2008 and drivetrains
 

So...
what kind of drive trains do you guys suggest this year, and mroe importnatly - why?

I dont tjink high traction is needed this year as there will not be much pushine envolved, The bigger your wheels this year the better it is.

I also dont see an advantage that big for a 6WD on a 4WD.

Re: 2008 and drivetrains
 

Right now, we are looking at either a mecanum or holonomic (4 omni wheels at 45 degrees) drivetrain. The big advantage would be the quickness that the robot could turn corners, or I should say strafe. This would thus eliminate the need for turning around the corners

Re: 2008 and drivetrains
 

Agreed, Mecanums are going to be popping up left and right this year.

Re: 2008 and drivetrains
 

I would say any drivetrain that includeds either omni or mecanum wheels would be the best idea for a drivetrain this year. the competition is on carpet, so high torque would not be necessary, less traction would be better, if u want to slide which for some teams will be doing that if they decide to build a robot to only drive. for pushing the ball i would suggest mecanum b/c they allow you to keep control of the ball (if u create something to hold the ball). traction is not necessary for this b/c of carpet, so go with omni or mecanum.

Re: 2008 and drivetrains
 

Yeah, mecanum, kiwi, four-wheel omni-wheel designs, and swerves are probably going to be the class of the field. That said, my team has decided to do a light, fast, low traction, two-speed 6WD with adjustable centre wheel drop. We figure that practice is the key to this game and getting a fast, working drivebase with potential of some optimization (we intend to find the ideal centre drop) done early will pay dividends come regionals. What good is a omnidirectional design if your drivers don't know how to use it?

Re: 2008 and drivetrains
 

It would be kinda fun to try swerve in this year's game, but our level of sophistication prohibits that. My preference is for an adjusted version of our 2007 robot, Uppercut (photos here), for a few reasons:

a) It's proven to be a heck of a performer as-is
b) Easy and quick to assemble--no real machining required.
c) Can be tuned relatively easily; we can change it from lightning-fast to a more mid-tempo robot with better pushing with a Saturday and a sprocket order.
d) We're just suckers for the kitbot, what can I say?

However, it should be noted that the team has yet to make a decision. We'll see what's up soon.

Re: 2008 and drivetrains
 

We are looking at using the two kit wheels on a front wheel drive and omnis on the rear instead of casters. You will have the weight of the ball over the drive wheels if we decide to carry it around before hurdling. We have used this in the past and it turns great. We thought about four omni drive but we have a new driver this year and afraid of lack of practice time to try this.

Re: 2008 and drivetrains
 

Seeing as this is the appropriate thread imo.

Why type of drivetrain would I want to use if I wanted to be able to turn fast yet be easy to control.

Re: 2008 and drivetrains
 

most will disagree but i think a traction drive system (six wheel for example) will be a good choice this year, it is going to have a lot of control and not be giving way during all those high speed collisions

Re: 2008 and drivetrains
 

I think I agree with you - high traction and speed in the forward motion (this is a fairly straight course when you get down to it) with the ability to make a turn. some manouverability will be needed and some good instincts for driving to see objects ahead of time. 6wd with Omni's in the corners (not mecanums) and traction or kit wheels in the middle.

Re: 2008 and drivetrains
 

We are going with the same track system as last year, and with a little SLOWER high speed since our high speed was a tad uncontrollable last year, but I believe (especially in hybrid) it will be nice to tell our robot to go somewhere and be pretty sure it will make it.

Re: 2008 and drivetrains
 

Remember that "tank drive" robots don't need to turn.... or at least not turn much... they can just go "forward" down one side, then "backwards" down the other, just like mecanums and other omni-drive systems.

I would recommend, however, that teams using mecanums get them finished earlier than usual so that the programmers and drivers can have time to get all the control loops worked out. Building a successful mecanum drive (especially with Banebots gearboxes and AM wheels) is much more of a programming challenge than a mechanical one.

