Originally Posted by Ether (Post 1100014)

I should have been clearer. The point in contention is this: Timz3082 is claiming* that the motor portion of the PG71 (am-0914) is the same motor as the 9015 (am-0912). I was asking where he got that information.


* see post #5: "That is with the gearbox, without it is 180 W"

Originally Posted by Andy Baker (Post 1099807)

These numbers, posted by me on the AM website two days ago, are not correct. They have been updated to much more realistic, and larger numbers. We at AndyMark are changing these numbers a bit after some further testing this weekend. Sorry about this change. Please check our PG71 web page for any further updated information.

Here is more to the story.

When I was updating the web page for this motor on Friday, getting it ready for Saturday's kickoff, I saw that the stall torque was listed at 11 amps. This is information we got from the manufacturer. So, I called Mark, who was out at Manchester for kickoff to see what was up with this. He created and interpreted the performance numbers a few weeks ago, and listed the stall torque at 11 amps. We both thought about this some more and agreed that was waaaaay too low. He got home today and did a bench test that repeatedly performed at these numbers below. This test was ran with a 12.8 volt battery providing voltage directly to the motor. The stall torque is 23 ft-lbf, and the max current reading is 28.6 amps. We believe this translates to approximately 350 watts as the max power for the motor.

Tested at 12.8 volts
23 ft-lbf max torque at stall
28.6 amps pulled at stall
Estimated 350 watts of power

Here is Mark's setup. He had a force gauge measuring an arm's pull at exactly 1 foot away from the motor. The force gauge showed 23 lbs of force and the amp meter showed 28.6 amps. It was a simple setup, and we ran it about 10 times. The numbers were consistent. These numbers make much better sense to me compared to the "11 amp stall torque" numbers I posted on Saturday.

Again, sorry for these erroneous numbers yesterday, and please check out the PG71 website for future updates.

Sincerely,
Andy Baker

Originally Posted by theprgramerdude (Post 1100370)

I don't know if I'm doing this right (actually, I'm pretty sure I am), but if you input 28.6 Amps at 12.8 Volts, that's equivalent to 366 watts of electrical power being put into the system. Yes, that's how you would calculate the electrical power into the motor at stall. There is zero power output at stall.

350 watts of output power translates to >90% efficiency for a 12V motor, something that is ridiculously high. There is no mechanical power output at stall. You can't divide the 350 by the 366.

Or, maybe I'm reading this wrong, and you're simply stating that it can pull about 350 watts of power, and not the output power. Power rating should be the mechanical output power. See this post for how it's calculated.

Originally Posted by BeltSanderRocks (Post 1100358)

are there any motor curves up yet? The page on the FIRST website does not have this.

Originally Posted by BeltSanderRocks (Post 1100358)

Does anyone know which motors are back-drivable and which motors are not?

Also are there any motor curves up yet? The page on the FIRST website does not have this.

Originally Posted by RyanCahoon (Post 1101483)

Motor curves are linked on this page. Currently, the PDF file is here, but the filename appears to be changing with each revision.

Originally Posted by fox46 (Post 1101492)

do the specs on that PDF look kosher

Originally Posted by rbrown1 (Post 1101550)

Maybe someone can help me. The Fisher Price motor we have in the kit supplied this year is a 00968-9013. Is there any motor data for this motor available?

Originally Posted by John (Post 1101572)

Does anyone know why the stall current for the left handed Denso motor is higher than the stall current for the right handed one? If they are just flipped versions of each other shouldn't they be the same?