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Hobby Lobby MiniAC Motor Review

Smaller in diameter than a 280 and only a little longer, this little motor really turns in the performance while keeping the current draw in Speed 400 territory. If you like Speed 400 airplanes, the MiniAC motors have a lot to offer: Use the same battery packs and keep the same current levels, but up your prop rpm a couple thousand and cut your weight at the same time!

Splash

Specifications

Magnets:

Neodymium

Resistance:

.117 Ohm (20 turn), .086 Ohm (16 turn)

Kv:

3000 rpm/volt (20 turn), 3800 rpm/volt (16 turn)

Max Efficiency Current:

5 - 10 A

Max. Current (20 sec):

16 A max (20 turn), 18 A max (16 turn)

Cell Count:

6 - 10 cells

Length:

48 mm (1.89 in.)

Diameter:

22 mm (0.87 in.)

Weight:

48 g (1.7 oz.)

Motor Shaft:

2.3 mm

Mounting Holes:

2.5 mm, 16 mm center to center

Gearing:

Direct, 2.33:1, 4.64:1

Controller:

Jeti 18-3P sensorless

Props Used in Testing:

APC 4.75x4.75, APC-E 8x6, APC-E 10x7, Graupner CAM 10x8

Tested Cell Counts:

7 or 8 500AR's

Price:

$79.00 (current Hobby Lobby International, Inc. web pricing)

Available From:

Hobby Lobby International

Introduction

It seems like no matter what the sport or activity in which I've been involved, simplicity and low cost eventually give way to sophistication and greater complexity. Consider Speed 400 racing, a competition designed around a cheap motor that was supposed to offer a fun, low-cost way to get involved in racing.. A few years ago when this all started, Pat Mattes and I took first and third places respectively at a meet in Indianapolis. Pat was flying a plane made out of a cardboard Ultracoat tube with a foam wing, and I was flying a design of his made from sheet balsa with a foam wing. The 2nd place finisher was flying a Grigg's Rocket, a simple balsa racer. I believe the NATS were won that year with Tom Hunt flying his Bare Bones, a stick-built balsa plane. The next year everyone was flying slick fiberglass planes that completely outclassed (and outran) the previous year's simple wood designs. In fact, the designs became so sophisticated that they completely outclassed the motor. Of course, power systems were the next thing to make the jump, and in a few years we had rare-earth magnet and brushless motors that would absolutely run circles around the lowly Speed 400 motor. Some of this was probably negative, in that Speed 400 racing was no longer a cheap, entry level sport, but on the plus side the motor development gave us some really hot, small motors that opened up a whole new class of small airplane performance.

The one fly in the ointment to all this motor development was the ability to feed these systems. Performance improvements usually meant increased current draws, and the poor 600AE cells just couldn't keep up. 500AR's could handle most of the load, but they quickly departed the scene. Going to 800AR's or the new CP1300's meant larger and heavier airplanes. What seemed to be lacking was a quality motor with good performance that could still be fed by 600AE's (or comparable) and fit in a Speed 400 airframe.

That deficit in the motor scene has now been rectified by the Model Motors MiniAC 1215/20 and 1215/16 motors. Sometimes called brushless 280's, they're really light, small, efficient Speed 400 equivalents (although you can also run them with lower current draws on lighter 280-sized cells). Smaller in diameter than a 280 and only a little longer, this little motor really turns in the performance while keeping the current draw in Speed 400 territory. If you like Speed 400 airplanes, the MiniAC motors have a lot to offer: Use the same battery packs and keep the same current levels, but up your prop rpm a couple thousand and cut your weight at the same time!

The Motor / Controller

Model Motors MiniAC motors have a rather unique look. A carbon case keeps things light, while giving the motors a high-tech appearance. Of course, appearance isn't the real reason most modelers will take interest in the MiniAC motors - more than likely it will be the size and weight, coupled with the efficiency and performance a brushless motor affords. While a 280 motor measures 24mm in diameter, the MiniAC motors are only 22mm in diameter. Weighing in at 1.7 oz, the MiniAC's are only .2 oz heavier than a 280 motor. The power potential, however, is much greater - more like a 480. You can run these motors propped to around 15 amps (although you can also run them with a gearbox at lower current levels for use with 350 mAh size cells). The shaft is 2.3mm, the same as a Speed 400 (which makes mounting props easy), and the mounting holes are 2.5 mm on a 16 mm circle (also the same as a Speed 400).

