Why not to shift?
 

Other that cost, what are some downsides to shifting gearboxes in the drivetrain (either COTS or custom).

We are considering shifting this year, and while I can find numerous threads on the benefits of shifting, I can find relatively few on the disadvantages.

Additionally, what are some pitfalls to avoid when using shifters? What are some useful things to know.

Re: Why not to shift?
 

If you do decide to use shifting gearboxes, be sure that you have easy access to the shifting mechanism. We had this problem with a summer robot and had to cut holes in our bellypan (solid sheet of 1/8" aluminum) at Calgames this year.

As to disadvantages, they take up more space and weight because of the shifting mechanism and extra gears

Re: Why not to shift?
 

Added complexity. Servo-based shifting is slow and somewhat unreliable. Pneumatic shifting is much better, but if you have no other pneumatics on your robot the compressor is going to be a giant power suck. It's also easy to pick the wrong gear ratios and end up with a low ratio that's too low and a high ratio that's too high.

There's also the issue of training your drivers to use it properly.

Ideally, pick a gear used only for pushing and climbing (mounting the bridge, etc.) and another for regular driving.

Re: Why not to shift?
 

What are some ways to counter this? How do teams that to manual shifting train their drivers "how to shift."

Re: Why not to shift?
 

I actually edited it to be a bit more clear. Done properly, that shouldn't really be an issue. The most successful shifting teams I've seen primarily use one gear for pushing and the other for driving, but don't really switch otherwise.

Re: Why not to shift?
 

A downside to shifting is the added complexity of your robot and maintainence. More moving parts, more components, etc. Another area with increased chance of failure if not done properly and the last place you want failure is your drivebase!

We have had a issues in the past two seasons with our pistons slipping out of gear either limiting us to either low, high, or neutral. Thankfully our team has never experienced neutral in match but it has happened during drive practice. We use AM Supershifters and we haven't found much of a remedy aside from checking the pnuematic mounts every few matches but once you release the air from the system its not hard for the AM shifters to switch gears. If we use shifters again in the future we'd look into better ways to get around this problem like using springs to keep the piston in low gear when their isn't pressure in the system and redo some of the mounting for a more permanent/solid fit.

We did have an issue during 2011 where the shifter was sent with an extra washer resulting the one gearbox being compressed when assembled. It resulted in the jags on one side being overworked and shutting down at various points in the match. It was hard to chase because we took apart that shifter so many times each time it was tighted differently. Our first event it happened once a match but during our second event it was happening every 5 seconds. Lesson learned: make sure you know everything about your shifter what belongs and what doesn't!

When using shifters especially COTS you really need to make sure you need them. For teams who make their own transmissions it is easy to customize your ratios and mountings for better speeds to fit your strategy and save weight.

Of the robots I've worked on we have used supershifters three times:

2010 (1519): We used supershifters mainly to have high torque and low speed for crossing the bump and defense. They were very handy to have we spent most of our matches in low gear but high was great for quickly transitioning from one goal to another to get around defenders or get another balls. Super low speeds were used to get balls off the wall and line up with the goal.

2011 (3467): Our design as a rookie placed defense as a top strategy with our minibot and low row arm. We had a nice 6wd and planned to use shifters for defensive pushing matches. IMHO bad move. It was hard for our driver to transition from low to high speeds easily to adjust for what was happening on the field. Low gear was too slow to keep up with opponents and instead we played in high gear to keep up with faster robots and once we got into a T-bone push we'd were supposed to switch to low. I believe our driver kept just kept it in high gear to keep up some quick machines like 177, 40, 131, 33, 1718, 118, etc. We could have done the same with toughboxes and used the weight elsewhere but since defense was our priority it served us well. If we replayed 2011 I would push for single speeds dependent on our strategy.

2012 (3467): Used them for crossing the bump, balancing, and lining up on the bridge. I know a lot of people asked why you would need high gear but we made use of it by quickly going to the other side to grab balls before heading back and spent most matches collecting balls in high gear. Great choice for our robot.

It really comes down to your robot as a whole and the field you play on when decided whether to shift or not. While most powerhouse teams have two speeds they aren't required to win events or do well on the field. Using single speeds is one way you can keep your robot simple and focus energy on other areas.

As for when to shift it depends on why you put those shifters on. Was it to push? Was it to cross something that required low speed? How high is your center of gravity and what speed is safest for when your manipulator is up in the air?

Re: Why not to shift?
 

