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Old Aug 13, 2013, 11:31 AM
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Mini-Review
iPower MultiMate Series

Jack Erbes, motor-head and prolific rcgroups poster in Maine, has generously lent me several iPower Multimate motors which he had received for evaluation from the folks at www.iflight-rc.com.

#1: iPower MultiMate MT2208-1400 (56g, ~1428Kv)
The subject of this first review is the smallest motor I received, the iPower MultiMate MT2208-1400 (listed as 45g, 1400Kv, 16.88A/156W max., 8” prop recommended). This motor, with the supplied accessories, was neatly packed in a black cardboard box. The labeling on the box simply gives motor size and mentions “EZO bearings, dynamic balancing and 0.2mm silicon steel sheets” – no mention of specs such as max. amp/watts/Io/Rm/prop size nor is there a pamphlet with this information inside the box (Specs for at least some of the motors in the MultiMate Series are available from the www.iflight-rc.com website). Designed for multicopters, the motor has exceptionally long (45cm) tri-colored motor leads with factory-fitted 3.5mm bullets. It comes with an X-mount with four 3mm x 5mm machine screws for the motor, and a bolt-on (four 2.35mm x 7 mm machine screws) radial adapter with threaded 5mm shaft. The motor is very nicely machined, anodized in all black; the bell seems to be true, the bearings spin freely, and the windings look very neat. Jack commented that he had disassembled several of these iPower motors and he was impressed by the neatness of the machining and the windings. All of the iPower motors are advertised as having commendably thin 0.2mm laminations on their stators The MT2208-1400 is a 12-arm stator, 14-magnet pole motor and, as supplied, is configured for rear-mounting and with the prop adapter bolted on, but not the X-mount, weighed in at 56g. (perhaps the advertised “45g including hardware” does not take into account the weight of the long leads). The bell is 27.8mm in diameter and the motor is 23.4mm front to back. With the radial adapter fitted, overall (including 16.5mm of threaded 5mm shaft) the motor is 47.3mm in length.

I used my standard test stand set-up: Thrust stand [Version III in Pusher mode], Ohaus CS2000 Digital Scale, Zurich DS-304M Power Supply, Medusa Analyzer Plus, Eagle Tree v3 with Power Panel and RPM and Temperature sensors, E-sky servo adjuster, Hobbico Digital Mini-Tach, RayTek IR temperature gun.

I ran my usual no-load tests at 7v, 8v, 10v and then a series of prop tests (at 7v thru 11v, and 14v for certain props) starting with 4.1x4.1 EMP and working my way up to 9x5 GWS HD. Using a Motrolfly 20A ESC the motor started well every time and ran extremely smoothly at all power levels with each prop I tried, and, as can be seen from the DriveCalc computations , fairly efficiently too (75% max.) ….. only when I pushed the envelope a little with an 9x5 GWS HD (15.6A/156W) did the motor temperature get above 50°C by the end of a series. The RPM as a percentage of Kv x V is a telling parameter… ideally this figure should be above 70%, and this motor managed that with every prop I tried up to and including the 8x4 GWS HD… 8x4 APC E was marginal (67%) and both the 8x6 APC E and 9x5 GWS HD dragged it down well below 60%. Drive Calc suggests that max. current for this motor would be 13.8A, somewhat less than the “spec” 16.88A. It is a very good motor and is happy with smallish props at around the 120W mark… a brief burst at 14v with a 7x5 APC E drew 16.85A/233W (almost 4W/g) yet it did not get excessively hot.

DriveCalc computed the Kv as ~1428Kv (close to the listed 1400Kv). iPower lists the Io as 0.39A (at what voltage?) and Rm as 0.127Ω (I measured Io at 0.65A @ 10v, and for Rm, DriveCalc gave me, as is typical, about twice their figure…. ~0.266Ω).

Of the props I tested, the best one for thrust on 3s, without pushing the motor too hard, is the 8x4 GWS HD (643g/22.64oz from just 11.1A/117W @ 41mph). For speed, the 6x5 EMP on 4s would be a good performer (598g/21oz @ 74mph from just 10.50A/146W).

Cheers, Phil
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Old Aug 13, 2013, 02:08 PM
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Jack Erbes, motor-head and prolific rcgroups poster in Maine, has generously lent me several iPower Multimate motors which he had received for evaluation from the folks at www.iflight-rc.com.

