Are two speed transmissions worth it?

[thefro526]

After numerous discussions with team members and doing a bit of research I'm still wondering are two speed transmissions worth the money, weight, time, etc... I am speaking more along the lines of the AM gen 2 shifters not a custom one off application. It seems that in most cases it depends on stratagies but in a overall statement are they worth it?

A few people on my team believe that there is no point to having them. I always say to them that we've always had robots in the mid speed range ~7-8 fps and I'd love to have two speeds somewhere around 5 fps in low and 10 fps in high. It seems that we always try to tell our alliance partners yeah we are offensive primarily but we can play defense but it always seems to be that we never have the required power to push other robots out of the way. Not saying that we need super pushing power or light speed but I would love know that I have a little extra power and a little extra speed.

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

[AdamHeard]

Two great examples of efficient use of a 2-speed shifter this year are 968/254 (custom) and 330 (AM).

Both had a low speed around 5-6 fps and a high of 15-16 fps.

It may seem unnecessary, but I have a great perspective on these drive trains as I have played defense on 330 in about 5-6 matches (including 3 in finals) and in their shop on their practice bot. I also played defense on 968/254 in at least 4 matches.

Their low speed gave didn't allow me to out push them, and their high meant that they could easily break away. All of these teams used this advantage very well.

For reference, we had a single speed at 10 fps with a small CIM, big CIM and FP that was traction limited.



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.

Overall, shifters can be very useful if you have the weight. You will never get a group to agree on this though, as it is a hot issue.

The value of shifters varies directly depending on your driver. If your drive uses them a lot to their advantage (take 254 for example), then yes, they are worth it. If your drive almost never uses it, then no, it's not worth it at all. However, if you plan to train your drive to take advantage of, or otherwise build your drive around the robot, then yeah, I think they're totally worth it.

[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.

[Cody Carey]

If they work, then yes. We had 3 speed this year, and The bottom one, (2.6 fps) was the only way we could score with heavy defense (Yeah, you 48 )

But before we perfected them, That thing on our control board wasn't a shifter at all... It was a "Get stuck between gears and Lose the match" lever.

[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.

[slickguy2007]

I thought they were very useful this year. I shifted about 6 times in a match and especially when defense was getting played on us, I thought it came in handy.

[AdamHeard]

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.

You could do this with encoders.

If the measured speed of the robot is significantly less than what it should be, it must be hitting something and then it shifts down. If the robot is in low and going 95-100% speed, then it isn't hitting anything and will shift back up.

I made a vex robot with that exact functionality.

[Joel J]

Originally Posted by AdamHeard

You could do this with encoders.

If the measured speed of the robot is significantly less than what it should be, it must be hitting something and then it shifts down. If the robot is in low and going 95-100% speed, then it isn't hitting anything and will shift back up.

I made a vex robot with that exact functionality.

Yep. I knew about this option, but measuring current draw appeals to me more. It seems as though it would be "simpler" to get a definitive answer as to which gear the robot should be in. 1126 and 33 have succesfully done auto-shifting on a 4 speed transmission using the encoder approach.

[=Martin=Taylor=]

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.

[Cuog]

Like has been said above it really depends on the game. Also it depends on how well your team can make them. If you cannot shift and get stuck between gears you will only hurt yourselves so if you are thinking about doing it, make some prototypes in the offseason see if you can pull it off.

For shifting maybe I'm old fashioned but I would prefer a manual selection of gears to give the driver exactly what they need/want.

[Alpha 997]

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.

Yeah but there are shifting device that does not require pneumatics thought. Forgot what they are called but they run on electricity and weights like nothing.

[Alex Cormier]

Originally Posted by Alpha 997

Yeah but there are shifting device that does not require pneumatics thought. Forgot what they are called but they run on electricity and weights like nothing.

servos.

I love transmissions and like the 4 speed auto's better then anything else. They give you the speed and pushing power you need and a mix in the middle to not lose power.

[Cuog]

Are you thinking of solenoids? Also I have seen teams use servos to power the shift mechanisms.

curses other Alex beat me to it

[Alpha 997]

Originally Posted by Alex Cormier

servos.

Yeah, that's it.