Re: Best Drivetrain
 

They have used the same basic drive and arm strategy for a while now.

But I am sure they do NOT use the same mechanism from year to year! We were all surprised when they unveiled the V6 in 2007. They improved it the next year.

Oh, by the way, if you're going to accuse 118 of this, then you also need to go after the following:
--254/968 (drive)
--60 (drive)
--25 (drive)
--330 (most of the robot, 2005, 2007-2008)
--16 (drive)
--233 (arm and drive)

You see my point? A lot of teams build on old designs. They don't necessarily use the same parts (which is also prohibited--no build pre-kickoff, and no re-using mechanisms from old robots). So I'm guessing that they just say, "Does this work for the game? If not, how do we change it?" and then re-engineer to optimize for the new game. They build in 6 weeks just like every other team.

Re: Best Drivetrain
 

That is quite an accusation, and I am sure they did build the whole thing from scratch after the kickoff date.

Re: Best Drivetrain
 

once you build a drivetrain, it becomes very easy to build again from scratch, so although it may seem prebuilt (because they finish so fast) its not, its just they have all the resources set up to build something, all bugs were worked out on the other system, and all upgrades were prototyped.

I know for a fact it took us 3 weeks to build our Linkage drive during build season, and I know we could put another one together (given we have metal to do so) in about 4 days. Once you have a plan, things come together very easily.

Re: Best Drivetrain
 

wrong answer my friend...

Your first assumption that is completely wrong is that they have been using the same mechanism each year. Look at their DT last year and this year....they are not the same, although they may accomplish the same result (swerve/crab drive that totally rocks)


What else have you heard about other teams?

I guarantee they build the entire thing in their given timeframe.

You cannot make allegations with no support against other teams on this forum, its not fair to them, or to anyone else that cruises chiefdelphi because then someone has to take the time to explain to you how wrong you are about this.

There is no rule in FIRST about tweaking an old design and using it again in a year, this is the advantage experience brings.

Re: Best Drivetrain
 

The robonauts have been using a swerve drive since 2005. Each of their robots have had turreted manipulators seated on top of it during those 4 years. The similarities end quickly after that. They have constantly evolved, just unveiling their "V6" last year, and updating it again this year (no DeWalt this time). They have made massive updates and advancements to their electronics each year, and their manipulators have varied greatly as the games vary.
Just because a team uses similar designs each year, doesn't mean they cheat. It means they have found a system that they find works for most games, and ways to implement it year after year successfully. And just because its complex doesn't mean it's cheating either. 118 has a history of technical proficiency, some of the best mentors, and very smart and dedicated students. I'd suggest you do a little more research before making such bold claims.

Re: Best Drivetrain
 

Wow i didnt meen this to come off like this..
First of all, i am truely sorry i've accused 118 for bending the rules. It was based on nothing and it was a false accusation.

The other teams i was reffering too are mostely from Israel, where this rule is not beeing checked at all and when i think about it, its probably for a good reason:
Because there are a lot of things that we have to order from the states and are not available here. Usually it takes there things about a week and a half to arrive and the cost us about three times of the original price because of the delivery and custom payments. As you can see i was reffering to the order of parts, thats at least what i've meant.

So im sorry for my previos posts and if i've affended anyone...

Re: Best Drivetrain
 

I would like to make one note: While you can't actually build anything for the competition robot before Kickoff, you can order parts and test designs pre-season. Then it's a lot easier to do them in the season, because you already have some idea of what's going on.

Re: Best Drivetrain
 

Another good source of parts are previous years robots. 949 in it's seven year history has only kept three and a half robots complete, the rest have been taken a part and reused in other years robots. You can't use the machined aluminum but the bearings, wheels, and sprockets are all in good condition. You do have to remember the cost of the parts from year to year to report it on the parts list.

-Jim

Re: Best Drivetrain
 

Yep, that is legal, provided that they're not assembled into the mechanism that they were in on the old robot. Also provided that they aren't custom when removed.

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I wish weve had three and a half robots to keep alive. every year we are forced by budget issues to take out all of the parts you mentioned from the previous robot..

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I really hope someone from GDC is reading this. IMHO, we are overdue for a new robot footprint. I'd like to see it get smaller, maybe 35" x 25" or something similar.

A smaller footprint would encourage lighter robots. It might also encourage finesse (read: manueverability and control), rather than raw traction, as a distinguishing feature of FIRST's most capable machines.