#2: iPower MultiMate MT2212-850 (70g, ~900Kv)
The second motor in this series to be reviewed is the iPower MultiMate MT2212-850 (listed as 65g, 850Kv, 13.5A/158W max., 10x4.5 prop recommended). Like the MT2208-1400 reviewed in Post #1, this motor, with the supplied accessories, was neatly packed in a black cardboard box. The labeling on the box simply gives motor size and mentions “EZO bearings, dynamic balancing and 0.2mm silicon steel sheets” – no mention of specs such as max. amp/watts/Io/Rm/prop size nor is there a pamphlet with this information inside the box (Specs for at least some of the motors in the MultiMate Series are available from the www.iflight-rc.com website). Designed for multicopters, the motor has exceptionally long (45cm) tri-colored motor leads with factory-fitted 3.5mm bullets. It comes with an X-mount with four 3mm x 5mm machine screws for the motor, and a bolt-on (four 2.35mm x 7 mm machine screws) radial adapter with threaded 5mm shaft. The motor is very nicely machined, anodized in all black; the bell seems to be true, the bearings spin freely, and the windings look very neat. Jack commented that he had disassembled several of these iPower motors and he was impressed by the neatness of the machining and the windings. All of the iPower motors are advertised as having commendably thin 0.2mm laminations on their stators. The MT2212-850 is a 12-arm stator, 14-magnet pole motor and, as supplied, is configured for rear-mounting and with the prop adapter bolted on, but not the X-mount, weighed in at 70g. The bell is 27.8mm in diameter and the motor is 27.3mm front to back. With the radial adapter fitted, overall (including 16.5mm of threaded 5mm shaft) the motor is 50.6mm in length.

I used my standard test stand set-up: Thrust stand [Version III in Pusher mode], Ohaus CS2000 Digital Scale, Zurich DS-304M Power Supply, Medusa Analyzer Plus, Eagle Tree v3 with Power Panel and an RPM and a Temperature sensor (this latter attached to a motor mounting bolt on the aluminum AXI 22xx motor mount), E-sky servo adjuster, Hobbico Digital Mini-Tach, RayTek IR temperature gun.

The prop recommended for this motor was “10x4.5”, and fortuitously Jack had sent me two gorgeous iPower carbon fiber props – 10x4.5 CF and 10x4.7 CF. These two props are quite different in design (see photo)….the 10x4.5 CF (with “10x4.5” molded into one blade) is of typical “aircraft prop” shape with a thinner hub and narrower blades than the “SF or possibly multicopter-style” 10x4.7 CF (which had no indication of size molded into a blade).

I ran my usual no-load tests at 7v, 8v, 10v and then a series of prop tests (at 7v thru 11v) starting with 8x4 GWS HD and working my way up to an 11x7 GWS HD. Using a Motrolfly 20A ESC the motor started well every time and ran extremely smoothly at all power levels with each prop I tried, and, as can be seen from the DriveCalc computations, very efficiently too (80% max., but at only 3.5A) ….. the recommended 10x4.5 CF drew only 9.35A/100W and even the 10x4.7 APC SF drew only 10.9A/116W… for none of these 8”-10” props did the motor temperature get above 40°C by the end of a series. The RPM as a percentage of Kv x V is a telling parameter… ideally this figure should be above 70%, and this motor managed that with every prop I tried, up to and including the recommended 10x4.5 CF and the 10x6 GWS HD. Both the 10x4.7’s dragged it down to the mid-60’s%. Drive Calc suggests that max. current for this motor would be 12A, somewhat less than the “spec” 13.5A…. and I found that an 11x7 GWS HD drew exactly that (12.00A/127W). To test this motor’s ability to cope with this amount of power, I then did something which is not usually recommended (for good reason)… I ran it with the 11x7 GWS HD at WOT continuously for well over four minutes, monitoring the temperature on the Power Panel read-out, very carefully. Following a typical small drop in current draw, after perhaps a minute it had settled into an absolutely steady state at 11.20A/120W……after using just over 800mAh in this WOT torture test, with the temperature-probe reading 52°C, I decided enough was enough. My IR thermometer measured a temperature at the windings of 66°C. A minute or so later the probe reading peaked at 74°C. Managing a WOT RPM of only 60% of Kv x V, this motor is somewhat over-loaded with an 11x7 GWS HD, but it a strong motor and I imagine that, if thrust is of primary concern, it could cope with brief bursts of full throttle, even with such a large prop. I did try momentary bursts to WOT with an 11x5.5 APC E (~11A… okay) and an 11x7 APC E (~13A, possibly a bit much).

DriveCalc computed the Kv as ~900Kv (close to the listed 850Kv). iPower lists the Io as 0.5A (at what voltage?) and Rm as 0.127Ω. I measured Io at only 0.35A @ 10v, and for Rm, DriveCalc gave me a much larger figure than theirs…. ~0.335Ω).

The various 10” props I tested gave me remarkably similar figures for thrust (635g - 692g) ….. the 11x7 GWS HD gets you an extra 60g-120g, at apparently higher pitch speed (though there is some doubt whether this prop’s pitch is really as high as 7”).

