Is a shifting transmission really necessary?
 

There have been a lot of great discussion threads regarding how to design/build the best shifting transmission. These discussions almost imply that it is a foregone conclusion that shifting is better. I personally do not agree with this point of view and think the topic merits discussion.

Maybe you don’t need to shift at all.

I would argue that for the last two years shifting was not necessary. If you can attain your desired top speed and still have enough low end torque to break loose all of your tires/tracks in a pushing match you do not need to shift. Electric motors unlike internal combustion engines make their max torque at stall, which is where you want the most torque and pushing force. For max speed you need enough torque to go only as fast as you can drive. For us this is about 10 ft/sec. At neither extreme do you need to be at the max power output of your motors.

In 2001 and 2002 we could pick up movable goals. In 2002 a robot could pick up part or all of the two 90# goals at once and drag them back to their scoring zone while dragging another robot backwards. This was a season to have a shifting robot. For the past two years we did not have the ability to transfer any additional weight onto our robots during a match. We will make the shifting /non-shifting decision after the game is announced.

What are the risks rewards of having a shifting transmission?

Risks: Reliability, robustness, weight, packaging space, cost, complexity, time and energy required, etc.
Rewards: Maximum low end torque / top end speed.

A transmission is sexy and lots of fun to design and build. We have built three different two speed transmissions and a CVT. We have never put a shifting transmission on the field. In the last two years we have played over 200 matches (in season and post season) and have never lost a match because of a transmission problem.

Many teams do not really have the resources to put a shifting transmission on their robot but will proceed to attempt it anyway. This can divert scarce human and financial resources away from the other robot systems that need them: ball grabbers, hanging devices, etc. In many cases, I feel that this should not be done.

Re: Is a shifting transmission really necessary?
 

I agree :)

Re: Is a shifting transmission really necessary?
 

i think that is why people like andy baker and mark koors are building the "AM Shifter" so people don't have nearly as many problems as you describe....to each his own, but to me is it necessary? no...is it nice to have? absolutely.

Re: Is a shifting transmission really necessary?
 

This is a debate we've had MANY times on these boards before.

Jay,
You're logic is absolutely infallible. I agree with your points 100%.
But, there are certainly arguments (within your own logic) that show it can be important to shift. (I'd like to go over those quickly, for our viewers at home.)

My calculations prove it is ABSOLUTELY necessary for the functions we'd like.

Design Parameters:
-130 lb robot, no weight added.
-4 motor drivetrain (2 drills + 2 chips)
-80% efficiency
-1.4 Coefficient of Friction Wheels (experimentally determined)
-Max Desired Motor Loading @ continuous push = 50 amps.

Desired:
-12+ fps speed

My calculations show with the above setup, in order to design your robot to not only slip your wheels while still maintaining the 50 amp continuous max current draw... one must gear their robot at about 8 fps.

So... if we're using the parameters listed above, I must design our transmission at about 8 fps (I ran some quick calculations).

Granted, I could either load my breaker a little more (maybe I'll risk 60 amps continuous draw), or decrease the traction of my tires... but I don't want to.

Another option is to over-gear my robot, and just trust my driver not to get into extended pushing matches, or possibly even implement a current limiting circuit to protect my breakers... but these options just don't cut it for me.

OR... I could put some more motor in my drivetrain.
Maybe 6 motor drive is the way to go. Right now, we'll say it's not.


In this case, I need to ask myself, is 8fps good enough?

Not for our team, no.
We'd like to be faster. We're also not willing to trade off our pushing power.
This means, we NEED to shift.

It's all about what you're willing to give up.
We feel (for most FIRST games) it is beneficial to go the extra mile and build a shifting transmission. However, maybe next year's game will be the exception.

What it boils down to for us is:
-There is always a time you want to push through someone else.
-There is always a time you want to outrun someone else.

Either we put enough motor power into the drivetrain to do both, we sacrifice one for the other (in some capacity), or we shift gears.


Again,
Only try it if your team can handle it.
To be argumentative... last year we never lost a match due to a transmission problem either. In fact, we had NO problems last year with our drivetrain (the arm was a different story!) There were definitely times where the transmissions proved themselves a worthy investment of time and energy.
Depending on the game, we will strongly consider shifting again.

$.02
John

Re: Is a shifting transmission really necessary?
 

The transmission is a means to and end...
It is the engineers answer to a set of functional requirements.

The more important questions are:
-Is it really necessary to go 10+ fps?
-Is it really necessary to push with 200 lbs of force?

If yes, then... the transmission is one perfectly viable solution.
Obviously, some sort of solution is "necessary".

Physics isn't just a polite suggestion, it's the law.

John

Re: Is a shifting transmission really necessary?
 

I believe that shifting is a nice luxury to have. Should all teams attempt to build one? This would be a yes. The issue is when should they try. I am with Team 188 and this year we had a shift on the fly transmission with 3 motors per side. This was the 1st year that we have successfully put one on the field. Last year we attempted one and failed. It was an excellent learning experience. It ended up teaching us not to wait so long before leaving the idea and that a gearbox can be built in 2 nights. The fact that we tried at this point shows that we did not jump headlong into it. Our team has been learning and growing and this was just another step in our growth curve.

Every year a team should look at it's resources and decide what they can and cannot do. This is not limited to just transmissions. Our team tried to do everything this year and we had the manpower to try. Everything was not perfect but we were proud of our team and robot. That is what FIRST is all about. I helped teams that did not attempt nearly as much and yet when they were finished they were just as proud of their accomplishments as we were.

I don't believe that there is any right or wrong here, but dreaming, that is what makes FIRST great.

Re: Is a shifting transmission really necessary?
 

I agree with Jay TenBrink. 2 speed is always nice because you have speed and the power at the same time. you can have speed and torque with one speed transmission, but you can have more advantage from a 2 speed transmission. Is shifting necessary? not really, it really depends on the game, shift in fly is nice to have since you dont waste time to stop, shift and then go. for example, 2003 Stack Attack, a lot of teams have used 2 speed transmission in order to have speed and torque at the same time. some team went with 1 speed... like Baxter Bomb Squad, they were really fast and reliable. so what i say is, it really depends on the game. :)

Re: Is a shifting transmission really necessary?
 

Well, for what it's worth, 1293 ran one speed last year. The end result wasn't the speediest thing on two wheels and casters (see http://www.billfredinthenighttime.co...owmotor_hi.wmv for video), but we could easily push around an office chair with a high school junior (now senior, I think) on it, which runs about the weight of a mobile goal. And we could juke and jive with the best of them.

This year, a two-speed is one of the things we've spoken of. Of course, <Dave-speak>things could multiply at any given time.</Dave-speak>

Re: Is a shifting transmission really necessary?
 

we ran onespeed last year and felt it wasnt enough..
right now for OCCRA, ive designed our chain ratio so we can change our ratios through the drill transmission. we leave it in 2nd gear most of the time.(our "standard" gear) and when we feel our opponents might push us around or we want to be aggressive, we switch to 1stgear.. and then of course when we want to zoom around we go to 3rd gear. (oh i love this new dewalt tranny)
of course we cant shift on the fly.. more like cant shift for a whole match, but if we watch our opponents it should help us some. :D

Re: Is a shifting transmission really necessary?
 

