CVT, which teams are planning on using them for next year?
 

There has been some talk of CVTs on CD lately. So how many of you teams are actually designing them for your drive train for the 2006 season?

We are actually working on it, we have a 'prototype', if you will, but it's not working as we would like, but we're still working on it.;)

Re: CVT, which teams are planning on using them for next year?
 

you should talk to with santosh and me weve thrown ideas back and forth for a couple months. i know he has some cool ideas. i however have some other things (hush hush top secret stuff) im working on.

Re: CVT, which teams are planning on using them for next year?
 

If you get a chance, talk to Matt Krass, I have seen few of his designs. He will be able to give you some good ideas. Even better, If Andy or John get a chance, you can also talk to him about the design, I am sure he will be willing to give you guys ideas. Yes I am talking about John V Neun. :)

Re: CVT, which teams are planning on using them for next year?
 

Never had any plans for a CVT. Too difficult to get working well because it is all friction based. And friction has a much greater potential for slipping than a postive engagement setup like gears. I design for reliability and robustness(notice I did not say simplicity) and to me a CVT just is not it. However, if people do it, and it works, I'd be more than glad to see it. :)

Re: CVT, which teams are planning on using them for next year?
 

After the thread where about half of the people are against even basic shifting or anything other than the FIRST drive train, I doubt there will be many going for a CVT ;).

Re: CVT, which teams are planning on using them for next year?
 

We currently do not have a design in the works, but we did prototype one over the summer of 2002.

Our CVT was very basic and consisted of a big round aluminum disc mounted to the side of Skyway's bead lock wheels(http://www.skywaywheels.com/products_002.htm), an aluminum frame, drill motors/transmissions, and the best part gum rubber.

We mounted the two wheels and discs to the center of the frame, mounted high traction wheels (gum rubber) to the output of the drill transmissions, and then mounted the drill transmission to a moveable assembly that would allow us to move them farther towards the center of the axis of the wheel for more speed or father away for less speed.

The problem was we did not have enough traction to keep the wheels from spinning on the aluminum discs.

This simple cvt prototype/idea was a basically taken from the little CVT's in push lawn mowers.

I don't have a picture of it, I don't even know if we took any of it... so I have included a Paint drawing of what it looked like.

For those of you who know us by our gum rubber wheels (2003) robot and our gum rubber omni wheels (2005) this little project is where found out all about different kinds of rubber and what worked the best, thus GUM RUBBER!

Re: CVT, which teams are planning on using them for next year?
 

I'm thinking a rubber coated disk and a knurled aluminum wheel would be better than a smooth aluminum disk and a rubber wheel.

Re: CVT, which teams are planning on using them for next year?
 

Using belts is definately a good idea. You can put tons of tension through a v-belt and get brilliant traction on pulleys. So.. just figure out how to get a pulley that changes size. Not so hard anymore, eh? I'm sure the brilliant young minds of FIRST can figure out how to do it.

Re: CVT, which teams are planning on using them for next year?
 

Wouldn't that aluminum wheel + rubber wheel have a fairly large amount of friction losses? I mean, unless the rubber wheel has a very small contact point, then it's going to slip along pretty much all of its surface cause the aluminum disk will be travelling faster at the outer edge vs the inner edge. As I understand it, that's why other roller designs use hard rubber designed to contact at a point.

And in answer to the thread, 57 doesn't look to be using a CVT in the foreseeable future.

Re: CVT, which teams are planning on using them for next year?
 

The most important thing with CVTs (Ive been researching them allot). One weight is a big issue and you need to carefully choose material. Two durability is going to be a problem. Constant grinding causes the CVT to wear down which is part of the reason they aren't in cars (the other is reason one and the last reason). The third thing to keep in mind is friction. It doesn't matter if you can get a great torque ratio if every time you try to push against something the gears are slipping! What you need is a durable, lightweight material, that has great friction which brings us to the last thing to consider, cost. If you want a nice drive train its going to cost you! I don't doubt that some of you might differ in opinion but this is just my opinion based on my research. I however very much recommend pursuing this venture and figure out the best way to use them. These are very worth while to make and if you want i have some links of good materials and sites that will help you develop one. I'm very interested in teams that build them and i would love to here an ideas you have.