Cheers, Phil
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Old Sep 04, 2013, 03:43 PM
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Jack Erbes, motor-head and prolific rcgroups poster in Maine, has generously lent me several iPower Multimate motors which he had received for evaluation from the folks at www.iflight-rc.com.

#3: iPower MultiMate MT2217-880 (87g, ~947Kv)
The third motor in this series to be reviewed is the iPower MultiMate MT2217-880 (listed as 94g, 880Kv, 25A/252W max., 12x4.5 CF prop recommended). Jack has already done his typical competent review of this motor [http://www.rcgroups.com/forums/showt...php?t=1979431], so I will not repeat the details of the motors dimensions and construction.

For my tests I used my standard test stand set-up: Thrust stand [Version III in Pusher mode], Ohaus CS2000 Digital Scale, Zurich DS-304M Power Supply, Medusa Analyzer Plus, Eagle Tree v3 with Power Panel and an RPM and two Temperature sensors (Sensor A was attached to a motor mounting bolt on the aluminum AXI 22xx motor mount, Sensor B [generously sent to me by Jack] was pushed in against the motor windings at the rear of the motor (see photos)), E-sky servo adjuster, Hobbico Digital Mini-Tach, RayTek IR temperature gun.

Jack had sent me several gorgeous iPower carbon fiber props, which he, himself, had used for his test runs with this same motor – 8x5 CF, 10x4.5 CF and 11x4.7 CF. After no-load determinations, in my first series of test runs I tried to duplicate Jack's testing.. same prop at the same voltage. Using my adjustable Power Supply I was able to undertake "~3s voltage" prop tests at closely similar voltages, but for "~4s voltages" my voltage was usually lower than Jack's due to the limited capability of my Power Supply. In general my data correlated fairly well with Jack's, but for whatever reason the temperatures I recorded on v3 probes A and B were a lot higher than Jack had measured.

For my second series of test runs I used the same protocol I always use, in order to make the data for this motor directly comparable with that I have obtained from all the other test motors I've run. I ran my usual no-load tests at 7v, 8v, 10v and then a series of prop tests starting with 8x4 GWS HD and working my way up to an 11x7 GWS HD.....at 7v thru 11v, but for the two largest props (10x6 GWS HD and 11x7 GWS HD) also at just over 14v). Using a Motrolfly 20A ESC the motor started well every time and ran extremely smoothly at all power levels with each prop I tried, and, as can be seen from the DriveCalc computations, very efficiently too (almost 80% max., but at only 5A). For the 10x6 GWS HD and 11x7 GWS HD I extended the "4s" runs until v3 Sensor B read 60C. The RPM as a percentage of Kv x V is a telling parameter… ideally this figure should be above 70%, and this motor only failed to achieve that with the largest prop tested (11x7 GWS HD). Drive Calc suggests that max. current for this motor would be 18A, considerably less than the “spec” 25A….. on its "4s" run, the 11x7 GWS HD drew close to the 25A limit... 23.20A/322W.... but it got very hot, very fast and I cannot see the motor surviving for long if extended WOT is used at such a high power level. Managing a WOT RPM less than 60% of Kv x V on "4s", this motor is clearly over-loaded with an 11x7 GWS HD....it took only a brief (22 second) burst of WOT for the Sensor B probe to reach 60F. The recommended 12x4.5 CF would be even worse for it. A 10x6 GWS HD seems a more suitable prop for this motor.... on "3s", it delivers thrust more efficiently than does the 11x7 GWS HD and maintains an ideal RPM of 75% of Kv x V. Even on "4s", the 10x6 GWS HD is still okay [RPM was still at 69% of Kv x V]. It stayed cool enough and I had to subject it to well over a minute of full WOT running before the Sensor B probe on the windings reached the 60C limit.

DriveCalc computed the Kv as ~947Kv (considerably above the listed 880Kv). iPower lists the Io as 0.55A (at what voltage?) and Rm as 0.097Ω. I measured Io at only 0.50A @ 10v, and for Rm, DriveCalc gave me a rather larger figure than theirs…. ~0.218Ω).

I've attached three tables of data, and a photo showing the motor on the stand, and the two temperature sensor probes, to illustrate their placement.

Cheers, Phil
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Old Sep 06, 2013, 09:48 AM
Jack
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Thanks for all the reports, Phil! And the kind words too!

And I guess that makes it official! When Dr Kiwi says these are pretty good motors that means they are pretty good motors!

His continuous WOT "torture test" on the MT2212-850 has inspired me! This might be the definitive testing method for all motors! So I worked out a similar testing method and added it to my review of the MT4108-475 motor:

http://www.rcgroups.com/forums/showp...14&postcount=2

I think the details in those kinds of reports give more insight as to what can be expected from the motors.