Obviously, but what I was referring to was the shifting, thus the topic. Reminder (for our viewers at home): Is a shifting transmission really necessary?

necessary? no (no you do not need a shifting transmission to do well in this competition, Team 25 anyone?) ...is it nice to have? absolutely (I would like to shift given I can sacrifice whatever weight, time, etc...necessary to produce such a shifting transmission)

thx :rolleyes:

Re: Is a shifting transmission really necessary?
 

Sparky has never used a shifting tranny yet, although we have thrown together various ideas and have one in blue sky session.

As a principal of FIRST that has been reiterated again and again by Dean, you DON'T need Andy Bakers or other great engineers to build a robot, so a shifting transmission isn't needed to function in the game. We have never used it and we have won two regionals in our 5 year history, plus we made it to the eliminations in Champs.

As Johnny said before, if you want to do some things, you might want to look at a shifting transmission. Back in 2002 it was a good idea to use one to push around the goals, especially if you were like Sparky 3, MOEhawk, or Beatty that year and wanted to tackle all three at once.

Re: Is a shifting transmission really necessary?
 

John,

We design for a higher max current draw. With the addition of the little blue battery this year it is possible to increase the max current draw of the drive system without putting the controller to sleep if you momentarily drop under 8 volts.

Our efficiency is such that we can achieve 10 ft/sec. max speed (which is all we feel we need) and we are also able to break all four knobby pneumatic tires loose at the low end.

In 2003 we had a 4 motor system with a robot weighing 115#. This year we weighed 130# and had a 6 motor drive.

You are extremely correct: It is important to get there fast. Once you are there, you want to be able to stand your ground. We have been able to accomplish both with a one speed gearbox.

Thanks for the comments all,

Jay

Re: Is a shifting transmission really necessary?
 

It depends on the game, your strategy, and your machine. We have never had a shifting tranny. However in 2002 we wish we had.

Team 25, in 2002, comes to mind. They would fly out to the goals, grab them and then shift gears.

In 2003 it would have been nice for certain situations, but certainly not needed. We compensated for single speed with very high friction tires. We feel that our tires helped us win many matches.

For 2004 I really don't see any use for a shifting tranny at all.

But again, it depends on YOUR situation. Although, it is very cool to have one. :D

Re: Is a shifting transmission really necessary?
 

Note: much of the theory here, and the debates between 4 motor vs 6 motor vs shifting were discussed in depth last year in this thread: http://www.chiefdelphi.com/forums/sh...ad.php?t=22604


Jay,
Would you be willing to share more details about your gearbox?
Ratios and such?

Based on experience running these numbers, I know how the power output from a 6-motor drive would be enough to slip wheels at 10 fps. (As I discussed in my initial post.)

This is really the "other" option.
Again, it's all about tradeoffs -- either you build a shifter, or you add more power (more motors). 494 has taken the Tim Allen approach, and it has suited them well.




I'm just curious about where exactly you're loading your motors.
Obviously, I know how well it works (I've seen you in action several times now).

How far can you really push the envelope?

Probably further, than I am willing.
Perhaps my reluctance to toe the line is hurting me, I know I've been accused of this before.

I'm never averse to taking pointers from a national champ,
John

Re: Is a shifting transmission really necessary?
 

Jay,

Good question.
This thread also discussed the same issue. As I stated in the other thread, we have shifted gears every year since 1999. While you point out the obvious rewards, there are more. Robot driving control and voltage conservation are two major rewards that come from shifting from a high gear to a low gear. These are two benefits that you did not mention.

A robot with 2 speeds can be driven more precisely than one with just a high speed. From my experience, FIRST robot drivers who have 2 speeds to work with can have more control over their robot as opposed to drivers with only a high speed. Also, if a driver wants to move their robot into a tight position, it is easier to do while in a lower gear.

Also, a typical FIRST robot that is geared to go above 9-10 ft/sec gets hot when running multiple matches in an elimination scenario. If a robot is using a 4-motor drive setup, it is good to have a low gear to switch over to, in case motors get hot and circuit breakers begin to trip.

I do think that this explains much. The 2003 game was unique in that it did not require much precise positioning, and allowed for less control of robots. The 2004 game required more precision, and I can see why a single-speed, 6 motor drive base was successful.

I still like the 2-speed design. There are good 2-speed designs that are reliable, robust, and lightweight... and they don't cost too much either.

It really does depend on the game. If a game comes around like 2002, a 2-speed will be a hot commodity.

Andy B.

Re: Is a shifting transmission really necessary?
 

Just to add my two cents...
I understand the up side to dual speed but (a big "but") is it really needed on a 48 foot long playing field with other robots and field pieces in the way. The difference between 8f/s and 12 f/s is only 2 seconds from end to end. As to the design current draw, the circuit breaker although rated for 50 amps will require a current 6 times that great for more than fifteen seconds before the circuit breaker will trip. Add in the influence of the wiring resistances, the "on" resistance of the speed controllers, internal resistance of the battery, and all of the other factors and it is impossible to deliver full rated stall current to any motor in a functional competition robot. Given that max stall current will occur when motor brushes are in contact with two commutator segments (two motor windings in parallel) a multi motor drive will likely place more than one motor in such a condition during a standoff. Depending on slip in the transmission(s) motors are likely to rapidly alternate between two and one winding while in a standoff thereby changing (lowering) the load current. Granted a six motor drive will have more motors in this condition and therefore would get closer to max trip current than a four motor drive. I think that anyone who spent anytime in the Martians pit and watched the results of the dyno test or the Matians superior pushing ability would have to concede that there is an alternative (and a good one) to multispeed transmissions.
Also, what is the risk to add speed change decisions to the drivers? It seems that adding another variable into the driver equation would tend to slow down response times. Although speed changes on the transmissions is fairly rapid, is it the right thing to do in a 105 second match? In rough guess of perhaps four speed changes in a match, you may have lost 2-4 seconds of match time in decisions and speed changes. As we all know, that length of time could make or break a match.
So the question still remains and decisions to weigh the alternatives still exists. I for one think dual speed transmissions are cool but adding up all the factors (time, current, weight, complexity) I still favor single speed.

Creativity is necessary.
 

Is a shifting transmission really necessary?

The better educated engineers above me have pointed out most of the pros and cons of shifting or not. That doesn't really address the question.

The correct answer is, it depends on the game and your game play strategy. Its been mentioned before, but it has been buried inside justification-by-feature.