What I am looking forward to is the emergence of "car" steering. We are seriously considering setting up just like a sports car... rear wheel drive, front wheel steering. While it doesn't have a "zero" turn radius like tank drive, it should work great for high speed cornering and swerving around other robots heading down the straights.

But we've got a few other tests to run before we commit to that just yet.

Jason

Re: 2008 and drivetrains
 

My understanding was that these drive trains were for sale last year. It's good to see that Outback has agreed to sponsor teams directly instead of selling these drives to them.

Re: 2008 and drivetrains
 

I think this is one of the best years for Ackermann-steering that FIRST has presented in a long time.

Re: 2008 and drivetrains
 

Same here, looks like a great opportunity for the car guys to put some knowledge to work :)

But we'll try out the other two drive trains we have sitting in the shop right now...6wd and mecanum....(the programming for mecanum is really not that difficult, if you use a canned solution...according to my son who made it work pretty easily)

Re: 2008 and drivetrains
 

I think teams that quickly jump to mecanum and omni wheeled designs may regret that choice later on.

Yes, FIRST is discouraging defense, but do you really think with 6 robots on the field and 4 40" 10 lb balls there isn't going to be any collisions and interference? Knowing this is probably going to happen, I'd rather be the 6WD bot with nice high traction wheels than a holomonic (guess who is going to be knocked of course more....).

Now, a crab drive is ideal; but we can't all pull it off.

If there was ever a year to call Wildstang's, I think this is it.

Re: 2008 and drivetrains
 

I'm interested in seeing how the lower traction systems will fair considering the forces that will be on the robot when attempting to turn at high speeds.

I suspect that those robots that can maintain speed while turning inside of their opponents will have a distinct advantage in this game. Which is why we're looking at low CG wide frame and high traction.

Oh, and just like NASCAR, I expect robots to "trade paint" ... so build 'em robust.

Re: 2008 and drivetrains
 

I call it "trading foam". "Trading 1000 Denier Cordura Plus" just doesn't have the same ring to it.

"Trading noodle"?

Re: 2008 and drivetrains
 

Sounds cool - but can I suggest you consider rear-wheel steering? Think about forklifts and how the ball moves, you might be better off. And if you drive the wheels you are steering you can still have a zero turn radius just like a forklift.

Re: 2008 and drivetrains
 

All the mentors for our team were thinking a car-like drive system this year. The students quickly and outright shot it down... maybe they're scared... :confused:

Re: 2008 and drivetrains
 

Personally I don't think omni's or mechanum are going to be very good for this game. First off you need your bot needs to be fast and with omni's or mechanum systems you can't gear them too quickly or you won't have enough tourqe to strafe controllably and with how congested this game will get there will be times where you need some tourqe and traction to get out of the congestion. A swerve drivewould be great for this game if you have the weight for it with a beffy arm.

Re: 2008 and drivetrains
 

No, Since the game does not have any climbing, almost no pushing and since its really about reaching for a target and going fast. 2-Front wheel drive is very easy since you will have to push a ball around. In addition to the 2 wheel drive you can use the stock kit to build your drive platform. and focus on the design of game arm.

Check out my PDF I posted about 3 years ago, its got great info on these systems.

Re: 2008 and drivetrains
 

personally i like tank because i think its much more simple and would be easier to fix than an omni system

question: can you drive under those lane dividers??

Re: 2008 and drivetrains
 

no, it was the first thing we though about, there is plastic there.

Re: 2008 and drivetrains
 

our team is thinking of using two high traction wheels in the front and free spinning omni's in the back because the closer to the ball your turning axis is the less the ball wants to run away while turning.

Re: 2008 and drivetrains
 

Right now I like mecanums, traction wheel + partial omni, crab, and ackermann, but it depends on the strategy and how the manip is holding the ball...choices choices

Re: 2008 and drivetrains
 

Tangling with pasta.

Re: 2008 and drivetrains
 

I can't wait to see the first Ackermann steering robot in competition :D

Re: 2008 and drivetrains
 

i would love to see a team that has rack and pinion steering

just to see how they pulled it off cuz that requieres some serious changes being that the wheels have to be covered

Re: 2008 and drivetrains
 

team 2669 is gonna be having one, but we are only participating in the Israeli regional which is between weeks 4 and 5.

