Can we please stop arguing about the pros and cons of light-weight gear box or how to save weight? That is not what this thread is for.
They designed it and built it!! They have been redesigning / refining their shifting transmissions each year since '02 I think.
Here’s their '02 shifting transmission…
oops… a better pic in CD-Media
Sure have come along way since then! I’m not sure how much more improvement can be done… 6 motor CVT’s?
Ohh… Did 254 build theirs too?
254 and 968 collaborate and work together.
Every part (except the bolts and bearings of course) of the transmissions were custom machined. You can not buy them at all.
Currently the two best (for overall FIRST use), off the shelf (which seems to be what you are looking for), shifting transmissions are the AndyMark two speeds and the Dewalt drill 3 speeds.
The dewalts take more work, but are 3 speed and cheaper.
The AndyMarks are easier to work with, are already done and can take two motors without modifications.
Personally, I would take the andymarks.
I agree, 1726 used DeWalts last year, and had some troubles with them. We used the AM air shift transmissions this year and they worked just fine, runout, weight, and all.
There is not much available to buy as far as shifting robot transmissions. You need to be able to make parts yourself, adapt parts yourself (such as the modified AM transmissions you have on this year’s robot), or get help from someone who has the ability to make this stuff. It’s not easy!
I’m gonna rank transmissions in a little list here. Keep in mind these are all my opinions and observances, so yeah.
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Best! Your own custom tranny. You can build it to the weight, size, and everything that you want. It also gives you great control over your bot, as you can change everything to be what you want.
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The upcoming (soon to be sold) transmissions from Trossen Robotics partnered with OutBack manufacturing. These are still in the design phase, but they’ll be quite the system. Very robust and light, as well as decently cost effective.
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AM shifters. I’ve never used these because my team keeps making me design and build my own, but I love these things! They’re incredibly cost effective and robust for their weight. They’re also proven, reliable, and an all around good system. They get the Craig Seal Of Approval.
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Dewalts. These are a great budget tranny, but I’m not a fan of their robustness. People may brag about them being sturdy, but I’ve seen too many of them shatter. There’s just a certain amount of structure you gain out of going with larger and non planetary systems. I’m not dissing these, I still think they’re great. Personally, I would limit them to budget bots and Crab systems looking for multi speeds.
Don’t forget this one: http://www.chiefdelphi.com/forums/showthread.php?t=26490
That’s a custom tranny. It falls under the first one, because you can change it to fit your own bot. However, it is really nice… except for the cluster shifting. Make it dog and I’d love it.
I believe it was a collaboration between 254 and 968.
Acually in '03 they didn’t have a shifting transmission design until the Cal Games comp seen here…
That design went into their '04 bot seen here.
'05 was further refined when they added FP’s with AndyMark Planetaries…
'06 seemed similar to '05… pic here
There are some transmission designs in the white papers section - check them out. I remember looking at Andy Baker’s design back in '03 and inspired us to make our own and it looked like this… It was so heavy and bulky we never actually used it in a competition bot. With the motors on it, it weighed in at 22 lbs.
Then we got inspired by Paul Copioli, Thunderchickens, and tried to make our own version of CVT (kinda) that looked like this…. That never worked as well as we hoped, but nonetheless the students learned A LOT by trying.
So do some research and start designing a transmission of your own. Even if you don’t use it, you’ll be ready to adapt to any new changes FIRST makes for the upcoming seasons.
One advantage that nobody has mentioned for a lightweight transmission is rotational inertia. Force must be applied over a longer period of time when the wheel (in this case the gear) has greater mass. On startup this means that batteries will experience a current surge for a shorter period of time. Less weight also means faster acceleration.
This year was the first year we built a custom two-speed transmission. It is a ball-shift with a 1:9 and 1:3 ratio gearing with a single Minibike motor. See here: http://www.chiefdelphi.com/forums/showthread.php?t=55786
We learned from our stupid mistakes, like you never calculate from unloaded speed (oops), and look at power ratings before choosing motor (oops again). Although an impressive achievement, it has weight issues that could have been addressed by using smaller diametral pitch gears (I’m thinking 32 DP). We learned alot from our experience, and expect to see big improvements next year.
I think the main advantage to reducing weight on the robot is so that if you go over (as we along with many other teams did) then its just another piece that can be lightened.
I understand the worry that you would add the weight higher on the robot but I believe that the trade off of guaranteeing lighter weight over messing up where you put weight is worth it.
Also I find it easier to simply not put weight high rather than trying to monitor your weight all along with a heavy gearbox.
For the past two years Team #39 has tried to use the transmissions that come with the KOP. We felt it would be easier to help rookie teams if we had to overcome the same problems they had. After the Banebot problems this year we do not want to use them next year. My question is, do you think the KOP will have the Banebot transmissions next year? If they do, I think we will return to the AM trany.
Ken
Will the KOP have banebots next year?? My guess is probably…
After experiencing the problems they had with them this year, will they be the same exact banebots 56mm trannys?? my guess is no…
FIRST learns from their mistakes, and I think after seeing the huge struggle teams had with these this year, they WILL correct it.
As far as trannys go…254/968…the thing is just unbelievable. If you haven’t seen it yet, hop around delphi and check it out:
http://www.chiefdelphi.com/media/photos/28070
http://www.chiefdelphi.com/media/photos/27018
Serious props to the guys over on the left coast for designing this thing. My entire team was drooling over it (and the rest of your guys robot 
). Travis, thanks for explaining the hard anodize process to me, its definitely something we’ll be looking in to.