These photos show the relative size of the MiniAC motor compared to a Speed 400 and a Speed 280.

Hobby Lobby recommends using the Jeti 18-3P controller with the MiniAC motors, so that's the controller used in these tests. The 18-3P has the same solid reliability as the other Jeti sensorless/brushless controllers, but with less size for smaller motors. Other than having a brake and an on/off switch, these Jeti controllers don't have a lot of options, but that also makes them very easy to use. Solder the leads to the motor and the battery side leads to your favorite connectors, and you're ready to go. As with any sensorless controller, if the motor turns the wrong way, simply exchange any two of the leads going to the motor.


MiniAC motor with Jeti18-3P controller soldered to the back. The controller is actually relatively small for a brushless unit, but the diminutive size of the MiniAC motor makes it appear almost large!

How It Works Together

Performance Characteristics
In order to get a handle on how these new mini motors perform, I checked several motor/gearbox/prop/battery combinations for current and rpm. I also compared a couple of Speed 300 setups that I had been flying in my Miss Bohemia to see how they compared. The following chart details my findings:

Motor Gearing Cell Count Prop Current (Amps) RPM
1215/20 Direct 7 4.7x4.7 11 15000
1215/20 Direct 8 4.7x4.7 13 16,500
1215/20 2.33:1 7 8x6 10.1 6600
1215/20 2.33:1 8 8x6 13 7300
1215/16 4.64:1 7 10x7 11.1 4700
1215/16 4.64:1 8 10x7 12.4 5100
Speed 300 4:1 7 10x7 14.3 4900
Speed 300 4:1 8 10x7 17.8 5500

All the batteries used in this test were the older 500AR red cells. The 2.33:1 and 4:1 gearboxes are MP Jet units while the 4.64:1 gearbox is Model Motors planetary unit. All props are APC-E props. I expected a little more out of the 8-cell pack, but in later flying I found it may not be in as good of shape as the 7-cell pack (a matched pack from DMA). In the future I may try to find a constant voltage source to help keep things more consistent. As you can see from the above chart, these motors spin their respective props at a relatively high rpm considering the moderate current draw. A geared Speed 300 gave equivalent or slightly better performance, but at a notable increase in current draw (more than should probably be fed through the Speed 300).

Direct-Drive: MiniAC 1215/20

In my testing of the MiniAC 1215/20 motor, I opted to try it first as a direct-drive motor, and then with the MPJet gearbox (and Hobby Lobby's ring adapter). I first used the motor in my Pylon Buster, a light sport plane. Pat Mattes also had one of these motors he was using in a Kelly mini sailplane (from Hobby Lobby International), so I asked for some feedback from Pat about how his motor performed as a sailplane launcher.

Pylon Buster

The Pylon Buster is an old-style stick construction Speed 400 racer and sport plane, formerly produced by Joel Maxwell as an ARF. With 7 500AR's and the MiniAC 1215/20 motor direct-drive, Jeti 18-3P controller, 2 HS-55 servos, Hitec Focus III AM receiver, APP connectors, and an APC 4.75x4.75 prop, the all up weight came to 14 oz. We've flown these planes on a standard 6V Speed 400 and an Astro 020 brushless. The Astro was definitely our favorite performance setup, but the planes flew very well even on a Speed 400. Going to the MiniAC 1215/20 gave us a good taste of both worlds - performance approaching that of the 020, current draw of the Speed 400, and less weight than either. This combination seemed to be an excellent match for a light, fly anytime sport airplane, and I liked it. The only downside I could find was that once in awhile the controller seemed to get a little confused at startup (the first time I've experienced this with any Jeti controller), but backing off the throttle and starting over again seemed to solve things. Once in the air it was never an issue.

The Pylon Buster, a light stick-built sport plane produced by Joel Maxwell as an ARF. this particular version was lightened even more with additional holes cut into the sheet and light Oracover applied to the framework.
The Pylon Buster in flight. Performance was quite strong - much more than a Speed 400.

Kelly Mini Sailplane

Pat Mattes set up his Kelly with the MiniAC 1215/20 direct drive using a CAM 4x2.4 prop and a 7-cell pack of 350mah NiCads. Current draw was only 5.8 amps with this setup - well within the range of the 350 NiCads, which kept the Kelly nice and light. Pat's analysis: the Kelly Sailplane was now a Pocket Hotliner! Pat told me the climb was tremendous, and he worried at times when he went into a dive that the speed might be excessive for the plane. It wasn't F5B, but the MiniAC 1215/20 and the Kelly made a wonderful fly anytime sport sailplane setup.


