In an effort to come up with the ultimate 1s setup for UM planes I came up with this:

To fit it I needed to wrap a piece of tape around it 2 times:



Here's the weight compared to a stock brushed motor:



This motor is used in the newly released mCPX BL helicopter. Its primary function is to directly drive the tail rotor. The part # is: BLH3904

Specs (Snagged from here):

Motor diameter: 8mm
Motor length: 18.6mm

Shaft: 1.0mm in diameter
Shaft length: 4.4mm protruding

Weight: 3.6g AUW

There are no screw holes - only cooling holes.

However:

This setup turned out to be a bit of a turd in the punch bowl on both 1s and 2s.

Here's what some people have wrote about the 1s performance:

Originally Posted by NitroCharged

Here it is:

http://www.youtube.com/watch?v=LAHHBLgl8QQ

.

Originally Posted by NitroCharged

Anyhoo, here endeth all speculation.

The inrunner will spin a UM prop in a UM gearbox on 1S at ~5200rpm's.
The stock motor spins a UM prop in a UM gearbox on 1S at ~6900 rpm's.

The inrunner draws much less current on 1S (less load thanks to lower kV)

Having said that - Sweet mercy! she had some thrust on 2S! I didn't dare go full throttle.

We may have to work on different ratio gearboxes. I think I still have some old different ratio gearbox combo's from back in the day - I can't remember the name of them though - they came with folding props.

Originally Posted by Tarak

I know this seems silly, and more than likely a moot point for our current crop of UM BNF or RTF birds that we were hoping this would be a direct drop in for, but what about propping up the gearbox for more thrust? Would that work, or am I missing some other key component of the equation? Just a thought...

Originally Posted by microheli

Some calculation for 1S:

Volt    kV    Gear   Slip    rpm   Thrust(5030)
3,7V * 8100kv  / 4  - 30% =  5200 = 25g

3,7V * 13000kv / 4  - 30% =  8400 = 65g
3,7V * 8100kv  / 3  - 30% =  7000 = 44g
3,7V * 8100kv /2,67 - 30% =  7800 = 55g

Other props are also worth to try and 2S with limited Throttle Curve seems possible but need some tests.(current, temp, cooling)

Now here's my thoughts on 2s performance

Originally Posted by valiantGLX

I just ran a 2s thrust test, here's how it went:

http://www.youtube.com/watch?v=pcyRh1DkEPY

My conclusion: This motor and gearbox combo is a dud whether on 1s or 2s It makes about 60g of thrust on 2s with a UM eflite 2 blade prop but the motor cant sustain it. It gets incredibly hot quickly even at around half throttle

My advice: If you have some on order cancel it asap, if they are already on the way try to return them or leave them in the package and flog them off on ebay. Even with 1s you'll need an abnormally large prop to make the same if not less thrust than the stock motor by the sounds of things.

...And here's a 2s thrust test in case you missed it:

mCPX BL tail motor in a UM gearbox on 2s FAIL!!! (1 min 5 sec)

So on to the next motor..... The AP05 5000kV 1s BL motor looks like a winner!

The AP05 5000kV 1s outrunner, it ticks all the boxes, well almost all of them!

1. its 1s
2. it produces 70-90g of thrust with a 5030, and thats not speculation either
3. will work with eflite props, so scale looking props and enough ground clearance for LG is very possible
4. weighs about the same as the stock gearboxed brushed motor

Only downside it that you will need to add a motor mount, but that wouldnt be any more difficult than building your own gearbox or trying to make an aftermarket gearboxed BL motor fit in.

Micronradiocontrol sells both the The AP05 5000kV and mounts for them.




Heres their thrust data for both the AP05 3000 & 5000kV:

3000Kv:
Prop Volts Current Thrust
4x2.5 3.5V 0.9A 32g
4x2.5 7V 2.2A 87g
5x3 3.5V 1.2A 45g
5x3 7V 2.8A 110g

5000Kv:
Prop Volts Current Thrust
5x3 3.7V 4.5A 90g









1s ESCs:

ESC: As I dont know for sure how many amps this little motor will draw its hard to select a BL ESC. HobbyKing has a few options though:

6A 1S Brushless Speed Controller


Pros - This would be the easiest one to use for sure, its more or less plug and play. Also it has a built in brushed to BL signal converter, so it will work if you plug it into the motor output of the HH 1s AS3X boards. This ESC has a host of built in programming features too, which dont need a programming card to activate.

