pic: 222 3 speed closeup/cutaway

[CD47-Bot]

[cdm-description=photo]17477[/cdm-description]

[Kevin Sevcik]

Sweet looking tranny. I like the idea, it's nice and simple. I'm just curious if you guys have any bearing surface between the free spinning gears and the output shaft. Is it just steel on steel with lots of lube, or is there a bronze bushing in there?

Also, how do you guys index it so that shifting rod only moves part way?

Other than that, it's a really awesome, simple idea.

[tkwetzel]

Sweet looking tranny. I like the idea, it's nice and simple.

I agree that it is a sweet tranny and an amazing idea, but is it really that simple? The concept might seem simple, but the production seems very difficult. Kudos to team 222 for doing it though.

Also, are those trannies powered only by the CIM motors?

[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.

[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.

[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...

[henryBsick]

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.

[team222badbrad]

Thanks for the heads up guys. We tried filling the bottom with oil but that got too messy.

We ran the trannies for hours and didnt have a problem. We give our robots the robust test every year...

Our robot never missed a shift once and that is almost amazing considering we always had problems with shifting the drills in previous years.

[MikeDubreuil]

Preface...Control systems guy with fetish for understanding mechanicals.

How do the balls capture the gear? And how do you control which gear gets captured?

[henryBsick]

Preface...Control systems guy with fetish for understanding mechanicals.

How do the balls capture the gear? And how do you control which gear gets captured?


In the picture, the balls in the shaft sit down in thier holes, not above the exterior surface of the shaft. We have a rod that moves in and out of the shaft which pushes the balls up locking them into the little notches in the gears. The rod is on springs so when it touches the 4 balls (on one gear) on the inside of the shaft the balls do not jump up into the gear by force they go when ready so not to grind. the balls fall back into place once the rod is removed. So by moving the rod to different places it locks in different sets of gears choosing our speed.
I hope i didn't confuse anyone to badly.

[jskene]

How do you prevent the balls from moving radially outward when the shaft is spinning? I would think that the centrifugal force on them from the spinning shaft would tend to push them out into the slots in the gears.

I (and from reading this thread, many others also) would be very interested in seeing a photo or drawing of how your sliding rod works to move the balls in and out. I would also be interested in knowing how you cut the slots in the gears.

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?

[team222badbrad]

The force your refering to is just inertia (a body in motion will remain in motion unless acted upon by an outside force). This is a comon mistake that people make mistaking intertia with centrifugal (which does not exist). The ball bearings remain in the shaft until the air inside shaft pushes the balls out and locks the gear. :cool: Even if they did push out the balls would be forced back in by the rotation of the gears and shaft

[jskene]

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?

[team222badbrad]

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.

[MikeDubreuil]

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

[henryBsick]

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?


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

[dan 322]

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]

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]

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]

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]

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.

Here (http://www.chiefdelphi.com/forums/showthread.php?t=26624) is a pic. of it on the bot

[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.

http://www.chantillyrobotics.com/team/documents/3-speed-gearbox.jpg

[team222badbrad]

http://www.tahsroboticsteam.org/autodesk/cd%20coolo.jpg
http://www.tahsroboticsteam.org/autodesk/cd%20coolo%20ball%20hole.jpg
http://www.tahsroboticsteam.org/autodesk/cd%20coolorod.jpg

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.

[henryBsick]

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!!

[jskene]

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.

[henryBsick]

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.


Not a problem. I love to answer questions. Brad has all the dimensions written down somewhere for the inventor so he can post it.

3 2/3 hrs till i leave for annapolis!!!!!!!!!!!!!!!!!!


I just found out about the PM sorry for the wasted post.

[jskene]

Congratulations on your stellar performance in Annapolis! Sorry I missed it. I see that you won every match, and seldom got less than 100 points. Very good numbers. You also got some awards - excellent work. Was one of these for your transmission?

Regarding your transmission, I want to clarify the size of the ball bearing that you use - is it 5/16"?