Model Motors MiniAC 1215/20 mounted in the nose of the Kelly Mini Sailplane.

Model Motors Planetary 4.64:1 Gearbox, MiniAC 1215/16

After playing with the 1215/20 direct drive for awhile, I was anxious to try out the MiniAC 1215/16 motor mated to the new Model Motors 4.64:1 planetary gearbox. The 3800 rpm/volt Kv of the 16 turn motor is too high to allow the motor to be used direct-drive with a prop of reasonable size, but these high rpm units make great ducted fan and geared setups. In checking the performance of this setup, I opted to try out the geared 1215/16 in a fun-fly type plane and in a larger Speed 400-size sailplane.


This is the Model Motors planetary gearbox, a nice, light all metal unit.

This shows the gearbox disassembled and the components laid out.

The motor is shown here with the pinion attached (attachment is easy by means of a set screw).
A couple of photos of the motor and gearbox fully assembled.

PB Fly Mini

I first flew the geared 1215/16 motor in the PB Fly Mini from Hobby Lobby International. This is a carbon tube, fun-fly style plane for Speed 400. With the 16-turn MiniAC 1215/16, 4.64:1 planetary gearbox, Jeti 18-3P brushless/sensorless speed controller, 2 HS-55 servos, Hitec Focus III AM receiver, APP connectors, APC 10x7E prop, and 7 500AR's the weight came out to 15 oz.

Planetary geared MiniAC 1215/16 installed in the PB FlyMini.

Flying the MiniAC-powered FlyMini was a thrill - there was plenty of aerobatic potential. The PB Fly Mini was not quite able to hang on the prop, but it had plenty of vertical performance for most maneuvers. With 8 500AR's and an APC 10x7 electric prop, it would almost hover. A little larger prop would probably have given me hovering ability. Loops, rolls, etc. were easy and the power was plentiful. I found the throttling superb - I could get the prop slow enough that I could just about count the blades, and it had pretty close to a scale sound as I throttled up. I kept thinking this would be really cool in something like a Speed 400-size Stearman biplane. I did find that the gearbox shaft had a lot of fore and aft play, which at first was disconcerting, but it didn't seem to affect performance. I also found the shaft is fairly soft, but straightens easily if bent. Overall I think the 4.64:1 gearing and the MiniAC 1215/16 motor made an excellent fun-fly combo.

A couple of photos of the PB FlyMini ready to go with brushless power.

Whisper 1400

Now it was time to move on to bigger things. My daughter's ACE Whisper 1400 sailplane is a sweet flying floater on a direct-drive 6V Speed 400 (I converted it to three channel operation a couple of years ago), but I wanted to see if we could increase the climb rate a bit by going to the geared MiniAC 1215/16 motor and a larger prop.

For this test I outfitted the plane with the 16 turn MiniAC 1215/16, 4.64:1 Model Motors planetary gearbox, 12x8 CAM folding prop, Jeti 18-3P controller, 7 or 8 500AR cells, 2 HS-81 servos, Hitec Focus III AM radio, and APP connectors. I didn't check the weight, but it was comparable to the Speed 400 version (lighter motor, heavier prop and controller).

Installation of the geared 1215/16 in the nose of the Whisper. I had to open up the firewall a bit to allow for the longer length of the motor and gearbox.

Climb performance of the Whisper 1400 was much improved over the stock Speed 400. Here's where I found out my 8-cell pack wasn't doing too well - performance was notably better with our 7 cell pack! Climb angle was probably 30 degrees or more, and I could perform continuous loops with ease. The other thing we noticed was the long duration of this power setup. Since climb performance increased so dramatically with no increase in current, we used a lot less power getting to altitude, which in turn gave us much longer flight times. I think this would make a great AULD platform using CP1300's or the 1700 mAh 4/5 AUP NiMH cells.

My son Daniel holding the Whisper 1400, and a few photos of the Whisper 1400 in flight. A great combination for strong climbs and long, soaring flights!