Jack
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Old Sep 06, 2013, 12:28 PM
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I don't have the graphs for the "torture test" but here is the plot for the 2217-880 with a 10x6 GWS HD on 4s voltage.... for an extended run of ~70 seconds. One can read a lot of useful information from one of these Eagle Tree graphs. Let's look at each parameter in turn.

A. Voltage:
you can see that my power supply was initially at 14.7v, but dropped under ~18A load to around 14.2v constant (packs would tend to keep dropping).
B. Amps: As the motor heated up the amp draw diminished a little over the course of the 70 second run.. but only by perhaps 0.5A.
C. RPM: as with amps, RPM diminished as the run progressed, but only by <500rpm.
D. Temp A: (probe attached to motor mount): initial temperature diminished over the first 20 seconds of the run, due to cooling airflow [in my pusher set-up air being pulled by the prop flows over the motor from the rear forward]. However internally generated heat then overcomes this cooling effect and the Temp A keeps increasing, and would continue to do so the longer the run went, presumably until the motor overheated. Basically the motor is in "thermal runaway" mode, since as the run progresses the motor keeps getting hotter! I shut down the motor with Temp A at ~34C. Once the motor was stopped the temperature recorded by Temp A kept increasing, as heat from within was conducted out, reaching a peak of around 58C about 40 seconds later.
E. Temp B: (probe inserted directly into the windings): shows a tiny drop immediately after start up, but then the temperature inexorably rose as the windings became increasingly hot. Again the motor is in "thermal runaway" mode! I shut down the motor with Temp B at what I consider a prudent upper limit of ~60C. Once the motor was stopped the temperature recorded by Temp B kept increasing, reaching a peak of around 70C about 20 seconds later.

Note: I measured the temperature of the external surface of the bell at the end of this run with an IR Gun..... only about 30C [little different from the "end of run" Temp A (34C)]. But it can be easily seen that data from the two temperature probes indicate that the bell's external temperature is not a good indicator of how hot a motor has become internally. From the IR Gun pointed directly into the windings, the end of run temperature was recorded as 62C. If one does the finger-tip test on a motor's bell, and finds it too hot to hold (~50C-60C), the inside of the motor is going to be MUCH hotter.
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Old Sep 06, 2013, 02:15 PM
Jack
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Wonderful details to read about how you test. And a great explanation for the folks looking at the graphs. I know if you're not using them regularly, you can kind draw a blank on some of the things seen there.

I'm going start doing something like these on all the reviews I think. And if you start throttling back when you get a little below that prudent upper limit you can find the point where the temperature will stabilize and that is a good start on finding the maximum throttle setting for continuous or sustained operation.

I've been using 120F/49C as the throttle back point and 130F/54C as the highest temperature I would want to see from the sensor on the windings with the motor running. If I get a motor up to that and just stop it the temp will go up 15-20F or more. But throttling back and running at lower RPM until the temperature drops 10 degrees or so take a lot of hear out of the windings.

If you land a plane and find the motor hot after typical throttled back a little approach and landing, you can bet it was a lot hotter during the flight. And multicopters are a whole different game because they need as much or more power in the final moments as they did during the flight.

I've been flying my tricopter a little now and am noticing things like how difficult it can be to stop a descent if you let the descent rate get very high. I still have so much to learn about that thing...

Jack
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Old Sep 11, 2013, 07:51 AM
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Jack Erbes, motor-head and prolific rcgroups poster in Maine, has generously lent me several iPower Multimate motors which he had received for evaluation from the folks at www.iflight-rc.com.

#4: iPower MultiMate MT2212-1000 (71g, ~1065Kv)
The fourth motor in this series to be reviewed is the iPower MultiMate MT2212-1000 (listed as 65g, 1000Kv, 13.8A/150W max., 10x4.5 prop recommended). Since this motor is simply a slightly higher Kv variant of the 2212-850 reviewed earlier, I can dispense with the details.

I used my standard test stand set-up: Thrust stand [Version III in Pusher mode], Ohaus CS2000 Digital Scale, Zurich DS-304M Power Supply, Medusa Analyzer Plus, Eagle Tree v3 with Power Panel and an RPM and two Temperature sensors (Temp A attached to a motor mounting bolt on the aluminum AXI 22xx motor mount, and Temp B inserted into the windings), E-sky servo adjuster, Hobbico Digital Mini-Tach, RayTek IR temperature gun.