Also, you mention that there are 2 different size holes - I guess these are the holes through which the balls protrude. Can you describe what you mean by 2 different sizes - are the holes stepped - that is the entrance hole is bigger than the exit - so the ball doesn't come out to far?

[crazyone]

Congratulations on your stellar performance in Annapolis! Sorry I missed it. I see that you won every match, and seldom got less than 100 points. Very good numbers. You also got some awards - excellent work. Was one of these for your transmission?




As far as I know we recieved both design awards for our tranny at Annapoilis, I was not there, but I did get word of our acheivements. All of this was because of our Mechinist Bob. Unfortunatly, due to weight issues, we only had 2 gears ( I am unsure of this, please correct me if I'm wrong) to run with, but still the tranny proved it's value. THANKS BOB :D

[frank_a]

As far as I know we recieved both design awards for our tranny at Annapoilis, I was not there, but I did get word of our acheivements. All of this was because of our Mechinist Bob. Unfortunatly, due to weight issues, we only had 2 gears ( I am unsure of this, please correct me if I'm wrong) to run with, but still the tranny proved it's value. THANKS BOB :D

Actually, we did still have three speeds. Removing a set of gears was something we talked about before shipping while sitting at the usual 132# with three days to go. Like always, we managed to loose weight without sacrificing vital functions.

On the awards...Friday's Delphi Driving Tomorrow's Technology award was primarily for the tranny and the way the students were able to describe it to the judges.

Saturday's Motorola Quality Award was the combination of the tranny, the robustness of the machine and the applicability of the overall design to the game.

[team222badbrad]

I am glad to see Frank has rose up from the dead. He hasnt posted in years. :rolleyes:

Yes their are 2 different size holes. The bearing 5/16 and they are steel. The first hole is the size of the bearing and is drilled partway down into the hollow shaft. The 2nd hole is all the way thru so that the bearing doesnt fall down thru. This hole also allows the bearing to protrude thru the hole so we can push it up thru. I do not know the depth of the first hole or the diameter of the second hole. sorry

[Brandon Holley]

awesome awesome tranny...we saw u guyz and experienced you in action at chesapeake. good job. but we still pushed you....j/k j/k, but we did!! no hard feelings

[team222badbrad]

Not really. You guys were chasing us around in first gear. ;) I do recall from the video when both of our robots front wheels were off the ground to form an A. And our base operator knows that we do not get involved with pushing other bots. He knows how easy we tip. :ahh:
We will have to get in a real match at PARC :cool:

I do like your drive train though. Its very sweet that you can change it out quickly if you have too.

[henryBsick]

Not really. You guys were chasing us around in first gear. ;) I do recall from the video when both of our robots front wheels were off the ground to form an A. And our base operator knows that we do not get involved with pushing other bots. He knows how easy we tip. :ahh:
We will have to get in a real match at PARC :cool:

I do like your drive train though. Its very sweet that you can change it out quickly if you have too.


Thanks for all the complements and questions. We are always around in the pits too for specific detail. Brad is geting good at explaining these.

As for the pushing...
I was instructed specificly not to push anyone, just to accomplish the task at hand. We do tip, but I have not tipped since practice rounds, note they are practice rounds. I was trying new stuff. I also only ran away in first gear, because well, I am stupid, no, um, i just didn't shift up Figured we were going to the step to climb. It didn't matter when I got there so why risk hitting the corner of the stairs? BUt I will break out second gear some more if anyone wishes to see it. We ran our auton in second and I occasionaly jumped up when making the drive for a distance. Plus, balls +any other gear than 1st = bad, most of the time. We don't run up on them a lot with our lexan teeth but they get bent. So I avaoid higher gears and balls. BAD!!. Anyway, don't worry out there in Philly 11, I will show some more of our machine's capabilities. Annapolis was just a warm up ;) :D . As Cliff has said. We've got some stuff up our sleeves...

[indigofire79]

amazing design.

