defense if needed. This combined with the general stigma against Mechanums makes them a mark against you in the scouting department even if your robot is quite good.

Good luck on all your future drivetrain endeavors! (and I'd love to hear thoughts if your team ends up designing/building a WASPdrive.)
Regards, Bryan

[Clem1640]

Originally Posted by MICHAELABICK

I highly reccomend perfecting your 6wd before you look any further into special drivetrains. A good 6wd will carry your team for many years. Once you have a solid drive, you can expand from there, based on what your team wants.

While mecanum, swerve, octocanum, and nona(and many others) are known to provide extra "manuverability", I personally find that this manuverability is often not used correctly, and better performance will usually come from more driver practice instead. I think it would be more worthwhile your time to look into a drivetrain that uses less resources or improve your current drivetrain(reduce resources too).

One promising drivetrain is butterfly. Butterfly can be built using very little resources. In addition, it offers performance increases over typical 6wds like getting out of t bones, straighter tracking for auton, and being unturnable(also butterfly can be built to have two different speeds).

There are many additions you can do to a 6wd too. We personally have added motors, used wider wheels, reduced resources to build our 6wd(primarily using new COTs parts), and reduced weight. Other notable additions that we are testing during the offseason are belts and drop down omnis/ball casters to get out of tbones.

As a team that likes swerve and has done swerve for the past four years, I would strongly recommend building your base competencies with 6wd first. 6wd is pretty darned good. Master this first. After you've got 6wd nailed, expand to other options.

We use off-season (summer-fall) projects to experiment with new concepts, both drive-train and in other areas. This allows us to build institutional knowledge outside the frantic pace of build season.

[Oblarg]

Originally Posted by Clem1640

We use off-season (summer-fall) projects to experiment with new concepts, both drive-train and in other areas. This allows us to build institutional knowledge outside the frantic pace of build season.

This, here, is the crux of good FRC drive development. The time for crazy ambition and reach-goals is the offseason, when you have neither strict time constraints nor immediate demand for success.

As a rule for drive, I promote the following: During build season, you should never consider a drive system which you have any doubt about your ability to execute. Any sufficiently complicated drive system should not even be on the table for build-season unless you have successfully executed it within the working memory of the team. The best way to build up your catalog of usable drive designs is thus to devote time in the off-season to experimentation with new designs.

Keep in mind that it is human nature to be overly-optimistic (often to silly extents), and that you must make a conscious effort to place your judgment of what you are able to do significantly below your initial feeling. This holds true for all design goals, but is especially pertinent for drive. For a drive, reliability trumps every single other concern, no exception. If your robot is unable to move, you are not able to play the game.

[KrazyCarl92]

Originally Posted by Oblarg

For a drive, reliability trumps every single other concern, no exception. If your robot is unable to move, you are not able to play the game.

Rules compliance. Sadly this is overlooked nearly as often as reliability. I would say those are the two criteria that every single drive train in FRC should meet. The kit bot meets both if done according to directions, so there is truly very little reason for a drive train that is not reliable and rules compliant.

[cadandcookies]

Originally Posted by tuXguy15

Our team wants to experiment with different drive trains and was wondering which would be the best to play with. What are the advantages and disadvantages of them?

I (and many of the other people here) could probably fill multiple encyclopedia-sized tomes with the advantages and disadvantages of different drive trains and configurations of drive trains. There's an entire world of custom drive trains that opens up the moment you step outside of the appealing and excellently designed kitbot-shaped box.

I'll reiterate for a moment what KrazyCarl said-- before you even start thinking about what kind of custom drive train you're going to build, consider very carefully your resources-- what kind of budget does this have? How much time is your team willing to spend developing it? What kind of sponsors do you have? What are the lead times on parts from those sponsors (we have a waterjetting sponsor that needs us to give them CAD files at least three weeks before they manufacture, which limits their use during build season)?

Once you've answered all those questions, then brainstorming is a good idea-- if it's just for the joy of designing something out of the box, then you might very well consider octocanum or swerve drive or any of the other myriad of cool custom drive trains out there-- if you're developing it for competition, your goals are probably quite different. If you're developing specifically for competition, in fact, you'll probably want to stick to making a 6WD that you can manufacture and start driving super fast, in addition to being as flexible as at all possible. There has never been a year where you couldn't complete the game challenge with a well-designed 6WD (at least in recent memory).

In terms of awesome projects for drive trains, a lot of great ones have already been mentioned-- an octocanum is a very cool project (in fact that's what my team has been working on). Butterfly is, as mentioned, a nice, relatively simple project (considering that 3928 has so kindly used a good deal of COTS parts and posted many pictures). This late, I wouldn't suggest developing swerve-- you might be able to pull it off, but there's a lot of mechanical and programming complexity there.

Another suggestion would be to CAD all of the above drive trains-- it's good practice and you'll learn a lot about your program of choice. And CAD has that nice thing about being free. If you do that, then you can look at all your designs and pick out the one that makes most sense/ you'd like to build the most.