In 2002, it was absolutely necessary for some teams to shift to get to the goals faster. The difference between 8fps and 12 fps was a full second of personal time with the goals. However, Beatty didn't need a shifting transmission because they thought outside the box and engineered another solution to the problem. Now, because of rule changes, their file card trick won't work anymore, but I am POSITIVE that there is another way to pull off a similar outside-the-box solution to a movement problem.

Is a shifting transmission really necessary?

I'd say no, not because the features are unnecessary, but because limiting yourself to one solution is a bad idea in FIRST.

Wetzel

Re: Is a shifting transmission really necessary?
 

That means you can get to the center of the field a full second earlier. In the 2004 game, beating the opponent to the bonus ball tees and mobile goal in autonomous mode was critical to many teams' success. Two seconds is not terribly important in itself, but in competition against another robot every advantage helps.

A well-designed shifting transmission, controlled by an experienced driver (or a clever bit of software), is an advantage.

Re: Is a shifting transmission really necessary?
 

I agree with most that you need to first work out your functional requirements before making a decision. There are a lot of possibilities that are not really considered by the topic.

2 motors versus 2 motors + shift?

2 motors + shift versus 4 motors?

4 motors + shift versus 6 motors?

6 motors + shift versus ... ?

Many people have been going down the 4 motors in a gear box + shifting for a while. This seems to be a pretty wide area in functional space for the general constraints that FIRST has been imposing.

Having a shifting gear box design in your tool box is probably a pretty good idea. In 2004, as an example, if you used a hanger to pick your robot up, you would probably want a shifting gearbox. Hanger Up = FAST, low torque, Hanger Down = SLOW, high torque. In other words, having a shifting gearbox in your tool box does not mean you will only use it on your drive system.

What appears to be another wide area in functional space is the six motor, independently driven wheel design.

This design gives both low end torque and high speed, without a transition point that would come in a transmission. One thing which has not been talked about is getting up to speed. Unless you have a shift-on-the-fly transmission, you have to tolerate low acceleration to get to high speed. This may account for 1-2 seconds delay for a 12 fps relative to a multi-driven-wheel design.

Therefore, the multi-driven-wheel design has an attribute which I will call "quickness." This translates into an ability to maneuver (which can also be accomplished by an omni-wheel design).

The other advantage to a multi-drive-wheel design is "failure tolerance." If one motor blows out, freezes, over-heats, you still preserve the majority of your function. As an example, in 2004, one of our drive motors burned out. We noticed that the robot "pulled" to that side, but it took two matches before we realized that we had lost a motor.

If you only have one drive axle per side, a single failure can eliminate half your drive system. In our case in 2004, with three driven axles, it would take a triple failure on one side to take us completely out of commission.

My experience in FIRST has taught me that, whatever you do, make sure that no single failure can eliminate half your drive system. Whether this is a resetable breaker, drive shaft, drive chain, speed controller, pneumatic pump, etc., make sure that there is no single path to failure. The worst feeling in the world is having your robot driving around in circles when there is critical business to be done on the playing field.

Re: Is a shifting transmission really necessary?
 

Just to throw out there my thoughts on the matter. A shifting transmission is a hot commotity, it's nice to have, wether it be a 2 speed or up to a 6 speed, it doesn't matter. Looking at the whole thing from an automotive standpoint it's just a quicker way to get to top end, but that is with a combustion engine, I know. A quote comes to mind when thinking about the way we build robots, we bash them, we crash them, we abuse them. Our drive shafts can get buggered up and torqued. And a quote comes to mind: A shifting transmission can be awsome, you get multiple speeds and torque, but you can have problems, gears grind and teeth break, dogs can crack, and all kinds of bad things can happen. You can get wobbel and warp, and then you are in trouble. Being on Team 384 for 4 years, and now I'm a mentor, and from the great mentors I learned from, the more simplifed your robot, the more robust you can create it. I'm not saying it's not nice to have a shifting transmission, it is, but i don't think it's truly necessary for a competative robot.
mark

Re: Is a shifting transmission really necessary?
 

A shifting transmission is not necessary, but they sure do bring in the technical awards!

:D :D

Re: Is a shifting transmission really necessary?
 

I don't disagree there. For example an iron block is very simple and very robust. Strap a control system on it and it will meet the requirements of being a FIRST robot. However, it sure doesn't do very much, nor is it innovative.

Re: Is a shifting transmission really necessary?
 

Robustness is good, but a competitive robot must also be capable. A consistenly winning robot must be more capable than its opponents.

A shifting transmission is only one way to make a capable drive system. It happens to be a popular one, and with the proliferation of good shifting designs (and now commercially available ones), it's a relatively easy one to use.

Re: Is a shifting transmission really necessary?
 

i think if your team can do it then its worth it! but a half working one is still worse than a fully working single speed !

Re: Is a shifting transmission really necessary?
 

Many people ask "Why should I have a shifting transmission?"

A better question may be "Why not?!"

I see many advantages in having a shifting transmission. Most of the technical aspects from the mechanical side have been covered, so I will give my pros and cons from a programmers perspective.

Reason 1: Having a shifting transmission and a well written program will enable your robot to be "smart" For example, lets say it is autonomous mode. Under normal conditions in high gear, the drive motors draw 'X' amount of current, and output a corresponding 'Y' amount of speed. Your robot collides with another robot and a pushing match begins. Your program senses that the amount of current going to the motors has increased, and the speed has decreased. (A considerable amount) Your robot could then know to shift to low gear and beat out the other robot. And for what I know of the mechanical aspect of this situation (probably not much), by going to a lower gear you can output more torque while drawing the same amount of current.

Reason 2: Creating an option to shift also creates another form of control. Whether this is controlled by the drivers or the robot is entirely up to you. Don't be quick to jump the gun and assume that drivers always have to control your shifting transmission. We have the resources in our KOP to create an "automatic" manual transmission (a manual transmission that is shifted by the computer) I believe team 33 did this last year, but i may be wrong. This can give you a good advantage, and your robot will deliver speed and power when needed, respectively. Now I'm sure there is some way of achieving the same goal with a 1 speed transmission, but most people (like me) just dont know how and will default to what they know, such as shifting transmissions for changes in power and speed.

Reason 3: Its sexy.

Re: Is a shifting transmission really necessary?
 

There's one more subtle issue that I think is worth pointing out. Say you're designing a robot for Zone Zeal in 2002, and you want to make a ball pickup robot that tows the goal around behind it. Assume that you can make a robot with a 1-speed gearbox that goes 10 feet per second and can slip its wheels just before stalling, and that your driver is good enough that uncontrollability is not an issue.

From most of the posts above, this would seem to be an ideal drive system - but I would argue that there is still an advantage to having a shifter. Say your wheels slip at 90% of stall torque, and you can pull a goal at 80% of stall torque. Yes, you can pull the goal, but at that point you're running too close to stall to get max power output - if you geared down slightly, you could pull the goals around a lot faster. It won't help you push another robot (traction is still the limiting factor) and it won't help you get to the goals faster, but if you're towing a goal around for a large part of the match, it could still be very useful.

