Are two speed transmissions worth it?

[thefro526]

The pneumatics are not a problem we always use them.

[rachal]

We got two speed working pretty well in 2005 and 2006 with no technical problems, but the drivers got so caught up in the match that they would forget to switch gears and got pushed around. I guess it's fine when your drivers have had enough practice though

But yea, besides the question of whether your drivers will use it, a nice 5-15 two speed is really worth the extra work.

[Danny McC]

Yes. According to everything these people have said i would pretty much say they are worth. And apparently if i dont say that they are i cant work on the robot next year. And that makes me sad =(

[AustinSchuh]

Originally Posted by AdamHeard

I would recommend the AndyMark.biz shifters for getting started. They take all the work out of it, and even 254/968 are planning on using the guts of them next year. My team is currently doing a prototype of the previously mentioned base with them integrated.

We bought AndyMark.biz dogs, and the smaller dog gear from them. We would have never been able to manufacture a dog like it ourselves. We had few to no problems this year shifting. We manufactured our own second dog gear, but not having to manufacture both was a life saver.

[Goldeye]

Originally Posted by Joel J.

Something I'm curious to investigate is some sort of current-based shifting "algorithm." Have the drive default to a reasonable high gear (9-10 fps), then shift to low whenever the current draw grows beyond a certain value for a certain period of time. Then shift back to high when the current draw falls below a certain value for a certain length of time. Then have a manual override of some sort. Pretty much, the system only shifts to low to push.

I tried to do that this year. More to enhance our pushing power (ie prevent spinning out) than to shift gears but that was the next step. Never had time to collect data and get it working, though.

[kramarczyk]

Originally Posted by thefro526

...
Also are my speeds a bit off? Would the speeds that come out of the transmission be higher or lower with normal gearing (KOP gears)? And what experiences have you had with your teams transmissions? My GMP (Grand Master Plan) is some kind of six wheel or eight wheel drive (like 1270) with IFI high traction wheels. Any advice on 6 or 8 wheel two speed drive trains would be greatly appriciated

-Dustin

This year we used a 6WD with 8" Roughtop AM Performance Wheels and the AM servo shifter (2 speed) with a pair of the little CIMS into each. We also had a 10:24 out to the wheels which gave us theoretical hi/low speeds of 15.6 fps and 6.10 fps resepectively and more realistic continuous 30 amp speeds of 12.3 fps and 4.8 fps. Calcs were largely done in this spreadsheet by JVN. http://www.chiefdelphi.com/media/papers/1676

[newton418]

Originally Posted by Joel J.

Something I'm curious to investigate is some sort of current-based shifting "algorithm." Have the drive default to a reasonable high gear (9-10 fps), then shift to low whenever the current draw grows beyond a certain value for a certain period of time. Then shift back to high when the current draw falls below a certain value for a certain length of time. Then have a manual override of some sort. Pretty much, the system only shifts to low to push.

We tried this but found that usually, if we were in 2nd gear and all of the sudden had a current spike, the motors were already close to stalling, or they were pulling so much current they would reset the RC. Well, in either of these cases the DeWalts we used weren't able to shift.
Basically, I'm sure it can be done, but keep in mind that the motors might not be turning when the robot is told to shift, so design your shifter accordingly.

As a driver, I think I liked the control over the system. 1st gear (5 ft/s) is painfully slow in a 2 min match, and getting pushed around is so frustrating you have to downshift.

[Doug G]

Originally Posted by Joel J.

Something I'm curious to investigate is some sort of current-based shifting "algorithm." Have the drive default to a reasonable high gear (9-10 fps), then shift to low whenever the current draw grows beyond a certain value for a certain period of time. Then shift back to high when the current draw falls below a certain value for a certain length of time. Then have a manual override of some sort. Pretty much, the system only shifts to low to push.

We experimented with the allegro current sensors in the off season of '05 and had it working exactly how you said. We integrated it into our '06 bot with AM pnuematic shifters, but it annoyed our driver and so he always used the override mode and manually shifted. Perhaps with more practice a driver could get used to this autoshifting behavior. I say current based autoshifting is a cool thing to look into - make sure to set it's thresholds high enough so that it's not shifting when turning if you use high friction wheels and skid steer.

[Billfred]

<insert standard "it depends on your needs" text here>

1618 used Gen2 AndyMarks this year. The result was about the fastest thing on six wheels at Palmetto, while still enabling us to push as needed. (Sorry, 342.)

