Check out the team 33 4 speed transmission. I may be biased, but I think it’s the easiest to build, and it’s definately the lightest. You can also just build half of it and have a two speed transmission. I think the 4 speed costs something like $80 in materials, and the two speed is even less.
While the off the shelf trannies are great and work wonderfully - don’t cheat yourself or students out of the learning experience available by designing and building your own. Look at it a another project. Pick a couple of ideas choose the style you want then begin designing it to meet your own criteria. The pride developed by doing this is immense. Our team loves our 3 speed trannies based off of 222’s. We made our own tweaks and such and they hae worked great this year.
Most of all this can be fun and frustrating - start early - and test to refine your work of art.
Ken
Although I have no direct experience with multi-speeds, when my brother was on team 900 in '03, they made a two speed. It would have been great, but they messed up their gear ratio calculations, the high speed was way too fast and nearly uncontrollable. Beware of incorrect ratios. Mind you, I’m not one to talk, the four speed double dog design I was pushing at the beginning of this year had a 4th gear with a speed in excess of 20 ft/s! :ahh: (It got canned due to budget and lack of machining capability)
PS Shouldn’t this be in Technical Discussion?
When it comes to weight the AndyMarks do help.
Last year we milled out the gears in our Kit Transmission, all in all the Kit Transmission was about 1-2 lbs lighter. When we got our AndyMarks this year we took our Kit Transmission from our robot last year and weighed it against an AndyMark. The AndyMarks were about 5-7 lbs lighter.
We actually designed a 2-Speed that used helical gears instead of spur gears. Our intentions were to use it on our robot this year, but we ran out of time and bought 2 AndyMarks. I must say that the AndyMarks are, IMHO, easier to install and maintain than even the Kit Transmissions! They easily integrated with the rest of our robot and we didn’t have to change a lot on our drive train.
With that said, making your own transmission is a very valuable experience for students. Even though I personally didn’t design the transmission, I learned a lot by watching the transmission be designed. I had no clue what meshing gears was or what dog gears were, but by the time we started putting together the first prototype of our 2-Speed transmission I knew what the difference was between meshing gears and using dog gears. For the students, actually getting to see a transmission designed, built and used will be an awesome learning experience.
Even though the transmission we designed was not ready to be used on this years robot, we learned a lot from how the AndyMarks that we want to use to improve our transmission. There were somethings we didn’t spend much time considering, like how to mount the gear box or how to save space by changing the placement of the output shaft.
The bottom line is that I would 100% recommend designing your own transmission, if you have the money and machining capabilities, but don’t over look existing or off the shelf transmissions.
We love our 2-speed transmissions. We got the AndyMark transmissions and they work wonders.
Our team made 3-speed (2002) and 2-speed (2003) planetary-gear transmissions however, we didn’t really see the need for it in the last three competitions. The only problem with them was that we used pneumatics for shifting and that added a huge amount of weight and battery drain. If we see another game where there both high torque and high speed are needed during a match, then we will probably use a multi-speed transmission again. Otherwise IMHO it’s probably not worth the design time or the expense…
I like the challenge of trying different technologies, although my team members prefer simplicity and robustness.
In theory a continuously variable transmission is the way to go, sensing the motor speed and adapt the gear ratio to it.
You’ll find already so many different ideas and patents out there and you may even invent something new.
After some web-search, I found this one, which is my personal favor:
http://www.fallbrooktech.com/NuVinci.asp
I would like to use this post to thank all of you who are providing me with this info. I would send each of you an email, but I don’t have the time to do so, seeing as how so many of you posted with ideas and thoughts. This forum is still open, but I just want to say thanks for all your help, it’s things like this that make me want to come back to first each year. Once again, thanks. 