MP Jet 2.33:1 Gearbox, MiniAC 1215/20 Motor

The other gearbox I had on hand to test was the Speed 400 size MPJet gearbox (bearing version) and an adapter ring Hobby Lobby was now offering to allow the MiniAC motors to fit the gearbox. In this case I opted to mate the 20 turn motor to this gearbox and use an 8x6 prop. This seemed like a great combination for a sport plane in the Speed 400 size range. Some of the larger planes would really benefit from the larger prop a gearbox allows. I didn't have a plane readily available for the MPJet gearbox and MiniAC combination, so I turned it over to Pat Mattes to try in one of his foam flying wing creations.


Comparison of Model Motors MiniAC 1215/20 motor and MPJet gearbox (on top) with a Speed 300 and MPJet gearbox (on bottom)

Here are the components of the assembly laid out. You can see the adapter ring made necessary by the small diameter of the MiniAC motors. Locktite is included with the pinion in the package for mounting to the shaft.
Adapter ring in place in the gearbox and pinion installed on the motor.
Motor and gearbox ready to go. The motor is held with a friction fit, but it's tight enough that it's doubtful the motor will come loose without substantial effort.

Foam Flying Wing

Pat Mattes is almost a legend for his foam creations, so it was not surprising he whipped out a neat little flying wing with which to test the 2.33:1 geared MiniAC 1215/20 motor. Pat likes to keep things lighter and lower in the current spectrum than I normally do, so he outfitted his plane with the MiniAC geared 2.33:1 with MPJet gearbox and adapter ring, APC 8x6 prop, and a 7-cell pack of 350mAh NiCad cells. Current draw was 7.5 amps. According to Pat, his flying wing exhibited very strong flight performance. He was able to do vertical 8's with the plane. It wasn't hoverable, but climbouts were quite strong. Pat's comment: Not bad for 350 mAh batteries!

Pat's foam flying wing with MiniAC brushless power.
Basically a short Blue Foamie, I think the plane was way out-classed by the motor, but it made a fun combination nevertheless.

Conclusion

Compared to a Speed 400, these MiniAC motors seem very efficient - Speed 400 current draws with much higher rpm, providing great sport plane performance. The MiniAC 1215/20 makes an outstanding direct-drive Speed 400 upgrade - lighter weight, smaller (easier to fit in small planes, like pylon racers), and more powerful with the same current draws. If you want a little more thrust rather than speed, both motors do a nice job of turning a larger prop when attached to a gearbox. Although I didn't try it, the MiniAC 1215/16 is considered to be a very nice small ducted fan motor. No matter which way you go, I think you'll be quite pleased with these high-performance lightweights.

Discussion

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Old Jun 30, 2003, 11:15 PM
An earthbound misfit, I
hobbystuff's Avatar
Victoria, Canada
Joined Jun 2003
307 Posts
The ModelMotors MiniAC units are wonderful performers. We sell a lot of them and have recieved positive comments.

www.hobbystuff.ca
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Old Jul 05, 2003, 11:02 AM
Registered User
E-Challenged's Avatar
United States, CA, Garden Grove
Joined Oct 2000
11,878 Posts
Nice review but wanted more detail on why the 16 turn is not recommended as direct drive with a "reasonable size " prop. I guess article means that it revs too high with the optimum direct drive prop but then I wonder how well it hangs together in ducted fan service.(?)
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Old Jul 07, 2003, 12:05 PM
Registered User
Steven Horney's Avatar
Joined Jan 1999
419 Posts
Hi, E-Challenged,

The Kv of the 16 turn motor is too high - your current would be more than what's recommended for the motor. It should be a great ducted-fan motor, however, and many people seem to be using them for that purpose. I have a ducted fan, but no airplane for it at the moment, so I wasn't able to test that configuration for the article.

Steve
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Old Jul 13, 2003, 04:00 PM
Flying Free
erashby's Avatar
Utah
Joined Aug 2001
1,938 Posts
Off topic but similar

How about the Razor 300 as a direct drive motor. Would it also rev too high? I have one on back-order that I was planing on trying out DD with a 3x3 or 3x2 or 4x2 prop n my 5oz MiniSpeed Wing. And then probably moving it geared 5:1 to a 3D plane. Would I be better off with a Razor 350? or the 400/ or the 2500?

Opinions without direct Razor experience are okay.
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Old Jul 15, 2003, 04:47 PM
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AndyMb's Avatar
Maribor, Slovenia
Joined Oct 2002
132 Posts
I have the 1215/16 sitting around with Master18. Also I have an 400 (schwerdtfeger) ducted fan. How would it be on 8 or even 10 Kan950 ?
I should measure the amps with 8 cells. Where ared the limits ?

