Drive Train Choices
 

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?

Re: Drive Train Choices
 

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!

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

Re: Drive Train Choices
 

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.

Re: Drive Train Choices
 

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

Re: Drive Train Choices
 

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

Re: Drive Train Choices
 

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.

Re: Drive Train Choices
 

We just want to try something new so we have some experience during off season instead of fulling around with it during build. I think its safe to say that my team has just about mastered 4 - 6 Wheel Drive. We want to try new stuff to see if we like it and want to use it in a future year instead of the same 4 - 6 drive every year. We just don't know which one to pick to start with.

Re: Drive Train Choices
 

IMO there's still a ton of development your team can do within 4-6-8 wheel drives.

Once you've iterated through those, the only one I'd suggest next would be butterfly or octocanum. But, I'd say continue on the route of further refining your drives. Try belts in a 6 or 8wd, try custom gearboxes, try new wheels, etc...

Re: Drive Train Choices
 

"Which drivetrain should we prototype in the off-season?" is a whole different question than "what are the advantages of each drivetrain?"

If all you're looking for is a simple answer to the former question, I'd recommend mecanum for a few reasons. One is that it can be mastered in a season. Two is that if all else fails, swap out regular wheels and you'll have a drive that you're familiar with. Three is that it will make a good demo bot all by itself, since most people aren't familiar with mecanum wheels.

Hope this helps.

Re: Drive Train Choices
 

I'll echo what everyone else has said about making sure your 6wd is perfect. It's important to have a strong "default" drive system. However, I don't think you came here to read a couple of posts that are not helping you make a decision like you wanted! However, you could still experiment by designing or iterating your own gearbox (or other improvements to a standard Tank system)! My team is currently examining this possibility because we recently acquired new machining resources and it would be a cool project and a valuable resource to have in our pocket.

Hm... Well, Mecanum drive is a good one to prototype during the off-season. It's a challenging exercise for your programming and mechanical subteams (which is a reward of itself). It also opens the door for Octocanum drive in the future (which I've wanted to look into for a while). The wheels and gearboxes are going to be kinda costly but other than that it can be mounted to a standard C-Channel chassis, which is nice if you don't want to mess with a special setup system.

I've wanted to check out Butterfly drive for a bit as well (if you were unaware, Butterfly drive is Octocanum but which omni wheels instead of Mecanum wheels, it has the added maneuverability without the strafing and cost of the wheels). It's a fancy system that will also challenge your mechanical and electrical teams, as the development of a good, reliable wheel-switching system could be a bit of work. This is also a fairly new drive system, so there is a lot of experimentation that can go into it because not much has been done with it already. The machining of the modules might require resources beyond the standard team's availability though, so research into a design is required beforehand.

If you don't want to venture too far away from your Tank drive systems, Drop Center 8 Wheel Drive has been becoming increasingly popular. I'm not sure what the strict advantages are to it over 6wd, but there are some teams now (some of whom are very high-leveled) who are swearing by it now, so there must be something that makes it so desiring.

It all depends on what kind of drive train you want to have up your sleeve. If your team really just has an itch to play around with a drive train, then present a couple ideas to the team and see what sticks! You might find one that really interests all the people on your team. Just remember to consider cost, machining requirements, needed man-power, general complexity, and the support the FRC community can provide in the endeavor!

Looking forward to see what you guys come up with! Feel free to share if you make something cool!

Re: Drive Train Choices
 

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).

Re: Drive Train Choices
 

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.

Re: Drive Train Choices
 

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

Re: Drive Train Choices
 

As a big fan of tank drives, I'd suggest you try the 8WD, with the two middle wheels lowered. I only know one team that does it, 2630 from Israel, but I'm sure it's a common design, I just never looked into existing designs (since I know people on 2630 that does it so when I have a question I just ask them).
The great advantage of this design is that you have a very small wheel base, even smaller than dropped-wheel 6WD, and since you have two lowered wheels, it only rocks when you have high-speed collisions. The major disadvantage is it's way more complex than 4/6WD, and you can't use the KOP to build it (not enough wheels, you need special c-channels since the KOP ones only have one lowered hole).
2630's drive in 2010, first time they did it. It's kinda hard to see but if you look closely you'll notice the external wheels are a bit higher than the lower wheels.

Did you ever do a west coast drive? If not, you can try that too. It too is harder to make than the standard drive, but it clears up a lot of space inside the chassis, which makes component placement much easier, and in some cases allows for better game mechanisms.

Side note: most of 2630's 8WDs were west coast drives, if not all.

EDIT: Sorry, I didn't see the "different wheels" post. I'm keeping the post though, for anyone else who might be interested in trying something new and looks at this thread.