Shifting gearboxes are cheap this year, and the stupid cylinder restrictions are long gone. That means the set of circumstances where a shifter would not be beneficial is exceedingly small.

That said, the main disadvantage for a competently built shifting gearbox is the fact that it inherently spends some of its time out of gear before resuming under power. (CVTs don't have that issue, but they're quite rare in FRC.)

Think of it in terms of a diminishing return: for each ratio, you add complexity and unpowered time every time you accelerate and shift through the gears, but gain output efficiency (by running your motors more optimally). At some point, the losses of time equal the gains in acceleration. Consider the situations in which your robot will be expected to perform, and estimate whether you're running into the practical limits of the design's utility.

Also, don't underestimate issues like being in the wrong gear and running out of air, or synchronizing two shifters.

(For my own amusement, I enjoy having two speeds and six drive motors very, very much. Incidentally, it's a good combination for a lot robots in a lot of games.)

Re: Why not to shift?
 

If you're concerned about pneumatic shifters losing air, use single acting cylinders. They're air powered one way and spring powered the other. If you lose air, you won't be stuck in neutral. They're also lighter, cheaper and require less plumbing. McMaster part number 6498K195 works perfectly at $18.02 each.

Re: Why not to shift?
 

Factors favoring single speeds:

1) You might be able to use a one stage gearbox instead of a 2-3 stage to get better efficiency. That gives you the same benefits as using more powerful motors, except you don't have to draw the extra current and produce the extra heat.

2) Single stage gearboxes are lighter by a pound or more.

3) Pneumatics weigh several pounds, so you have significant weight savings available if you're not using pneumatics for anything other than shifting.

4) Single speed boxes are thinner, and you could have certain situations where that becomes important. For example, you can fit a battery between the CIM motors sometimes, but using thicker gearboxes could eliminate that possibility depending on the setup.

5) Cost is a factor, of course, but consider that it's even more of a factor if you're on the edge of being able to make a practice robot. Now that components are cheaper, more teams will hopefully look at practice robots. When you have to buy four of every transmission, the $110+ difference between single and double speeds turns into $440+, which is a decent chunk of your second robot.

6) It's easier to make a custom single speed transmission than a custom two speed transmission. That has benefits, but the one that I'll mention is that you can more easily make a direct drive robot with a custom gearbox that mounts to your frame in some convenient way of your choice. Direct drive can increase your reliability and decrease complexity. It can also make it possible to drop another reduction stage (see item #1).

Re: Why not to shift?
 

After your game analysis and main strategy lock, ask yourself this:

Is there any reason why you will need a low gear for the extra torque?

If you definitely think you'll need a low gear with more torque, then shift. If not, a single speed will do you just fine.

Re: Why not to shift?
 

Coming from one team who does shifting almost every year to another that has never had a shifting robot, here's my take.

Pro, it significantly simpler. I'm not very mechanically inclined, but I could look at the drives and understand exactly what was what, what it was doing, where it came from and where it went. I could even maintain them a bit, which I could never do on my old team. Weight is also a factor, especially when you consider the pneumatics required for instant shifting. 67, I believe I read, had window motor powered instant shifting, which obviously still eat up weight.

Cons, hands down, was versatility. Especially from a coaching standpoint, it was really nice have the ability to shift to low gear for power. I can't count how many times I wished the robot had shifting, either when interacting with other robots or tackling the bridges. If the robot had shifting this year, I don't doubt they would have done much better. That's not to say shifting adds to success directly, but having the added ability is very helpful in matches.

Personally, I would like to make a push for shifting in the future. Buying shifters is out of the question; the team simply can't afford them. But if we can develop a solid, custom design that suits our resources, I'd be thrilled.

Just my take.
-Leeland

Re: Why not to shift?
 

Shifting is an interesting solution to an interesting problem.

First, what is the problem that teams are trying to solve by shifting?

-My answer would be that, "we want to go fast and push hard." This stems from needing to go fast to get somewhere on the field and pushing hard to get through someone in your way while trying to get there.

A single speed transmission needs to maintain enough torque to not trip its breakers while pushing. Most of the time that much torque is not needed while driving around on the field. However, when it is needed it better be there or the robot's breakers will likely trip.

A two speed transmission still needs to maintain enough torque to not trip its breakers while pushing. However, using it's second (higher) gear it can drive around most of the time at a faster speed that it would not be able to safely push in.

Of course, there is more then one way to skin a cat, peel an orange, or make your drivetrain go really fast without tripping its breakers.

