pic: In_CIM_erator

[Hawiian Cadder]

the Series of Motors are only rated for 200 watts total, which leads me to believe that have quite a bad bias, (they are for drills after all) and i do not believe that those are the motors we have, the smaller rs775 more closely matches what we were supplied, if the Bane-bots 12v is one of those, but at 12v, then it will be a different size physically, the smaller series of motors here: http://www.mabuchi-motor.co.jp/cgi-b..._ID=rs_755vcwc


and 4/9 times 270 is 120. however efficiency also drops as current/voltage rises, so that puts the motor at somewhere around 90-110 watts.


Edit

The Bane bots motors are the smaller of the two motor spec sheets i initialy gave, verified by physical size. spec sheet here

http://www.mabuchi-motor.co.jp/cgi-b..._ID=rs_755vcwc

[rahilm]

Originally Posted by Hawiian Cadder

also, power is current * Voltage

according to the Bane Bots website peak efficency current is 5.7

5.7 * 12 is 68, which fits the 70 watt power output number, i think all the other info on the BaneBots website is correct, except the power calculation, think that was taken at 18 volts.

First thing, peak power is NOT peak efficiency. If you look a motor curve, you will find that efficiency is maximized at a much lower current than where power is maximized (at the intersection of the torque and speed lines).

Also, if using the electrical values to calculate output torque, you have to multiple the electrical power value by the motor efficiency at that point.

[Hawiian Cadder]

Originally Posted by rahilm

First thing, peak power is NOT peak efficiency. If you look a motor curve, you will find that efficiency is maximized at a much lower current than where power is maximized (at the intersection of the torque and speed lines).

Also, if using the electrical values to calculate output torque, you have to multiple the electrical power value by the motor efficiency at that point.

you are correct, my mistake

i still think it warrants closer inspection however.

[Tristan Lall]

By the way, does anyone have documentation that BaneBots is using that particular RS-775 motor from Mabuchi? (I know there's a part number under the sticker affixed by BaneBots...I just haven't had the opportunity to look underneath and confirm it.) In the past, their motors appeared not to have been Mabuchi-brand.

(And just in case anyone is wondering, yes, this comes up all too often at inspection. Inspectors will often be noticing things like number and shape of vent holes and the colour of the plating on a motor, to quickly assess its legality.)

In fact, the same goes for the other BaneBots motors too. It would be instructive to publish a list of the manufacturers' real part numbers (to forestall future questions about which motor is which).

In 2009, BaneBots shipped totally different RS-550 and RS-385 motors to FIRST teams, despite presumably knowing that there was an FRC parts restriction (given that they were a supplier of KOP motors), and without updating their website to reflect the changes. Given that previous miscue, we probably ought to be cautious.

[martin417]

Originally Posted by Hawiian Cadder

pretty sure the 18 volt version is the same, we ran ours and found it MUCH weaker than the RS 550, if anything the 18v version should be weaker than the 12V version, the only difference is the gauge of wire.

Just curious about how you measured the power of the 775 vs the 550. Did you use a dynamometer? Or did you use the motors in a lifting application with a gearbox? Did you compare the work done over time?

The only info I have to go on is the motor curve provided by FRC, and the data sheet on the Banebots website. If you look at the data for the 18V motor, it maps pretty well to the FRC motor curve when run at 12V instead of 18V. I have to believe the FRC motor curve since we based our design on that. We won't know until we get our gearboxes, maybe next week.

[Jared Russell]

I can tell you that the RS775s are much closer to the CIM's max power than to the RS550's. We had been using 6 CIMs in our drive prior to receiving our CIM-U-LATORs, and the pushing power and acceleration with 2 CIMs replaced by RS775s are pretty close to identical.

[Chris is me]

The 18v RS775s at 12v are not "a measly 70 watts" - Banebot's spec sheet even says otherwise (just not FIRST's, which is wrong).

Hawaiian CADer, I've corrected you on this at least 3 times - for the sake of other teams PLEASE do not post things you don't KNOW to be true as fact, repeatedly, lest you cost someone valuable time in their season.

Be aware that Max Efficiency is different than Max Power.

[Vikesrock]

Originally Posted by Chris is me

The 18v RS775s at 12v are not "a measly 70 watts" - Banebot's spec sheet even says otherwise (just not FIRST's, which is wrong).

The Motor Curves document on the Kit of Parts website has been updated and contains the proper curve for the RS775-18V scaled down to 12V.

[artdutra04]

Originally Posted by Hawiian Cadder

the Series of Motors are only rated for 200 watts total, which leads me to believe that have quite a bad bias, (they are for drills after all) and i do not believe that those are the motors we have, the smaller rs775 more closely matches what we were supplied, if the Bane-bots 12v is one of those, but at 12v, then it will be a different size physically, the smaller series of motors here: http://www.mabuchi-motor.co.jp/cgi-b..._ID=rs_755vcwc


and 4/9 times 270 is 120. however efficiency also drops as current/voltage rises, so that puts the motor at somewhere around 90-110 watts.