Re: CVT, which teams are planning on using them for next year?
 

Actually CVT's are in a lot of cars today. The new Toyota Prius Hybrid uses a CVT transmission, so does the Mitsubishi Colt Plus, and Ford's Escape Hybrid uses a CVT. I don't exactally see how constant grinding = CVT wearing down faster. Straight-cut gears in a gearbox grind more than a CVT do.

As for slipping, that depends on how much torque you're putting through the friction plates/wheels/belts/pullies/etc... Since torque and speed are proportional, one could just gear the area where the cvt can potentially slip to a high rpm, where there's relatively low torque.

And as for materials -- material selection varies with your restrictions, you don't have to have deep pockets to make a really good FIRST competition drivetrain, it's all in the design and how you implement that specific design.

Re: CVT, which teams are planning on using them for next year?
 

Actually, a good number of cars use them now like the Escape hyrbid and I think the Ford 500 too and probably many more.

EDIT: NoodleKnight beat me to it.

Re: CVT, which teams are planning on using them for next year?
 

Yes they are now and for this refer to my final example. they are just making a comeback. CVTs have been in the car industry for a LOOOONNNNG time but they never gained popularity until recently. Yes i know their are exceptions as their always are!

Re: CVT, which teams are planning on using them for next year?
 

I hate to debate this every time CVTs come up, but all the cars using the Toyota Hybrid System (this includes the Prius and the Ford Escape) do not have CVTs. The initial Prius advertising did say that the car had a CVT, but after a lawsuit they removed any mention of the term CVT from their advertising. The Hybrid System uses a single speed planetary transmission that is very similar to the ThunderChicken's CCT.

However, there are quite a few CVT cars on the market now in the US, including the Ford 500, Focus, and Freestyle (say that 5 times fast!), the Audi A4 and A6, Nissan Murano, MINI Cooper, the Saturn VUE, the Honda Insight and Civic, and the Chrysler Sebring and PT Cruiser. In fact, Nissan has said that they want to sell 1 million vehicles equipped with continuously variable transmissions annually by 2007.

Incidently, I came across a really cool LEGO CVT. I don't know how well it works, but I guess anything's possible.

Re: CVT, which teams are planning on using them for next year?
 

THATS AMAZING! the design really is simple. thanks for posting that link ill foward it to some other teams who are researching this.

Re: CVT, which teams are planning on using them for next year?
 

The gum rubber drive wheels as about 3'' in diameter and was about 1/2'' thick.

We probably could have Knurled the aluminum disk, like Sanddrag said, but that would probably eat up the rubber quickly.

Like you said, I think the design would have probably worked better with a drive wheel that had a curved contact point rather than one with a flat contact point 1/2'' wide on the aluminum disk.

We basically scrapped the prototype because we knew that it would be very difficult to get enough power the the wheels, without the drive wheels slipping.

I am sure we could still make it work.

Thinking back, we could probably have added a lot pressure to the drive wheels, thus we would have needed to add thrust bearings on the wheels.

We also probably could have made a better method of moving the drive wheels in and out on the disk.

Re: CVT, which teams are planning on using them for next year?
 

Well there are these cone pulleys (STOP WHAT YOU ARE THINKING NOW). These pulelys arent being used as most cone pulley desigins put them to use.
These cone pulelys ride next to eachother as in the flattned tip of the cones almost touch eachother. There is also a V Belt riding in between these cones. The cones have grooves in them that do expand, but so does the V-belt.
There is another pulley at the other end that the belt also wraps around. The single pulley is the one that has the drive motor running it.