-------------

I agree the best drivetrain is the one that gets your robot in position for a scoring attempt, or to stop an opponent's scoring attempt, or to support your ally's scoring attempt, and right quick. Which type that is will always depend on game design.

931's last five drivetrains were:

2004 -- custom 4WD with four independent motors, two 9" pneumatics, two 9" custom dual omniwheels. Not finished early enough to perfect control, but reasonably effective.

2005 -- 6WD with #35 chain and 4" Colson wheels, powered by two kit transmissions (thanks, Paul -- those were incredibly tough and easy to use). We unfortunately put a great drivetrain on a questionable chassis, made from 8020 with poorly reinforced corner joints.

2006 -- custom holonomic. We built our own ominwheels and gearboxes, and a custom chassis made from aluminum channel with gusset plates and lots of 1/4-20 clinch nuts. A work of art that won a design award at IRI, but not particularly effective for keeping our ball shooter on target.

2007 -- 6WD with kit gearboxes on a kitbot chassis, #35 chain to the kitwheels on the center and #25 chain to the AM aluminum omniwheels on the corners. Very reliable and manueverable, resulting in a good offensive robot when the defense was light. We were easy to turn when defended heavily.

2008 -- custom live axle 8WD with #35 chain to the four center wheels, and #25 chain to the 1/8" raised corner wheels. AM Supershifters with one CIM per side. Very controllable, resulting a consistent 4 line hybrid mode and good speed during teleo.

Our custom drivetrains in '04, '06, and '08 were all fun to build and we learned a lot. But my overall takeaway is this: if it looks feasible to use a 6WD kitbot chassis next year, I'll be pushing the team to do that.

931 won regional Chairman's Awards in both of the years that we used 6WD with kit gearboxes. :) Coincidence? Or does spending less time fiddling with custom drivetrains allow us more time for other aspects of our program?

Re: Best Drivetrain
 

I thought the weight/height rules last year were a good start. How about leaving the footprint the same and reducing maximum weight by 25%? That would generate some creative engineering, and force some serious priority-setting.

FRC robots have been pretty much the same since I've been with the program. I think it's time to start making some steam rise up from overactive brains.

Re: Best Drivetrain
 

I think that the width requirement was intentional - just barely small enough to get through doors with the bumpers on. The GDC is trying to give us problems to solve wherever we go with the robot. One of the disadvantages I see to going to a smaller footprint is the impressiveness factor. One of the most common comments that I get is "I didn't realize the robots you kids make were so big." Bigger is not always better, but it is often good for showing off, one of the best ways to promote FIRST.

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I understand that you are mostly correct. Back in the day, the teams with 36" by 36" robots had a hard time fitting through standard doors, as I understand it. So they changed it. They changed it again, before bumpers didn't count against weight or size.

Re: Best Drivetrain
 

If you build a preseason prototype drive and decide it fits the game, it can become your practice bot. When the season starts, give it to your auton programmers and let them tune their code while the mechanical teams are building the competition robot. If you build similar drive trains every year keep your old robot together because it can also be used for this.

Re: Best Drivetrain
 

heh, one thing we do pride ourselves in is that our robot is practically completely designed and built by students on our team. and i assure you, if we can lay out a great chassis with a t-square, anyone else can, at least with little bit of care and thought, anyone can learn to draw a line strait or drill a hole right, thats what mentors and teachers are there for. what i am saying is that #25 chain is as simple and easy to use and work with as 35. also, sprocket spacing is a lot easier (each link is 1/4 inch long, making spacing a snap)!

Re: Best Drivetrain
 

#35 chain has much more room for spacing and alignment error as it larger and stronger.

For a team already struggling with a drive, get it done with #35, and then maybe work on #25 in later iterations.

#25 isn't a magical thing to be afraid of, but definitely requires decent tolerances.

Re: Best Drivetrain
 

I believe one of the factors of not changing the footprint in recent years is due to cost. If the footprint were to change, lets say to double the size, that would mean a larger kit frame, longer chain, etc. which may cost FIRST or some other vendor more to create. It may also not be feasible for the playing field size to have 6 robots on at the same time.
I truly believe one of the big issues with the 2008 game is that the field was too small to have 6 robots fighting traffic trying to achieve the game challenge.
Also, if the footprint changed by just a few inches, why even do it?

Re: Best Drivetrain
 

For the same reason that they changed it in 2005. Prevent teams from pre-building drives.