I ran my usual no-load tests at 7v, 8v, 10v and then a series of prop tests (at 7v thru 11v) starting with 8x4 GWS HD and working my way up to an 11x7 GWS HD. I also ran an 8x4.5 iFlight CF prop on 4s voltage because I guessed that might get the motor close to its 3W/g limit (which it did... 215W) and a 10x4.5 CF because this was the recommended prop. Using a Motrolfly 20A ESC the motor started well every time and ran extremely smoothly at all power levels with each prop I tried, and, as can be seen from the DriveCalc computations, very efficiently too (80.8% max., but at only 4A) ….. the recommended 10x4.5 CF drew only 10.2A/139W... somewhere short of the suggested 13.8A/150W max. The RPM as a percentage of Kv x V is a telling parameter… ideally this figure should be above 70%, and this motor only managed that with a couple of the smaller props (8x4 GWS HD and 9x5 GWS HD. With the recommended 10x4.5 CF (and the 10x6 GWS HD) it only managed 66% and an 11x7 GWS HD dragged it down well below 60%. Drive Calc suggests that max. current for this motor would be 15A, somewhat more than the “spec” 13.8A…. but I found that a 10x6 GWS HD coped well enough with 12.85A/136W... so I reckon the 13.8A spec is very reasonable.

DriveCalc computed the Kv as ~1065Kv (just a bit higher than the listed 1000Kv). iPower lists the Io as 0.5A (at what voltage?) and Rm as 0.127Ω [remarkably, exactly the same figures iPower gives for the lower Kv MT2212-850!]. I measured Io at 0.40A @ 10v, and for Rm, DriveCalc gave me a much larger figure than theirs…. ~0.265Ω).

It seems that the best 3s prop for this motor would be the 10x6 GWS HD or the 10x4.5 CF..… both gave very similar figures (bearing in mind that the 10x6 GWS HD is really about 10x5). If one wanted to be a bit easier on the motor, 9x5 GWS HD provides only a little less thrust at considerably lower amp draw.

Cheers, Phil
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Old Sep 11, 2013, 04:34 PM
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Jack Erbes, motor-head and prolific rcgroups poster in Maine, has generously lent me several iPower Multimate motors which he had received for evaluation from the folks at www.iflight-rc.com.

#5: iPower MultiMate MT2814-810 (119g, ~770Kv)
The fifth motor in this series to be reviewed is the iPower MultiMate MT2814-810 (listed as 94g, 810Kv, 24.75A/375W max., 10x7, 11x4.7, 12x5 props recommended).

Like the MT2208-1400 reviewed in Post #1, this motor, with the supplied accessories, was neatly packed in a black cardboard box. The labeling on the box simply gives motor size and mentions “EZO bearings, dynamic balancing and 0.2mm silicon steel sheets” – no mention of specs such as max. amp/watts/Io/Rm/prop size nor is there a pamphlet with this information inside the box (Specs for at least some of the motors in the MultiMate Series are available from the www.iflight-rc.com website). Designed for multicopters, the motor has exceptionally long (45cm) tri-colored motor leads with factory-fitted 3.5mm bullets. It comes with an X-mount with four 3mm x 7mm machine screws for the motor, and a bolt-on (four 2.5mm x 7 mm machine screws) radial adapter with threaded 6mm shaft. The motor is very nicely machined, anodized in all black; the bell seems to be true, the bearings spin freely, and the windings look very neat. Jack commented that he had disassembled several of these iPower motors and he was impressed by the neatness of the machining and the windings. All of the iPower motors are advertised as having commendably thin 0.2mm laminations on their stators. The MT2814-810 is a 12-arm stator, 14-magnet pole motor and, as supplied, is configured for rear-mounting and with the prop adapter bolted on, but not the X-mount, weighed in at 119g. The bell is 35mm in diameter and the motor is 33.5mm front to back. With the radial adapter fitted, overall (including 15mm of threaded 6mm shaft) the motor is 59mm in length.

I used my standard test stand set-up: Thrust stand [Version III in Pusher mode], Ohaus CS2000 Digital Scale, Zurich DS-304M Power Supply, Medusa Analyzer Plus, Eagle Tree v3 with Power Panel and an RPM and two Temperature sensors (Temp A attached to a motor mounting bolt on the aluminum AXI 22xx motor mount, and Temp B inserted into the windings), E-sky servo adjuster, Hobbico Digital Mini-Tach, RayTek IR temperature gun.

I ran my usual no-load tests at 7v, 8v, 10v and then a series of prop tests (with the PS set at 7v thru 11v, and at 14.7v) starting with 11x4.7 iPower CF and working my way up to an 13x6.5 iPower CF. I also ran an 9x5 GWS HD prop on 3s, just to get a low power datapoint for DriveCalc computations. It was immediately obvious that with such a low Kv, on 3s this motor would have needed a huge prop to get to the recommended 27.5A max. The most I recorded on 3s was just over 20A with a 13x6.5 CF. Only with this 13x6.5 CF prop (outside the recommended range) and then only by using 4s did I get up to, indeed a bit over, the 27.5A spec. Using a Motrolfly 20A ESC the motor started well every time and ran extremely smoothly at all power levels with each prop I tried, and, as can be seen from the DriveCalc computations, fairly efficiently too (78.3% max., but at only 7A).