Re: Is a shifting transmission really necessary?
 

I am with Jay on this one. I have said it many times before: 2002 ruined a lot of us by making us think shifting is a neccesity. In 2002 shifting (of some sort or another) was essential because you could transfer over 360 lbs to your robot base (two goals at 180 lbs each. you 3 goal grabbers are excluded from my argument). 2003 and 2004 did not need shifting if you had at least 4 motors driving your drive base. I bet some teams did fine with two motors and no shifting, but 4 or more without shifting was plenty.

Speed and accleration are key and the race to the middle depends on both. Don't make your high gear too high or your acceleration will be horrible. If you do not shift during the race to the middle (goals, end, whatever) then there is not much difference in time between a 12 fps robot and a 8 fps robot (with the same motors driving). Teams like the Killer Bees who have an automatic transmission are taking full advantage of shifting with automatic speed/torque based on current speed of the output.


We shifted in 2002 and 2003, but not in 1999, 200, or 2001. We will not shift in 2005 unless we can transfer weight to our robot.

-Paul

Re: Is a shifting transmission really necessary?
 

I think the transmission issue depends on the robot itself. For example, an auton hanger (like 190, that uses the ramp and then hooks on to the bar) doesn't need a transmission (except when facing 716 :D ) on the wheels. During design session, I suggested a robot with a transmission on the arms to cap quickly, and to use power to hang. A crazy smallball robot may even use a tranny on the small ball mechanism. It all depends on the type of robot. For this year's game, I would suggest trannies for the wheels, since it was a robust pushing game.

Re: Is a shifting transmission really necessary?
 

Good thread.....I agree with many points stated above.

No, you do not need to shift.
Yes, it is a good option to have.

Team 33 has make multispeed robots for many years.
As the kit had gotten better and the motors have gotten bigger, the need to shift has diminished. If you tried to get your 1999 robot to go 12-15 ft/sec you could not do it without a shifter. Now you can simply brute force the issue by throwing tons of power at it. I still like having a shifter for a couple of reasons:
1. Power budgeting: Liberating some of the good motors for something other than driving around is a good thing. After all who want to build a high speed brick that does nothing but smash into others.
2. Control: As a programmer one thing I know very well is you must have a mechanically capable design in order to have good controlabilty. In FIRST, you often have very distinct operating modes for your machine during a match: i.e. Push like crazy to get past someone and then run full speed down the field. Having gears selected for both of these actions well enables you to do both well.

Regardless, shifters are a detail. The major items of FIRST are still what they always were.....understand the game, build a reliable quality machine to play it, train you drivers to use it to its full potential. If you do these things, you can win with or without any specific machine feature.

Re: Is a shifting transmission really necessary?
 

I would just like to ask a slightly different question:
How many national champions had shifting transmissions?

I can't think of any. Apparently there is more to it than the drivetrain (beside in 2002).

Raul

Re: Is a shifting transmission really necessary?
 

173 - 2002 had a shifter.
They shifted the drill transmissions with a servo, if I'm not mistaken?

Still Raul... your point has been well made. ;)

Re: Is a shifting transmission really necessary?
 

I may be incorrect but I’m almost positive that 469 2003 also had a shifting transmission.....

But Raul's point is well taken, I can list off a ton of bots just off the top of my head that have performed very well without shifting transmissions

2002 Divisional Champions without Shifting Transmissions
71, 144, 64, 25,
2003 Divisional Champions without Shifting Transmissions
292, 236, 175, 341, 25, 494, 111,

These are just teams off the top of my head...I can't guarantee 100% correctness...

I'm a firm believe that shifting transmissions are great to have, but they certainly aren't a guaranteed winning bot, a good driver and a good mechanism will take you far in any game.

Chris
229

Re: Is a shifting transmission really necessary?
 

469 shifted in 2003

Re: Is a shifting transmission really necessary?
 

Having a shifting transmission has it positives and negatives, on the positive side you can slow the robot down if you need to make a slow and precise movment, negatives are that there are more moving parts which means more things that can break and go wrong

Re: Is a shifting transmission really necessary?
 

Geez, how could I forget that about our 2003 partners?!

Re: Is a shifting transmission really necessary?
 

well as for breaking apart... most of the times if the shifter is messed up or something you can just lock it in one stage... and then its basically just a heavy dual motor drive system.... i can't really think of much more going wrong with a shifting tranny ... now a planetary drive .... yes ;)

Re: Is a shifting transmission really necessary?
 

Hi!
the only competition I have seen was the '04 competiton, where I co-piloted for our team, 1425. We did not shift. We did not have time to put together a tranny, but our team leader would have really been tickled if we could. I personally didn't see a reason for a transmission. In the '03 competiton, I could see why speed was required (a lot of space, a race to get to the top, ect.) but in the '04 competiton, I didn't see a reason, because there wasn't much room to get up to speed, and there wasn't anything that could have been taken back with some shoving. (not a FIRST-encouraged manuver, but these things happen.) I totally agree that it depends entirely on the competiton and what you are doing. Like I said, I am a rookie, so my test pool is minute, but I think generalizing about whether or not you need a transmission won't get you anywhere.

Sparks

Re: Is a shifting transmission really necessary?
 

Our teacher put it this way. Their is always an advantage to shifting. But is expending the extra resources to build it worth the advantage?

Re: Is a shifting transmission really necessary?
 

The rules specifically indicate that pushing [shoving] is OK and expected. Why would you say it's not FIRST-encouraged?

This is, in fact, the main reason for a low gear in a transmission.

Re: Is a shifting transmission really necessary?
 

Actually, last year we used our low gear for climbing so that we could avoid all the pushing and shoving. But with the dynamics of last year's game we felt that anybody who got into a shoving match, was probably doing the wrong thing. The 02 and 03 games were a different story. There was a lot of space to cover and you had to be able to hold your ground when needed.

Design for how you plan to play the game. If you need two or more clearly definable speed regimes, then shift. If not, then don't.

ChrisH

Re: Is a shifting transmission really necessary?
 

“Education is directly proportional to the amount of equipment you burn up”

I will now enter the discussions about shifting transmissions. For a rookie school I strongly suggest that they stay away from a shifting transmission. Like several of my learned colleagues have stated so elegantly that it is a can be a waste of time, weight, money and resources that need to be allocated elsewhere. A good single speed transmission with the ability to easily change the gear rations to determine speed is a solid selection. After the first year and the teams have started to climb the learning curve they can change to multi-speed transmissions.

Re: Is a shifting transmission really necessary?
 

no its not necisary, but it helps. It also allows your team to decide if they want torque or speed during the game.

Re: Is a shifting transmission really necessary?
 