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I think you can essentially create the "same/similar" type drivetrain even if the dimensions change by a few inches.

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Who says that's why they did it then?

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Something I heard back then. I'm not sure on accuracy. Maybe they did it just to give an extra challenge.

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I just don't remember any discussion about such a situation, back then.

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This year we (1251) decided to try something new for us. An 8 wheel drive, it worked great for us, lots of traction when being hit/pushed side ways and it could also turn on dime. The key was how far apart the wheels were width wise and having the front two wheels 1/8 higher.

As far as chain goes we love 25 chain. We have used it in 07 and 08 w/o major problems, in both arms and drive train. Last year we were having issues at our last competition because our robot had such a beat up. and the sprockets on the wheels started to get bent and throw the chain off. The important thing to use 25 chain successfully is the alignment of the sprockets. This year (2008) we used live axles and 25 chain and we never lost one. The chains that were put on the robot back in February are the same ones that are on there now.

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Agreed! This is one of the best ways for us, as a team, to get interest. Something that is big, flashy, makes noise and looks dangerous (even if it isn't) always seems to draw attention from us high school students (and I'm not sure why...:P)

Re: Best Drivetrain
 

Do you really think a 2 inch change is going to be so noticeable that people are not going to be impressed by the size of your robot?

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I dont see the point in reducing it by only two inches! every other change has been at least 6 inches (if I'm not mistaken).

And I find a 6 inch change to be huge! our 2007 bot is 6 inches smaller than our 2008 bot, and its surprising to here students comment on how much bigger our 2008 bot is, and how "wimpy" (there words not mine) the 2007 bot is lol.

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The last one was 2" in each direction. You could tell the difference.

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Yes you can tell the robot is a little longer, and little skinnier but saying that takes away from the overall impressiveness is just plain not true.

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Why do people go to Monster Truck shows? :p

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To see stuff getting ran over/crushed.

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by giant trucks!

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thats what im talkin bout!
mike d

Re: Best Drivetrain
 

I agree that it was done to make it easy for robots to get through doorways. We blew up the trackball inside our robotics room this year, then realized that the ball was 40" in diameter, but the doorway was only 36" wide. Not a big problem, since the trackball deforms with enough force, but if it had been the robot instead of the trackball, I would've cried.

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i saw that fight

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Cory has to go in for surgery next week.

Re: Best Drivetrain
 

One recommendation for any type of drive train: make sure you can accomodate for unforseen problems in the future regarding weight. Try to make it as light as possible. Budget out your weight strictly.

We had to remove a wheel from our omniwheel drivetrain. This is why we were fishtailing so badly during the MN regional.

-Vivek

Re: Best Drivetrain
 

From my experiences I would recommend that most teams build 6 wheel skid steers with slightly dropped centers.

On another note, swerve has the most capability because it has full power in all directions and can instantly change direction.
My advice would be to try to develope a swerve drive in the offseason and if you aren't comfortable with the swerve drive by the build season then go with six wheel skid and finish developing your swerve drive for the next year.

Re: Best Drivetrain
 

Swerve cannot "instantly change directions", it has to allow for the wheels to be re-oriented. Holonomic and Mecanum systems are as close as any FIRST team has come to instantly changing directions, but even they still have to overcome momentum and interia.
Additionally, while you retain essentially full power from your drive motors, you don't apply any of the power from your steering motor into your drive (in any swerve system yet implemented in FIRST), so it never really has "full power". However, it still can apply equal force to a scrub steered (4WD, 6WD, etc) system, something that holonomic and mecanum systems cannot do (assuming the same motor configurations).
Swerve has a great deal of capabilities and potential, and allows you a lot of strategic options. Some methods, however, do reduce (or eliminate) certain functionalities while enhancing others. 118 and 148, for example, could not rotate their robot's frames. 148 had no reason to, though, and 118 overcame it by placing their manipulator on a turret. Both were able to save weight and increase power by centralizing their drive motors though. It is also the most resource intensive drive system.

Re: Best Drivetrain
 

What about the crab and tank drive trannies?

Re: Best Drivetrain
 

What about them? What do you want to know? We can answer, but you'll need to be a little more specific than that.

Re: Best Drivetrain
 

For starters how to build one. The pros and cons. Also the weight comparison and some pics of the best ones

Re: Best Drivetrain
 

I think the team to look at (or teams) are 118, 16, and 148. Those three raise the bar/push the limit every time they do a crab/swerve. 111 as well. (Two championships and a finalist on crab/swerve, plus regional wins/finalists, isn't bad.) Weight comparison--can be heavy compared to tank drive.

