pic: 222 3 speed closeup/cutaway

[team222badbrad]

Yes the shaft and gears are steel on steel. Both of which I think are heat treated. We also used some kind of spray on lubricant that sticks to the gears.

If you look on the other pictures there are shifting stops to keep it from shifting too far.

Since this is our first year ever building a tranny we went overboard. The production could be simplified greatly. There are lots of different things we could modify such as the side plates and the whole shifting mechanism could be redesigned!

Once I finish the inventor award (due 3/15) I hope to find time to make a white paper and redesign it!

thanks for the comments

[tkwetzel]

I hope to find time to make a white paper and redesign it!

I'm looking foward to seeing a white paper on this beautiful tranny.

[Joe Johnson]

I hate to say this because I think I am only adding fuel to the fire* but... ...I like it!

The part I like best is your method of transfering the torque via the balls. Very elegant.

Nice job.

Joe J.

*I have discussed in many posts that I question whether all this shift on the fly mania (yes, I say mania) is worth the bother when you consider that you can make a relatively robust transmission shifter with a standard drill gearbox and servo.

The only thing that has me thinking is Jim Zondag's 4 speed with automatic shifting (and I suppose your 3 speed would work about as well). Perhaps there is a game where such things make sense. I am still pretty much for simplifying things, but perhaps I was too hasty to close my mind. Time will tell...

[dan 322]

Originally Posted by Joe Johnson

I hate to say this because I think I am only adding fuel to the fire* but... ...I like it!

The part I like best is your method of transfering the torque via the balls. Very elegant.

Nice job.

Joe J.

*I have discussed in many posts that I question whether all this shift on the fly mania (yes, I say mania) is worth the bother when you consider that you can make a relatively robust transmission shifter with a standard drill gearbox and servo.

The only thing that has me thinking is Jim Zondag's 4 speed with automatic shifting (and I suppose your 3 speed would work about as well). Perhaps there is a game where such things make sense. I am still pretty much for simplifying things, but perhaps I was too hasty to close my mind. Time will tell...

Awesome design, but I have to agree with Joe.......seems like the simplest & most robust robot always wins. We had an awesome 3 speed planetary gear, shift on the fly tranny two years ago. Debug period was horrible, but once we got it fixed it was great. I just hate wasting a regional to debugg. ROBUST, ROBUST and ROBUST if you want to win. If not, at least have a lot spared parts pre-made and assembled for quick change.

[henryBsick]

Originally Posted by dan 322

Awesome design, but I have to agree with Joe.......seems like the simplest & most robust robot always wins. We had an awesome 3 speed planetary gear, shift on the fly tranny two years ago. Debug period was horrible, but once we got it fixed it was great. I just hate wasting a regional to debugg. ROBUST, ROBUST and ROBUST if you want to win. If not, at least have a lot spared parts pre-made and assembled for quick change.

We thought of this and tried them out. I am not kidding when i say that i ran it until the motors were burning hot then waited untill they cooled and again and again shifting a ton to break them in. They never missed a shift. Plus all of the auton we tested. Wow, all the late nights were on the auton and drive practice. We ran in it a lot in the few days we got and it did perfectly. I think it will cary us through the season and mini's prety well.
-Henry

[sanddrag]

I still can't really picture the "plunger" type deal that slides within this shaft and pushes the balls out. Can I get a real or Inventor picture of that? Thanks. Also, I don't get how when the "ball pusher outer" is not under the ball, how does the ball not just fall into the shaft. Sorry for my less than technical terminology.

[jskene]

I too would love to see a more detailed drawing of the inner slider that pushes the balls up.

It seems that it should be possible to design this slider so that there is a neutral in between each gear, where all the balls are retracted. This would make it easier to synchronize the rpm of the input and output shaft for smooth shifts, as described in my earlier post.

It should also be possible to design an electromechanical, sequential shifter using an electric solenoid. This would likely be lighter and faster than a pneumatic shifter. I'll see if I can some up with something.

[henryBsick]

Originally Posted by jskene

I too would love to see a more detailed drawing of the inner slider that pushes the balls up.

It seems that it should be possible to design this slider so that there is a neutral in between each gear, where all the balls are retracted. This would make it easier to synchronize the rpm of the input and output shaft for smooth shifts, as described in my earlier post.

It should also be possible to design an electromechanical, sequential shifter using an electric solenoid. This would likely be lighter and faster than a pneumatic shifter. I'll see if I can some up with something.