The RPM as a percentage of Kv x V is a telling parameter… ideally this figure should be above 70%, and this motor managed that with all but the 13x6.5 CF. This prop seems rather too big for it, since on 3s it dragged it down to 65%, and below 60% on 4s. Drive Calc suggests that max. current for this motor would be 25A (60% effic.), a bit less than the “spec” 27.5A…. but from the efficiency curves, I reckon 24A (62% effic.) is a bit more reasonable.

DriveCalc computed the Kv as 770Kv (rather lower than the listed 810Kv). iPower lists the Io as 0.65A (at what voltage?) and Rm as a very low 0.063Ω. I measured Io at 0.80A @ 10v, and for Rm, DriveCalc gave me ~0.265Ω… four times as high as their number!).

It seems that the best prop for this motor on 3s could be the 13x6.5 CF, but it would be well over the top for 4s……for 4s use the 12x6 GWS HD generated decent thrust at respectable “RPM as % Kv x V”, without getting excessively hot. I suppose I should have tried something like a 14x8 GWS HD on 3s and a 12x8 on 4s…. those may have got the motor to draw close to my suggested 24A limit.

P.S. While making these test runs I completely forgot that I had the Motrolfly 20A ESC on the stand, rather than the Motrolfly 30A or Castle Phoenix 45A I had meant to use….. happily the Motrolfly 20A seemed quite at home, even at 30A!

Cheers, Phil
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Old Sep 15, 2013, 10:30 PM
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Jack Erbes, motor-head and prolific rcgroups poster in Maine, has generously lent me several iPower Multimate motors which he had received for evaluation from the folks at www.iflight-rc.com.

#6: iPower MultiMate MT2814-750 (119g, ~770Kv)
The sixth motor in this series to be reviewed is the iPower MultiMate MT2814-750 (listed as 94g, 750Kv, 24.75A/375W max., 10x7, 11x4.7, 12x5 props recommended). These posted specs from iflight-rc are identical to those for the 810Kv version reviewed in Motor #5 above (given that this Motor #6 is meant to be of lower Kv, the specs should NOT be the same... but more on that in a minute).

Using the same testing procedure as for Motor #5, I found that DriveCalc computed exactly the same Kv (~770Kv) and the same max. amp draw (25A) for both Motors #5 and #6. If you look at performance with the one common prop (12x6 GWS HD) the numbers are (within the range of error in my crude test equipment) essentially identical.

Thus this Mini-review will be very short!

The only departure from "essentially identical motors" is in the Io measurements (and perhaps, consequently, the Rm's)... initially I had used a Motrolfly 20A ESC on Motor #5 (MT2814-810) and switched to a Dualsky 40A ESC for Motor #6 (MT2814-750). The MT2814-750 had significantly lower Io (0.60A @ 10v versus 0.80A @ 10A) but essentially identical RPM... thinking it might be the differing ESC's I re-measured Io again, using both ESCs on each of the two motors... identical results.... the MT2814-810 had the (0.80A) higher Io, the MT2814-750 the lower (0.60A) Io.

Using these Io measurements and prop data, DriveCalc computed Rm for the MT2814-810 as 0.265 ohms, and for the MT2814-750 0.153 ohms.

My question: Why do two apparently identical motors (exactly the same size, construction and Kv!) exhibit different Io? Does Io affect Rm or vice versa? I'm guessing the higher Io and higher Rm of the MT2814-810 could translate into marginally lower peak efficiency (78% v. 82%), too.

I have attached the data table for the MT2814-750 for your perusal.

Cheers, Phil
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Old Sep 25, 2013, 07:01 PM
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iPower MultiMate MT4108-580 (116g, ~588Kv)

Jack Erbes, motor-head and prolific rcgroups poster in Maine, has generously lent me several iPower Multimate motors which he had received for evaluation from the folks at www.iflight-rc.com.

#7: iPower MultiMate MT4108-580 (116g, ~588Kv)

The fourth motor in this series to be reviewed is the iPower MultiMate MT4108-588 (listed as 116g, 580Kv, 32.3A max. , 25.3A/566W continuous, 2s-6s, props from 12x3.8 up to 17x5.5 recommended).