Another potential answer to the same problem is to add motors to the drivetrain. Their isn't any law that says a drivetrain has to be four CIMs. By increasing the overall available power one can gear the robot higher (improving its speed) while maintaining the same level of torque.

Another solution is decreasing the overall drivetrain weight. While the robot can be geared faster and not trip its breakers the overall pushing force of the robot decreases because there is less normal force on the wheels.

Now what if we used a shifter, had 6 motors, AND decreased the overall robot weight?

Just some things to think about.
Regards, Bryan

Re: Why not to shift?
 

Our team has never used shfiters in the past. That being said, we have focused a lot of our driving in the past two years on defensive strategies. Keep in mind the decision to be primarily defense was probably the first design decision that the team made. From there the desired gear reduction was picked.

We have found that if you pick the right gear ratios, you can be just as maneuverable and still pack a solid amount of pushing power.

Also, we have been playing around with the idea of "shifting" in a differant respect. Rather than shifting gears in the transmission, last year, we implemented a dynamic lift into our drive system. The robot was an 8 wheel drive, with the center four wheels dropped 1/8". This yielded a very agile drive base. But when we got into a bumper to bumper situation with another bot (which happened frequently, as we were a defensive machine) our driver could hold a thumb button, dropping the outter four wheels 1/8" giving us a true and level 8 wheel drive. Once the thumb button was released, the outter wheels would lift back to their home positions automatically.

Although this probably doesn't provide as much pushing power as shifting to a lwoer gear, it did give us better traction and would stop a spin out from happening instantaneously. The drops were actuated via two PG71's and two one inch sections of threaded rod.

Just another method of making your drivetrain more dynamic with out integrateing gear shifters.

Re: Why not to shift?
 

The one thing that I haven't seen mentioned that a shifting robot can give you is more precise control.

Those slow speeds give much better control to the driver when making fine movements like placing scoring pieces and the extra power is also better for overcoming scrub at lower speeds.

Re: Why not to shift?
 

I thought about this after I posted.

When we competed at Ruckus and would try to line up and take shots, we would just turn REALLY slowly and hope we got a controllable speed and didn't overspin when we stopped. This would have been much easier had we had a low gear. Low speed and controlled movements. It would have helped us out A LOT.

Re: Why not to shift?
 

Why we haven't shifted in the past:

1. Adds complexity to the design
2. Adds weight to the design
3. Servo shifters can be unpredictable
4. We often don't have pneumatics on the robot already; adding the compressor for one purpose is a poor use of weight/real estate
5. Adds complexity to the programming
6. Adds cost
7. In some games, we don't see ourselves driving far and fast often enough to justify shifting mechanisms
8. Physical barriers on the field reduce effectiveness of shifters
9. We had a non-shifting drivebase done in a matter of days - we could use this for testing, practice, etc.

Re: Why not to shift?
 

In the last 2 years, having a single speed transmission allowed us to actually complete our robot before ship date and under weight. This is HUGE. Do not underestimate this. We've had our best-ever on-field success in the last 2 years because of this. Go listen to Karthik's presentation. Go now! Then come back.

As the coach on the field, at no point in the last 2 years did I WISH I had a shifting transmission to power through a given situation. Sure, it may have helped inherently ease one or two situations on the bridges in 2012, yet the issue was more about the bridge lowerer than the control getting up.

Thus, unless we're climbing some incline like 2010 (and even then, only if climbing the incline provides enough reward) or we're forced to traverse a wide open field like 2008, I doubt we'll do a shifting transmission in 2013.

Re: Why not to shift?
 

THIS is a key point. In 2001 we found that a low gear allowed the driver to better align the robot for hanging tubes. In 2012 it allowed the driver to shift into a lower gear and

1) climb onto the bridge with more control

2) Play defense and push an opponent

One other thing we've always done when shifting is to definitely go for the air shifter as long as pneumatics are on the machine for another reason. The servo shifters do work but we feel they're not as good as 'shifting on the fly' as pneumatics.

As far as the driver getting used to it? Driving practice is a HUGE help.

Re: Why not to shift?
 

I hope everyone posting on this thread understands the diferamce between power, torque, and pushing force. When a robot is in low gear, it generates moretorque at a given power, which resuts in more robot pushing force.

Re: Why not to shift?
 

This is straight our of 67's 2012 Engineering Design log. Now, this is beyond my level of mechanical comprehension to really understand what's going on. But the jist of it is 67 used a window motor instead of a servo to shift their two-speed gearboxes. Because the window motor is more powerful, it allowed for shifting on the fly, as opposed to a delay of seconds when using servos.

