Direct Drive Main motor for microhelis finally ready!!! - RC Groups
Shop our Airplanes Products Drone Products Sales
Thread Tools
Feb 09, 2004, 12:55 PM
cd brushless motors rule!
niels polfliet's Avatar

Direct Drive Main motor for microhelis finally ready!!!

Hi guys!

after many houres of winding, rewinding, searching the computer company's garbage can, i finally got it right
Here it is , the (first?) direct drive motor for microhelis.

The stator comes from a hard drive motor. its a 15 nut outrunner motor. It gets it's hudge torq from it's large diameter , which is just 3mm more diameter than the hummingbird main gear. It is'nt an lrk either, but it has the torque required to turn the hummingbird rotor with cut blades. About 1500 rpm that is.

It has 120 magnets for now, al N45 3*6*1,5 and 2,5*5*1,5. I want to try 5*5*1,2 N50 next, but i'll need a new ring for that...

The motor weights about 70grams, which is a little more than the stock motor. But you don't need the main gear, so the weight is approx. the same as stock, even a little lighter..

The complete heli weights 265 gram with 2s 350 uhd cells. The light cells do much work actually, because they're so light...I'm ging to try thicker motors is the future, which means wore weight, but with better magnets this schouldn't be to much. To give you an idea, this motor gives just enough power to ascend with 3Setec1200 (320gram) at full throttle, so just a little more would be great...

Te motor takes about 4 amps at hover, which means 32 watts. According to the weight, the eff. is about 0,12watt/grams. Quite good i think. 4 amp shouldn't be a problem for the 350 uhd's.

And of course, the sound is great! Really silent, except for the noisy fan (to be replaced bij DDtail later). It really sounds like a helicopter, even wore when you're steering..

Pic's!! dont mind the badly arranged electronics, I'm going to do something about it asap...

How do you like it? lett me know...

Last edited by niels polfliet; Mar 11, 2004 at 01:23 PM.
Sign up now
to remove ads between posts
Feb 09, 2004, 01:01 PM
Registered User
Lynxman's Avatar
That is awesome! I didn't think I'd ever see a direct-drive helicopter.
Feb 09, 2004, 01:25 PM
Spent too much already..
JJfromUK's Avatar
Niels that's fabulous

I have recently offered up a stator to the main gear, and postponed the experiment until I have finished playing with my other motors. I imagine you would want to be careful with the starting torque of your motor.
Feb 09, 2004, 01:57 PM
Registered User
Very Cool!
I have been thinking of doing the same thing for some time. Can you tell us the layout of the windings for your motor? I calulate that you would have had to group 5 sets of windings.

Greg Sutter,
Madison Wisconsin
Feb 09, 2004, 02:04 PM
Registered User
Wow!! Nice! Keep up the good work. I think my next upgrade will be brushless also.

Feb 09, 2004, 02:22 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
CD-ROM for ducted fan, direct drive motors, what's next Niels? You, sir, are disgusting

Groeten Ron
Last edited by Ron van Sommeren; Feb 09, 2004 at 02:37 PM.
Feb 09, 2004, 02:52 PM
Frequent flyer
how well does it fly? it seems like there might be quite a bit of flywheel effect there, especially for a FP. (bet that would be great on a CP!)
Feb 09, 2004, 03:37 PM
Registered User
Hi Niels,
welcome in the club of direct drive helicopter superspec.designers.
Now we are 3 .Dieter Melber,Niels and my.
Next i want to build a counter rotating airlift,that can lift sailplanes straight in the air an start them.The design is simple just a double stick for the batteries and a big outrunnermotor.The case is mountet to the stick and holds the lower rotor and the shaft is conected with the uper rotor.The sailplane holder is conected with ringballbearing to the stick and can carry two planes.
Feb 09, 2004, 04:52 PM
cd brushless motors rule!
niels polfliet's Avatar
Hi Christian!

Nice to hear from you! Are there 3 direct drive heli's? I saw a 30+ cell heli on a website somewhere, is the other one 30 cell too?