Now, how to build...Coaxial? Crab? Swerve? (There is a difference between crab and swerve.)

Pros: maneuverability and power and speed in one package to a greater extent than skid/mecanum/omni drive

Cons: may take time to turn, may require a turret, heavier, more complex.

If you're going to do one, start prototyping now.

Re: Best Drivetrain
 

In addition to the teams who have already been posted, I would add 1625. There swerve drive was up there with the best of them and they published a lot of info about it on this site that a simple search should find.

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Turning is definitely something to look into, either programming a way for the wheels to turn a certain direction when told to go to a specific point (if doing a coaxial, they may take the longer way around). As far as the turret goes, we powered the front/back wheels separately and were able to tank drive sideways at the start of the season to reorient (slow/painful). However during/after our 2nd regional we developed "drift" buttons. Pressing one of these buttons would cut power to either the front or rear gear box, allowing the robot, while moving sideways, arc in orientation. Once our drivers figured out how to best optimize these buttons, reorientation was much easier and a whole lot less painful (we still used tank steer, but not nearly as much).

Thank you for the recognition. Our team is very proud of our third iteration swerve drive, which handled 3 regionals and champs without any throwing of chains or any mishaps at all, actually. Being able to drive a swerve is something else, but the control system this year takes a lot of practice.

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Yeah, just ask my brother, Aren Hill, if you have any questions about our swerve or just swerves in general. He has done our drive train the past 2 years and made our swerve a beautiful thing to watch. If you want to know how good our swerve was, you can take a look at his signature which has a quote from JVN.

Re: Best Drivetrain
 

Are the banebot gearboxes any good? In 07 the teeth kept chipping and it locked up 6 times in 2 regionals and the championships. Also any personal experiences?

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I don't have the most experience with them, but I am very familiar with the AndyMark line of gearboxes. No matter what good experiences people have had with the 56mm banebots, I've heard far too many horror stories for me to ever consider using them. The AM gearboxes are a far superior option in most situations.

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Drive train: simplicity is key. keep your center of gravity low.we have used the same chassis for three years and it will except about anything you through at it. the past couple of years we have use a 4 wheel drive because it is simple and so versital.

also our programmer and figured out how to get crab to rotate so we dont need a turret.

Re: Best Drivetrain
 

I have actually been thinking about that. Couldn't you lock the wheels of a crab in a 4wd orientation and (if you have each side independently driven) just turn like a 4wd bot?

Has anyone attempted this?

-Vivek

Re: Best Drivetrain
 

Yes, teams have done this before. Look at 111's swerve drive for a great example.

Swerves have a great deal of flexibility in how they perform and how they are built. Each configuration will result in different strengths and weaknesses.

Re: Best Drivetrain
 

You can do pretty much anything you can imagine with a swerve. Just if you have a coaxial like 148 or 118 where there's only one central gearbox providing power to all of the wheels you can't turn like a tank. With some tricky Programming and the ability to steer either side independently then you could turn in theory but it wouldn't be easy. My suggestion would be, if you have a vex kit you could prototype a bunch of swerve drives and try different motor configurations and control systems.

Re: Best Drivetrain
 

That's not necessarily true. The reason 148 or 118 can't turn like a tank is because it has on central gearbox powering the entire drivetrain (not the rotation but the wheels). Coax crab can still be accomplished using two (or more depending on your preference) independent gearboxes that control the wheel nodes independently. If you only have one gearbox then regardless of programming you won't be able to turn like a tank.

Re: Best Drivetrain
 

If the wheels are steered separately in pairs, one pair can be turned 180 and steering in place is possible.

Re: Best Drivetrain
 

Right, exactly. You also don't necessarily need to limit them to 180 degrees of rotation (I understand the argument of why you would I'm playing devil's advocate). You could use a coaxial style setup (shaft inside of shaft) and run two sides of the robot independent of each other. In that case you are still doing a 'crab drive' as we have coined the term. The difference being the two sides are independent of each other rather than being run all off the same rotator and power transmission.

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lol that's what I said earlier, but it's still only spinning in place.

Re: Best Drivetrain
 

It really depends on the game... our 2008 bot drove like a car. 2 Cims, direct drive, to each rear wheel, with an electrical differential. The front wheels drove used the acrynom principal, so when the bot was turning left, the Left front wheel turned more than the right. It was really strong this year, but it probably won't for any other game.