Edit

The Bane bots motors are the smaller of the two motor spec sheets i initialy gave, verified by physical size. spec sheet here

http://www.mabuchi-motor.co.jp/cgi-b..._ID=rs_755vcwc

I wanted a definite answer on this, so I began searching further to try to find the original source of the BaneBot RS775-18 motors. While I don't have access to a BaneBot motor to peel the sticker off of, I did find this clear image of the 775 motors:

http://www.chiefdelphi.com/media/photos/36263

In the full-resolution version of the photo, two things are obvious: The last four numbers on the first line are "8514" and the last two letters on the second line end in "CW". On the Mabuchi website, they do sell a "775WC" motor with the part number "8514". These published specs at 18V match the published specs (for 18V operation) on BaneBots' website. The likely reason behind the letters printed on the BaneBot motors being in the wrong order are due to the fact that Manuchi is a Japanese company, and the BB motors were all made in China (possibly by a clone manufacturer).

So the Mabuchi specs list the power of the Mabuchi 8514 at peak efficiency as 273 W. The BaneBot spec sheet for their RS775-18 at 12V lists power at peak efficiency as 119.25 W. If they are the same motor, then 273W * (4/9) = 121.33 W would yield the expected power output at 12V. The expected and actual power values are only 1.7% off; if BB published their RS775-18 at 12V spec sheet from dynamometer testing, this 1.7% likely could have been due entirely to manufacturing tolerances of the 775 motors.

Thus, unless someone has dynamometer data to prove otherwise, these specs for the RS775 are accurate.

[Tom Line]

Originally Posted by artdutra04

I wanted a definite answer on this, so I began searching further to try to find the original source of the BaneBot RS775-18 motors. While I don't have access to a BaneBot motor to peel the sticker off of, I did find this clear image of the 775 motors:

http://www.chiefdelphi.com/media/photos/36263

In the full-resolution version of the photo, two things are obvious: The last four numbers on the first line are "8514" and the last two letters on the second line end in "CW". On the Mabuchi website, they do sell a "775WC" motor with the part number "8514". These published specs at 18V match the published specs (for 18V operation) on BaneBots' website. The likely reason behind the letters printed on the BaneBot motors being in the wrong order are due to the fact that Manuchi is a Japanese company, and the BB motors were all made in China (possibly by a clone manufacturer).

So the Mabuchi specs list the power of the Mabuchi 8514 at peak efficiency as 273 W. The BaneBot spec sheet for their RS775-18 at 12V lists power at peak efficiency as 119.25 W. If they are the same motor, then 273W * (4/9) = 121.33 W would yield the expected power output at 12V. The expected and actual power values are only 1.7% off; if BB published their RS775-18 at 12V spec sheet from dynamometer testing, this 1.7% likely could have been due entirely to manufacturing tolerances of the 775 motors.

Thus, unless someone has dynamometer data to prove otherwise, these specs for the RS775 are accurate.

And following that graph, at about 40 amps, the motors put out approximately 260 Watts of power unless I've been reading it wrong all season...

[Hawiian Cadder]

to eliminate all of the spec sheet madness from this, i decided on a simple test, today i made a small hub that pressed onto the axle of the 775 and had a .5 inch diameter, hooked the motor directly to a battery, and was able to prevent it from spinning with no problem at all. i did the exact same thing with a 555 and have a rather nasty burn on my thumb from trying to hold the motor and failing. the rs550 is significantly more powerful than the rs775 18 volt version that came in the KOP.

edit for clarification

i let both spin up to full speed, then attempted to stop them spinning by gradualy applying pressure to the outsides of the .5 drum. both motors were mounted to a block, and that block placed in a vice, and both were running off direct connection to battery with the same length of wire.

[kevin.li.rit]

Wouldn't looking at he motor constant (Rpm/V) values tell you that the motors perform differently and they are two different motors with he same package.

[kevin.li.rit]

Originally Posted by Hawiian Cadder

to eliminate all of the spec sheet madness from this, i decided on a simple test, today i made a small hub that pressed onto the axle of the 775 and had a .5 inch diameter, hooked the motor directly to a battery, and was able to prevent it from spinning with no problem at all. i did the exact same thing with a 555 and have a rather nasty burn on my thumb from trying to hold the motor and failing. the rs550 is significantly more powerful than the rs775 18 volt version that came in the KOP.

edit for clarification

i let both spin up to full speed, then attempted to stop them spinning by gradualy applying pressure to the outsides of the .5 drum. both motors were mounted to a block, and that block placed in a vice, and both were running off direct connection to battery with the same length of wire.

This isn't an accurate test of the motors power output but rather the stall torque.

[Chris is me]

Originally Posted by Coffeeism

This isn't an accurate test of the motors power output but rather the stall torque.

things such as free speed come into play too.

you're really going to refute manufacturer provided dynamometer specs with a thumb test?

[Tristan Lall]

Speaking of Mabuchi, my guess is that the BaneBots RS-775 motors are not made by them...see http://www.chiefdelphi.com/media/photos/36278 and look closely at the motor, and then at the drawing posted on Mabuchi's website. Observe the shape of the rear vent holes is different. While that's not conclusive proof of anything, it's a reason to doubt that the BB RS-775 is that particular Mabuchi model. (I've seen another pattern, with no vent holes, on some Mabuchi motors; that isn't it.)

As far as I know, none of BaneBots' KOP motors are made by Johnson or Mabuchi. The best refutation of this would be to find their logo: Johnson often stamps a "JE" mark on the front face of the motor (where the mounting screws are), and Mabuchi usually prints a stylized "M" on the label (they haven't used painted numbers on FRC motors in the past).