For those who are opposing shifting when pneumatics aren't being used elsewhere on the robot. It's an interesting idea. If you're willing to give up the motors for it.

Re: Why not to shift?
 

All though this is off topic slightly. Our team has triggers and buttons on our controls that are slow mode and turbo mode. No physical shifting required I know it is not the same thing but I am curious as to the benefits between them programming method and the actual shifting method.

Re: Why not to shift?
 

Shifting gives you an actual increase in pushing power. This means that it is useful for getting around defense in addition to having more controllability.

Re: Why not to shift?
 

If I understand what you're saying right, 1511 doesn't shift, rather, change the speed at which the motors run?

I gave heavy consideration to doing this to help line up for shots at Ruckus. Not much time to do so, I'm afraid. This method does offer controlled movements and speed when necessary. For teams looking for those things, it's a good alternative to shifting. Obviously it won't offer much in terms of advanced power. But a good alternative nevertheless.

As to the topic of the thread, "Why not to shift?", you wouldn't shift if you required controlled movements and high speeds, but not a change of power in the drive system, I suppose.

Re: Why not to shift?
 

I agree that the pushing power is different but both slow modes provide control and precision.

Re: Why not to shift?
 

Shifting reduces the torque demand on the motors, which brings the motor's top speed and loaded speed closer together. That means a smaller jump in speed when you go from heavily loaded to lightly loaded, which means better control in many situations, such as making small rotation adjustments on a sticky 6-wheel drivetrain.

Simply scaling in programming is never going to achieve this because the problem is in the dynamics of the electromechanical system. Speed or position feedback control of the drivetrain could help with this, if it's tuned well enough, however.

If anyone's interested, I'll add a post with all the math explaining why this is so.

Re: Why not to shift?
 

To add to that:

Power = torque * speed
Power is work / time
Work is force * distance
So, torque * rotations / seconds = power

Acceleration requires torque. To accelerate faster, you need more torque (unless you're traction limited, then you need more controlled torque output or less torque).

For DC motors, since the power curves are linear (or extremely close), peak power usually occurs at 1/2 speed (which is also 1/2 torque), so peak power is indicated as (1/4)(torque)(speed) if you convert units correctly. You have 0 power at stall torque or free speed. This point splits the 'good side' and the 'bad side' of the power curve. Motors are very very unhappy with the bad side of the curve (lower speed, less torque). Don't design to be on the bad side for too long.

For DC motors, speed is inversely proportional to torque and proportional to voltage. That means, at free speed, you are producing no torque. Since you always require torque due to friction losses, you will never be at free speed.

Torque is also proportional to current, and motor heat output.

Voltage = current * resistance. The entire electrical system can be represented as a resistor, so you can estimate voltage drop based on motor current.

A gear reduction adjusts speed and torque while maintaining power. If you cut speed by 1/3, you get 3x torque and power remains the same (neglecting the slight efficiency loss)

If you gear for too high of a speed, you will see several issues:
-Increased torque at the motor during acceleration increases current draw, draining the battery faster, possibly tripping breakers, and increasing voltage drop in the electrical system.
-Running too long on the 'bad side' of the power curve could thermally damage the motor. Some motors are more notorious for letting out the smoke than others.
-You will take longer to accelerate if you gear higher than a certain point, as you will be torque limited by the motor at a lower speed. Essentially, you need torque to accelerate, if you don't have enough, it will take longer to accelerate to the same speed (even if your top speed is higher)

In a car, shifting is done for several reasons:
-Engine power curves are very nonlinear, they usually want to stay in the efficient operating region and sometimes in the peak power or peak torque region
-Acceleration is faster if you're shifting at the optimal points. Imagine graphing the wheel torque vs speed in all gears on the same graph. There are intersections where it becomes more efficient to shift as torque drops off. If you shift at the right place, you will stay in the most efficient place. A CVT would always stay at the optimal place, transmissions with many gears also shift often, but it's a tradeoff between staying in the optimal operating region and shifting a lot.

In a FRC robot, where shifting is generally manual, shifting is done for slightly different reasons:
-To optimize pushing power, to become traction limited at a point where you can't trip the breakers in match play
-To optimize speed so you can still drive fast during the rest of the game

You could alternatively optimize two gears to accelerate faster, if you shift at the correct points.

