hey got a tech question about AM Trannys

[Uberbots]

Originally Posted by Holtzman

For the people who have had issues breaking roll pins in the shifter assembly, are you sure that the shifter was properly adjusted and that the nylon stroke limiting spacer was installed?

I have seen these roll pins break if the nylon spacer is omitted, or if the shifter is adjusted poorly.

You should be able to adjust the Shift Block such that when the cylinder is at full extension, the dog gear is nearly flush against the 48 tooth gear, and when the cylinder is retracted against the nylon spacer, it is again nearly up against the 35 tooth gear. When adjusted properly, the roll pins only see significant load during the shift. If they aren’t adjusted properly, the roll pins are loaded constantly, and this can lead to premature failure.

In the first match of the GTR finals, we broke the 1/16" Roll pin in the shifter block. This was caused by omitting the stroke limiting spacer. After re-installing the spacer, and replacing the roll pins, and properly adjusting the cylinder, we’ve experienced no further issues.

Also, the 3/32" Roll pins through the dog gear can be replaced with these "High Strength" roll pins from McMaster Carr. Part number 95755A131. They seem to be a tighter fit than the pins that come stock with the gearboxes. As for whether they are actually any stronger than the ones that come stock with the gearboxes, our very limited testing says "So far so good".

These shifters are quality engineered and built products. If your breaking roll pins, you’ve probably got something put together wrong.

Well i dont remember any spacers on the piston, so i guess that needs to be put into the wiki for next year (=
And yeah, we tried stronger pins, but then the next weakest thing broke- the bearing the the pin holds against X=

[Pat Roche]

We actually ran into the pin issue at NYC. The robot shifted for the better part of two competitions before finally shearing a roll pin in our last qualification match. We are currently looking into replacing the roll pin with a hardened dowel pin to give it some strength. Be careful doing something like this though, because the shaft is so small at the hole's location. You need to make sure you won't damage(via shifting not installation) the shaft changing to a dowel pin. At the competition we would have normally just changed the air pressure but it was needed for other parts of the robot.

[Travis Covington]

Are any of you limiting the piston stroke to ensure that the piston isn't shoving the dog into either dogged gear?

I have never worked closely with the AM trannys but on our own gearboxes we pay very close attention to the side load that the dog puts on the gear, making sure there is a gap of some sort so that the dog doesnt physically push on the dogged gears when the dog teeth are engaged. We use 1/4" ID nylon spacers to limit the pistons stroke to just under the distance required to move from being fully engaged in one gear to being fully engaged in the other.

I should note, we run at a full 60 psi and use a #3-48 stainless SHCS instead (which is MUCH weaker than the included roll pin) We have yet to break a screw under normal conditions. A few times we failed to tighten the jam nut on the piston rod which allowed the dog to push on the dogged gear, and only during those few times did we have any problems.

Couldn't hurt to throw it out there...

Edit: Oops... I didn't even see Tyler's post. This just reaffirms what he said though!

[Cory]

Originally Posted by Uberbots

we downed the psi to 40 after breaking like 10 pins
25 though? that seems a little low. i wonder if the solenoid will even shift at 25 psi... doesnt it take 30 before it does anything?

In 2006 we shifted at 20 PSI just fine.

[Travis Covington]

Originally Posted by Cory

In 2006 we shifted at 20 PSI just fine.

This was with the SY3000 series SMC valves. The festo may perform differently though?

[Pat Roche]

With the AM's this year just above 10 psi still shifted gear perfectly fine. It started to get hairy anywhere under that.

[Uberbots]

Originally Posted by Travis Covington

This was with the SY3000 series SMC valves. The festo may perform differently though?

Really?

whenever we boot up the robot from a no-air state, it takes a noticeable amount of pressure before any of the solenoids will trip. i believe this is at about 20-30psi, so ??

[Andy Baker]

Originally Posted by jax1488

does anyone know the final output RPM of an andymark tranny? of high and low gear?
i cant find any information online

Originally Posted by jax1488

servo shifter (gen 2), with 2 small cims a piece.. i dont understand how to do the math

All... looking through this thread, I really don't think that the original question was answered.

