One speed vs Two speed gearboxes

Originally Posted by asid61

You don't need full autoshifting. Just enough such that your driver doesn't blow the breaker.

Or just design your robot not to trip and make sure your drivers know its limits.

[Lil' Lavery]

Originally Posted by Rauhul Varma

I would beg to differ on all accounts. You can definitely make light and small 2 speed gearboxes. Additionally the amount of air required to shift is extremely small, for example the volume of air required for a single shift on 192's 2014 gearbox was (9/16)^2 * pi * 3/8 = 0.373 in^3 of air, which is nothing as many tanks hold around 35 in^3 of air.

Even if some teams can find ways to minimize the additional costs in space, weight, and air doesn't mean they don't exist. By default, adding the additional gearing and shifting mechanisms will take up more space and weight than not having them. By default, triggering a pneumatic cylinder to shift will consume more air than not triggering that cylinder.

Heck, some teams might not even install a pneumatic system if it weren't for two-speed drivetrains.

[hrench]

I agree with the posters that say you can't decide this until you've seen the game.

Originally Posted by asid61

Autoshifting is done by either current sensing or heat sensing on the main breaker.

I've considered designing a mechanical 'flyball governor' to autoshift. Have any teams ever fielded one of these? Seems easy enough to conceive of. No air, no software and it would down shift when you got slower automatically.

[asid61]

Originally Posted by Andrew Lawrence

Or just design your robot not to trip and make sure your drivers know its limits.

I can see why you would do that, but that severely limits your speed. A 20fps+ drive can trip in seconds, and even an exeperienced driver can make mistakes (see: 1678). To prevent that you have to cap out your speed, thus limiting your competitiveness. One less thing for the driver to worry about IMO.

Originally Posted by asid61

I can see why you would do that, but that severely limits your speed. A 20fps+ drive can trip in seconds, and even an exeperienced driver can make mistakes (see: 1678). To prevent that you have to cap out your speed, thus limiting your competitiveness. One less thing for the driver to worry about IMO.

Team 71 won a world championship with a dominant robot in 2002 spending the majority of the match traveling only inches each second. If you think you need 20+ ft/s to be successful in FRC I suggest you take a step off the California powerhouse hype train and re-evaluate what a drive system is supposed to do. Better yet, attend my class on Strategic Design at the WRRF workshops on December 13th and I will personally explain to you why this isn't necessary.

I understand where you're coming from - I once had a similar mindset as well - luckily I had some good mentors knock some sense into me. We're fortunate to have some of the best mentors to learn from here in California - especially in the Silicon Valley.

[Andrew Schreiber]

Originally Posted by Andrew Lawrence

Team 71 won a world championship with a dominant robot in 2002 spending the majority of the match traveling only inches each second. If you think you need 20+ ft/s to be successful in FRC I suggest you take a step off the California powerhouse hype train and re-evaluate what a drive system is supposed to do. Better yet, attend my class on Strategic Design at the WRRF workshops on December 13th and I will personally explain to you why this isn't necessary.

I understand where you're coming from - I once had a similar mindset as well - luckily I had some good mentors knock some sense into me. We're fortunate to have some of the best mentors to learn from here in California - especially in the Silicon Valley.

In a time when moving was a major challenge and almost everything was custom and there was less power available in the KoP. Things were slower then.

[Michael Corsetto]

Originally Posted by Andrew Lawrence

Team 71 won a world championship with a dominant robot in 2002 spending the majority of the match traveling only inches each second. If you think you need 20+ ft/s to be successful in FRC I suggest you take a step off the California powerhouse hype train and re-evaluate what a drive system is supposed to do. Better yet, attend my class on Strategic Design at the WRRF workshops on December 13th and I will personally explain to you why this isn't necessary.

I understand where you're coming from - I once had a similar mindset as well - luckily I had some good mentors knock some sense into me. We're fortunate to have some of the best mentors to learn from here in California - especially in the Silicon Valley.

If I understand correctly, asid61's stated hypothesis is this: limiting speed reduces competitiveness.

In the context of Aerial Assist, I agree with this. I believe our speed on the field was a component of our success this season.

All aboard the California powerhouse hype train. Next stop, Einstein 2015

-Mike

[Abhishek R]

Originally Posted by Michael Corsetto

If I understand correctly, asid61's stated hypothesis is this: limiting speed reduces competitiveness.

In the context of Aerial Assist, I agree with this. I believe our speed on the field was a component of our success this season.

All aboard the California powerhouse hype train. Next stop, Einstein 2015

-Mike

I agree, I think speed was one of the factors that separated a good team from a great team. 1678 is a perfect example of this.

Originally Posted by Michael Corsetto

If I understand correctly, asid61's stated hypothesis is this: limiting speed reduces competitiveness.

