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Unread 10-02-2011, 01:26
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Re: pic: In_CIM_erator

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Originally Posted by Hawiian Cadder View Post
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.
Any quantitative tests? lifting a load, dynamometer...those spec sheets don't magically appear out of thin air.
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Unread 10-02-2011, 01:36
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Re: pic: In_CIM_erator

here is the link to the actual source of the motors, BaneBots Buys them from here, and according to this spec sheet

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

the "BaneBots rs775 at 12 volts" does somewhere barely above 200 watts at 14.4 volts. the 18 volt version does somewhere around 70.


I am fairly sure that the numbers on BaneBots website are inccorrect, they do match up with a larger motor from this supplier.

http://www.mabuchi-motor.co.jp/cgi-b..._ID=rs_775vcwc

this is the larger motor, but as you can see it is not sold in a 12 volt version, so the 70 watts is close to what this would produce at 12 volts as well, none of the Mabuchi specs come even close to the BaneBots specs.

Last edited by Hawiian Cadder : 10-02-2011 at 01:46.
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Unread 10-02-2011, 01:56
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Re: pic: In_CIM_erator

Quote:
Originally Posted by Hawiian Cadder View Post
here is the link to the actual source of the motors, BaneBots Buys them from here, and according to this spec sheet

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

the "BaneBots rs775 at 12 volts" does somewhere barely above 200 watts at 14.4 volts. the 18 volt version does somewhere around 70.


I am fairly sure that the numbers on BaneBots website are inccorrect, they do match up with a larger motor from this supplier.

http://www.mabuchi-motor.co.jp/cgi-b..._ID=rs_775vcwc

this is the larger motor, but as you can see it is not sold in a 12 volt version, so the 70 watts is close to what this would produce at 12 volts as well, none of the Mabuchi specs come even close to the BaneBots specs.
I think you're confused a bit. Motors are spec'd at a voltage, but will run at any voltage (although, they won't last long once you hit a certain voltage).

A motor rated for 18V will run fine on 12V, it will just be roughly 4/9 the power of it on 18V.
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Unread 10-02-2011, 02:00
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Re: pic: In_CIM_erator

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Originally Posted by AdamHeard View Post
I think you're confused a bit. Motors are spec'd at a voltage, but will run at any voltage (although, they won't last long once you hit a certain voltage).

A motor rated for 18V will run fine on 12V, it will just be roughly 4/9 the power of it on 18V.
i am aware, but (4/9) times to 200 watts max power that the supplier has tested for still leaves less than 100 watts of power, unless it is the 14.4 V nominal opperation motor, in which case it will output around 70 watts. according to the people who made the motors, there is no way any of them that size will output more than 100 watts at 12 volts.



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.

Last edited by Hawiian Cadder : 10-02-2011 at 02:08.
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Unread 10-02-2011, 02:10
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Re: pic: In_CIM_erator

Quote:
Originally Posted by Hawiian Cadder View Post
i am aware, but (4/9) times to 200 watts max power that the supplier has tested for still leaves less than 100 watts of power, unless it is the 14.4 V nominal opperation motor, in which case it will output around 70 watts. according to the people who made the motors, there is no way any of them that size will output more than 100 watts at 12 volts.



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.
The mechanical output power can be calculated from torque times speed.

If you take the motor at half free speed, it is also at half stall torque, for the 775 this works out to over 250W of power.
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Unread 10-02-2011, 02:43
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Re: pic: In_CIM_erator

Quote:
Originally Posted by Hawiian Cadder View Post
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.
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Unread 10-02-2011, 02:54
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Re: pic: In_CIM_erator

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Originally Posted by rahilm View Post
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.
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Unread 10-02-2011, 03:34
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Re: pic: In_CIM_erator

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.
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Unread 10-02-2011, 02:13
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Re: pic: In_CIM_erator

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Originally Posted by AdamHeard View Post
I think you're confused a bit. Motors are spec'd at a voltage, but will run at any voltage (although, they won't last long once you hit a certain voltage).

A motor rated for 18V will run fine on 12V, it will just be roughly 4/9 the power of it on 18V.
Where did the 4/9 come from. I must have missed something in my math.
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Unread 10-02-2011, 02:17
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Re: pic: In_CIM_erator

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Originally Posted by John G View Post
Where did the 4/9 come from. I must have missed something in my math.
Mechanical power is torque x speed.

Stepping down from 18 to 12V is a 2/3 change.

Power = 2/3Torque x 2/3 speed. Works out to the power at 12V being 4/9 that of 18V.
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Unread 10-02-2011, 02:18
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Re: pic: In_CIM_erator

none of the motor specs on the maubichi sheet indicate a power rating of more than 200 watts at 18 volts. thus i dont think it is possible for the 775's to output more than 133 watts MAXIMIUM negating friction.

Last edited by Hawiian Cadder : 10-02-2011 at 02:23.
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Unread 10-02-2011, 02:32
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Re: pic: In_CIM_erator

Quote:
Originally Posted by Hawiian Cadder View Post
none of the motor specs on the maubichi sheet indicate a power rating of more than 200 watts at 18 volts. thus i dont think it is possible for the 775's to output more than 133 watts MAXIMIUM negating friction.
the 18v - RS775 WC version is supposed to output 273.03 W of power at max eff. - 18v
the 18v - RS775 VC Version outputs 208 W or power at max eff. - 18v

here is the spec sheet are ya looking at this one?

The 775 VC outputs 41.4 W at 12v - 5.7A and 775 VC outputs 156 W at 12v - 18.7A

the 775 WC outputs 168 W at 12v - 18.7A and 775 WC outputs 39.9 W at 12v - 5.7A
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Last edited by ttakashima : 10-02-2011 at 02:41. Reason: Mistake
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Unread 10-02-2011, 02:40
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Re: pic: In_CIM_erator

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

Last edited by Hawiian Cadder : 10-02-2011 at 02:44. Reason: Clarification and update
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Unread 10-02-2011, 18:34
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Re: pic: In_CIM_erator

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Originally Posted by Hawiian Cadder View Post
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.
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Unread 10-02-2011, 20:44
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Re: pic: In_CIM_erator

Quote:
Originally Posted by artdutra04 View Post
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...
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