Team #322 shifted (pneumatically) in 2002 (Zone Zeal) and 2003 (Stack Attack). It gave us great speed and power, depending on what we needed at the time. It was a robust design... once the kinks were worked out. LOL. I think we had a really good design. I'm not totally convinced that this year's game needs it, and the extra weight of the trannies is better spent elsewhere. So, is it necessary? No, especially not for this game. Was it cool when we had it? YES!! I still fondly dream of the days of the little diamond-plate-covered Tweetie machine.

Kelly =)

Re: Is a shifting transmission really necessary?
 

I've seen a lot of people bring up the point of robustness in shifting transmissions. The thing is, just because it shifts doesn't necessarily mean it is less robust or less reliable. For us and many other teams, we have made a shifting transmission that has had no failures over the course of the competition and demonstration. We design things to work properly and not break, and I hope everyone else does to. And the end result is they work properly, and they don't break. As long as this step in the design process is taken, anything can be robust enough to not fail. There are plensty of single speed gearboxes out there that have had serious issues, and plenty that haven't. It all depends on the design and the quality of fabrication. Making a gearbox shift does not at all preclude that you will have problems with it's robustness or reliability.

Also, this issue of size and weight has been brought up. A shifting transmission will almost never be smaller or lighter than a comparable single speed, but the difference can be made very small. Also, say your transmissions come out to be a few pounds more. Now, would you really want those extra pounds out at the end of an arm, or don't you think they'd be better nice and low in the base. If you make one thing lighter, you are going to make another thing heavier since the total weight is almost always a constant. So, it is a matter of exactly where you want those pounds to be. And I vote for them to be nice and low in the base.

Re: Is a shifting transmission really necessary?
 

Remember:

The number of moving parts squared is proportional to the probability of something going wrong.

If making a shifter adds too many more moving parts, reconsider your design. Apart from the pneumatic moving parts, there should not be that many more bearings or gears between a one speed and a two speed. However, there are two speed designs that only add 2 gears and two bearings, as in one more moving part. Keep it simple!

Re: Is a shifting transmission really necessary?
 

I believe that 2005 changed this debate significantly. This year for the first time the kop included a very usable frame and drive train. There is no reason even a rookie team with no resources can't have a robot base driving by at least week 3 or sooner. The implications for the power teams that build more complex drive trains is that if their development and build time drags out into week 5 or 6 they are going to be going up against teams that have been training their drivers and debugging for quit a while. Also by having the kop frame and drive train together early the programming team has something to do instead of waiting to week six and then having to perform miracles. Our drivers and programmer spent week 4 finding the right joy stick control algorithm and tried different wheel traction combo's. The rest of the build team spent their energy on the arm with out drive train distractions. We went to the regional this year with experienced drivers and a debugged solid robot. We were a very resource limited team and we performed very well making it to the finals. I believe our success was directly attributed to the kop drive train. Going forward, I think every team should look real hard at what the investment of time and resource in a custom trans and drive train will do to their project schedule. Does the gain and game justify the expenditure of the resources and time. The 2005 kop changed things.

Re: Is a shifting transmission really necessary?
 

the only real benefit in FIRST for a transmission is if you want to go from high speed to high torque (like if you want to climb stairs) but i think that within FIRST a drive train is less a technical feature and more of a prestige piece.

Re: Is a shifting transmission really necessary?
 

Very true for all the points you listed. While the 2005 kop gearbox most likely provided a higher degree of success as a whole, I think it caused an astonishingly lower degree of innovation as a whole, and on a case by case basis in the drivetrain department. You are correct in saying that using a simpler system is a good stategic decision to get more debug time, but even so , I still hate to see teams not strive for more. Many teams made a good strategic decision to use the kop gearbox, and some went on to win events possibly because of that decision. There are so many good things that came out of the having kop gearbox, that I can't really make a case to shoot it down. But all I can say is this: I truly miss walking around the pits and seeing the wide array of custom made gearboxes and drive systems. I really miss it. :(

And when all the robots have the same frame and the same wheels too, it makes it even less fun to be a pit browser. I have always regarded the frame and drive system as just as important as any other part of the robot. So to me, lacking innovation in those is just as bad as lacking innovation in an arm or manipulator.

When I started in FRC, I thought one of the greatest things about the buildup was that it was not a put together kit. It didn't come with a manual, it did not come with instructions. It was not bought in a store. Every piece of metal was cut, every shaft was machined.

This year, we achieved a higher degree of success as a whole in the sense that nearly every team manipulated the scoring object, and manipulated it well. But that same old smile while browsing the pits doesn't come to my face anymore staring at the same grey gearbox, and the same hole-filled frame rails, and the same 6 spoke wheels.

It can be made analogous to a situation like this. Do you want every highschooler to only pass geometry before they graduate? Or do you want some to only make it to Algebra and others to rise high into Calculus? It is a tough call to make, one that I certainly can't to.

I like seeing everyone being proud of their functioning robot. But I like seeing some teams being proud of thier unique and different robot too. However, I'm afraid these don't coincide, and the latter doesn't come without the cost of others being left with a poorly functioning robot.

There is no way possible to get what I want to see. I have no solution, for what I see as a problem. The problem is I think the Kit is becoming too much of just that, a kit. Where will it go next? 4th and 5th year teams are taking the easy way out by using what they are given, instead of striving for something more.

I think the KOP gearbox and frame are fine pieces of hardware that has made the competition more do-able and more enjoyable for many. But for some like me, the fun and pride in some aspects of the robot and the competition has been taken away.

Re: Is a shifting transmission really necessary?
 

Sanddrag, I still do not understand why you believe that it's so bad that people not go all out and make crazy drivetrains. Why innovate when what you have suits the game perfectly? There's no reason to make a super cool 4 speed 6 motor drivetrain if a single speed, 2 or 4 motor drivetrain will get your strategy done just as well.

It makes no sense to me to go and make a super cool drivetrain, just because it's super cool. If there isn't significant upside to doing something significantly more complicated and time consuming, what's the point?

2005 wasn't a game of drivetrains like 2004, and particularly 2003 and 2002, which the vast majority of the teams recognized and took into account.

As to the analogy to settling for passing HS with geometry, or moving up to Calculus, why take calculus if your career doesn't utilize anything above geometry? Same thing with FIRST. Why waste resources to do something that doesn't fit your strategy and won't give you a tangible advantage?

It's the mark of a good team to know what to use, and when, not to use the most insanely cool innovative feature known to FIRST, just because.

At any rate, I don't think you can conclude "4th and 5th year teams are taking the easy way out" because they use kit parts, because FIRST's mission isn't innovation, it's to recognize science and technology. Innovation can certainly be a part of that, but it's not a necessity. If a team has successfuly used a simple drive year after year, congratulations to them for finding something that works well for what they do.

And mechanicalbrain: Without a drivetrain, the best arm becomes useless :p 2005 was certainly not a year of standout drivetrains, but the previous three games sure were. 2003 was essentially a contest of who had the most powerful drivetrain, as was 2002 with a few twists thrown in.

Re: Is a shifting transmission really necessary?
 