Re: 2008 and drivetrains
 

http://www.delphielite.com/modules/g...twg_album=2000

Unfortunately, none of the pictures show the steering mechanism. I could go to our old robot retirement home and take some current photos if anyone cares. I don't think it was 100% truly an Ackermann design, but it did have fixed powered wheels in the back and two steered powered wheels chained together up front.

Ah, 2000 - the beginning of the Extruded Aluminum Era for Team 48, which ended abruptly when we faced off against Team 60 in Florida in 2002....

Re: 2008 and drivetrains
 

Ackerman Steering would be really interesting to see, although I know we have tried it, and it has some large kinks that need thought out before hand.

And yes, outback has decided it would much rather sponsor teams then sell the tracks, it would be a pain to be considered a FIRST supplier.

Re: 2008 and drivetrains
 

Team 284 did it last year, I'll see if I can find a photo of it.

<EDIT>

Re: 2008 and drivetrains
 

ackerman was pretty common in 2003 (or a crab that would drive ackerman during autonomous). A few teams did it in 2007 and I'm it was sprinkled throughout the years since FIRST has started.

Re: 2008 and drivetrains
 

The one I remember in 2003 was 812.

Re: 2008 and drivetrains
 

Front 2-wheel drive with casters in the back won't allow you to turn fast, since the rear will break out.

Re: 2008 and drivetrains
 

Yea my team in 2003 had 2 steered casters in the front with a 4 wheel drive in the back, it worked pretty well but there were a couple of things i would have changed, and yes you could really fly while turning which was pretty cool.

I can also remember several teams that have employed some kind of steering, obviously all the crab drives, but 16 baxter bomb squad a couple years ago had a tricycle setup with all 3 wheels driven and 1 steered, worked very well from what I remember.

Re: 2008 and drivetrains
 

Heh, this is EXACTLY what happened to us last year - we couldn't drive our own robot! Loks like we're gonna be doing two powered wheels in front, two powered omnis in the back, tank drive, so we can 'drift' around the corners.

Re: 2008 and drivetrains
 

Before you lock on that drive, think hard about the 'drift'... it wont be pleasant.

Re: 2008 and drivetrains
 

I really think a well designed Ackerman system is the way to go.

I'm lobbying my teammates for:
- Ackermann
- Rack & Pinion Steering
- 2 Speed Single Power Plant
- Limited slip differential

I already have a differential design that is fairly easy to make (I'm currently working on reducing the weight a little) and I like the AM SuperShifter. We're looking at various RC car designs for some practical solutions. :cool:

Re: 2008 and drivetrains
 

I don't know. If you're going to go Ackerman you'd better have a good turning radius and some good programming for your controllers. It seems to me that there is a lot of space open on the field (each lane is 13 feet wide) but I also think that there's going to be a lot of robot crowding, especially when robots are extended. It seems to me that Ackerman would be difficult to steer precisely when it's on the opposite side of the field; especially with trackballs that are so big they could potentially completely block the view of your robot. The other issue I forsee is a difficulty in turning around unless you intend to be using reverse (another adventure in steering with Ackerman). I'm not saying it can't be done but it will take a lot of practice for the drivers to get good and precise with their steering considering they have a fixed point of reference instead of one on the object (like in a car).

In either case, it will be very interesting to see what drive trains everyone is using. We're thinking of a 6-wheel drive for this year; power when you need it, maneuverability when you need it.

Re: 2008 and drivetrains
 

My team is thinking of doing 4wd with car drive as the control does this have any intrisic advantages over tank drive or should we just go with tank drive?

Re: 2008 and drivetrains
 

Programming should be fairly simple, a pid loop to control steering angle and the Y-Axis direct to the powerplant (ok maybe a rate limiter). I don't see the complexity. Am I missing something?