When the cones are pushed together, the belt has to ride up the cones becasue it has nowhere to go. as the cones are pushed together, the overall diameter of the touching point of the 2 cones grows and your gear ratio changes.

And that Nissan Murano with the powerplant under its hood, the 3.5 liter engine, with a CVT will be awesome.

1002 the CircuitRunners would love a CVT on next years bot, but that is if we can find one that can handle a lot of torque an one that will be reliable. We however will not build one if the game next year doens't call for one. Purpose over pimpness is a policy that we are trying to adhere to.

Re: CVT, which teams are planning on using them for next year?
 

Santosh, are you talking about something like this?

Taken from HowStuffWorks.


If it is, how could you change the diameter of the pulleys and still have a reliable drive train?

Re: CVT, which teams are planning on using them for next year?
 

These are called variable diameter pulleys. They have been used for many years for variable speed drives on things like drill presses and mills. Team 1114 successfully adapted this concept for use on their robot cart in the fall of 2003. You can buy variable diameter pulleys from a company called hi-lo . The website is www.hi-lo.com

You might also want to look into a design by Jay Tenbrink from 494 a couple of years ago. They successfully designed and build a set of variable diameter pulleys that used a fly weight system to adjust the pulley diameter automatically.

Re: CVT, which teams are planning on using them for next year?
 

I have spent some time looking over the pictures of their CVT on their website repeatedly, and I have some difficulty in understanding just how the diameter of the pulleys is changed by the weights. From looking at the pictures, I see that the weights fold out when the shaft is spinning faster, but I see that the pulleys remain at the same diameter. Is this a friction based CVT, because I see that the man's hand in the background is holding onto the shaft tighter in one of the pictures than in the other.

Can someone on team 494 possibly give more information?

Re: CVT, which teams are planning on using them for next year?
 

I too have always wonered exactly how that one worked, or if there was a video of it running.

Anyway, I wonder if it would be better do to a CVT on a smaller scale like right off the motor so it is in the first stage of reduction. That way, it wouldn't have to carry as much torque. But, it might be too fast.

Also, the key is not just to having a CVT, but having a CVT that can react to present conditions. It has to be fully automated either mechanically or electronically.

Re: CVT, which teams are planning on using them for next year?
 

i like the idea of a small one right off the motor since the size really doesnt matter and you can make it as small as possible. im curious though why it has to be automated? why not use it like you would a normal transmission and just hace more control over torque and speed. however if you want to have autonomous control i would recomend some type of backgroung program that uses info from the accelerometers. for example when it marks that you are incountering esistance (moving slower than you shoud based on speed controllers) it ups the torque. you would need something to govern how much it ups the torque based on what and when to lower the torque (maybe when your speed suddenly increases after overcoming an obstacle).

Re: CVT, which teams are planning on using them for next year?
 

I think you'd want current draw to abe a big factor in the auto "shifting" program. Also, it would have to be automated because I don't think a driver is skilled enough to control an infinitely variable transmission to the best of its potential. There is too much other stuff going on to think about exactly what torque/speed setting you need. Some drivers don't even make good use of a two speed.

Re: CVT, which teams are planning on using them for next year?
 

Well...maybe have it automated by using shaft encoders, but then if you got into a pushing match, and there was a problem and the CVT was still in high gear, maybe using the buttons on the controller, the driver could manually change the pulley diameters to low gear by pressing the buttons to slowly change the diameters. Or instead...maybe preset diameters that when the driver presses the left joystick button, it automatically goes to lowest gear for more torque, and then the right joystick button, middle gear for getting across the field more quickly.

For automating, you could probably have it that when it starts from 0 fps, the pulleys could automatically be at the smallest pulley to biggest pulley for most torque, and then gradually increase. Or something like that..

Re: CVT, which teams are planning on using them for next year?
 

i think it would be easiest to have the driver control it. instead of specific ratios a driver could push a button for more torque or one for more speed. i think my biggest fear would be the gears just slipping and a sliding.

