Just wondering if there was ever any robot in FIRST with a 3 shifting transmission… or if anybody is planning to do one during any of the coming up years… probably just for a 2 minutes match… its not really necessary to have a 3 shifting tranny…
There was a Michigan team that had a 3 speed transmission a few years back, but I can’t really recall who it was right now. I want to say that their sponser was GM.
I’ll do my best to try to look it up in the forum archive.
EDIT: Ok, I believe it was team 322.
http://www.fireteam.org/images/trans.jpg
That’s the transmission. Found it here. and here.
While a 3 speed transmission would sure be cool and probably would win you a technical award if pulled off, I am sure that everyone here will agree with me when I say that it is most definitely not worth it for the added weight and complexity.
The key is justification for something so complext as this… it’d be a VERY hard to do, unless there was a situation where you had a very steep hill perhaps, where you wanted to have a medium gear ratio so you could go over the hill quickly. However… I think again I’d just set that ‘medium’ ratio as my “fast” and be done with it.
It would have to be one heck of a game to justify it on our team.
Two cents in the jar. Clink Clink.
Matt
My team had an idea for a 3 speed transmission that we prototyped back in fall 2002. Our main reason we wanted it was so that if there were very heavy objects in the game again such as in 2002, you’d be able to get to them very fast, start pushing them in low, and then once they got moving well you could switch up to medium and push them a little faster. The shifting mechanism was moved back and forth with a globe motor, we just couldn’t think up a very good way of indexing it so the robot would know where it was during the match. Then when the 2003 game came out we put the idea on hold since it wasn’t needed at all.
The use of a 3 speed transmission is a very intresting idea, but, is it really needed? You must factor in weight, cost, and effectiveness on the field. But honestly I would like to see one in competition though.
Ivey
add the time (2:00 mins) factor too…
ok… I know this thread had been dead for a few weeks but…
My question for you:
If you had a design for a 3 speed transmission, and the weight was 4 pounds per gearbox (without motors), and it wasn’t SO complex, why not make it?
Ok, maybe my question should also include, what are the good sides of a 3 speed tranny? I’ve discussed it with my team’s engineers and advisors… and all I’ve gotten back is that it’ll probably work but… “why do we need such a transmission”.
Here’s my reasons:
Pro:
- 3 speeds brings complexity and probability of innovation in design awards.
- if you gear it right, you can outrun and outpush almost anyone.
- nobody (almost) has made a 3 speed transmission.
- with my design, the complexity from 2 to 3 speeds doesn’t increase that much. In fact, complexity from 3 to 4 or 5 speeds doesn’t increase much either. It just gets bigger.
- if you make this transmission, and get your electrical people to make it automatic, you have a go at the leadership in control award.
- you can reach REALLY high top speeds
Con: - 3 speeds brings complexity. Expensive, will take forever to machine, needs to be CNC’d, etc…
- why not 2 speeds? It seems that you will never need 3 speeds in a FIRST game.
- if something is mis-aligned… death of a gearbox. The complexity mixed with errors in manufacturing will kill you. But… holes can be line bored, so the misalignment problem is small.
- you will never have enough time or room the accelerate to 3rd gear
Thats all I can think of right now…
Complex, prone to problems, not really needed, tough to machine and assemble, consumes too much power -
I sure hope someone builds one for 2004 -
It would push the envelope a litttle bit further and that is what its’ all about.
well there could be a lot of benefits to having something like this… You would be very fast… somewhat strong and fast… AND extremely strong all in one…
many people look at this at this as almost like a car transmission… but remember in high gear ( at like 6:1 ish ) you can get your bot flyin around the course… w/ little acceleration and be going just about as fast as the average driver could handle
But see thats just the thing… in the size field we’ll be using… you could never really go any faster than that and have it handle well at all…
unless you went with something like a strong… stronger… strongest
Ie ( on a chip motor ) like 20:1 … 45:1… 130:1
Infact… making a 3or 4 speed transmission would not be much more complex than a 2 speed… a simple 2 speed… you can use a dog shifter or simply insert the gears to mesh… well what happens when you put 2 shifters per gear box… with 2 sets of gears each. You have a 4 speed transmission… with little added complexity… just bigger.
1 pro I can think of especially would go in the area of slippage if your a wheel use team. If you monitor your wheels and sleepage via sensors and If your wheels pick up when they are slipping ( ie your in a pushing match ) and you down auto down shift… 3 or 4 speeds would give your more down shifting capability… and instead of having to reduce power to the wheels to slow rotation and gain traction again… you would infact gain a ton of torque and more traction with every down shift.
Then there is the pride factor… You do it… It works… You show it off… The crowd loves it… Its a good feeling… This is more important to a lot of teams than just winning flat out… There aren’t many teams that do it… You can take pride in it… If teams start to follow your lead then its a good feeling to know you were one of the first to do it.
Only problem again is… why?.. There is no game that I think FIRST will develop that would require more than 2 speeds. Infact… all games can be efficiently played with a strong single speed. There are more things to go wrong… and it would be more difficult to build and program.