Making a gear box shifting or single speed requires precission machining. If a team doesn't have acess to the equipment and mentors with the Knoledge to use them a team before 2005 was at a major disadvantage. To go out and buy the part requires lots of funding. Our team had neither. All we had where hand tools. If the KOP trans had not been in the kit this year, we probably would have used the Fisher price solution and it would have been a marginal solution. I know because we used it before and it"s limitations probably would have put us at the middle bottom of the heap at the regional. The KOP trans this year allowed us to inovate in other areas. Our arm was made out of composits. Pulltrustions, Cabon fiber lay up, and epoxy chopped fiber cast parts. All done with hand tools. OUr arm weighed 23 pounds with motors, the same design in aluminum would have weighed 44 pounds. So there was some major inovation on our team. The Kop trans is a competition leveler. The point of my post was that teams need to realize this and may be pay more attention to where they allocate there resources in the future.

Re: Is a shifting transmission really necessary?
 

My team didn't do shifting this year - instead, we went the way of custom gearboxes and a 6 motor drive train. That was great and all, but it drew a LOT of current (over 100 amps at times or so I was told) and it was just two less motors for us to use elsewhere.

Shifting would have allowed us to have the torque when we needed it and the speed when we wanted it, without all the motors and wastefulness of the 6 motor drive train. And shifting doesn't add any driving headache (you just have current sensors and at some threshold auto shift up or down) so if you have the resources, I don't see why you wouldn't want to strive for more.

Not to mention what a great learning experience it is to help design and manufacture one...

Re: Is a shifting transmission really necessary?
 

Cory this is directed at you. its very easy to make a simple drive train because most people will copy a design or buy one. there really is little ground for new creation. i think one common idea held by a lot of FIRSTers is that having a good robot is the complete objective and i feel kind of sad to see that. if we don't continually push the bar than eventually people will find a comfortable niche and get mired in it. in short by doing something crazy like a six speed drive train it shows the team has a true understanding of the given concepts and in doing the extreme they might be inspired to create new designs like the ball drive train. basically it encourages people to be creative something i push for hard. (i don't really feel like being criticized about encouraging impractical designs because if anyone feels like doing so then they really don't understand my post. this is just something i forsee someone posting)

Re: Is a shifting transmission really necessary?
 

I completely agree. Putting resources into something elaborate when only something simple is required would be considered by many as a poor strategic decision.

Like I said before, I can't really define my point sharply. I can't really make any sort of case or argument against the kop gearbox. I even said it is fine piece of hardware that has made the robot more enjoyable for many.

I have no case or argument against it. All I'm saying is that I like to see kits, rules, and games designed that challenge teams in the area of drive systems. To me, for every team to be handed a beautiful, reliable, and capable gearbox right from the start, instantly eliminated a large part of the challenge in the robot building for many teams. In some cases this was a very positive thing, in other cases I believe it wasn't.

It is very clear that there will never be one set of rules or one set of parts or one type of game that suits every team well. Due to variances in resources, skill, and experience, it will always be easy for some, and hard for others. The only thing I'm trying to say about the KOP gearbox is that I believe it made it too easy for too many. You are probably wondering "why make it hard and have people struggle, wouldn't you rather have them succeed from the start?" Well, the beginning of everything I learned in FIRST, was by helping design and build a gearbox for the first time, and have it fail. And look where I am today. I'm not saying one must fail in order to learn, but I think teams would get more out of this if they had to design their own gearboxes just like in the good ol' days.

Before anyone makes a reply attacking what I say, it is merely an accummulation of some trends I saw, and some ideas I had. I'm not trying to argue anything or make a case against anything. I'm not trying to offer any solutions to any problems. I'm not taking a I'm not really sure where I'm going with them.

Re: Is a shifting transmission really necessary?
 

I agree with Sanddrags statements, and feel them on a personally in the competition. while the KOP is great for teams that don't have the ability or resources to create a custom drive train, it gives the game a standard. However I think it also makes the game more uniform. Our mentors heavily pushed for using the KOP, and our drive train designer was really disappointed at not being able to create our own. I personally feel this more in electronics as we have no choice but to use most of the parts FIRST provides. this leaves me with less of a choice with deciding what pieces of electronics would be cool, and leaves me focusing more on how I can mount the required peaces efficiently and how to wire them. overall electronics is just like putting Lego's together. it really provides no room to grow other than sensors. (i know this because I'm hitting the glass roof with what i can do with our system)

Re: Is a shifting transmission really necessary?
 

Instead of making the build process easier to level the playing field, I'd like to see the game challenge be made wildly differetn and oodles more challenging in order to level the playing field. Make it something no one has done before, and then all will be at the same level, and all will ba challenged.

Re: Is a shifting transmission really necessary?
 

Even if it's something nobody has ever done, the "powerhouse teams" will all still have a significant advantage, while rookies get left behind in the dust.

Innovation is not a problem. If the 2005 game had required an innovative drivetrain, teams would have innovated, but it didn't, so neither did the teams.

Re: Is a shifting transmission really necessary?
 

Two things. One I think you under estimate the ability of small teams. Second I think that just becuase a game doesnt require that a team to be inovative with something certianly doesnt mean that they shouldnt do it anyway. If we arent always pushing the bounds of our knowledge how can we expect it to grow?

Re: Is a shifting transmission really necessary?
 

I'm not underestimating small teams, I'm being realistic. Rookies will have trouble with an excessively complex game. It would only increase the gap between rookies/teams without lots of resources and a small knowledge base and well established teams. The current teams that do well will continue to do so, because they have the resources and engineering know how to come up with a solution for whatever FIRST throws at us.

Sure, you can push your bounds of knowledge, but it makes zero sense to make something that isn't useful for a given competition. Why waste six weeks building an overly complex drivetrain that won't perform any better than the standard kit drive, when you could have spent that time working on programming or an awesome end effector?

When given a problem to solve, real engineers are going to look for the simplest way to do so that they can possibly find--not the most time consuming, expensive, complex way.

If innovation isn't coming in the drivetrain department, it will come somewhere else.

Who really cares what a team does as long as the students are inspired? If a team doesn't use a single part that didn't come from the kit, but the students have an awesome time and get to learn even a little bit about engineering and want to come back for more, who cares if they didn't create something completely new and super cool?

Re: Is a shifting transmission really necessary?
 

OK Ive seen rookie teams beat out plenty of experienced teams with designs that were far superior, and I'm not saying a team HAS to have something cool or new but the point is that they should be inspired to be innovative. I'm obviously not limiting this to drive train just that in someplace the team should at least be trying to be creative. you should read my earlier posts on this thread as it explains this. the point is teams shouldnt limit themselves.

Re: Is a shifting transmission really necessary?
 

