Our team has used Vex 3 CIM two speed shifting gearboxes for years with good success. Last year we used three NEO’s on each side and basically never shifted. So, the debate on the team is: should we shift to single speed gearing for our drive train given the new power available from the brushless motors? We would reduce weight and complications, but can we find the right gearing to allow both pushing power and sufficient speed for games like the last two years?
Question 1: How much pushing do we really do anymore? This year’s lack of protection meant more than in the last couple years, but so much effective defense can be played by bumping or crowding rather than shoving.
Question 2: How long will your sprint distance be in 2020?
Question 3: Will shifting actually shorten your sprint time compared to a thoughtfully-chosen single gear for a given set of motors?
Arguably shifting gearboxes were never needed… it’s so rare that a driver effectively uses a shifting gearbox to actually improve their cycle time. Most of the time in my experience drivers will develop a preference for one speed or the other and leave it in that gear for a large majority of the match.
We want to choose between a very fast offensive approach (3v3 offense) or be ready for or to actually play defense. It’s a leap next year we’re thinking of making, and while it might not get used every match, the matches it does get used, it’ll be better to have it then to not have it.
I think dual speed gearbox are great for reducing battery draining also its helpful when it come to defense because the motor works less due to low gears tork in order to push the opponent robot.
in others words less heat generated,
Less heat equal better efficiency,
Better efficiency better performance!
And a longer life expectancy from the motor!
Did you ever need em in the first place?
I don’t think the debate’s changed. You can get an extra 100-200W of drivetrain power I guess, but it’s no paradigm shift. The majority of drivers on shifting boxes don’t effectively utilize shifting anyways.
We have never used a two speed gearbox before and have done pretty well I believe. I dont think our drivers have ever thought, wow, we wouldve done a ton better if we had shifting. There have been a few times where the extra torque wouldve been better, but that’s not the main reason we lost we felt.
We did do a PTO gearbox last year, and I personally felt worked pretty well. Allowed for a strong and fast climb. PTOs only get more valuable I feel like as the motors get stronger.
Thank you all for your thoughts - this is helpful to us. If I could steer the conversation a bit, I’d like to hear more about whether the more powerful motors available now would make the shifting argument different. Our team has seen value in the past with shifters, so we don’t really have a question with past available motors.
The question we are looking for thoughts on - have the new more powerful motors changed the decision point significantly?
Not for us. We gave up on shifting in 2017 anyway, and wouldn’t see much value in adding all that complexity for most scenarios. Kinda want to get good at playing the game rather than adding more weight, losing more space, and taking more time to build and repair.
I might be able to answer the original question at some point after January 6, 2020.
It really depends on the game. In a game like 2014, where the field is wide open, or 2017, where you have to get end-to-end to score, but still line up for a shot, I think a shifting transmission would–in general–be beneficial. Obviously that’s going to be team-dependent, but full-speed full-field runs around defense plus pushing the D out of the way… I smell shifter. A game like 2016, 2018, or 2019 where there’s a lot of short sprints, not so much. That’s definitely arguable.
However… shifting speeds of the drivetrain is NOT the only purpose of a shifting gearbox. If you need a two-speed elevator (2018… 2019… just sayin’…) or a PTO, then a shifting gearbox becomes essential.
Like anything in FIRST, it was never needed.
In my personal opinion, shifting is becoming obsolete because teams don’t want/ can’t sink the resources into making shifting really good. Really good shifting would not only occur automatically, but will optimize your acceleration curves. This is can be very complicated for a relatively low payoff, so you will see less and less teams using it.
Anecdotal evidence: my team bought into shifters during the offseason going into 2016.
Never used them in 2016.
Used them extensively in 2017.
Never used them in 2018.
Bought out of them into single speeds for 2019.
Until we get another game like 2013, 2014, or 2017 that requires frequent full-court travel, they will not be needed again. And it’s debatable if they’re even needed then.
So probably not.
The more powerful motors of the last several years have made the argument different. When I started in 2004, you were allowed two CIMs, a couple drill motors, maybe two of that Fisher-Price motor…not a lot. Your robot’s power budget was greatly limited and thus your ability to make an accelerating robot was limited. Shifting was a big advantage then, because you could apply that power band broadly.
To me, the jig was up once FIRST started allowing Mini CIMs, 775pros, and eventually CIMs in unlimited quantities.
I expect the use of shifting drive gearboxes to continue a downward trend. This trend will be pushed a bit by the more powerful motors becoming available, but it is mostly being driven by the crowded fields we’ve seen most years in the “theme” era, and the associated shorter sprint distances. Another factor is the unprotected scoring areas. Whenever a few sharp bumps in the scoring (and/or pickup) area is effective, there isn’t as much need to completely shut down movement through pinning and pushing.
No matter how powerful motors become our limit will always be the amperage that we are allowed to use. 40 Amp breakers are the limiting factor in drive trains these days (and battery capacity), so in reality the more powerful motors will not matter much. The amazing thing about the new motors is their weight. The more motors you have on any subsystem the lower the required amperage will be per motor. Instead of using a shifting box I would recommend trying a 6 NEO or Falcon 500 DT. They are probably lighter than a shifting gearbox and much simpler.
So often it seems that teams try to “speed up” their robot by decreasing gearing ratios to get a higher top speed. The things about FIRST is that a slower robot (lower top speed) often equals a faster result from point A to B. In many cases a robot that travels at 11-12 FPS with a single speed gearbox will be faster than the vast majority of the robots on the field. It is also slow enough that you will still have some decent pushing power. Couple that with some good driving skills and you won’t miss the shifters.
But what if you could have…CVT?
Saw your new modules at RR. They look fantastic and like an excellent improvement from your many previous iterations, both in terms of simplicity and strength. Looking forward to seeing how these fair.
I’d never use a shifting gearbox except with autoshifting.
With autoshifting, however, it gives you a very nice, zippy drive.
That’s exactly why you need CVT.
In my opinion it depends on what region or district you are in. If you are in FiM, FiT, ONT, or Mid-Atlantic: I would say that they are still worth it and beneficial. FiM is known for having brutal defense no matter what the game ends up being. Having the ability to push people out of the way when you can’t get around them in a timely manner is almost a must when you get to MSC (particularly in elims). FiT and Mid Atlantic have very similar reasons. The difference being that you have more teams that focus purely on offense and don’t worry as much about playing defense or having to deal with defense. Yes there are teams that do consider defense and some teams specialize in it in these regions.
For teams that aren’t in those regions: The ability to have a high speed and a low speed does have its benefits. For shooting games, when you stop to shoot, go into low gear to help with auto targeting if you have relatively in experienced programmers and help the robot stay in place when someone inevitably tries to bump you so that you either miss or it takes longer to get in a shooting location/orientation. For all types of games (except for recycle rush), having the ability to drop into low gear when getting defense played on or when you have to play defense is very beneficial. Especially when you have to deal with power house teams. (For those that would argue bumping them when they try to score or on their way to score is better defense: I agree that it is effective but, pinning and straight up pushing them further away from their desired destination massively increases cycle times and in some cases completely shut them down. You can do this in addition to bumping them or other opponents whenever you get the chance. And what happens when the team that you are playing against has a shifting gearbox and you don’t?)
Summary for those of you who don’t want to read this mini essay: I think that the little extra weight for the 2 speed gearboxes are worth it in most if not all cases because, there are uses for them in almost every game, (sorry Recycle Rush), either for defense or precise positioning.