Re: 2008 and drivetrains
 

Both basic systems are not very efficient at making left hand turns......

Re: 2008 and drivetrains
 

That's great to hear. How many teams has Outback agreed to sponsor? Is there an application process? I can think of a few local teams who'd love have this type of sponsorship.

Re: 2008 and drivetrains
 

Hey, any pictures or video on that "drifting" robot yet? CAD or hand drawn at least? That's EXACTLY the idea we came up for team this year, too.

Re: 2008 and drivetrains
 

We too are looking seriously at rear wheel drives, independent suspensions, Ackerman steering in the front (and perhaps also the rear), two drive trains and software differential. All this is of course before we apply KISS and also depends on where we settle with our base strategy.

I've seen lots of posts suggesting that perhaps the math hasn't yet been done by some of the teams. Centripetal force is square law and high traction is necessary for high speed cornering.

I AM glad to see a new challenge where just the same old 6WD skid steered pushbot of yesteryear may not necessarily be the optimal drive configuration. However, I am not looking forward to the mechanical carnage we are likely to see on the field from mv**2/2 from 10 sources.

Re: 2008 and drivetrains
 

KISS might eliminate the suspension, rear steering, and differential....and just leave two motors and one transmission per side in back, and steering in front operated by a window motor.

Re: 2008 and drivetrains
 

m*v^2/2 doesn't sound right... isn't it m*v^2/r. Ya that sounds a little batter...

In either case I love the idea of a nice easy to control skid steer system like a 6wd since it doesn't turn to easy but also doesn't turn too hard. In the past we had a bot that went from unable to turn to uncontrollably easy to turn when we changed from 4wd to casters and I don't like the complexity of the ackerman.

I hate to be a follower after 3 years of omni but I have to say that I don't think the maneuverability of a mechanum or omni is going to help (especially after driving them) and I hate pretty much all forms of normal 4wd so my votes in for 6wd.

Re: 2008 and drivetrains
 

We debated using a steering system for the first few days, but as of recently backed off of it. My gut says that the field will get congested enough that the loss of manueverability will hamper the advantages of a steering system set up.

A few students on our team feel that crab is the optimal choice - but we're too nervous about going down that road without testing in the offseason. This year will definitely be a season with varied drive trains.

Re: 2008 and drivetrains
 

m*v^2/2 is the Kinetic Energy of the objects (Balls and Robots) that will be flying around the field looking for your robot.

m*v^2/r is the centripetal force required to turn the mass. m*v^2/r will hurt you only if you haven't got it. Then you will find out what m*v^2/2 will do to you. :)

Re: 2008 and drivetrains
 

I think the result of yesterday's team discussion about drive systems, is that the 3 we considered (6wd skid steer, 2wd car steering, mecanum) all have enough advantages and disadvantages that none really stands out as the best drive.

So we may end up going with car steering to learn something new, or with 6wd because we know how, or with mecanum because it's so fun to drive.

My guess is that engineering/cost/material considerations will weigh heavily in the decision.

Re: 2008 and drivetrains
 

I think the biggest key to drivetrains this year is going to be driver practice. Regardless of what kind of drive system you have, your drivers are going to have to be comfortable with your machine. It may be better to have a simple, reliable design done with time to spare, than to have a complex one that you have to finish at your first event (and therefore get no practice).

Re: 2008 and drivetrains
 

We're creating a six wheel drive with the center wheel driving off the transmission and the back wheel driven by chain. The front wheels will be free, and both the back and front wheels will be omnis. This is a modification of last year's drive.

Re: 2008 and drivetrains
 

I was hoping for a more standard game with a standard drive as this is only our teams second year.

But we are looking at driving two traction wheels in the front, with some form of turning the back wheels.

And I agree this year the drives will want as much experience they can get driving their robots.

Re: 2008 and drivetrains
 

How do you mount the faceplates on a kitframe??

Re: 2008 and drivetrains
 

Our team did car steering last year and found some troubles. For one you deffinatly DON'T want to use servos. When we got to worlds, they constatly cut out and left us with no steering. If you used a rack and pinnion Your robot could be reliable, agile, and fast with a good drive train.