Re: CVT, which teams are planning on using them for next year?
 

^agreed. You get most of your power at a certain RPM. And yes if you do have a pushing match, you want to keep a very high RPM on a high torque setting.

Re: CVT, which teams are planning on using them for next year?
 

i wonder if you use a simpler design if you could make a mini disk CVT. as long as it stands up to the stress i think you can make them miniscule.

Re: CVT, which teams are planning on using them for next year?
 

Remember that torque x speed=transmitted power. On a cvt disk,( or even with gears or sprockets) the smaller the diameter, the greater the force required for a given torque. In other words if you make it small, it needs to spin really fast, or have really high contact force (or both). Even if the materials could withstand the contact forces, heat buildup due to inefficiency of non-point contact could be an issue and would be more troublesome as you go smaller as there is less surface area to dissipate the heat.

Re: CVT, which teams are planning on using them for next year?
 

ooh good point. darn physics. :mad:
actually my second fear is the heat build up. any suggestions on how to minimize it?

Re: CVT, which teams are planning on using them for next year?
 

The V-belt variable pulley size drive was exactly what I was hinting at. How it works.. simply, is that you take a standard v-belt pulley, cut it in half, and ride a belt over it. If you bring the half pulleys together, the belt rides higher on the pulleys. If you bring them apart, the belt rides lower. The problem is not how to get traction from the pulleys, thats the easy part. The hard part is how to reliably controll the distance between the pulleys. If that was figured out, CVT would be a joke for me. But untill then, I'm cadding new ideas.

Re: CVT, which teams are planning on using them for next year?
 

lead screw and potentiometer, or a bunch of limit switches!

I have to agree with sanddrag, the CVT should be controlled via computer based system -- the driver won't easily be able to smoothly control the CVT's "shifting" as a computer-based system would, and by setting designated shift points for the driver to select, then you might as well have been better off building a shifting-gearbox with n-number of shiftpoints.
Manual override is always nice, yes, but only if the program dies or if the driver really needs to shift fast.
The CVT's shifting program should vary the transmissions reduction ratios on current draw (like sanddrag said) versus wheel speed. If the current draw is high and the wheels speed is low, the transmission should increase the reduction for more torque, etc...
And I don't really think that slipping in a CVT is a big problem, just build it around a high RPM/low torque area -- shouldn't having high RPM's help shifting anyways?

Re: CVT, which teams are planning on using them for next year?
 

I think that slippage is a big issue. That is a big reason why teams are staying away from it. ABout that motors drawing amps thing, couldn't you have something on the controls that the drivr could see so that he doesnt draw too many amps.

I think however, that the driver should be able to control the positioning of the belt BUT, a program could change the position of the belts if the motor is about to kill itself from drawing too many amps. Am I making any snse. It would kinda be like a guided shifting systm howevr it would only shift for you if you were about to kill the system

Re: CVT, which teams are planning on using them for next year?
 

Wouldn't placing the CVT in a high RPM, lower torque area fix that slipping problem? V-belts and pulleys, or friction plates & wheels would at least hold up in those conditions, or at least stick enough so that the wheels will break traction first, or am I missing something?

I get what you're saying, basically a fail-safe system that will stop the robot from dying. IMO, the point of a CVT is to eliminate the need for driver-interaction with the shifting mechanism and let the computer dynamically control the shifting-ability. But hey, don't let what I'm saying influence your designs, I'm just giving my viewpoint and searching for answers.

Re: CVT, which teams are planning on using them for next year?
 

I believe a spring on the output pulley forces those split sheaves together, which tensions the belt which spreads out the sheaves on the input shaft. The weights on the input shaft, through cam action, apply a counteracting force to push the sheaves together.
Someone correct me if I'm wrong here but I believe, additionally, the belt will tend to seek greater mechanical advantage by riding lower in the input shaft groove when it encounters a load. As the load increases, the ratio adjusts for greater mechanical advantage, and the input sheaves spread apart until reaching an equilibrium with the sheave "squeeze" force resulting from rotating weights. As the motor goes faster and/or the load decreases, the input sheaves are forced together, until there is a new equilibrium point, and of course, a new ratio.