Here is why I make crazy drive trains.
I am not the person that particularly cares about the game. I make the drive train. It is proven that most drive trains can play every game in the existence of FIRST. One could have easily used a swerve drive every single year. The reason why I make what I make is because I want to learn more. However, there always is the rest of the team to negotiate drive trains with. So, when the team choses a particluar style of power train, (ex: swerve, 6WD, omni, etc...) I agree. And then I go the distance and make it as outrageous and advanced as I can with the time and resources that I have. In my case, I have a fully capable CNC shop that can make a complete drive train in 12 working hours. So what do I do? I design up the craziest thing I can possibly make. For example, if I ever do swerve drive again, its gonna be two speed, with a shifter on each module. Big? Heavy? No. It all depends on how you design it. But why add the extra 2 or 3 pounds, and the time, instead of making 1 speed swerve? Because I want to gain experiance, gain knowledge. Cory, you said that FIRST is not about innovation. It probably isnt. But I'm not one that can settle for making the same drive every year. I take risks, chances, and in the end make drive trains that make people's jaws drop.

Remember, people have a different mindset. I respect 8th year veteran teams that decide to use the kit of parts chassis and drive train for the lack of resources. I would do the same. But if I have the resources, I'm gonna have fun with them. And please, never scorn a team that makes something outrageous, like a 4 speed 6 motor transmission. They learned how to make a 4 speed 6 motor transmission, while you didnt.

On a side note: it is my opinion that learning from what you made is more valuable that winning with what you made.

Re: Is a shifting transmission really necessary?
 

Couldn't agree more. I see a lot of teams use the same drive train (or very similar) over and over every year because it's good/powerful/whatever - but they don't learn anything. Their students don't get anything out of that. And I think that if you want to do what FIRST is really about (inspiring people), you have to let them learn.

Re: Is a shifting transmission really necessary?
 

These are some outstanding words. Veselin has hit the nail on the head, in my opinion. FIRST is defined by inspiration, not winning. Sure, everyone likes to win matches, but the point of the program is to be inspired and succeed in life.

Thank you, Veselin, for this wisdom.

Andy B.

Re: Is a shifting transmission really necessary?
 

he's my FIRST idol everything he said is exactly what i strive for! i agree and though you can't hear it im claping.

Re: Is a shifting transmission really necessary?
 

Striving your hardest to win, trying your best to design a competitive elegant solution is DEFINITELY what FIRST is about.
This is the medium provided to us to inspire HS students. Otherwise FIRST wouldn't give us a game, they'd say "build a cool robot". (Wildstang would probably win. ;))

Learning how to distill a problem, and find a simple solution is critical to the FIRST process (as it is to the engineering design process).


Which design is worthy of more praise?

• An overly complex system which innovates for the sake of innovation. A system which (while technically incredible) is overkill for a FIRST robot, and unneeded for the current game.
• A system which is laughable in it's simplicity, yet incredible in it's functionality. One which fulfills the needs of the game with a minimum of "effort".

Personally...
I prefer the second option.

Here is another question, which is more education/inspirational to the students who design and build it?

I argue that they are equally beneficial.
I would even go so far as to venture, that option 2 is tougher to do, and much more beneficial to the students who accomplished it, in the long run.



Many in this thread have been quick to scorn those who do not innovate, which REALLY pisses me off. Having elegance in simplicity is often times more virtuous than being innovative.

Re: Is a shifting transmission really necessary?
 

First off, I must say very nice post john.

When I used to be a freshman in high school, I used to think about drive trains, specially the ones which has a lot of complexity. I used to say "Woooo, it's so cool, let's build them." But over years I have learned (Thanks John) that simplicity is the answer to solution. It is much more easier to solve a problem when you think simple.

Is two speed necessary? If you ask me, I wouldn't do it for a first or second year team. I would build a robot that is fast enough, build a very simple mechanism which serves the purpose of the game. But at the same time, if my team built few prototypes in the pre-season and knows EXACTLY how it works, I would go with it. I would go with what I know works. The team would only have 6 weeks to work on the robot and then ship it off. Its not much time to experiment with new drive trains and such. In another word, I would go with the 2nd option that John pointed out in the previous post.

Re: Is a shifting transmission really necessary?
 

I agree with all the things being said but I never look down upon a team (and I'm not saying any of you do) for pushing the limits, challenging themseleves, and striving for more, even if it is without reason.

Re: Is a shifting transmission really necessary?
 

JVN's "How to determine if a shifting transmission is really necessary?" Cookbook:

First you need to figure out a few things:
(We will ignore things like efficiency, in this exercise. Sorry Patton.)

1. Determine: Wheel Friction, Robot Maximum Weight (with lifted weight, i.e. balls/goals) These factors can all be calculated based on overall robot decisions. (What tread do we use? What is our robot going to do?)
2. Determine: What motors will go into the gearbox?
3. Determine: What max speed do you want your robot to go?

Now Run some Calculations:

1. Based on the breaker limits (i.e. 40 Amps) how much torque load can each of your motors have on it without blowing the breakers?
2. Based on this max torque load, what reduction is necessary to "slip" the wheels (using the robot weight and wheel friction values listed above), if the robot is pushing against something, in the max loading condition.
3. Based on this required "slip" reduction, what is the speed of the robot?

Now... we know what our "pushing speed" is. This is critical, because every robot should be able to slip wheels while pushing a wall, and not pop the breaker.

Here is the big question:
Is this calculated robot speed at least as fast as the max speed we want?

If yes:

1. Woo Hoo! We're done. Gear the robot at the max speed, and live happily every after with a 1-speed gearbox.

If no, we have some options:

1. The Tim Allen approch (add more power). Adding additional motors to the drivetrain will allow the robot to be geared faster, while still slipping the wheels.
2. Decrease Load: Reduce Wheel Friction, or Decrease Robot Weight. By decreasing the load on the motor, it allows a faster speed, while still slipping the wheel.
3. Pop breakers: "Math, shmath... we'll be fine". Gear the robot as fast as you'd like, and not worry about it.
4. Add an additional speed. This allows for a "high gear" for moving around the field, and a "low gear" for pushing without popping breakers.

If none of the first 3 options are available... you'd better try a shifter.
This isn't the end of our trouble, because now we actually have to DESIGN the shifter, then we have to BUILD the shifter but that is a challenge for another time. Whether or not a team is capable of doing it, certainly doesn't determine if it is necessary. If they can't do it, well they'd better try options 1-3.



In short, the 2 main determining factors for whether a shifter is needed or not are:

1. What the team "wants" for Physical Robot Characteristics
2. What the team "wants" for a robot top speed.
3. Nothing else...

For more information on drivetrain gearing calculations, check out the following: http://www.chiefdelphi.com/forums/pa...le&paperid=498




If you posted an opinion in this thread and aren't familiar with the process I outlined above. (The actual mathematical justification behind a shifter.) I directly question the validity of your opinion. Shouting random platitudes about drivetrains, without understanding the physics behind them is meaningless.

...yes, there are several people this is directed to.

Re: Is a shifting transmission really necessary?
 

I CERTAINLY would not do this.. live and let live...
So... let us "simple-elegant" fools live too.