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Ackerman principle, not acronym principal. :]

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We did, We had one gen2 driving the front two wheels and one on the back two. So if we wanted to "tank drive" we just pointed the wheels sideways and drove around like a wide bot (wider=less effort to turn). This setup also enabled us to create "drift" buttons, We had 2 buttons on the joystick base and each one cut power to the respective transmission. So when we were going sideways we could kill a gearbox and the other one would drag its end around. This enabled us to effectively reorient on the fly, which greatly decreased our lap time.

Re: Best Drivetrain
 

I was wondering, what if you leave omni's in the front and put one dewalt to each of the remaining wheels. Direct drive or chain drive???

Re: Best Drivetrain
 

I'm guessing your talking 6wd? If so this would create a very robust drive if done correctly, yet i suggest you mechanically link the driven wheels on each side so if one set is off the ground all the power still is driving the wheel touching the ground. I believe RUSH 27 has used a similiar setup before, at least in '06.

Re: Best Drivetrain
 

So youre saying to power each wheel but link them by using chain and would this style of drivesystem be more effecient than the standard gearbox on each side thing

Re: Best Drivetrain
 

I'm not sure about efficiency, but you don't have to worry as much about putting, say, 2 CIMs into one DeWalt. On the other hand, you just added 2 DeWalts to your robot, which adds weight. (Assuming a 6WD.) You may gain efficiency (fewer gears in interface) or lose it (chain slop, twice the gears for the same amount of power). You have a fully redundant drive system, though; theoretically, any one motor can power the entire side even if the other motor's gearbox explodes all over the field.

Re: Best Drivetrain
 

It still wouldn't be as much weight as a supershifter and i remember that rush got up to 18 to 20 feet per second with drive system and Erich, you are right about the slight chance of losing efficiency

Re: Best Drivetrain
 

Now I've done searches, but I've never seen any team attempting a "ball drive" drive train. It might be under a different name, but it's simply a drive train that uses spheres for wheels. I've tried to think of a few ways of doing this, but because I have no examples to follow I can't say any of my ideas would work.

With spheres you could rotate the ball in different directions without having to rotate the thing that holds the ball inplace. The ball wouldnt have to be a complete sphere.

Has anyone tried to do this successfully?

Re: Best Drivetrain
 

Team 45 prototyped such a design a few years ago. I'll see if I can find it.

[edit] Tom beat me to it.

Re: Best Drivetrain
 

Team 45's ball drive
http://www.chiefdelphi.com/media/photos/15197

Re: Best Drivetrain
 

That's a really neat drivetrain. It's interesting because this is much different from all of my ideas I've had so far. I turned my thoughts away from doing it like this because I always imagined the ball would slip around or would be too smooth to control. It's nice to see an effective way to use balls instead of wheels.

But are there any designs which are effective using only balls and no wheels? That's what I'm going for.

Re: Best Drivetrain
 

Not that I know of, however, it could be done given enough motors. I think the reason is, not enough decent motors. You need 2 per wheel, and that means 8 motors. Yeah, we have that many. No, they aren't all what we'd want for that. We'd need 4 CIMs, 2 FPs, and 2 globes. Not enough decent motors left to put much on top of the drive, unless pneumatics are used for an arm. (Banebots, window, and maybe van door are left.)

Re: Best Drivetrain
 

Actually pretty much all of my designs require 5 or less motors. One for each ball and one to change the direction all of the balls spin.

My newest design requires as few as 2 motors, but it would be extremely impractical with only 2. It would require 3 or 5 to work well. I'm sorry I can't really describe it, but I'm only willing to explain once I get the design done in solidworks.

Another thing I need to work out is how I can hold the balls in place so they're held loose enough to rotate freely, but it would be impossible for them to come out of it's casing without taking it apart.

Re: Best Drivetrain
 

I think that's what we call a crab drive.:p

I think the main reason that ball drives aren't more popular is that there are swerve, crab, omni, and mecanum drives to choose from, some of which are simpler and some of which are more complex to plan and easier to build.

Re: Best Drivetrain
 

Actually, yea, it is pretty much crab drive... but it still would like pretty:cool:

But my latest design is far different from what I originally intended to do. My first designs involved using a sort of gear like wheel above the ball which would be attached to the motor. The gear would run along the top of the ball and on the poles there would be a turning mechanism where you could stop moving the ball and turn in another direction. The wheel above would rest on a turning device which would be controlled by controlled by the 5th motor.

