Re: pic: 222 3 speed closeup/cutaway
 

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!!!!!!!!!!!!!!!!!!


[edit/] I just found out about the PM sorry for the wasted post.[/edit]

Re: pic: 222 3 speed closeup/cutaway
 

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?

Re: pic: 222 3 speed closeup/cutaway
 

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

Re: pic: 222 3 speed closeup/cutaway
 

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.

Re: pic: 222 3 speed closeup/cutaway
 

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

Re: pic: 222 3 speed closeup/cutaway
 

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

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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.

Re: pic: 222 3 speed closeup/cutaway
 

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...

Re: pic: 222 3 speed closeup/cutaway
 

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.).

Re: pic: 222 3 speed closeup/cutaway
 

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!

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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:

1. 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?
2. What material did you use?
3. What diameter is the inside hole?
4. How far out to the 5/16" ball bearings protrude when they are pushed out by the inner ring?
5. 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?
6. Does the shifter rod rotate with the axle, and if so, how do you push or pull on it?
7. 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?
8. 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.

Re: pic: 222 3 speed closeup/cutaway
 

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

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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?

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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

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



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