With our pneumatics, we can only go all the way out all the way in or no air presssure and ram the wedge at a 90 degree angle to push the the cylinder into 2nd. It only gives us three postitions, therefore eleminating the possibility of a neutral. If we used other methods like a lead screw or what you atre describing, yes, we could have neutral position. Our original plan was for a leadscrew and a pto actuall, we scrapped it to geta faster lighter shifter.

Brad will post an inventor soon I think.

Thanks for the comments, questions, and suggestions. We are always eager to answer more.

[Stephen Kowski]

Originally Posted by Henry_222

With our pneumatics, we can only go all the way out all the way in or no air presssure and ram the wedge at a 90 degree angle to push the the cylinder into 2nd. It only gives us three postitions, therefore eleminating the possibility of a neutral. If we used other methods like a lead screw or what you atre describing, yes, we could have neutral position. Our original plan was for a leadscrew and a pto actuall, we scrapped it to geta faster lighter shifter.

Brad will post an inventor soon I think.

i can't wait to to the drawing.....question though, I don't see the wedge anywhere.....can you describe it and how it works a little more cause I'm having trouble understanding the wedge.....

[henryBsick]

Originally Posted by Stephen Kowski

i can't wait to to the drawing.....question though, I don't see the wedge anywhere.....can you describe it and how it works a little more cause I'm having trouble understanding the wedge.....

I will try my best without the inventor pic.
Our pneumatic cylinder pushes a rod that ataches to two shifting forks. They thn move the "plunger" to push out the balls. The rod that the cylinder pushes has aplate on it. On this plate are two roll pins positioned verticly. When the air is dumped from the primary cylinder and put into the cylinder with the wedge, the wedge pushes between the two roll pins moving the primary cylinder a little bnit left or right depending on which gear we were coming from to go to second.

[edit/]Here is a pic. of it on the bot [/edit]

[jskene]

I have done a sketch of a possible shifting mechanism for this type of transmission, and inserted it below. I have spaced the 1/2" gears 1/8" apart and designed the 'bump' on the shifting rod so that there is a neutral in between each gear. This would allow the robot controller to match shaft speeds before shifting into the next higher or lower gear. I'm not sure whether this is really necessary, as I don't know how rough the shifting is with team 222's existing design. (Any comments here from 222?)

The next item needed is some means of moving the shaft 3/16" per slot to engage each gear - 1,N,2,N,3. This needs to have some "springyness" (technical term here) to ensure that it doesn't jam the balls into the gear before they are ready to go. I don't yet understand how 222's transmission does this.

[Kevin Sevcik]

In that case, for your redesign I'd suggest a bronze bushing or some such between those free running gears and the shaft. I just got lectured by my design prof about galling, and it wasn't pretty. Apparently, two very similar metals have a tendency to stick together. Thus, if your lube ever gives out, the gears will sieze and bad things will happen. so as a corollary, check the lubrication whenever you get a chance, just in case.

[henryBsick]

Originally Posted by Kevin Sevcik

In that case, for your redesign I'd suggest a bronze bushing or some such between those free running gears and the shaft. I just got lectured by my design prof about galling, and it wasn't pretty. Apparently, two very similar metals have a tendency to stick together. Thus, if your lube ever gives out, the gears will sieze and bad things will happen. so as a corollary, check the lubrication whenever you get a chance, just in case.

As you can somewhat tell, the word, well, name "FRED" is on the inside of the tranny. I just noticed it myself but, I believe it is there because he is NOTORIOUS for greasing, greasing, and well, greasing. We should be ok and he should have some fun this year, but thanks for the heads up.

[Andy Brockway]

This is certainly a nice, compact design. Reminds me of my dual range Suzuki I had in the late '70's. I have looked at how to easily do the machining and am very interested in seeing your white paper.

As for the lube. We are lucky that we run short matches and that the total life of our robots is measured in hours. Greasing on a regular basis allows us to run on the edge with our designs. I do agree with Kevin's professor provided this was on production equipment. The Suzuki I had (actually I still have the motor and gearbox) was steel on steel but ran in an oil bath.

[Kevin Sevcik]

Speaking of Kevin....

I just had a test today in that class, and it reminded me that the issue is worst if the metals are of the same or similar composition, same hardness, and relatively low hardness. The threshold for same hardness is within 5 HRC of each other. Soooo.. if you have a hardened steel shaft there, and the inside of your gear isn't hardened you should be reasonably ok.

Also, I'd still be concerned even though this isn't production equipment. Our prof showed us a few examples of some coupling threads that suffered from galling, and that's obviously not a high-cycle kind of thing. so mostly, I'd just keep it lubed and keep these things in mind in your white paper.