I've seen they're all high pole count LRK's. I thought the lrk way too, but I think the stator material (12 pole 35mm) isn't large enough..(?). If i use the excell sheet for 35 mm lrk, it says 50 winds, but i guess this isn't accurate at these low KV's?

mmm, airlift...what controller are you going to use? Make your own?

@Greg, just all clockwise or counterclockwise...

@Ron; i keep continueing this "invention adventures" till you get back in this hobby It's for heli's now, Am I getting closer?

Letts say I'm "collecting" for the Nijmegen meeting

@Rkramer, we'll see.It isn't strong enough for CP yet...
Just ordered a direct drive edf50 motor to upgrade the tail. Flying while holding the tail with your hands isn't that nice..

Feb 10, 2004, 07:02 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Hush! You're getting dangerously close

Dieter Melber's direct drive helicopter motor:

Christian Lucas' direct drive motor:

Feb 10, 2004, 09:12 AM
Registered User
Steve McBride's Avatar
Very nice work, all of them!

Would a direct drive lend itself better to a CP hali than a FP heli? I would assume a direct drive would be a bit difficient in the necessary torque to spin up the main rotor as quickly as a geared setup. With a CP, the main rotor runs at a relatively constant speed and therefore would not need as much torque except in extreem pitch excursions.

Just some questions I have, but I admire the work none the less!

Feb 10, 2004, 02:58 PM
cd brushless motors rule!
niels polfliet's Avatar
hi guys!

It has flown!

No difference with the stock brushless heli I think. The giant diam. motor doesn't seem to have any gyroscopic effect.

The spinup is ok too. It's a tad slower than with gear, but it's no problem for flying.

The pics shows it with 2s kokam 350UHD, with a new winding for 2S lipo's. I tried an 3S etec1200 too, and it works ok too!

That means i can use 2S kokam350HD for indoor (270gr) of 3S etec1200 (320gr) for outdoors

btw i have a cp hornet head laying around, with 3S it sould work...If i only managed to get it setup properly...

some pics out of my garage

Maybe i can make a video too? Anyone has some bandwith left?

Last edited by niels polfliet; Feb 10, 2004 at 03:01 PM.
Feb 10, 2004, 04:59 PM
Registered User
Hi Niels,
super flyshot´s,your feeling about the flight is like that i had with the heli.My motor has moore overload power so it can aclerate as fast as a geard version.With a good esc it will outperform a geard drive because the inertia is lower with direct drive.The inertia rise ² with the gear ratio,so the high turning motors react slower .The heli fron Dieter Melber is the 30 cell power and my is powered with 12 cells and for a reseach project with a fuelcell.
With 1 liter liquide hydrogen we have 12 houres flight time.
You are right with the 35 mm stator material,i have done some calculation with the Flyware t-rex stator that has 54 mm dia,12 slot for the piccolo Icarus heli and a 5mm staple would be enough.
After i have seen your heli,maybe the next project.
Feb 10, 2004, 09:43 PM
Registered User
Hi Christian Lucas
U mention u use Fuel Cell. Can you tell me where do u get that fuelcell? I wanted to try fuel cell for very long time.

Feb 11, 2004, 04:10 PM
Registered User
Hi Super-Hornet,
the fuel cell i use are from my work at and the sisterfirm .At my work i do reseach of new powersystems for future transportation use.We step in with fuelcell bus and cab´s.We had the first fuelcell bus in Germany,earlyer than Daimler Chrysler,and as we like to demonstrate this technologie we have some toys to demonstrate the power and easy handling of this units.One is a fuelcell bike and some cars and my heli.I have start fuelcell research at megnetmotor with my partner Dr.Koshany who has leaved MM and started with his owen firm Novars where he goes for smal fuelcell for handys,Laptop and bikes.For bikes he makes the fuelcell for Aprilia Motorcycle in Italy.The Aprilia Hydrocycle is a very powerfull electric bike witch can start with a wheele,it has a 3 KW fuelcell.He had a reseach conection to Manhathen Scientific see the link,,where you can see the 3 Kw Fuelcell.At the bike you can see the size under the stear bar the small round can.This fuelcells are not comerzial sold.
Last edited by Christian Lucas; Feb 11, 2004 at 04:15 PM.