Like the MT2208-1400 reviewed in Post #1, this motor, with the supplied accessories, was neatly packed in a black cardboard box. The labeling on the box simply gives motor size and mentions “EZO bearings, dynamic balancing and 0.2mm silicon steel sheets” – no mention of specs such as max. amp/watts/Io/Rm/prop size nor is there a pamphlet with this information inside the box (Specs for at least some of the motors in the MultiMate Series are available from the www.iflight-rc.com website). Designed for multicopters, the motor has exceptionally long (45cm) tri-colored motor leads with factory-fitted 3.5mm bullets. All of the iPower motors are advertised as having commendably thin 0.2mm laminations on their stators. Since this design’s 4mm shaft protrudes only 5.5mm from the front of the motor, a standard collet or set-screwed adapter can not be used, so the motor comes with a bolt-on (four 3mm x 6 mm machine screws) radial adapter with threaded 6mm shaft. The adapter has a bullet-shaped nut for attaching the prop. This multi-copter motor is a radical departure from typical aircraft motors in that it is a large diameter 24-arm stator, 22-magnet pole motor, and, as supplied, is configured for rear-mounting with four 3mm threaded holes at 25mm centers and three 2.5mm threaded holes at 27.5mm centers. With the prop adapter bolted on, the complete motor weighed in at 116g. The bell is 41mm in diameter and the motor is only 27.5mm front to back. With the radial adapter and bullet-shaped nut fitted, overall the motor is 63mm in length.

Since this motor is of large diameter and has mounting holes at 25mm centers I had to use a modified "Aeronaut beam mount for Speed 600" to fit it to my test stand [see Photo #2] (not for the first time... I've previously used it for Mega 600 motors, and a big Castle 3412).

I used my standard test stand set-up: Thrust stand [Version III in Pusher mode], Ohaus CS2000 Digital Scale, Zurich DS-304M Power Supply, Medusa Analyzer Plus, Eagle Tree v3 with Power Panel and an RPM and two Temperature sensors (Temp A bolted directly to the motor back plate, and Temp B inserted into the windings), E-sky servo adjuster, Hobbico Digital Mini-Tach, RayTek IR temperature gun.

My test set up is not designed to handle large low Kv motors like this. My power supply is limited to 14.7v/25A, even if I joined 3s packs in series, I have no 6s capable ESC’s, I am limited to perhaps 14”-15” prop, and my digital scale can only cope with 2000g! Consequently I have conducted lower power tests sufficient to allow DriveCalc to compute Kv, Rm, max. amps and efficiency. I ran my usual no-load tests at 7v, 8v, 10v and then a series of prop tests at just 3s voltage (~11v) and 4s voltage (~14v) starting with 9x5 GWS HD and working my way up to an 14x8.5APC E. Using a Dualsky 40A ESC the motor started well every time and ran extremely smoothly at all power levels with each prop I tried, and, as can be seen from the DriveCalc computations, reasonably efficiently too (78% max., but at only 7A). Since I was only using very short bursts of WOT with each prop, just to get diagnostic data, I did not monitor temperature in detail, but looking at the PowerPanel I saw no temperatures above 40°C. The RPM as a percentage of Kv x V is a telling parameter… ideally this figure should be above 70%, and not surprisingly this under-stressed motor managed that with almost every prop I tried. The 14x8.5 APC E on 4s voltage produced “RPM as % of Kv x V” of only 67% [at 22.40A/316W] so I’d be concerned at pushing a lot harder. Despite the iflight-rc suggestion of 32.3A max., Drive Calc suggests that max. current for this motor should be only 25A on 3s…….so 25A on 6s (566W) seems optimistic.

DriveCalc computed the Kv as ~588Kv (essentially the same as the spec. of 580Kv). iPower lists the Io as 0.95A (at what voltage?) and Rm as 0.047Ω. I measured Io at 0.80A @ 10v, and for Rm, DriveCalc gave me a much larger figure than theirs…. ~0.16Ω).

Since my minimal testing provides only basic specs for this motor, we need someone with a test rig which can truly evaluate its performance at far higher voltages and power levels than my system can cope with.

Cheers, Phil
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Old Jan 16, 2014, 11:30 AM
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#8: iPower MultiMate MT4114-400 (158g, ~415Kv)

The eighth motor in this series to be reviewed is the iPower MultiMate MT4114-400 (158g, ~415Kv) , listed as "161g, 400Kv, 36.7A/480W max., 14x4.7 CF - 16x5.5 CF props recommended". Jack Erbes has already done his typical competent review of a lower Kv version of this motor http://www.rcgroups.com/forums/showthread.php?t=1980619, so I will not repeat the details of the motor's dimensions and construction.

Since this motor is of large diameter (46mm) and has mounting holes at 25mm centers I had to use a modified "Aeronaut beam mount for Speed 600" to fit it to my test stand (not for the first time... I've previously used it for Mega 600 motors, and a big Castle 3412).