On the AM Servo Shifter page, these gear reductions are listed:

Gear Reduction
Low: 10.67:1
High: 4.17:1
Difference between Low and High: 2.56:1

Here is my description on how to "do the math", in a nutshell:

A CIM motor has a free speed of about 5200. If two CIM motors are installed on an AndyMark gearbox, then the top speed (motor rpm) that you will be able to get is about 4300 or 4400. Let's call this the "top working speed". (The difference between the free speed and this working speed is because of efficiency losses, inertia, and friction in the mechanical system)

Using 4400 rpm as this top working speed, here are the resulting low and high speeds for an AM Shifter (servo or pneumatic):

Low: 412 rpm (4400 / 10.67)
High: 1055 rpm (4400 / 4.17)

This is the output rpm at the sprockets on the AM Shifter. Further reduction can be made, of course, with the sprockets on the wheels and the size of the wheel. Keep in mind that the smaller your wheel is, the less reduction you need to go an optimal speed.

Now... regarding the roll pins shearing and other stuff, I will make another post. Tyler's post is right on the money. However, the Super Shifter did see more vibration this year than the AM Shifters experience. The AM Shifters all use chain drive. The Super Shifters can be used in direct drive situations. Because of this, the Super Shifters experience more vibrational loading.

Like previously noted by Tyler and Travis, you must use stops on the cylinder so that the dog is positioned into place and held there, as opposed to continually pushing the dog into the gear. For servo shifting, this burns up the servo. For pneumatic shifting, this wears down roll pins.

Also, shifting at 40 psi seems to work the same as 60 psi. I do not suggest using 25 psi unless you are only shifting when not pushing against anyone. Also, servo shifting does not work when pushing against anyone. Servo shifting pushes with about 5 pounds of force. Pneumatic shifting at 60 psi puts out 33 lbs of force. Regulating the pressure down to 40 psi still gives 22 pounds of shifting force. This is still much stronger and more responsive than servo shifting.

Once again, I will say that I DO NOT RECOMMEND servo shifting, unless a team has absolutely no need for pneumatics on their robot.

We have some improvements listed for these gearboxes:

gearing options - other ratios (Toughbox, Stackerbox, maybe Shifters)
adding an encoder to the Toughbox and AM Shifter
higher strength roll pins
Longer output shaft for Toughbox
A better way to servo shift
Optional aluminum side plates for AM Shifters

These are in order of importance and priority. There may be more. We have a "to do" list on our main whiteboard at AndyMark central that is about 50 items long.

I hope this helps.

Sincerely,
Andy

[The Lucas]

Originally Posted by Cory

In 2006 we shifted at 20 PSI just fine.

Originally Posted by Travis Covington

This was with the SY3000 series SMC valves. The festo may perform differently though?

Originally Posted by Uberbots

Really?

whenever we boot up the robot from a no-air state, it takes a noticeable amount of pressure before any of the solenoids will trip. i believe this is at about 20-30psi, so ??

This also depends on whether it is a single or double solenoid because they usually have different pilot pressures. The SMC SY3000 (we use them too) has a min pilot pressure of 0.1MPa (~15psi) for the double and 0.15MPa (~21psi) for the single. We used a double for the shifter (regulated to ~25-30 psi) and singles everywhere else (to save SPIKEs).

Back to the roll pin topic, I believe we broke the initial pins in both of this year's AM shifters before shipping the bot. We never broke pins in any of the AM shifters we used in the prior 2 years. We replaced with higher strength pins and didn't have any more problems. I know 1503 broke their pin at FLR and used our stronger pins to replace (dont know how that worked out past FLR). Maybe a lower quality batch of pins this year or just too much shifting into Overdrive.

[Stephmthompson]

After FLR and using the stronger roll pin, 1503 didn't have any problems. A mistake we had made in our pneumatics was also corrected. We isolated the air control to the shifter (it had been tied into another sytem) so that we could have independent control of the pressure. And thanks to MOE's recommendation we also purchased the installation tool needed to install the roll pin in place without having to take the gearbox apart. We haven't had the chance to practice this one yet, but it will be one of our off-season drills.

[Joe Finkel]

We love the supershifters! (just ordered two more). 25-30 psi, 3/4'' bore
by 1/2'' stroke(no spacers) cyl. and you will be fine for regionals and a
few off-season.