Now I received criticism from my mentors that it would be too difficult to land on the exact tooth to have it turn. It would also be a slow job if it were possible since you would need to slow the motor down so it COULD stop when it needs to.

So instead of teeth the wheel on top of the ball would have bumps on it and on the sphere it would have sorts of crators. The bumbs would fit into it and because it would fit loosely inside you can stop at anytime and turn when you need to.

But yet again I'm rethinking the design. The whole point of what I'm designing is to make a drive train that is extremely menuverable and controllable which at the same time obtain a fast speed. Rolling it from the top like a normal gear doesn't sound like it could reach the highest speeds and having to stop the robot to move again everytime would make it even slower.

That's what I'm trying to solve and I think my latest idea might be an improvement compared to my original ones.

Re: Best Drivetrain
 

This comment got me thinking...
There's already been an idea posted to implement a ball drive in a similar fashion to a crab, but there are boundless other motor possibilities.
Once I have some free time I might try and run some vector calculations and see what I can come up with. Even toying around with the idea in my head I can think of a couple relatively simple ways to control the drive with 4 (or fewer) motors, in a very similar fashion to a holonomic system. The question then becomes to you gain any advantages over a holonomic system, and that's where I'd need to run a few calculations to see if this configuration could allow for any new types of movement (my suspicion is no), or more efficient movements in any direction.

Re: Best Drivetrain
 

I doubt you will find any advantage, besides the cool factor!

I think it would be neat to make a holo-ball drive!

(Thats also what I was thinking reading the other posts before you Larvey)

Re: Best Drivetrain
 

Great... I guess I now know how to find engineers/engineers-in-training. As in, give them a challenge.

I've done a little thinking and it could be pretty fun to try a coaxial crab on top of the balls. Then again, why not just put it on the floor?

Re: Best Drivetrain
 

I think 45 beat you to the punch on that.

Re: Best Drivetrain
 

That's the drive type we've been discussing today...

Re: Best Drivetrain
 

Well, with a ball drive system it would be kind of like having crab drive. I imagine it to be slightly better than crab drive. I know this can't be proven until an effective ball drive robot is made (only balls are used to drive the robot), but I suspect that since rolling a ball in any direction seems kind of more "natural" for a ball to do while rotating wheels around to drive in another direction doesn't seem so much so it sounds to me it's possible ball drive could potential perform better than crab drive. Like I said I can't prove this, but it's worth putting it to the test in my opinion. You can't stop trying to look for other ways to do things, or that really defeats the whole purpose of inovation.

Re: Best Drivetrain
 

you might have a little more manuverability with balls but I can see less pushing power as a sarcafice. I still think it would be mega cool to do. You would have to think of the balls material very careful and find the best balance of grip and slip lol.

Re: Best Drivetrain
 

Has anyone here taken apart a Dyson ball vacuum cleaner? I wonder if the innards of that ball drive could be retrofitted with an FRC kit motor?

Re: Best Drivetrain
 

Looking at it, I'd love to. Taking it apart and using it in FIRST, that might be difficult. Using the concept on a robot, very probable. Thinking about it, you could have the whole setup like a normal wheel, and then make the platform yaw left and right to turn the bot. This could get you down to two casters on the back of the robot for stability, and then you would have a pretty cool robot to show off.

Traction may be an issue, though...

Re: Best Drivetrain
 

Well, like I said before I'm trying to create a fairly simple design and as far as I can tell there would be no sacrafice of power. And the ball surface would be similar to bicycle tires.

Re: Best Drivetrain
 

I don't know if anyone has done this successfully, but I have never seen it done successfully. Most teams that are looking for motion like that would do a swerve drive or use mecanum wheels.

Re: Best Drivetrain
 

This isn't quite what you're describing, but take a look at this thread - http://www.chiefdelphi.com/forums/sh...ght=hemisphere - for an interesting drive idea that's similar.

Re: Best Drivetrain
 

Well, my the fact that swerve drive and mecanum wheels have already been used in quite a few robots before hand makes it clear that one of the reasons so few have tried to create a ball drive robot is that it just hasn't been proven effective. As I said before it's impossible to know until a good example of it has been made. By a good example I mean a ball drive robot that ONLY uses balls and doesn't use any wheels to help it move.

M.krass, that's an interesting idea. I'll take a better look at it later.