Re: Is a shifting transmission really necessary?
 

I guess the thing is, any way you swing it, a two speed thing isn't exactly innovating "just to innovate". It might be innovating just to teach kids, or just to stop drawing ridiculous amounts of current/blowing breakers, or just to make it so you can go that much faster when you want to while still having good torque when you need it. But it's certainly not what I would call innovating just to innovate.

Something crazy like a shifting crab (can you say CVT crab? :D ), yeah, that's ridiculous and even assuming it work be reasonably possible to do within the contstraints of FIRST, that would be innovating just to innovate. But up to that point, I have a hard time believing that doing something beyond the bare minimum is doing too much.

NOTE: It's fine with me if you choose to do a simple tank drive - I won't look down on you. I will just think that you are missing out on a great opportunity to learn and improve.

Re: Is a shifting transmission really necessary?
 

Yep, we are all crazy fools in our own ways. :D The reason we built a shifter was because we had never had one before, and we always wanted one, and we decided before the season that no matter what the game was, we would have a shifter. We were plenty capable of fabricating it, and it would not put us at any disadvantage in game play, and we were bound to learn a great deal from it, so we decided before the game even came out that we were going to have it. After the game came out, the reason we had six motors was "the Tim Allen Approach." Also, we knew a few teams might have 6 motor drives, we knew many teams would have shifting transmissions, and we knew nobody would have both. So, we did! We wanted to be able to face and win any and every pushing match or speed race that came our way. But unfortunately, the game didn't turn out to be played like that (speed yes, pushing no). But we still had loads of fun (and learning) designing, building, and driving our two speed transmission. It is loads of fun to upshift on the fly and then almost instantly be on the other side of the field. Downshifting on the fly is fun too, but at full speed it can almost bring the robot to a dead stop and send it onto it's nose! (2.66:1 difference between high and low). And the best part is that it has been the most reliable drive system we have had thus far (one minor incident due to a loose press fit) and it's very efficient too :)

Re: Is a shifting transmission really necessary?
 

A quick one...

Shifters are useful depending on what kind of driver you are. Just like in cars, you can keep it in "higher" gears and have a transmission that does not burn up battery power, but has small acceleration, or you can use your gearing aggressively to achieve maximum acceleration. JVN, while I agree with your post, I will mention that while your efficient single speed gearing style is good for having a top speed and big pushing power in one, having a gearbox geared "high" will result in slower acceleration. Having a shifter always increases your acceleration, at least by something bearly noticeable.

I am an aggressive driver. I'm the type that always, ALWAYS, starts the robot in low gear and accelerates to high, just like a car. Even if it only takes half a second to reach shifting speed. In FIRST, half a second can easily mean winning or losing. I think that for my stlye of driving, having a shifting transmission does give a bit of an advantage.

And finally, to adress the original topic.
Shifters are in no way necessary. You can have a winning robot, with a powerful transmission, without a shifter. Just do some math, optimize everything. Even with the KOP transmission you can get crazy power by just doing some math. If you think a shifter will help your robot's performance, enough so that it's worth making, do it! Always make the best of what you have.

Example: "If you have a 3 footh by three foot, inch thick slab of aluminum, don't let it sit and oxidize! Call up a watercutter and make your chassis out of a solid block this year"
*hint hint*

Re: Is a shifting transmission really necessary?
 

I am in the JVN "keep it simple" camp.

I have not always been in that camp. Here is the history:

Pre-Paul (pretty simple ...)

1999 - Van door motors directly coupled to wheels (2WD)

2000 - Drill motors directly attached to wheels (2WD)

(Paul sticks his nose in ...)

2001 - Andy Baker designed TechnoKats shifting transmission built right from his prints with 6 wheel drive (initially).

2002 - 4 wheel swerve drive using the CCT (see white papers section) shifter.

2003 - 4 wheel drive with rear steering using the Baker style shifter.

2004 - Single speed 6 wheel drive using a shifter for power take-off for the winch.

2005 - Single speed 6 wheel drive using the Tim Allen approach (4 CIMs and 2 FP).

2005 was, by far, our simplest robot yet and simplest drive base. Our acceleration was awesome, our top speed was good enough (9 fps). And, the best part of all ... we had zero problems at our first regional. I have found, at least for my students, that working right from the start is one of the most inspirational parts of the season. When what you worked on for so long works ... right out of the box.

I used to encourage my students to innovate just cause it is cool, but that just justed work for us anymore. I can tell you this: I don't innovate just because it is cool at my real engineering job so why should I in FIRST? Making an elegantly simple robot is definitely the way I will encouraging my team to go in the future.

As far as the game goes .. the drive base, once working, just isn't that big a part of the game (exception: 2002). Making an inventive manipulator is much harder than making an inventive drive base and as much fun. If you get inspired by making cool, inventive, and complicated drive trains then great; but I am staying on the side of the simple folk ........

-Paul

Re: Is a shifting transmission really necessary?
 

Wow Paul is certainly a tough act to follow, I will attempt to do my best though. :) There is no necessity to be able to shift first of all, shifting is a nice ability to have though. Second of all you should design to meet the requirements of the game. All I know is that this year some of the most successful robots didn't shift 67,71,217,108 and 33 I think didn't shift there are many others but just to throw some out there. So think about it is this really needed for our application and for the game. Finally designing transmissions may be fun, but it's not fun when a bad transmission leads to a whole bad FIRST season. 1251 (my team) built a fairly simple robot this year, we used kit transmissions and kit chassis and got two regional finalist awards. Just some food for thought when thinking about this subject.

My two cents,
Drew

BTW Paul the three motor transmission is crazy !!!!! :D

Re: Is a shifting transmission really necessary?
 

I don't know about you guys, but I'm thinking 6 wheel, 3-speed swerve next year! :ahh: ;)

Re: Is a shifting transmission really necessary?
 

Oh yeah, and I forgot to add - with independent suspension.

Re: Is a shifting transmission really necessary?
 

Raul, you would be one of the few people I thing might pull it off.

Wetzel

Re: Is a shifting transmission really necessary?
 

Raul, is it all right if you're my new hero? Haha, Wildstang has always been known for cools stuff. I would love to see it though... there is a point when something horribly complex becomes horribly beautiful.

And if you are really thinking about it, would you do individual module shifting, or coaxial? (I would do individual, its way more awesome, and trickier)

Re: Is a shifting transmission really necessary?
 

Of course nobody has bothered to bring electrical and controls into the discussion. (six wheel swerve with three speeds, jeesh! However, if FIRST allowed electrical solenoids, it could work?!?)

Re: Is a shifting transmission really necessary?
 

Perhaps Raul was pushing the point a little bit...but a four-wheel, three-speed passes the Billfred That-Might-Be-Crazy-Enough-To-Work test. (Of course, I'm thinking NBD--but that would be pretty big to steer around. Thoughts from those who've swerved in the past?)