With so much power in the motors now, it's getting more and more reasonable to design around a moderately high single speed (10fps-11fps) rather than use a 2-speed of ~5fps and ~13fps and shifting to accelerate. There's always something to be said for throwing more power at the problem.

Re: Why not to shift?
 

The danger is calling it "pushing power" when what one really intends is "pushing force" or "pushing ability". Most people will understand what the intention is, but some people will get power and force mixed up if they're not familiar with the difference between the two. I think that's what DampRobot was getting at.

/semantic threadjack

OP: all the main points have been hit: shifters add weight, complexity, cost, and are not always utilized enough to offset the first three drawbacks.

We're leaning towards going back to a single speed drive this year, mostly for a cost and timeliness concern, but also because we didn't use the shifters much in the last two years.

Re: Why not to shift?
 

This is neat feature we use and I know others do as well.

In 2010 IIRC we had three buttons that limited power to the drive motors. I think (1/2, 1/3, 1/4). It was a great feature for picking up balls of the wall and corners and to cut the power while turning. Add these buttons to a two speed transmission and our drivers had six different speeds to play with on the field!

In 2012 we had a 50%-75% (I don't remember the exact number one of our programmers played with the power setting to get a good balance) power button. This was great for lining up on the key, climbing the bridge either as a solo balance or the first bot on, and turning while in high gear. So technically we were a four speed transmission. :cool:

Similar to your team, you can use a single speed transmission and run constantly with a power of say 85%-90% and have a button for a low speed and a turbo button to give you an extra boost of speed to act like a high gear. Before pursuing this route, do the math!

As others have mentioned it doesn't give you an edge with pushing power but gives your drivers flexibility to pull off moves you can't do with a single speed. In 2011 if a low speed was all you wanted for placing tubes and lining up your minibot a wiser decision would be to have a programmed lower speed rather using shifters because you don't need the extra torque. This also allows you to keep a lighter robot which will equal faster speeds and less torque required to move!

For many teams, shifting is the answer but in most cases you can accomplish what you want with lighter, reliable single speeds and some basic programming additions!

Re: Why not to shift?
 

We preferred to line up for shots using a low gear vs a software-slowed high gear. Since we run an 18-20+ fps high gear, long acceleration times made precise movement difficult for our drivers.

Re: Why not to shift?
 

Understand the difference between "top speed" and "time to destination". A single speed robot geared for a top speed of 6 to 9 fps will get you from where you are to where you need to be very nicely, and still spin the tires in a shoving match. How often to you cross the entire field without stopping or turning? How many times to you accelerate from a dead stop? How much time & driver focus is spent shifting?

We have never used a shifting transmission. I won't say we never will, but I haven't seen a game (even Overdrive) where I regretted not having one.

Re: Why not to shift?
 

This past year actually our turbo mode came in handy. Our robot traversed the barrier with ease and could defend our lane before another drive team could see what was up.

Re: Why not to shift?
 

It also did substancial damage.

Re: Why not to shift?
 

Care to elaborate?

Re: Why not to shift?
 

At the rah cha cha ruckus this year, we found that turbo-ing over the barrier really damaged our robot. We did it once, and the radio fell off, and the entire underside of our robot was dented up and scratched, not to mention that our bridge actuator was all bent up. This was also contributed to by the pneumatic wheels having a lot of bounce in them, in addition our drivers extremely defensive driving style during those matches.

Re: Why not to shift?
 

So, what you are saying is, turbo mode isn't bad for a robot, it's just what was done while in turbo mode that was damaging to the robot.::ouch::
OK, good to know. ;)

Re: Why not to shift?
 

Going over the bump in high gear is fun too! For a moment it felt like Dukes of Hazard which was cool before the image of your robot mangled and broken in a heap fills your head! :p

We've done that move three times this season with only a few surface scratches!

Re: Why not to shift?
 

Only three times?

http://www.flickr.com/photos/daniele...57629155165512
http://www.flickr.com/photos/daniele...57629491142326


If you run a turbo mode, you are limiting your normal non-turbo driving in one of two ways:
-If you just divide/multiply the output by a constant, you're limiting the motor to substantially less mechanical power than it is capable of, and your acceleration will be worse in slow mode, due to reduced voltage, in addition to the high gearing.
-If you actually speed-control to a lower output speed, you will still maintain the acceleration of the actual gear but your drivers will still be limited. This is OK in some cases, depending on what you are trying to do, but you are still limited to the acceleration of the actual gear.