I used my standard test stand set-up: Thrust stand [Version III in Pusher mode], Ohaus CS2000 Digital Scale, Zurich DS-304M Power Supply, Medusa Analyzer Plus, Eagle Tree v3 with Power Panel and an RPM and two Temperature sensors (Temp A bolted directly to the motor back plate, and Temp B inserted into the windings), E-sky servo adjuster, Hobbico Digital Mini-Tach, RayTek IR temperature gun.

My test set up is not designed to handle large low Kv motors like this. My power supply is limited to 14.7v/25A, even if I joined 3s packs in series, I have no 6s capable ESC’s, I am limited to perhaps 14”-15” prop, and my digital scale can only cope with 2000g! Consequently I have conducted lower power tests sufficient to allow DriveCalc to compute Kv, Rm, max. amps and efficiency. I ran my usual no-load tests at 7v, 8v, 10v and 14v and then a series of prop tests at just 3s voltage (~11.1v) and 4s voltage (~14.7v) starting with11x7 GWS HD and working my way up to an 14x8.5APC E. Using a Dualsky 40A ESC the motor started well every time and ran extremely smoothly at all power levels with each prop I tried, and, as can be seen from the DriveCalc computations, reasonably efficiently too (83% max., at 22v/12A). Since I was only using very short bursts of WOT with each prop, just to get diagnostic data, I did not monitor temperature in detail. The RPM as a percentage of Kv x V is a telling parameter… ideally this figure should be above 70%, and not surprisingly this under-stressed motor managed better than 80% with every prop I tried. The 14x8.5 APC E on 4s voltage produced “RPM as % of Kv x V” of 82% [at 11.7A/167W] so there is no doubt it could be pushed a lot harder. The iflight-rc suggestion is 36.7A max., in line with Drive Calc's suggested max. current for this motor of 40A (60% efficiency).

DriveCalc computed the Kv as ~415Kv (essentially the same as the spec. of 400Kv). iPower lists the Io as 1.19A (at what voltage?) and Rm as 0.073Ω. I measured Io at 0.70A @ 10v, and for Rm, DriveCalc gave me a much larger figure than theirs…. ~0.195Ω).

Since my minimal testing provides only basic specs for this motor, we need someone with a test rig which can truly evaluate its performance at far higher voltages and power levels than my system can cope with.
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Old Jan 17, 2014, 05:57 AM
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Antony (France)
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Hi Phil
Good testings. excellent reports
As a summary about Kv's ( measured /announced )
#1: iPower MultiMate MT2208-1400 (56g, ~1428Kv) +2%
#2: iPower MultiMate MT2212-850 (70g, ~900Kv) +6%
#3: iPower MultiMate MT2217-880 (87g, ~947Kv) +7.6%
#4: iPower MultiMate MT2212-1000 (71g, ~1065Kv) +6.5%
#5: iPower MultiMate MT2814-810 (119g, ~770Kv) post #9 ?????
#6: iPower MultiMate MT2814-750 (119g, ~770Kv) +2.6%
#7: iPower MultiMate MT4108-580 (116g, ~588Kv) +1.4%
#8: iPower MultiMate MT4114-400 (158g, ~415Kv) +3.75%
It is better to use "measured Kv" instead of "announced Kv"
I recall that Power loading of a prop is rpm^3 (+6% Kv leads to +18% load)
Question
Are MT2814-810 or 750 on the same "config" , could be 12N12C14P (dLRK) ?
Louis
ps : 12C is for 12 coils, N for nuts or teeth, P for mag. poles
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Old Jan 17, 2014, 05:10 PM
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#5: iPower MultiMate MT2814-810 (119g, ~770Kv) post #9 ?????

Hi Louis,

For the Kv I just entered the measured numbers and that is what DriveCalc derived.. the same 770Kv for the "announced" 750Kv and the "announced" 810Kv. I didn't tear the motors apart to count turns or determine termination... I just assumed that the sweatshop workers wound 'em with the same number of turns when they should have made 'em slightly different.

Cheers, Phil
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Old Jan 17, 2014, 05:14 PM
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Antony (France)
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Hi Phil
May be the different Rm (millohm) means that the turns number are different.
It could be a "compensation" via magnets strength grade (or the airgap) or the magnets volume to get the same Kv.
Louis
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Old Jan 17, 2014, 06:40 PM
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I wonder why, in almost every motor I test, the Kv derived by DriveCalc is higher than the maker's "announced/stated/spec" Kv. I measure no-load rpm and it is almost always higher than the expected rpm from simply "voltage x announced Kv".[given losses and inefficiencies it should be lower]... then DriveCalc does its computation [which, being mathematically challenged, I can't even begin to comprehend] and the calculated Kv, as expected since no motor is 100% efficient, goes up even further.
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