Andrej
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Old Jul 16, 2003, 09:53 PM
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Steven Horney's Avatar
Joined Jan 1999
419 Posts
I can't answer how the motor would run on 8 or 10 cells with this fan, but the limits are around 15 amps. I would check with 8 cells before going much higher.

Steve
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Old Jul 19, 2003, 10:01 PM
sal
Registered User
NSP (Vermont)
Joined Aug 2000
2,695 Posts
Why are they called Hobby Lobby Mini AC motor? They are not owned by Hobby Lobby nor do they have an exclusive distribution in this Country. I buy them direct from Model Motors in CZ an sell them as well as several others.

It should be a Model Motors Mini AC review for Hobby Lobby.
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Old Jul 19, 2003, 10:04 PM
sal
Registered User
NSP (Vermont)
Joined Aug 2000
2,695 Posts
We use the 16 turn for pylon racers and it works great! The motor does not have the outpiut of the Hacker B20, the Razor motors or the new Chinese HiMaxx series but they are setup to be efficient at a lower amperage range.
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Old Jul 21, 2003, 03:01 PM
Registered User
Czech Republic
Joined May 2003
5 Posts
Sal,

It is true Hobby Lobby is our Exclusive Distributor for US market, including the Mini AC series of motors.

P.S. MiniAC 1215/16 have the output of the B20, but not B20L
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Old Aug 01, 2003, 10:59 AM
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kevin's Avatar
ohio
Joined Aug 1999
3,608 Posts
i used the 16 turn in the vasa 55 fan for my review of the flying styro A-7. if i remember correctly ( i guess i could go check) with 8 cells it was just under 13 amps and about 120 watts. it has about 30 flights on it now and still works great.
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Old Aug 13, 2003, 10:45 AM
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E-Challenged's Avatar
United States, CA, Garden Grove
Joined Oct 2000
11,878 Posts
Prop Gearbox Combinations

I'm flying my Switchback 3D with 10X8 GWS prop using MiniAC 1215/16 in GWS 300C B gearbox ( phew!) and it has great perfromance. What is the proper GWS gearbox for this motor using a GWS 8X6 prop? Would it over-rev and be damaged on an 8X6 at full throttle using the 300C "B" gearbox? ( As in a small scale model with short landing gear)
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Old Aug 15, 2003, 03:43 PM
A Clinger
rclark's Avatar
Butte, MT
Joined Sep 2001
7,073 Posts
Quote:
Would it over-rev and be damaged
. Electric motors don't over rev (unlike glow)! Remember that there is an RPM/V rating and that is as fast as the motor can go -- per volt (but to many volts and yes you can then exceed the motor max RPM rating...) . So you could run a 3x2 prop no problem -- just have a 'thrust' and 'speed' problem . Running the 8x6 would work fine just lower thrust and speed. You may want to go down in gearing ('A' box?) to get exceptable performance depending on what you are trying to accomplish (and that's half the fun (or frustration? ) of electrics selecting gearbox/prop/battery combos to fit our requirements )......
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Last edited by rclark; Aug 21, 2003 at 10:15 PM.
Old Aug 22, 2003, 02:00 PM
Registered User
Chicago, IL
Joined Mar 2001
38 Posts
EXTREME

What do you guys know about the 1215/EX 9 Turn?

I'm looking for a ripper to power a combat wing/racer(hoping for crazy over-kill for hunting the sky) with a 3s2p Etec 1200 LiPo pack and a Phoenix-25.

I've heard through a couple people that the extreme is appropriately named.

-JamesMadison10
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Last edited by JamesMadison10; Aug 22, 2003 at 02:20 PM.
Old Aug 24, 2003, 04:13 AM
Registered User
Houston, Texas
Joined Nov 2001
112 Posts
Group;

Where did the term miniAC motor come from? The industrial term AC stands for alternating current - designating a sinusodial alternating waveform where the voltage varies from a + voltage to a - voltage (where voltage excursions are equidistance from a common 0 voltage reference line). The motors you are refering to are brushless DC motors that runs on DC power that varies in frequency and varies from a 0 voltage to a + voltage. Why confuse things by using incorrect and inappropriate terminology?

Bryan Swinney
[(3*4)^2]*10^3=144000
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