pic: CVT drivetrain

[ahecht]

Originally Posted by santosh

^agreed. I was just kinda curious. Is acceleration with a CVT competitive or any better than acceleration with say just a regular automatic transmission.

In theory, comparing a car with an automatic transmission to an identical car with a CVT, you should see a 25% improvement in acceleration with the CVT. In practice it is slightly lower, but that is mostly because CVTs are much less mature technology.

I can say that even with a manually shifted CVT, 190's 2002 robot had incredible acceleration. Once it was working properly, it was first to the goals almost every time.

[mechanicalbrain]

yeah thats what i was thinking

[ChuckDickerson]

I have been fascinated with CVTs for a while and have wondered if any teams have successfully used them in FIRST. I know of the CCT but it is not really a CVT as I understand it. From what I can gather from this thread the only successful use of a true Toroidal CVT was Team 190 in 2002. Is this correct? I was not involved with FIRST before 2004 so I have no knowledge of it. Was it a Full-Toroidal or Half-Toroidal design? Can anyone point me toward some photos of it or a white paper or anything so I can see how it looked? Whether or not a true CVT is appropriate for FIRST robots (depending on the particular game) is a whole separate issue. I just think they are a cool idea and would love to see how Team 190 did it in 2002. A picture is worth a thousand words...

Thanks,
Chuck

[mechanicalbrain]

yes i agree i would be interested in a pic too.

[Kevin Sevcik]

So.... First and foremost, FIRST is about inspiring students about engineering, science, and technology. Probably it's debatable whether a well designed machine does this better than a finicky innovative one. Obviously, you'd really prefer to have a well-designed and working innovative machine, which would certainly be very award worthy and often does win awards at regionals I've been to. I'm just questioning why you'd give a team an award for a feature on their robot if it didn't work well. It's telling that team and other teams, "Hey, they tried something new and botched it, but it was new."

Anyways, aside from awards, I'm really questioning the design decision to put a CVT on a FIRST bot. Here's my thoughts:

Pros:
Faster acceleration - you can go places a bit faster.
Auto shifting - you don't have to think about down shifting to push.

Cons:
Expensive - belts and non-CNC machining or no belts and CNC
Time-consuming - 190 couldn't get it working well in a season, and the hung in auto in '04
Complex - look at the darn things.
Expensive - see above

Yes, it would be neat. So would any number of other highly complicated systems that could be built and but on a robot. But robots are supposed to be engineered to complete a task well, they're not show pieces or demo boards during the season.

[santosh]

I pesonaly think that if your team can handle the extra work and has unlimited funds when coming to building the robot, then go for it. It just depends on how much you value those pros and those cons.

[mechanicalbrain]

agian FIRST isnt about awards either.

[ahecht]

Team 190's web site is having some problem with the history section over the summer, but here are some pictures I was able to extract (you will need AlternaTIFF to view these, as quicktime sucks):

http://users.wpi.edu/~first/images/history/2002/resources/toroids_and_idlers.tif
http://users.wpi.edu/~first/images/history/2002/resources/with_sides_removedcomplete.tif
http://users.wpi.edu/~first/images/history/2002/resources/color_section_through_idlers.tif

[mechanicalbrain]

those rock!