We are rookies trying to build stuff in the offseason (yeah for us the offseason has already started and that sucks). Anyway, is the only thing keeping the gears from lateral movement along the axle the pressure from the sides, or it there a locking mechanism? Wouldnt the friction of the gears touching reduce efficiency?

Also, any generic advice on building trannys would be great. We have limited machining capabilities (no high tech stuff i.e. CNC etc.).

[tkwetzel]

Also, any generic advice on building trannys would be great. We have limited machining capabilities (no high tech stuff i.e. CNC etc.).

There are a few white papers on trannys on this site. There are many good white papers. Our team has posted a white paper for our 2-motor, 2-speed gearbox, that only requires a manual mill and lathe to create.

Another good and simple gearbox is team 33's 4-speed automatic gearbox this year. I don't know that there is a white paper available for it, but you might be able to get a lot of information from them about it. It supposedly can be made with a lathe and a drill press with an X-Y table.

Just some suggestions. There are tons of designs out there, as you can see by the variety just this year. A lot of it sometimes depends on the game. Good luck with your offseason work!

[jskene]

I am planning to build one of your transmissions in the off-season, and hopefully develop an automatic shift algorithm for it, which of course I will share on this discussion board. I have a few (actually, several) questions on your design:


It looks like you have used a fairly thick walled 1" diameter tube as the main axle. Was this machined out of a 1" rod?
What material did you use?
What diameter is the inside hole?
How far out to the 5/16" ball bearings protrude when they are pushed out by the inner ring?
Do you need to have two sizes of holes on the axle to prevent the balls from going in too far? Could you not just have the balls drop down and touch the spring?
Does the shifter rod rotate with the axle, and if so, how do you push or pull on it?
It seems that the balls might have a tendency to push themselves out due to the rotation of the axle, or at least drop down into a lower notch in a gear when the axle is at rest due to gravity. Do you have any problem with the balls coming out prematurely into the wrong gear?
How much force is needed to push the shifter ring against a set of balls to select the next gear?



Sorry to have so many questions, but I am quite interested in this design you have some up with, and want to experiment with it. I think it shows great promise for future development.

[jjdebner]

Those are really ellegant tranny's I always thought of a three speed as hard and complicated. This just blows my mind that it can be achieved that simple. Good Job. Now we should work on simplifying OUR 2-speed hahaha

[team222badbrad]

TO answer some of your questions:

1. Yes I believed this was machined from 1" steel rod.
2. above
3. I am not sure what hole you mean?
4. Less than half of the bearing goes up inside the gear. This is to prevent the bearing from getting stuck inside the gear.
5. You might be able to get away with only 1 hole. However we used 2 different size holes.
6. Yes the shifing rod does rotate with the axle. We have a brass piece that is captured inside a thing that looks like a pulley.
7. No the balls do not push out inside the gears when the axle is rotating. This was talked about earlier in this thread.
8. You could do it with your pinky finger. If the holes are not aligned then you have to push on the springs. This takes more force.

I hope to get a white paper compiled soon. I have yet to wait till FIRST season is over probably. I am very busy. I also have a VICA competition coming up soon.

Any more questions?

[jskene]

Thanks for the reply Brad. Your comments have been very helpful.

The hole diameter I was asking about is the hole you drilled in the 1" steel rod, through which the spring and ball-bearing pusher slides. It looks to be about 5/8" from the photo.

Thanks

[team222badbrad]

This is the shifting fork. You can see the brass piece attached to the shifting fork.

http://www.tahsroboticsteam.org/Pictures/2004/Build%20Season/000_0099.JPG

More pics of the transmission can be seen at: http://www.tahsroboticsteam.org/pictures.htm

[Nuson]

That's absolutely beautiful. What power source are you using to shift?

[team222badbrad]

We use a pair of 3/4 inch air cylinders. With a throw of about an inch.

They can be seen in this picture:

http://www.chiefdelphi.com/forums/pictures.php?s=&action=single&picid=6833&direction=DESC&sort=date&perrow=4&trows=3&quiet=Verbose

One air cylinder shifts between high and low and the other shifts the transmissions in 2nd!