This year we are thinking of using omni, but the 45 degree settings would cause a 30% efficency reduction on them. Any imputs?

Re: 2008 and drivetrains
 

We're going with something like that again this year. It'll be able to crab and be steered by just the one, so we're hoping that maneuverability's gonna help us out. That and we've got a (somewhat) working '07 bot for our drivers to start in on. Practice is gonna be huge.

Re: 2008 and drivetrains
 

Today we put together a quick ackerman prototype on the kit frame (one of our mentors welded together some simple spindles for this purpose). Even without the desired dimensions (long wheelbase, wide apart front wheels) and the geometry being off slightly, it has a pretty tight turning radius. We didn't get a chance to drive it, so we won't know about actual performance until tomorrow.

Re: 2008 and drivetrains
 

We are seriously considering ackermann steering, it seems to be the best option in terms of efficient turning, plus it has a certain familiarity to it.
depending on how complicated we want to get, we may power all four wheels, but at this stage it seems wisest to use KISS and just power the rear wheels.

i quite like this years game so far, and i think that a good drivetrain will be key in building a competitive robot. it could be a major mistake to build a very simple drivetrain and focus only on the manipulator. but i suppose only real gameplay will tell

Re: 2008 and drivetrains
 

the quick prototype GUI mentioned turned out to be a great success, being a better drivetrain in 2 days than our last year's 6WD in 3 weeks. A designed ackermann steering drive train will perform way better than even the prototype.

As far as our team is concerned, Ackermann steering is the way to go!

Re: 2008 and drivetrains
 

Kevin is exaggerating. The prototype was nowhere near as good a drivetrain as last year's. something about the steering motor not actually firmly attached to the linkage and the potentiometer mount falling off that doesn't seem to work well...

But the final chassis should be a simpler, lighter design than the previous year's.

Re: 2008 and drivetrains
 

Having completed the tests, we're going to go with 2wd "tank" drive.... traction wheels in front, omnis on back, gyro to go straight.

The deciding factor was, as suggested by others in this thread... Keep it Simple, Finish Early, and PRACTICE.

It is a bit of shame as we had some neat ideas for 4 wheel drive / 4 wheel steering, but as we discovered with our mecanum drive last year, "cool" and "competitive" drive trains are not always the same thing. We're keeping things pretty conservative this year and re-using some COTS wheels from a previous practice robot.

But I'm looking forward to seeing the many cool, competitive and off-the-wall brilliant outside the box ideas that come out this year. I think this must be a pretty good game if after one week there is still no consensus on what the best drive train design is likely to be.

Jason

Re: 2008 and drivetrains
 

we just finalized our drivetrain and we are using Ackermann steering:D

Re: 2008 and drivetrains
 

We are thinking of using ackerman, but we aren't sure that it gives us a huge advantage over two front wheel drive wheels with two omni's in the back, does anyone have any thoughts?

Re: 2008 and drivetrains
 

We briefly considered using a mecanum set-up for a holonomic system. Strafing could get around the corners quickly but then you have that 40 inch ball to move with you. We are still in testing mode as to whether omni-wheels on the rear will be needed on our basic four wheel drive robot seen here. Comments are welcome.

Re: 2008 and drivetrains
 

With our prototype, we yound that an Ackermann system is much easier to control than the other bots we were testing. Mostly everyone found the mecanum bot to be confusing to drive due to mecanum's tendancy to drift off course, and if you don't pay attention to how you are oriented it is easy to go the wrong way. With the six wheel drive, we found very finnicky controls, it is very easy to over shoot or undershoot a turn. The ackermann drivebase was very intuitive to drive, and goes where you want it. It can also be driven straight forward easier.

Re: 2008 and drivetrains
 

team 753's front drive wheels for 2008 we will have these wheels in the front working in conjunction with 2 omni wheels in the rear all driven by 2 small sims with chains and sprockets (through the andymark kit gear boxes)