hey got a tech question about AM Trannys

[Uberbots]

speaking of AM supershifters (gen 3)

did anyone have a problem with the roll pin in the shifter coupling breaking? (the thing that attatches the piston to the dog gear shaft)

[jgannon]

Originally Posted by Uberbots

speaking of AM supershifters (gen 3)

did anyone have a problem with the roll pin in the shifter coupling breaking? (the thing that attatches the piston to the dog gear shaft)

What pressure are you shifting at? We sheared off that roll pin in one of our Gen 2 shifters last year. Shifting these things at 60PSI is a big no-no. When I asked Andy Baker, I seem to remember him saying that 25PSI is more than sufficient. Though I guess it shouldn't be surprising that applying that much force to one of those pins would wreck it (as anybody who had difficulty assembling Toughboxes this year will tell you), it'd be a nice warning to have in the documentation.

[Uberbots]

Originally Posted by jgannon

What pressure are you shifting at? We sheared off that roll pin in one of our Gen 2 shifters last year. Shifting these things at 60PSI is a big no-no. When I asked Andy Baker, I seem to remember him saying that 25PSI is more than sufficient. Though I guess it shouldn't be surprising that applying that much force to one of those pins would wreck it (as anybody who had difficulty assembling Toughboxes this year will tell you), it'd be a nice warning to have in the documentation.

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?

Originally Posted by jgannon

What pressure are you shifting at? We sheared off that roll pin in one of our Gen 2 shifters last year. Shifting these things at 60PSI is a big no-no. When I asked Andy Baker, I seem to remember him saying that 25PSI is more than sufficient. Though I guess it shouldn't be surprising that applying that much force to one of those pins would wreck it (as anybody who had difficulty assembling Toughboxes this year will tell you), it'd be a nice warning to have in the documentation.

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?

We didn't use roll pins in our transmissions, in order to avoid the breakage issue. Actually, due to a flaw in dimensioning, we ended up with two different hole sizes. As a result, we used steel nails as our shifting pins. It seemed pretty ganky to us, but it worked really well. Plus, it was pretty cool to tell people that our robot was held together by nails.

Back on topic, we ran our shifting pneumatics at about 35ish, and never had any issues.

[Billfred]

Strange, we never had any roll pin issues while shifting at 60 PSI. (The pressure issue is news to me--I'll send some kids after the matter at the next meeting.)

I'll second the endorsement for JVN's calculator; our last two robots have been greatly improved for its use.

[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.

[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 ??

[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.