Cons - It is never in stock and it weighs quite a bit in comparison to the other choices.

5A 1S Brushless Controller


Pros - Weighs less than the 6a ESC, and its always in stock.

Cons - Its always in stock because its rubbish, just about every review is bad. There are no instructions for it, therefore no one knows how to program it if it is even possible.

XP 3A 1S 0.7g Brushless Speed Controller


Pros - Weighs just 0.7g, comes with 3-pin connectors and is programmable without a programming card

Cons - Hard to find any faults.


SuperMicro Systems - Brushless ESC - 3.5A


Pros - super light at 0.3g and 3.5a continuous power

Cons - Only 4a burst, not programmable, and doesnt include plugs

There are a couple of new 1s ESCs on the HK site but they're not really worth a mention.

Done exactly the same thing this end Valiant.

Just need to solder a different plug to the motor and it's go time!

Originally Posted by NitroCharged

Done exactly the same thing this end Valiant.

Just need to solder a different plug to the motor and it's go time!
]

Have you done any thrust tests yet?

Also I'm hoping that it will plug directly on to the ESC I bought, looks like it will be a good fit anyway.

Here's some thrust tests I did with the stock brushed motor:

E-flite and GWS prop thrust tests with the 1s UM motor and gearbox.wmv (1 min 30 sec)

Genius idea!
I just have to try this.
thanks!

Can't wait to see what you guys get for thrust with this. Anyone know what the KV rating is for the original brushed one? are we going to be using similar props?

I need to keep updated on this mod

Originally Posted by valiantGLX

Pinion:
M0.3 1.0mm 9T pinion


This one seems to be as good as any, and its cheap enough, so I threw it in with my ESC order.

A long time ago, I did order a 9T pinion from HK and it didn't work (still using old pinions from burned motors). It may have been another one, but I think it was this one. Just telling you because you may want to have a "plan B", just in case.

Originally Posted by RealGambler

A long time ago, I did order a 9T pinion from HK and it didn't work (still using old pinions from burned motors). It may have been another one, but I think it was this one. Just telling you because you may want to have a "plan B", just in case.

Thanks for the heads up. My prior plan A is actually my plan B mCPX 9t pinions should fit too, but they cost like 5x more.

Originally Posted by coreman

Can't wait to see what you guys get for thrust with this. Anyone know what the KV rating is for the original brushed one? are we going to be using similar props?

Me Too

No idea on the brushed kV rating do brushed motors even use the kV rating scale

The prop depends on what ESC you are using and the current draw, which is yet to be determined I would like to use the spitfire 4-blade though, its the best all rounder IMO

I am looking at buying a cheap multimeter, does any one know how I can test the amp draw with one (assuming that my ESC was here already)???

This will be a great read, and I hope you get this "mod" refined!

Gene K

(As concerns the HK pinion - I also wasted a few pennies hoping it would fit - it didn't. Glenn at RC Connectors sells the correct pinion, but likely won't reveal his source (of course - he runs a business, a great one at that).

Gene K

Great idea!

what other engines can fit a UM but conected directly to the prop?

Originally Posted by valiantGLX

I am looking at buying a cheap multimeter, does any one know how I can test the amp draw with one (assuming that my ESC was here already)???

Hard to tell from the picture if this one mesure DC amps or AC amps. You need something that mesure DC amps. But if I were you, I would buy a Wattmeter (check HobbyKing). Those cheap multimeter don't last long (particularly the probes), and give slow reading (one every second or so). With a wattmeter, designed for our hobby, you get instant result, and peak result (much more valuable). Trust me, much more valuable than a cheap multimeter!

(As concerns the HK pinion - I also wasted a few pennies hoping it would fit - it didn't. Glenn at RC Connectors sells the correct pinion, but likely won't reveal his source (of course - he runs a business, a great one at that).

Gene K[/QUOTE]

and RCBabbel recently said he had found a source also