In the context of Aerial Assist, I agree with this. I believe our speed on the field was a component of our success this season.

All aboard the California powerhouse hype train. Next stop, Einstein 2015

-Mike

For Aerial Assist, if your strategy played that way it is very true, however it's dangerous to think that an extremely high speed is required for all games, and that was the point I was trying to get across to asid61. Your strategy for this year was more successful with a higher speed and you pulled it off amazingly well. That being said, running your same speeds in a different year - 2012, for instance - may not play as well to your strategy than slightly lower, more controllable speeds. Of course I know you understand this, but I'm posting this to clarify for asid61.

[chrisfl]

I was watching one of the Behind The Lines videos which was on drive train design and they discussed modifying a 2-speed shifting gearbox to be one speed and when you shift, the motors run a different system on your robot. This is great for a game where you are either driving or doing another high load/speed task. For example, climbing in games like 2013 and 2010. Has anyone done this before? How effective was it?

[EricH]

Originally Posted by chrisfl

I was watching one of the Behind The Lines videos which was on drive train design and they discussed modifying a 2-speed shifting gearbox to be one speed and when you shift, the motors run a different system on your robot. This is great for a game where you are either driving or doing another high load/speed task. For example, climbing in games like 2013 and 2010. Has anyone done this before? How effective was it?

Look for "PTO" gearbox in search. Power Take-Off rigs allow the full power of the drivetrain (or half of it) to power something else. They've been used as far back as 2004 (60 and 254 winched themselves up to a bar with a PTO from their drivetrain, as I recall). They can be very, very effective, but only if used properly. For example, you probably never want to be driving at the same time the PTO system is on; you could do some serious damage to your robot!

You could also modify a 2-speed gearbox to be a 3-speed, with the third speed being the PTO.

[asid61]

Originally Posted by Andrew Lawrence

For Aerial Assist, if your strategy played that way it is very true, however it's dangerous to think that an extremely high speed is required for all games, and that was the point I was trying to get across to asid61. Your strategy for this year was more successful with a higher speed and you pulled it off amazingly well. That being said, running your same speeds in a different year - 2012, for instance - may not play as well to your strategy than slightly lower, more controllable speeds. Of course I know you understand this, but I'm posting this to clarify for asid61.

I understand many games require slowness. 2002 is not a good example, as IIRC there was only two cims in the KOP. Going 20fps was not an option. Now, 2010 was a year where speed was not very applicable, and where I think a single speed drive would make sense.
However, for games 2011-2014, fast robots are good. And to go fast and avoid trips (even accidental ones) you should really have a shifter.
Now 2012 I could see going under 20fps. However, six cim drives make going under 18fps almost pointless if you don't have to worry about breaker trips. So you slap on a shifter. The game is not just speed, it's distance/time. The greater that ratio is, the more maneuverable a robot is (depending on the driver, of course).
The primary downside of a shifter is space usage. Custom options are good for this. A team that needs to every inch of space on their robot for manipulators, etc. would need to go non-COTS.

[Jared]

Originally Posted by asid61

I understand many games require slowness. 2002 is not a good example, as IIRC there was only two cims in the KOP. Going 20fps was not an option. Now, 2010 was a year where speed was not very applicable, and where I think a single speed drive would make sense.
However, for games 2011-2014, fast robots are good. And to go fast and avoid trips (even accidental ones) you should really have a shifter.
Now 2012 I could see going under 20fps. However, six cim drives make going under 18fps almost pointless if you don't have to worry about breaker trips. So you slap on a shifter. The game is not just speed, it's distance/time. The greater that ratio is, the more maneuverable a robot is (depending on the driver, of course).
The primary downside of a shifter is space usage. Custom options are good for this. A team that needs to every inch of space on their robot for manipulators, etc. would need to go non-COTS.

Team 118 didn't shift in 2011, 2012, 2013, or 2014. They were still incredibly good in each of those years. They prove that you don't need 2 speeds to win the same way that Einstein proves, year after year, you don't need an omnidirectional drive to win.

[asid61]

Originally Posted by Jared

Team 118 didn't shift in 2011, 2012, 2013, or 2014. They were still incredibly good in each of those years. They prove that you don't need 2 speeds to win the same way that Einstein proves, year after year, you don't need an omnidirectional drive to win.

Yes, they were good. But could they have been better? That's not said as a challenge, but I am legitimately interested in why they go with a single speed over a two speed.
As a counterexample, 254 has been shifting for about a decade now, and they have two championship wins.
I would like somebody from 118's opinon on this.

[z_beeblebrox]

Originally Posted by asid61

if you don't have to worry about breaker trips.

Can I visit the magical world where this is the case?

I feel like what you've been saying about extremely high gears is true if and only if power management is not a concern.