Re: pic: 222 3 speed closeup/cutaway
 

Thank you for the clarification.
From what you are saying, am I to imply that you use pneumatics to control the balls? (you wrote: The ball bearings remain in the shaft until the air inside shaft pushes the balls out and locks the gear.) Henry seemed to indicate that there was a central rod in the axle that slid back and forth, and somehow pushed the balls out.

Did you use a water jet to cut the slots in the gears?

Re: pic: 222 3 speed closeup/cutaway
 

Sorry for the typo...

I ment to say that the rod is used to push the ball bearings inside the slots in the gears. The air cylinder moves the rod between high and low and a 2nd cylinder wedges it in 2nd gear.

We made the slots in the gears using a manual mill. Most parts were made by hand and the side plates were done on a brand new CNC.

Re: pic: 222 3 speed closeup/cutaway
 

Very cool, I think I might even understand how it works. Thanks for the explanation.

Re: pic: 222 3 speed closeup/cutaway
 

[QUOTE/]
If you put a sensor on both shafts, I think you could make a really slick automatic transmission with this gearbox.
When the software figures it's time to shift up to the next higher gear, indicated by high motor speed, the control computer would put the gearbox in neutral, then drop the motor speed down so that the input shaft speed, as measured by the period between sensor input triggers on the input shaft, matches the period measured on the output shaft, adjusted for the gear ratio of the next desired gear. At this motor speed the desired input/output gears are spinning at exactly the same speed. Then the contoller would shift to the desired gear, the balls pop into place on the output gear, and the controller applies power to the motor, accelerating away in the higher gear. A similar sequence can be used to down-shift, where the motor speed is increased while in neutral to match gear speeds. The system would work like a sensor-controlled synchromesh. (I would call is "automatic sensor synchromesh" if not for the unfortunate acronym :). Maybe "sensor controlled synchro - SCS would be a better term.)

In any case, this would be a neat project to work on. Any chance of getting some more details?[/quote]


This would seem feasable, but we do not have a neutral postion between gears with our pneumatic positioning. We could use a simple current sensor or two and a staement in the program that would be something like "if amps are greater than or equal to 35, shift down to next gear; if amps are less than or equal to 5 amps shift up to next gear " I know that is not how it would look in the code because i do not know C or any language for that matter. But it is the basic idea. And i think it is atainable with any shift on the fly tranny and a bit of testing.

Sorry for the misplellings i am not the greatest with techinical terms and such.
-Henry

Re: pic: 222 3 speed closeup/cutaway
 

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.

Re: pic: 222 3 speed closeup/cutaway
 

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

Re: pic: 222 3 speed closeup/cutaway
 

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.

Re: pic: 222 3 speed closeup/cutaway
 

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.

Re: pic: 222 3 speed closeup/cutaway
 

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.

Re: pic: 222 3 speed closeup/cutaway
 

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.....

Re: pic: 222 3 speed closeup/cutaway
 

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]

Re: pic: 222 3 speed closeup/cutaway
 

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.

Re: pic: 222 3 speed closeup/cutaway
 

These pictures give you more detail of the transmission

I will try to post more information later but I have to leave right now

(edit)
I am back. Earlier you asked what prevented the balls from falling through. As seen in the second picture their are 2 different size hole. Once that fits the bearing which are 5/16 in size. The red piece as shown in the above picture can slide back and forth on the orange shaft. The blue springs are used to prevent the ball bearings from being forced in the gear when the slots are not lined up. The red thing in the picture does not really have flat spots on them in the real robot, I just made it that way to make it easier to constrain the balls to them in Inventor.

The gear is also offset from the balls in the picture so you can see the insides better. The gear is really in the center of the ball bearings.

Re: pic: 222 3 speed closeup/cutaway
 

Right now, we do have a 2 neutral positions, between the 3 gears. It is impossible not to have them, otherwise two different gears would be locked in motion when you went to shift. What i am saying is there needs to be a point where lets say 1st gear is released, and 2nd gear is engaged. Bad noises and magic smoke otherwise. We do not have space between the gears, but the actual part of the rod that pushes the balls up into the gears is narrow enough to fit between the 2 sets of balls for different gears. The springyness comes from the springs that hold the "pusher"(another technical term) in one spot but allow it to move if gears are not ready to engage.

I think that is all, Brad, I know you want to say something so step up these are all your inventors (good job btw).

On a side note, once we shift to a different gear the previous gear will stay engaged untill the motors jog. The springs just compress on the rod so it doesn't go in and once the motors jog or the wheels stop or some change occurs, they go in. What i am saying is, I can run in 3rd gear up to something robot, goal, turn, etc. and already have it shifted into 2nd the same with 2nd to 1st. Once the bot hits its target it instantly shifts down which is a lot faster than me having to shift down. I can pre choose the next gear one up or one down from the current gear and have it go in when the target is reached. It is really nice. That way i can pre shift or shift at will with a small jog. I lub these trannies!!

Re: pic: 222 3 speed closeup/cutaway
 

Thanks for the update. It clarifies things quite a lot. What size hole did you use for for the 5/16" ball-bearing, and what thickness or axle did you use? From the drawing, it looks quite thick.