pic: CVT drivetrain

[jgannon]

Originally Posted by Cory

there's no sense in making (or being rewarded for) something that will perform poorly, because it is cool, instead of making something more traditional that will perform better

I'll concede that point. There's no sense in, say, making a drivetrain powered by one Globe motor. Would it be unique? Yes. Would it be cool? Sure. Would it perform well? It's safe to say no. However, I don't think it's fair to assert now that a CVT will perform poorly, particularly when only one design has been tested.

[alphastryk]

here is a non-friction-based CVT:

http://www.andersoncvt.com/device.wmv

i dont know if it is feasable to make this type of CVT, and you would have to ask this guy, because he has a patent on it, so...

[sanddrag]

Originally Posted by alphastryk

here is a non-friction-based CVT:

http://www.andersoncvt.com/device.wmv

i dont know if it is feasable to make this type of CVT, and you would have to ask this guy, because he has a patent on it, so...

I've seen that before. To me, that still does not look like a positive engagement system.

[Kevin Sevcik]

Looks like some sort of quasi-positive engagement system. You're relying on the pins on the belt not to shear or skip instead of a belt not to slip. It's interesting, but I don't think his demo there was under any sort of load, so I'd question the actual performance of the design when you toss an engine and a load on it.

On a completely other topic, I agree whole-heartedly with M Krass that inefficient, poorly working designs are less deserving of awards. FIRST is an engineering competition. Atleast that's what I've always been told. Engineers often design cool, innovative devices, but they always strive to design something that works well, is efficient, and is cost-effective. In my opinion, a cool, innovative, expensive CVT that bleeds power is a poor engineering choice.

As an example, a team could come up with a thoroughly innovative and cool device for a robot that serves absolutely no purpose whatsoever. Heck, they could put a cold fusion generator on there to power some decorations. Do you want to give them an award for a really innovative, utterly useless device?

[mechanicalbrain]

I'm curious how many of you have heard of using magnetics to create a change in processing path on a processor. it works allot like a hard drive and was turned down in favor of our current method by silicon valley. now however its being taken up with fervor. why because unknown to everyone it allows a computer to instantly specialize itself in any process it needs to do by rewiring the paths of its own circuits. this is a very good example of how something automatically labeled as inefficient turned out to be superior. i see allot of people claiming this as inefficient but i spent almost three days learning and talking to people and its become obvious quite a few posts are based on no physical information further more instead of criticizing an idea why not try to give suggestions. this system has many benefits that i feel are simply being overlooked. the problem with most drive trains is that when you change gear you have to slow down. while you can do it at high speeds it literally shocks the transmission. (this is not something i want to see argument because i checked this with my dad who drag races and my moms friend who teaches racing) a CVT can make these changes on the fly and not suffer a RPM drop. yes these systems have drawbacks mostly endurance but they wont be on a large strain. i would like to point out FIRST is not about having well designed systems its about showing innovation. so i ask anyone posting from here on please show some innovation I'm really tired of seeing lots of post turning down an idea and few posts (thank you to the ones who do) that show thought into creating new or improved ideas. i know im going to get allot of fire for this but im just tired of seeing all hiss and no ideas (agian i thank those who prove to be the exception).

[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. I am not going to sit here and argue about the innovation and coolness or whatever about his design and whether or not a robot with it deservs an award, but I mean a CVT is just flat out awesome to me. How can you make something better if you never make it in the 1st place to develop it.
Here is a link that someone on my team found that has tons of differnt CVT's.
http://www.gizmology.net/cvt.htm

[mechanicalbrain]

see reading this message put a huge smile on my face. i was expecting people just showing anger at my post but was impressed by your post. i think that is truly the spirit of FIRST and i think your team is lucky to have someone who shows such great creative potential. by the way the link was great and very informative. by the way i would be interested in talking with you.

[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