Re: CVT, which teams are planning on using them for next year?
 

Hmm.... ;)

http://www.lovejoy-inc.com/variablespeeddrives.htm

Good thing I work at a machine shop!

The DoAll horizontal automatic band saw at work has one of those in it to change blade speeds...

Maybe some of you can find these useful!

Re: CVT, which teams are planning on using them for next year?
 

You are correct about CVT needing less driver interaction, but it does also have a bunch of pros on its own. It servs a better than automatic transmissions becasue otherwise why would they put thm ther if there was already no driver interaction.Somewhere someone told me that ther was 25% better acceleration and you can build up pushing power faster. I do believe that a a program guiding the positioning of the belts would be easier to drive, but a manually controlled CVT would let you reap most of the benefits out of it. It is just like the choice, manual cars vs. automatic cars.

Re: CVT, which teams are planning on using them for next year?
 

I get what you're saying, but the information you speak of, the 25% better acceleration -- doesn't that information come from the automotive industry?
Internal combustion engines have a torque/HP curve, and the CVT chooses to vary its reduction ratios within that curve to get the best efficiency, where as with gears the driver has to go in and out of that curve (or the peak of the curve) while accelerating.
Electric motors have a linear torque line, where their peak torque is at stall.

Re: CVT, which teams are planning on using them for next year?
 

Cars and robots are two different things. On a car you know when the optimal shift point is. You're also only concentrating on one thing--staying between the white/yellow lines.

With a FIRST robot you're doing a multitude of things, and anything that allows the driver to have one less thing to think about is going to give you an advantage. It's like having a 4 speed transmission--does the driver have time to think about what speed he needs to be in, how much current he's drawing, etc, or do you just make an algorithm that shifts automatically to always keep the drive in the gear that gives optimum performance for a given situation?

If you think it'd be hard on a driver to find the right gear instantaneously with a 4 speed, think about how much thinking it'd require with an infinite number of gears.

Re: CVT, which teams are planning on using them for next year?
 

hehe you should see DARPAs grand challenge! :D also that should show you why its not wise to have too much computer controlled things.

Re: CVT, which teams are planning on using them for next year?
 

Sure it's wise. We just haven't figured out quite how to do it. That's the whole point of the competition. The future is in autonomy.

Re: CVT, which teams are planning on using them for next year?
 

right but their are going to be conditions where the computer will be wrong and you want more or less torque. atleast have it so you can disable it and manually control it if neaded.

Re: CVT, which teams are planning on using them for next year?
 

You're right Mechanicalbrain. Sometimes, it would be nice to have a computer control it, but then for driving, it's not that hard, so a driver can think about other things too. I was on the drive team this year and I had also been to go in and out of turbo very easily without really having to think about it and concentrating on it.
There are also some flaws if you have it controlled automatically. Sometimes, you may need to quickly switch to a higher torque setting while the robot is about to go into a pushing match, and if you hit the other robot at high speeds, maybe the sensor might get damaged and so the gearing has the chance of staying in the same position and it will not change your gearing for when you go to a stop and chances are you will be pushed around, while a driver that can manually override over it can start gearing it up so that you have more torque going into a pushing match so that you can possibly win. Something like this actually happened on our robot this year. We had a limit switch to detect when the arm is too high, so the motor powering the spool that pulls the cable stops. During one match, it had gotten damaged and we were not able to lift up our arm at all during the whole match just because of that. But also Cory, how you said the future is autonomy, robots aren't perfect yet. It would be nice to have it controlled automatically, so you are correct, but at times, a manual would be better.

