pic: 222 3 speed closeup/cutaway

[team222badbrad]

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]

Originally Posted by 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.

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]

[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]

Originally Posted by 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?

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

[frank_a]

Originally Posted by crazyone

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

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.

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

[team222badbrad]

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

[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/pi...&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.

[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]

Originally Posted by CJO

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]

Originally Posted by Henry_222

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.