I was actually a little surprised to find out that our driver was using them backwards from what I imagined--apparently, the cylinders were rigged to shift to low when the joystick trigger was pressed, instead of the other way around. Acceleration in high gear was still surprisingly good.

I'm not saying anything definite, but they're certainly on the short list for next season.

[mikeleslie]

We used the 2 speed AM trans mostly to reduce the power consumption in a heavily defensive match. When in low (less then 5fps) we were able to push most teams (6 wheel, roughtop) and still have the available power to use the rest of hte bot. In previous years (1 spd) , a pushing match would use up everything we had. This year, the field could really be viewed as "short" so a 2 spd trans was not as useable as the prevoius year, where you had a clear 50ft run.

Also, before you look the "auto-shift" think about the situations. If you just got into a pushing match, using up 1 or 2 cycles (electric shift) to shift will kill you. High gear is great for getting you close to where you need to be quickly (.5s faster at 1/2 field for example) and low gear makes the bot have finer control (more motor turns per foot) and more power to push.

As far as electric shifting, the servo works but it's slower than pneumatics, there are not currently any solenoids allowed as they are just another form of and electric motor.

[65_Xero_Huskie]

We never use a 2 speed transmission. I personally dont think its worth it, because our robot has always been fast enough for us and strong enough to push many robots. People always ask if we have 2 speed transmissions and are surprised when we say no. Its up to you if you want to try it.

[Tim Delles]

Originally Posted by Hachiban VIII

I am the only one to have voted "no" so far...

We used our 2 speed AM shifters 1 out of every 2 matches this year. They helped us dart across the field, but we never used them for an extended period of time.

I'll admit they weren't useless... but they weren't worth the weight of the pneumatics.

If you're going to use pneumatics anyways I would say "go ahead." But otherwise save the weight and put it where it counts - in the scoring device.

What about the servo shifters... in all seriousness you can do either (one is not better than the other they both do the same job)

But as to the actual shifting I have a couple questions for you.

have you ever bene in a match and thought to yourself dang i wish i could go faster to get there quicker?

have you ever thought dang i wish i could go a bit slower so i could have a little more pushing power?

I can almost give you 100% certainty that every team has thought that.

The easy answer to your question is yes you should ALWAYS have the option of shifting.

We have used a shifting transmission since 2003 (except for 2006 when we made a custom single speed). After last year I realized you should never do a single speed because throughout last year i was always saying yes to both of those questions.

This year we opted for the 2 speed AM transmission because of a few reasons.

1. Reliable - It has been tested by so many teams in first with very little if any negative effects.
2. Cost - Cheaper to buy the shifter than make it, when you account for the time spent on the CNC machine making the parts and the over all cost of everything put into it. (remember less time spent on one part is more time spent on another or more time for drivers!!!)

Just my 2 cents

[Tom Bottiglieri]

You can only "push" with as much power as it takes to break your wheels loose, so I think proper weight distribution and wheel selection is more important than shifting.

Our team has discussed this topic until we were beating a dead horse, and we have made the decision to look into a 6 motor, single (high) speed drive train. Heck, you don't even need 6 motors.

[rick.oliver]

Originally Posted by Al Skierkiewicz

Teams should analyze the game each year before they make a decision on the transmission or other parts of the robot. There are years in which two speeds are optimum and other years single speed is best. The same can be said for treads, crab drive, multi-wheel or omni-wheels, large diameter or small diameter, aritculated arms, etc. In a defensive game, low speed pushers may be best. In a game where a robot must travel a distance often than high speed might be best. In a year where you might climb a ramp, a high speed only box may not work. There is no hard and fast rule on this decision. Analyze, brain storm and play the game with miniatures or team members playing the robot parts. Use your technology wisely.

Well said, Al. We've used the AM two speed transmissions with pneumatic shifter the past two years and have been very satisfied with their performance and ours. We benefitted from the flexibility of two speeds in both games. I am quite confident that we would not have enjoyed the same success with a compromised single speed.

[robotguru1717]

Yes! being able to sit and push is very important and people have mention having a high speed gear to break away. Its also important for the defensive bot to have a high gear because i saw in several matches that a team that was ment as a pusher couldn't catch up to the other robot to do what it was designed to. The 2 speed transmition allows you all this flexibility. I think three speeds is a bit overkill however, but if you have the weight...why not.