[jskene]

You mentioned that the force required to shift the transmission is quite light. Would it be possible to use the torque produced by a servo motor to shift?

I have drawn a sketch below of the concept. Basically, the inner shaft shifter rod is pushed and pulled back and forth by a pushrod attached to a wheel that is rotated by a servo, in the same way that you would push up/down an aileron on a model plane. The servo can be directly controlled by any PWM output on the robot controller. The servo wheel can be set to any desired rotational angle by varying the PWM output duty cycle. Certain angles would correspond to 1st, 2nd 3rd gear, as well as the neutrals in between each gear.

Do you think a servo would have sufficient power? It would certainly be a smaller, lighter-weight solution compared to using pneumatics, and could probably provide control of 3-4 gears. Because the electric motor in a servo is not particulalry strong, it may be possible to eliminate the springs in the original design. If the transmission is not aligned properly for the shift to occur, the servo motor just stalls, and waits the fraction of a second required for the next gear to line up. It would then rotate just the right amount to engage the ball bearings on the next sequential gear.

http://chantillyrobotics.com/Images/gearshifting.jpg

[CJO]

Do you think a servo would have sufficient power? It would certainly be a smaller, lighter-weight solution compared to using pneumatics, and could probably provide control of 3-4 gears. Because the electric motor in a servo is not particulalry strong, it may be possible to eliminate the springs in the original design. If the transmission is not aligned properly for the shift to occur, the servo motor just stalls, and waits the fraction of a second required for the next gear to line up. It would then rotate just the right amount to engage the ball bearings on the next sequential gear.
What about using one of the rotary pnematic actuators. They include magnetic position sensors which turn them into high powered pnematic servos. The positioning is very precise, plus, you could still use a spring, which would save wear and tear on your turning device, as you would not be continually stalling it out.

On another note, how does the CIM work? We built a transmission over the summer, where the CIM was drawing huge amounts of power, and ended up for this year with something similar to the two motor design in the white papers. Does a single CIM work? And if so, doesn't manual shifting get confusing during a fast paced match?

Back to the earlier SCS thing. It might be possible to design a "steptronic" type control that normally shifts automatically, but could be overidden for climbing, &c.

[henryBsick]

What about using one of the rotary pnematic actuators. They include magnetic position sensors which turn them into high powered pnematic servos. The positioning is very precise, plus, you could still use a spring, which would save wear and tear on your turning device, as you would not be continually stalling it out.

On another note, how does the CIM work? We built a transmission over the summer, where the CIM was drawing huge amounts of power, and ended up for this year with something similar to the two motor design in the white papers. Does a single CIM work? And if so, doesn't manual shifting get confusing during a fast paced match?

Back to the earlier SCS thing. It might be possible to design a "steptronic" type control that normally shifts automatically, but could be overidden for climbing, &c.


Have to check on the rotary pneum.'s thanks for the idea.

Yes, it probably is possible to shift with a servo but we wanted to get away from them. We had troubles on the drill transmisions with the number being in the right spot to tell the servos where to stop. They worked every match but they occasionaly caused us grief.

We checked the power curve for the CIM's to figure in on a good ratio.

I drive it and it isn't bad. I shoot over some where quickly and then just get into a lower gear to push, pull, climb. It really isn't bad. I was talking to our programmer about adding a new switch and a current sensor to make it auto. We might we might not. It isn't really neccesary for this game to much.(for us anyway). But back ont to topic, no it isn't hard on the driver (me).

I am lost with the whole SCS thing since I saw the first post about it.

-Henry

[CJO]

I am lost with the whole SCS thing since I saw the first post about it.

Correct me if I'm wrong, somebody, but I thik the whole SCS thing was to add sensors to the transmission so that the computer would keep it in the most advantageous gear at all times, similar to the transmissions on most cars.

