Re: Best Drive Train
 

There is no universal best drivetrain, but if you look at complexity and cost vs experience, you CANNOT go wrong with the Kitbot on Steroids. It takes 3 hours to build, a couple more hours to wire and program, and it is a regional winning drive train. Heck, I bet there are teams that have gone to Einstein with this drive train.

Re: Best Drive Train
 

I would agree that there is no best wheel. But, I believe the universal best design concept is one like our butterfly drive, where you are able to incorporate 2 different types of wheels (we chose 1 fast omni & 1 custom wheel that provided traction) that provide features that the other one could not solely do by itself. This was a big thing that we took into consideration when scouting and selecting other teams for our alliance, as some of them had drivetrains (I believe mechanum was one) where they could easily be pushed around and couldn't hold their ground and play defense, which was fairly important in Ultimate Ascent.

Re: Best Drive Train
 

If this is the reasoning, why is it better than swerve?

Re: Best Drive Train
 

If you need help with your small team, I invite you to contact me or another 3476 member. My story:
Last year, I was a freshman, and brought CAD design to the team. We had very limited funds, tools, manpower, or space. We still build our robots out of extruded aluminum in a 2-car garage with a tabletop chopsaw and bandsaw. We built a simple robot- and won SDR with it. We had 15 students on the team, with a ~7 member "core" team. After that season, we impacted over 20,000 people and had our program grow to 22 students representing 16 different high schools and 6 homeschoolers.
We simply worked hard, and because of that we eventually got rewarded for that effort. Anyone can do that.

Re: Best Drive Train
 

1) It's WAAAY more reliable then swerve. We never once had any major issue with our butterfly drive train this year (with the exception of breaking an omni during practice because we ran over a floor power outlet. We can also lose pneumatics (such as we did in final matches #2 & #3 at North Star and we can still drive just on omni's. If we lost an encoder with the swerve drive (ie. got unplugged), which happened a few times too many last year, we couldn't drive and it took some power cables with it.
2) It's WAAAY easier to fix then swerve. To fix a butterfly module, all we had to do was to unbolt 1 bolt and we could easily change out the module ("plug-and-play" if you will). We would just have to remove 2 additional bolts to get to the actual drive train itself. Now to fix the swerve drive, we had to work in crammed quarters trying to unbolt a bolt (which wasn't fun) and to fix wiring issues.
3) It's WAAAY simpler. The mechanics behind the butterfly drive is so much simpler then the mechanics behind the swerve drive. The fabrication and assembly of the butterfly drive was much quicker than the swerve drive. We were able to machine the parts for our butterfly drive ourselves because they didn't need to have that much precision vs getting precision lazer cut parts at our sponsor for our swerve drive modules. Assembly time was MUCH faster (~2 hours to assemble 10 butterfly modules vs 9 HOURS PER swerve drive). It's worth noting that the programming behind the swerve drive is quite complex versus the simple coding required to drive the butterfly modules. It's this simplicity that makes butterfly drive more reliable and easier to fix than the swerve drive.
4) It's WAAAY lighter and smaller. Each swerve module weighed ~6 pounds vs the ~1-2 pounds per butterfly module. I can easily hold 2 butterfly modules in my hands vs 1 large swerve module. Our chassis was also 'designed' to easily accomodate the butterfly modules.

Re: Best Drive Train
 

Saves motors, time, and is incredibly easy to use. If you want a truly great swerve, you have to use 8 motors, which is a lot of the motors you have and use. An octocanum or butterfly is just as maneuverable and only uses 4 motors, but there is no pushing power to the side. Why is pushing power on the side needed? And as said, too much easier. Swerve is cool but fairly wasteful.

Back to the original post, as stated there is no perfect or best drivetrain. Discuss what is needed (maneuverability for an intricate field, or pushing power for obstacles). My personal favorite is octocanum, because it's easier to design and make and maintain. And it covers all your bases (it's two drivetrains!)

Re: Best Drive Train
 

Sounds legit. :D

Re: Best Drive Train
 

Well, that escalated quickly.

Re: Best Drive Train
 

Well put. I think the "best" drivetrain is one that is KISS'ed to fit YOUR needs. Sure you could spend the whole off season developing a super advanced wheel and drivetrain, but when push comes to shove, the simplest and easiest drivetrain will *almost* always excel the more complicated drives. As I stated earlier, there are more things that can (and will) go wrong in a more complex drive.
Another thing to consider for the "best" drivetrain is size and weight. I believe that the one listed below is a bit overkill. A robot should *generally* need only 4 "modules", which reduces a lot of weight and a lot of those "hole"y robots.

