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.

[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

[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

[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

[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.

[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.

[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.