Transmission help

[neo-cortex]

Our team is planning to work on a 2 gear transmission as well in the off season.. the details haven't been worked out yet but it's floating around

[thoughtful]

Originally Posted by Tom Bottiglieri

It might be worth the weight, but is it worth the delayed shift time and possibility of breaking?

I dont have much experience with shifting tranys, but can you ellaborate on the delayed shift time that occurs from servos?

[Jeff K.]

Our team is also planning on designing and prototyping with a 2 speed this offseason. We bought the AndyMark 2 speeds and we found them to be expensive, yet very reliable. We have the gear ratios and calculations for torque and what not down. And now just - CAD TIME.
We're hoping to have a sponsor machine most of the stuff...that is unless we get a CNC Mill sometime soon.

[ICE MAN]

If you can perfect the shift on the fly and have your low gear have high torque and your high gear have good top speed, you will most likely be a force to rekon with. Reason why? Most 2 speed transmissions have pretty bad low end torque and good top speed. the problem with this is that if you get into a push match then your extra gear is pointless because you cant get away to use it. so a high torque low gear would help you get out of push matches which of this year we all know from now on will happen, and a top speed high gear will help you get away from your oppentes with ease. so the choice is up to you. personaly that is a lot of stuff that has to work in order to just get the robot moving not even to mention the rest of the robot that has to complet the game. my advice, buy a 2 speed transmission from andy mark or some other robotics company, build it and see how it works. then if you think that you can do what a professional company could do it and make it run well in 6 weeks then I say go for it. But as for me and my team will let the big first dogs do that and we will stick with our simple yet effective transimission which has so far got us to the finals two years running. Good luck with your transmission and hope it al works well in the end.

[Mike Nawrot]

Originally Posted by thoughtful

I dont have much experience with shifting tranys, but can you ellaborate on the delayed shift time that occurs from servos?

one cause for delay would be the small difference between servos, so that one side shifts before the other, and kinda causes the robot to go in a not-so-good direction.
I developed my own two speed recently and i'm currently busy integrating it into a mock up drive train in autodesk. The transmission looks good on paper (or in this case LCD), but i'll have to see how it works in reality, with weight and costs and such. I've thought of my own little tricks for shifting and all, but those are my little secrets. As for the advantages to multi-speed transmissions, i think it is a great direction to go in. They destroy the generalization of function on the robot and open up the window of specialized functionality available in multiple scenarios on the same robot. In other words, if you're in a situation where you need to have detailed control over the robot, or you need power, you can get exactly that and nothing extra to get in the way. And then if you need the highest possible speed with no power, you can have that as well. Simply put, the two-speed's fuction has no downfall, it's only the approach towards the two-speed that can result in lost time, money, and weight.

[Paul H]

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.

[UCGL_Guy]

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

[lukevanoort]

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! (It got canned due to budget and lack of machining capability)

PS Shouldn't this be in Technical Discussion?

[Jon Jack]

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.

[Schneidie]

Originally Posted by litchfieldc

Me and a bunch of other members of team 1073 are going to be designing and building a new shiftable transmission with the help of our mentors. I'm just curious what other teams who had them think about them. Are they worth it, are they helpful for only certain times or helpful in every match. I don't need blue prints, (if you want to you can post them though ). I just want to know if this is going to be worth the trouble, thanks to all those who post, and see you all come next season.

We love our 2-speed transmissions. We got the AndyMark transmissions and they work wonders.

[CardcaptorRLH85]

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...

[stefwitt]

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

[litchfieldc]

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.