And if the problem comes to it that a driver starts getting nervous because he forgets how to control it, he should've maybe practiced somewhat before to get the feel of which buttons or however layout you're going to use, and also the layout of the control board plays a part into it. The driver should pick out the buttons for which function on it so that it is easier for him to drive.

That's just my two cents and my opinion. Just so ya..

Re: CVT, which teams are planning on using them for next year?
 

I don't think anyone here is against a manual option (redundancy is always good). You're not going to use the system's full potential if you don't setup some sort of computer control though.

Re: CVT, which teams are planning on using them for next year?
 

mechanicalbrain that's what I've been saying. You basically let the computer handle the CVT's shifting, but in case of a system failure or emergency, you'd have the option of a manual override.

Stonefan5271138, sure using your robots "turbo" option was relatively easy -- team 100 had it on previous robots as well -- due to the fact that you only needed to press a button, just two variables, on or off. Your brain can probably subconciously detect when you need that extra power boost or when you don't. With a two speed transmission it's almost the same, except instead of having a program-limited speed, it's now mechanically limited.
Like what Cory said before, once you start having more than two speeds, like a 4 speed transmission, it gets a lot harder for the driver to keep his/her attention on the competition while trying to get the right gear ratios. Sure with driver practice, one could almost master the system, but for some teams, practice time is cut short due to some unexpected situation.
Now, with a infinite amount of gears, getting the right ratio's will be an even bigger challenge. Sure you could just designate set ratios to n-number of buttons, but that pretty much defeats the purpose of a CVT with an endless amount of reduction ratio's, unless you plan on pushing many buttons for many different gear ratios, which would be kind of funny. (You could have your second driver do it, haha)
So, I'll say it again, CVT's should be autonomously controlled. Set it and forget it -- if the shifting program has a flaw, have a programmer fix it. Design the hardware to last for at least one more competition than your team registered for. And I never (at least didn't mean to) mentioned anything about ruling-out a manual override option. its always good to have a manual override -- It's why the field has a big red button to stop your robot in case something bad happens (although I heard on the 2005 field it didn't exactaly work).

Re: CVT, which teams are planning on using them for next year?
 

I see what you're saying NoodleKnight, about how a driver has more difficulty and how it's harder for like, 4 speeds and how it may seem impossible for a CVT by just pressing buttons. A 4 speed shifting gearbox has 4 buttons for the different speeds. For a CVT, really, you should just need two buttons to control the shifting of it. One to gear it up gradually, and the other to gear it down. You could probably just use the buttons on the joystick to do that.
For a Variable Pulley Diameter System, you could design it in a way that the two pulleys change diameters together, so that when one pulley diameter increases, the other will decrease accordingly. This part could be done by programming, so you are right that it can be done automatically and it would be easier for a computer to control it, but it could also be done mechanically. For the changing of the gear ratios can be controlled by simply pressing the left button on the joystick or the right button on the joystick to change it. If it's that simple, I really don't see much of a need for the programming to control the gear ratios.
So overall, computer control in a Variable Diameter Pulley is a good thing to control the 2 pulleys accordingly, but it is not needed if a driver could do it with just pressing one of buttons that he can easily reach and get accustomed to, probably in just a matter of hours.

But then for this type of CVT or another type, how would you program it to get the maximum efficiency out of it?

...That's just my two cents.

Re: CVT, which teams are planning on using them for next year?
 

CVTs would nead a pretty amazing program to utilize it properly. any ideas of how a program would guide it?

Re: CVT, which teams are planning on using them for next year?
 

I see what you mean, Stonefan. I was going to say: what if you needed to change ratio's really fast? but then again, I guess you could finally put use to that Z-axis on the joystick, or just make your own custom switch with potentiometers.

I sort of had that question myself. I know that in cars, CVT's start to change around their reduction ratios once the engine starts to reach the peak of its torque curve -- but in the case of an electrical motor, that torque peak is at stall, and stalling motors isn't a very good thing. I think the basic algorithm would go: shift up if current is increasing and wheel speed is less than some constant X, which is what the wheel speed should be when that amount of current is going through the motors, so you shift up while accelerating. If the current is increasing and wheel speed is decreasing, then shift down.
And there's more for when the robot stops, is slowing down, etc...
Sounds like a fun project for a programmer.