So, a turbo button is just limiting the drivers. It won't allow you to gear any faster, because your acceleration will suffer in non-turbo mode. My recommendation is to either gear a single-speed down to the speed you actually want to drive at, or run a real shifter.

Re: Why not to shift?
 

Yes only three thankfully! They were all accidental but when we did we went near vertical. We have footage of the first one which was the worst considering we went airborne!

Re: Why not to shift?
 

For a team with 6 drive motors (for example, let's say a 775 and two CIMs), how fast would the robot be traction limited at? I would assume if a 2 CIM drive is traction limited at 6fps, then with a 775, the traction limited single speed gearing allow for a top speed around 8fps. Could you, theoretically, just throw power onto the drive until you were traction limited at, say 13fps?

On a related thread, how many motors can you give a drivetrain while still drawing less current than the main breaker will pop at? An unsophisticated analysis says that even 4 CIMs drawing 40 amps (ie, accelerating from a stop) will pop the 120 amp main breaker. Is the limit on the number of motors which can reasonably be put in the drive dictated by the main breaker?

Re: Why not to shift?
 

Actually, those circuit breakers won't ever trip at the rated current. Take a look at the attached datasheet to get a feel for the trip times. According to the data sheet, at 200% rated current, they should take at least 10 seconds to trip. It looks like about 20 seconds at 150%. That's assuming no heavy bumps, of course.

So based off that, on a 4CIM drivetrain, you'd likely fault out jaguars or trip your 40A breakers before you tripped the main 120A breaker.

Re: Why not to shift?
 

I have to say pushing other teams is over rated. If your going to get a shifter to have more pushing power don't waste your time. Best thing to do is keep things simple. Get your robot to do one thing perfect trying to be jack of all will make you a master of none.

Re: Why not to shift?
 

I agree that you should master one thing, though I don't think many teams use shifters just for their pushing power. If you have a second speed, it allows you to gear your for a higher speed. This means that you are more effective at solving the game task. In addition however, it also allows you to be able to win many of the pushing matches you will face in eliminations. In my opinion, the shifter allows you to be a more effective scorer.

Re: Why not to shift?
 

Going across the feild at 22 fps and 10 fps will not save enough time for the average team. Slower is faster in the world of FIRST. The biggest problem teams have (i would say 90%) is they think their better then they are.

Look at the last few games where both alliances put up 0 points. Most of them were to worried about shooting fast or shifting to be faster when they can't even score 1 ball/tube. 2010 is a perfect example, you could have pushed 3 balls in and hung and won over 70% of your games.

Re: Why not to shift?
 

Agreed. Single speeds can play defense just as well as shifter.

Re: Why not to shift?
 

I definitely agree that shifters are overated. They only help teams that are already preforming well(teams that spend time at the end of the build season tuning and practicing with their robot). However, I think that there is little reason to not use shifters this year. Companies like Vex and WCP have made them super easy(and cheap) to integrate into whatever drive you choose to run.

Re: Why not to shift?
 

We went with a two speed 8WD setup last year, geared for 7.3 and 18.8 fps (14:40, 28:35 or 15:48, 28:40 with 4" wheels). This was created using standard AM gears and shifters that we packaged with our own sideplates.

In competition we never used high speed once. I think it was a combination of a) it was too fast for us, and b) with the field divided in half, there was never a time when we wanted to cover a lot of ground very quickly.

This year we're debating whether we want to have one speed or two. We already know we can do it, for us it will be a question of whether it makes sense for the game and whether the added complexity and weight is worth the effort. If we do decide to do it I have a feeling our fast speed will be a more controllable ~10 fps, pushing our slow speed down quite a bit lower than it was.

Re: Why not to shift?
 

We also didn't use our high speed the way we thought we would, but that's because we had a wide robot that ended up being more tippy than expected. We were really happy to have that low gear for climbing bridges and barriers last year. I think last year we were better off with a 5-6 ft/s robot (that can go 12 ft/s but doesn't) than we would have been with a single speed 9 ft/s robot. And I think we would have been no worse off (except in one particular match) with a single speed 5-6 ft/s robot.

If we do shifters this year (likely), then we will be looking at choosing a sane high gear that we can drive comfortably; perhaps 12 to 14 ft/s. And making it stable enough to actually be able to drive it that fast.

Re: Why not to shift?
 

We don't shift. I've always wanted to, mainly because I thought it would be really fun, but it seems to have worked out ok over the years.

Re: Why not to shift?
 

Being finalists on Einstein probably counts as "OK."

Re: Why not to shift?
 

What was it geared for?