hey got a tech question about AM Trannys

[jax1488]

does anyone know the final output RPM of an andymark tranny? of high and low gear?

i cant find any information online

[Alex Cormier]

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

Which transmission you trying to find information on?

They sell several two speed transmissions.

[MrForbes]

From the AndyMark web page describing the Supershifter:

STANDARD GEARING (this is what is shipped with a Super Shifter order)
Ratio between High and Low gears: 2.56:1
FINAL STAGE, w/ 45:20 GEARS:
Low Gear: 24.0:1
High Gear: 9.4:1

so just divide motor rpm by the gear ratio for low and for high and you'll get your answer. Of course, if you're using a different AM transmission you'll need to get the numbers for that one.

[jax1488]

Originally Posted by Alex Cormier

Which transmission you trying to find information on?

They sell several two speed transmissions.

servo shifter (gen 2)

with 2 small cims a piece.. i dont understand how to do the math

[Madison]

Originally Posted by squirrel

From the AndyMark web page describing the Supershifter:

STANDARD GEARING (this is what is shipped with a Super Shifter order)
Ratio between High and Low gears: 2.56:1
FINAL STAGE, w/ 45:20 GEARS:
Low Gear: 24.0:1
High Gear: 9.4:1

so just divide motor rpm by the gear ratio for low and for high and you'll get your answer.

Keep in mind, though, that your motors operate at less than the free-speed under load.

[Doug G]

Originally Posted by jax1488

servo shifter (gen 2)

with 2 small cims a piece.. i dont understand how to do the math

Small CIM has a free speed of about 5300 rpm - however at 40 amps it is more like 3800 rpm.

Therefore in high gear that would be between 404 rpm (40 amp) and 564 rpm (2.5 Amp).

Low gear would be between 158 rpm (40 Amp) and 221 rpm (2.5 Amp).

The speeds are the same whether you have one or two CIMs. Having two Cim's just doubles the torque

[waialua359]

Originally Posted by squirrel

From the AndyMark web page describing the Supershifter:

STANDARD GEARING (this is what is shipped with a Super Shifter order)
Ratio between High and Low gears: 2.56:1
FINAL STAGE, w/ 45:20 GEARS:
Low Gear: 24.0:1
High Gear: 9.4:1

so just divide motor rpm by the gear ratio for low and for high and you'll get your answer. Of course, if you're using a different AM transmission you'll need to get the numbers for that one.

just another note, the supershifters came with a 48:17 final stage option also.

[AdamHeard]

the output RPM of the gearboxes isn't *that* helpful of a figure.

If you are try to estimate a drive's performance, download JVN's mechanical design calculator from the whitepapers; Input your motor and gearbox specs (for efficiency, do .9ish for each spur/sprocket reduction.) and it will provide you some nice data on velocity, current draw, etc...

[EricH]

Adam's right, output RPM of the gearboxes might not help that much.

For example, it is ridiculously easy to change it. Just change the output sprocket or the one on the other end of the chain. Your wheel spins at a different speed.

Or, the final output to the wheels might be different from what it's supposed to be. (Note to self--Next time mecanums are used, reverse the Toughbox-to-wheel chain-run sprockets.)

[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.