Re: CVT, which teams are planning on using them for next year?
 

I was thinking for the controls if you did tank style steering and had the joystick 1 for a side, that you could possibly adjust the ratio with a pedal that you controlled with your foot. The harder you push the higher your belt goes up the pulleys.

Re: CVT, which teams are planning on using them for next year?
 

That would actually be a pretty cool way to program it. Might take some time and math to get it well though, but that would be cool and seems reliable, now that I think about it, it would be easier for a novice driver. It would be totally automatic and so he could focus on driving around.And ya, also that would be pretty neat to instead of having to use the buttons to change the gear ratios, using the 2nd axis of the joystick that the driver isn't using. That would be even easier if he had to use manual. But I was wondering, is there a way using some kind of sensor or with programming to detect current, or would you just go with shaft encoders to detect speed?

But ya, keep the ideas rolling.

Re: CVT, which teams are planning on using them for next year?
 

I believe that current sensors were shipped in the kit, or at least they were in 2004, I can't remember if they did in 2005 (I never bothered to look into the electronics, the kit bot was interesting). I'd go with both current and shaft encoders, I'd think you'd need to at least have two different sensor values to compare so the program can give the right gear ratio.
Also, when I meant Z-axis, I meant the 3rd axis, which is that little throttle thing that looks like a calibration wheel, but isn't. I don't think I've seen any team use it; on the new joysticks the thing is really small and hard to quickly manipulate, but on those old joysticks, the thing was pretty huge.

Re: CVT, which teams are planning on using them for next year?
 

That was true a couple years ago, but as others have said, not anymore.

A CVT is the only automatic transmission option on a MINI Cooper. It's a MINI Cooper - not a big car, not a big engine, but the transmission is really small (not light though...). I tinkered with the idea of buying broken ones from BMW for a robot but decided that it's not the least bit necessary. The company that manufactures the transmission and sells it to BMW for MINIs has a really really nice whitepaper on every aspect of their transmission and the 1.1L MINI engine combo.

The CVT on the MINI is really the only way to go if you like feeling your left leg after driving a bit - friggin' clutches :rolleyes: (the other option is a 6-speed manual). The belt I believe is entirely metal and there's not the least bit of "rubber-band syndrome" found in early CVT cars. You can select between 3 different shifting algorithms while driving, and if you don't value your warrantee, you could hack it and come up with some yourself (I would, but it's not my car...). I could extoll other aspects of the MINI too (now can use regular instead of premium because of a software upgrade :ahh: :D ), but most of them are true of many modern cars.

George

Re: CVT, which teams are planning on using them for next year?
 

On a different topic, if one was using a CVT with electric motors (itself a proposition only necessary because of voltage limits in FIRST - look at the majority of electric vehicles), a wise algorithm to use would not let the driver have any control at all... Merely, joystick position would correspond to a specific wattage input (measure with ammeters), with accelerometers indicating your speed so that the RC (or a suitable likeness) can decide the best gear ratio and throttle position to take the fullest advantage of the power. This would work in many scenarios, whether the robot is shoving or accelerating down the field.

not that I've thought about it for the past 4 months or am a programmer or an intelligent person or anything ;). Course, you need integrators and voltage-dropping circuits because have you ever tried getting a PIC18 to integrate at 400hz realtime even with interrupts (which are hard to implement anyway on the adcs)? coz I have. That was painful. and whatnot but hey, what do ICs cost nowadays? lol, integrating integrating integrated circuits into an integral platform to measure the integrity of the integrals from your integration of the integrating integrated circuits... ahh tonguetwisters and the many definitions of integral...

Hope that helps. ;). PM if interested.
George