Keep it simple stupid is always a good motto
But if anyone plans on building one of these good luck to yah and send me tons of pictures 
Well… driver dificulty is limited to the gear ratios you use. For example, you can have 1st be 3 ft/s, 2nd at 8 ft/s and 3rd at 13 ft/s. You can always have crazy top speeds too, like 25 ft/s, but as you said, nobody can control such speeds in such a small playing field. And you can’t really think of a robot as a car because you are using electrical motors, which work on a very different power curve than a car engine. A three speed transmission would just be like any other team’s 2 speed, but with a mid gear, not an even higher gear.
One good use for 3 speeds is when the weight of your robot changes. Like the 2002 game, where you could grab goals and become 360 lbs heavier (if 2 goals are grabbed). Here, you could have your 2nd and 3rd gears act as your normal gears when not attached to goals, and use 1st and 2nd when with goals. This is why team 322 used a 3 speed that year. They grabbed goals, accelerated on 1st to 2nd and were fast with the goals.
Anyway, as for the complexity issue, I don’t think thats the problem, but the problems that come with complexity, like the increase in the possability for something to die on you. As they say, the more complex, the more things that are to go wrong. But, this ‘disaster’ issue can be solved if you take a good look at your design and make it really rigid, and see where stress is the greatest, and fix that problem. The best way is to make a prototype and fix its problems in the final gearbox. But… how many teams have the time and money to make a prototype of a 3 speed transmission. Few. Not my team.
hey all, i was the driver on team 322 when we used the three speed tranny. as said beore by all of you guys, there were pro’s and con’s to having our transmission, but weight was not one of them. our three speed planetary gear box weight only two pounds more than our two speed we used last year (though this could be because we used six motors in our two speed). we found it a very good transmission for that game, but decided not to use it last year.
the only disadvantage was repairs. at first we had plastic gears to reduce weight, but later switched to metal because the plastic lost its grooves after switching to low gear. repairing was tough and very time consuming, but once we had it down pat, repairs were rarely needed at all.
this is how we used our three speed:
high speed: to the goals at the beginning (we were never beat to our goal). also used at the end to get “home”. (if you all rember extra points were given for returning home at the end)
medium speed: all purpouse gear where we manuvered our goals (used the majority of the match)
low speed: used durring shoving and pushing matchs. (we were one of the only few teams able to defeat beatie (71) they won the nationals that year)
in conclusion, three speed was practical and efficient in the game two years ago, and if it is practical once again this upcommin year, then team 322 will go back to it once again!
you’ll see it in 3 weeks, I promise
We have a 4 speed automatic transmission up our sleeves, but we don’t see it practical to use it this year. Check the 33 pits if we’re at any of the regionals that you are at, we may have a demo version.
How did you guys get it to shift from one planetary gearset to the other. Like how did you transfer power from one gearset to the other. That just boggles my mind in some ways. I was working on an idea, but found that I needed some sort of device to change the ratios, but I couldn’t devise one that would be productie.
ivey
We used small 3/4 bore air cylinders to change between 1st, 2nd & 3rd gears. After debugging this masterpiece, it was awesome. For this year though, I don’t see a need for it. As a matter of fact, we are only using a one speed tranny this year to free up wgt. for everything else.
Hmmm, I think I will retract my previous statement that a 3 speed transmission is too heavy and complex for FIRST use.
47 sure proved me wrong.
Cory
Team 222 has a three speed this year, and i believe 968 actually has a four speed…
Yes we do.
Huge inspirational praise to our machinist, “Just Bob”. He lead us all the way with this one and it works great. We can have a sweet accel. and a nice top speed. We only use the chips with it and the whole thing doesn’t weigh much. Brad posted a pic. and a quick explanation of it for all to look at. Hopefully it will do well though awards to other team inspiration and the competion. I haven’t seen it miss a shift yet since running so it is pretty good as far as reliability even though it really doesn’t follow KISS. Anyway come check us out at a comp. near you. Annapolis, Philly, and Nats.
Definitely… A well designed 3 or 4 speed can easily be simple and lightweight. (granted the 2 speed version of the same kind would of course be lighter.)
I would encourage all teams to try something challenging like a 3 speed or 4 speed tranny (or higher… but don’t get toooo carried away :D) Even if you are unsuccessful during the 6 week build period, you will learn a lot during the design and research process.
There are a lot of great people on this forum who are more than willing to help any of you that have ideas… Shoot em by guys like Andy Baker, Joe Johnson, and the hundred other engineers and mentors that are out there… You will be amazed and how knowledgeable and willing to help they can be.
As for our team…I do not think we will make a 4 speed next year… it is really nice to have the options open… and we have that “cool” factor… But, there just isn’t enough room on the playing field to 'let ‘er rip’, so to speak, for it to be worth it. Our team wanted to do something challenging and unique… and I think we accomplished that very well. We learned a lot, and had fun doing it. Isn’t that what FIRST is about? 