[henryBsick]

Correct me if I'm wrong, somebody, but I thik the whole SCS thing was to add sensors to the transmission so that the computer would keep it in the most advantageous gear at all times, similar to the transmissions on most cars.

I understand that something would be done to monitor the rpm's or another measurable function that would contribute to the horsepower. They would then shift up/down to get max. horsepower. The only thing was the specifics of the sensor. Where to put, what kind etc.

[tkwetzel]

Correct me if I'm wrong, somebody, but I thik the whole SCS thing was to add sensors to the transmission so that the computer would keep it in the most advantageous gear at all times, similar to the transmissions on most cars.

I understand that something would be done to monitor the rpm's or another measurable function that would contribute to the horsepower. They would then shift up/down to get max. horsepower. The only thing was the specifics of the sensor. Where to put, what kind etc.

The SCS was to be able to synchronize the gear and shaft. Automatic transmissions already put it into the most advantageous gear at all times. The SCS would lower or increase the power to the motors so that the gear selecting shaft would be running at the same speed as the next gear it is about to select prior to actually engaging the gear. It would cause less stress on all the components and give you smoother shifts.

[henryBsick]

The SCS was to be able to synchronize the gear and shaft. Automatic transmissions already put it into the most advantageous gear at all times. The SCS would lower or increase the power to the motors so that the gear selecting shaft would be running at the same speed as the next gear it is about to select prior to actually engaging the gear. It would cause less stress on all the components and give you smoother shifts.


I see now. Thankyou. There would be two set of sensors, and they would match rpm of the input shaft to that of the output shaft.

Great system but I see one probem with that. The shift wouldn't be exactly insantaneous, it would wait for shaft speed to = then shift. If a robust enough tranny is built i see no need for the matching of speeds, other than smooth shifting. Ours now is pretty smooth though thanks to the springs on the shifting rod. I have slammed it from 3rd into 1st many times (just to make sure) and it has skidded, I wasn't on carpet all the time, but it could take the throw of the ratio change. I still like both ideas though ;) . / thinks to self/ there is an offseason for a purpose :D /done thinking/

[tkwetzel]

The shift wouldn't be exactly insantaneous, it would wait for shaft speed to = then shift.

That is a very good thought, but without any load on the motors, the speeds would match very quickly and it would still shift rather quickly.

[henryBsick]

That is a very good thought, but without any load on the motors, the speeds would match very quickly and it would still shift rather quickly.

Yeah, oops, forgot about the neutral positions. It would require servos or some other sort of multi psitioning shifter instead of our 1,2,3 pneumatics.
/Learns more and more each day. :D /

[tkwetzel]

/Learns more and more each day. /

That is what FIRST is about!

[CJO]

Team 254 used the same sensors on their drive shafts this year as are used on cnc mills to determine table position (I forget what they're called)

~Christopher

[team222badbrad]

It would be cool to have an automatic shifter but I do not see the need for it.

I doubt a servo would last very long if it were used with our trannies. If it was stalled while the holes were not aligned it might hurt the little motors. The servos would also require very accurate maching methods for the shift rod and also require very good programing to align the shifting rod with the ball bearings.
However a servo could probably handle the job.

[team222badbrad]

Just like to let everyone know that you are more than welcome to come take a look at our transmissions. I hope to have a handout and a powerpoint presentation running. We will also have a display board at our pits.

Everyone will be more than happy to talk to you about it.

Good luck!

[team222badbrad]

Here is newly created webpage that has links to various sources of information on our transmissions.

http://www.tahsroboticsteam.org/Transmission222/transmissions

[Nuson]

I think you need to add a .htm to that page name brad.

[Charlie222]

Yes. That's what I get for giving Brad (my brother) access to our website.

This should work.....

http://www.tigertrons.com/transmission222/

[Nuson]

Thanks

[team222badbrad]

What do you expect when a Robotics Geek who knows squat about making a website accesses our website that was created by an almost graduate of Penn State who is going to get a degree in Information Science and Technology (IST) That would by my brother Charlie!

YAY for www.tigertrons.com