Re: Best Drive Train
 

Motors this year don't really matter. Honestly my view on it is you go all the way or you stay with the basics. We like our WCD because it is the fastest or one of the fastest in machining and assembly. This gives us more time to program, iterate, and practice(even more than butterfly or octocanum). For 99.9% of teams this is going to boost their performance more the the "extra" maneuverability will.

In response to runneals your points for 1 and 2 can be wrong. I've seen 1717 win the LA regionals in 2012 running through elims on 3 modules working(they replaced for the finals). Also with a fully independent module it is quite easy to make a module replace with the removal of 3 screws. Not quite as little as your butterfly but still very little.

Re: Best Drive Train
 

So there really isn't a "Best" drive train. It really is what the team prefers, or works best with. My team has done a 4 wheel tank drive using 2 speed shifters in the long configuration. Our drive train is very sturdy, and is great at pushing other robots out of the way. We have been using our design for the past two years, and have had no complaints.:)

A drive train that I personally want to design, test, and see how well it fares compared to our current is swerve drive.

P.S. If anyone saw 4471's robot at championship, that's our twin, both teams had difficulties with playing offense, so we were a defensive robot, and were pretty good at it honestly.

Re: Best Drive Train
 

Reading the original post i cant see any indication the poster was asking about resource draw, ease of maching, development time ect ect. from what i can tell he was just asking which is best, which is why i voted swerve, a perfected (shifting) swerve drive is the best drive train in FIRST. It allows for more versatility and options then any other type of drive train

Re: Best Drive Train
 

These two are not functions of concept but rather of execution. We are also in an exactly 0 failure year, and most of the components have never failed once in 4 years. Preventive maintenance on what are very few potential failure points (swapping wheel treads, and...well, basically that. Maybe a few things that take longer to pick up the wrench than to fix) is done off-robot after a quick switch; all 4 in maybe 5 minutes. There are very few things that could go really wrong that would require serious disassembly to fix.

Work, resources and weight I agree with (though ours isn't so long), but that's not the initial selling point you mentioned, which is why I asked. Motors I'm less worried about after this year. I can't imagine what I'd use all of them for. We did fully independent swerve and a 30 point climb with a shooter and allocations for a floor pickup and still didn't manage to run through them all.

Actually there's no pushing power along any other axis, which is a huge advantage when used correctly, but I understand that's not your point.

I have never seen an omni robot exhibit actual holonomic drive--full control of orientation while translating along any vector. Is this a function of physics or of execution? I can't tell from your page how the butterfly modules are oriented. If you had a real-time sequence of translational vectors and orientation headings, could (theoretically) you move through them simultaneously at will? (If so, remind me to make you do that when I want to push you :P)

Re: Best Drive Train
 

The only addition I would make to your drive base would be the addition of a strafe wheel in the center of your robot. You had the right idea with the butterfly drive, its pretty much a Jump Drive, but in order to make better use of your omni's I would have put a strafe wheel in the middle, otherwise you would have been better off just building a multi speed gearbox. Don't get me wrong, I love your butterfly concept, in fact, our team my try it out this summer, but you need to have a strafe wheel if you have omni's.

Re: Best Drive Train
 

We had Chris come in and give a seminar at Michigan State Championships on drivetrains. His insight is pretty amazing. He actually talked about this paper, and how it really no longer applies to FIRST robots. It'll tell you if you can turn, but beyond that the physics don't really work with FIRST anymore. The paper was written when teams used metal cleats that acted very different than roughtop does now. He went into the friction characteristics of interlocking materials versus ideal ones, and talked about torsional stiffness, weight placement, etc.

For instance - a major mistake our team has made twice is to directly center the weight in a 6 wheel drivetrain over the center wheel (2011, 2013) on a semi-tall bot. The result is a robot whose center of gravity constantly shifts. That creates a really ugly chatter through turns even with a very stiff frame. It also doesn't like driving straight because the weight shifts when you accelerate then shift forward again when you hit the brakes. It was really eye-opening, and explained why our driver spent the majority of the year driving with only two wheels on the floor :D