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Jun 20, 2013, 07:18 PM
Jack
jackerbes's Avatar
Thread OP
Mini-Review

iPower GBM4108-120T Gimbal Motor


iPower GBM4108-120T Gimbal Motor

iFlight RC has added the GBM4108-120T motor to it's lineup of motors for controlling two axis camera gimbals.

Specifications

Model NO.:GBM4108-120T
Weight:98g
Motor Dimensions:45x25mm
Stator Dimensions:41x8mm
Copper wire(OD):0.17mm
Configuration:24N22P
Resistance:12.4 ohms
Pre-wounded with 120 turns,4.0mm shaft
Bottom mounting holes: 19mm center to center and 32mm center to center
Top mounting holes: 12mm center to center
Camera range: 600-1200grams

I recently received two of the motors for testing and details on them are as in the images and as follows.

Disassembly notes

Weight = 94 grams (97 grams including longer leads)
Outside Diameter = 46.04mm
Length (face of dome to back of shaft) = 29.1mm

Magnet Housing = 46.04mm O.D. x 19.6mm height, is drilled and tapped for four M3-0,50 screws on 12mm x 12mm pattern. Dome has a cylindrical boss on inner side giving the shaft about 9.75mm of engagement in dome. Shaft is a pressed fit in dome (it was not removed) and retained by two M3-0,50 grub screws that are 90 degrees opposed and accessible through the dome's cooling openings.

Stator and Baseplate = 46.04mm O.D. x 17.9mm height, base plate drilled and tapped for four M3-0,50 screws on 19mm x 19mm pattern, and three smaller (2.5mm?) screws in a triangular pattern that is 32mm between centers

Stator = 40.6 O.D. x 8.2mm height

Stator details = 24 arms, 40 0.2mm laminations, appears to be glued to bearing tube

Motor leads = 30.4cm/13.25" 24 AWG silicone sheathed, ultra flexible wire, bare tinned ends (servo connector added for testing)

Windings (info from specs) = 1 strand 0.17mm 120 turns, Wye termination assumed (not visible)

Wind resistance (my measurements) = 14.2 Ohms (1-2, 1-3, 2-3)

Magnets = 22 magnets, 8mm height x 3mm width x 1mm thick, magnet gaps = 2mm, flux ring 42.3mm I.D. on flux ring, magnet gaps =

Bearings = two EZO (Japan) 694Z 11mm x 4mm x 4mm (O.D., I.D., width) metal shielded bearings

Motor shaft = 28mm x 4mm (just below flush with dome, no useable length exposed)

Motor was tested on a standard ESC. Slight stutter was noted at starting, that is typical for gimbal motors on standard ESC. Motor ran smooth and quiet, no evidence of warming was noted in over one minute of running at 3S pack voltage. No load tests indicate a raw Kv of approximately 52.81.

no load test = averages for 13 seconds = 667 RPM, 12.62V, 0.31A = Kv 52.85
no load test = averages for 12 seconds = 663 RPM, 12.56V, 0.31A = Kv 52.79

This motor and one just like it will be forwarded to SeismicCWave in Hawaii for gimbal motor testing in the next day or two. And his review of that testing will be appended here eventually.

Jack
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Nov 11, 2013, 09:43 AM
bacon and eggs
remvideo's Avatar
how many poles ?
Nov 11, 2013, 09:52 AM
Jack
jackerbes's Avatar
Thread OP
It is 24N22P = 24 slots or stator arms and 22 magnets.

Jack
Sep 21, 2015, 06:12 PM
Registered User
so, how many poles?
Sep 21, 2015, 07:52 PM
Jack
jackerbes's Avatar
Thread OP
Quote:
Originally Posted by CyberCrash
so, how many poles?
24N22P = 24 arms or slots and 22 poles or magnets, so 22 magnets is 22 poles in the motor that is the subject of this thread.

Jack
Sep 22, 2015, 07:47 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by CyberCrash
so, how many poles?
Whenever an ESC or logger asks for number of poles, it wants to know the number of magnetpoles. Not the number of teeth, slots, arms or coils.
One magnetpole can consist of several magnets, tiling, usually in large motors. E.g. www.jobymotors.com and the big Hacker, Lehner and Plettenberg motors.


Vriendelijke groeten Ron



www.jobymotors.com
Last edited by Ron van Sommeren; Sep 22, 2015 at 08:09 AM.
Sep 22, 2015, 07:59 AM
Jack
jackerbes's Avatar
Thread OP
Ron, is right of course, there may be more than one magnetic segment in a pole.

It is unfortunate that the image above calls the stator arms "poles" also. That creates some confusion. It is best to use different terms for the stator arms and the magnets.

The much used "N" for stator arms or slots and "P" for poles is a good way to describe motors and is based on their long standing in usage on German. N = nuten and it best translates to groove or slot. "P" = poles of course. 12N14P = 12 arms 14 magnets. 24N22P = 24 arms 22 magnets, etc., etc.

Jack
Sep 22, 2015, 08:07 AM
Registered User
Thanks for explaining the poles. It's confusing if you don't know the details.


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