BlitzRCWorks Giant MX2 - Page 4 - RC Groups
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May 06, 2011, 02:02 PM
Some Right and some Down angle is normal.
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May 06, 2011, 03:04 PM
smoke is my wattmeter
Or this one. It's a little smaller but it'll be easy to mount. I haven't heard many good things about those red/blue motors but haven't used any personally. I'm hoping the American version comes with a bigger motor than yours. Great looking plane though.
May 06, 2011, 05:28 PM
Registered User
Spouny's Avatar
Originally Posted by krexken
Or this one. It's a little smaller but it'll be easy to mount. I haven't heard many good things about those red/blue motors but haven't used any personally. I'm hoping the American version comes with a bigger motor than yours. Great looking plane though.
42 Amps continuous max (55A burst) for this Turnigy G32 motor
Under load, it may produce 42Ax14.5V=610W (it is rated to 620W).
It is less than what I have with the stock motor, not a good choice in my opinion.
I think that a comfortable power for this plane would be about 900W.
For 4S lipos, under load : 900/14.5=62A
For 5S lipos, under load : 900/18.1=50A

I wonder if it would be a good thing to choose a motor for a 5S set, fewer amps for equivalent power (thus fewer losses by heat).
For 4S and 5S lipos, I wonder which choice would allow the best flying time, given that for lipos of the same weight the 5S has a smaller capacity, but the config 5S consumes fewer amps...
May 07, 2011, 08:50 AM
Registered User
Spouny's Avatar
Today I have received a 14x7 APC E prop.
Measures with my EagleTree Datalogger :
About 40 Amps, 600W for this 14x7 APC E prop

What a pity to have nothing to measure thrust...
I wonder if I am on the wrong way or not, on one side the data which I measure correspond to what DriveCalculator gives (I selected an equivalent motor to mine, the same weight, 650kv and approximately 50A max), it is a good point, but on the other hand I read several reviews of persons which say that a 14x7 APC E on their motor consumes 65 to 70A, to produce 3000+ gr of thrust. I cannot believe that this difference is because of motors efficiency given that all the compared motors are cheap Chinese made motors.
Roswalt here even declares that its US motorization set is not powerful enough for 3D flights with this plane, and BananaHobby motorization set may be more powerful than mine...

Does somebody knows if really a 14x7 APC E prop produce 3000gr of thrust by absorbing 600W ?
If yes, what thrust is needed for 3D flights with a 2100gr plane ?
I am completely lost in the choice of the motorization, I wonder even if the stock motor is not sufficient... (for the moment I cannot try in flight because my 4S lipos are too heavy for this plane, I can use them only for tests on the ground).
Last edited by Spouny; May 07, 2011 at 08:56 AM.
May 07, 2011, 05:28 PM
smoke is my wattmeter
I guess it depends on how hard you're willing to push a motor and your style of flying. Many 3d flyers prop for close to burst rating, not continuous. Things get on the heavy side when you try to stay safe.
May 08, 2011, 10:34 AM
Registered User
Spouny's Avatar
Really wishing to know which thrust was produced by my motorization set, yesterday afternoon I have built a thrust bench, a few hours of work but very usefull and not complicated, here are some pictures (if some people want to build the same thing), that works very well.

OK.... now I can measure thrust

Moteur : B3648 650kv outrunner (stock motor Europe version)
ESC+BEC : 45 A (stock ESC Europe version)
Nanotech 4000 4S lipos, fully charged and in good condition
3 blade 12x9 prop (stock)
Power = 695 W (46A)
Thrust = 2600gr

APC E 14x7 prop
Power = 605 W (40A)
Thrust = 2850gr

I will try to find differents prop, 14x8, 14x10, or maybee 15x8, and measure wich one is the best on this plane.
2850 gr of thrust for a plane wich is supposed to weight about 2000gr is not so bad, for the moment I am going to keep the stock motor and build the plane, I shall see after a few flight if it is necessary to upgrade or not.
May 10, 2011, 10:34 AM
Registered User
Great job Spouny

and now my question
I'm going to order one and I would like to know the motor shaft width in order to order a new spinner.

Can somebody help me out ?

Also will this work with 2x3s 2200mah batteries in series as 6s configuration ? or is it too much for the speed controller and the motor ?

May 10, 2011, 06:35 PM
Registered User
Spouny's Avatar
I dont't know if motor and ESC are OK for 6S voltage, there is no information about that on the box, neither in the instructions manual.
My motor shaft = 6mm
For the spinner, stock one is 60mm (spinner for 3 blades prop of course), but 50 to 60mm will be OK, for my plane i'm going to order a spinner for a 6mm shaft and 50mm ext diameter as I prefer if the spinner is not too big.
But if you buy your MX2 in the US and particulary at bananahobby, it would be a good idea to call the shop to be sure the motor provided in there kit have the same shaft size.
May 12, 2011, 04:44 AM
Registered User
Originally Posted by Roswalt
I revised mine a little bit and tried again - Results were very positive.

The wheel pants and all foam pieces up to the attachment point were removed - Believe it or not, there is an appreciable amount of weight loss from that operation due to the density of the EPO foam. Also, I took the gear assembly off and rebent it on a vice in order to get a better taxi/landing stance. This helped the landing phase immeasurably. Like a different plane, as a matter of fact. My advice, as it usually is - Lose the pants!

In flight, once you get past the fact that it won't be a 3DHS demon, it flies pretty well. Much more of a "regular" plane with pop though. Axial rolls were impressive but the elevator will flex in sharp loops, so that will need to be addressed if you aim to snap-loop a lot.

I reworked the ailerons to independent channels and assigned a flaperon function - This was helpful but probably not necessary. It needed a lot of elevator trim when deployed. Having independent ailerons can really help on a number of different levels though.

I reworked my own DX8 in order to fix the jittering servos and strange "axial torque roll" that I had seen exhibited before. I feel pretty confident that those issues were tied to radio glitching of some kind.

The MX2 is proving to be quite a solid performer that has merit - Just not for the advertised purpose. I had five great landings and no mishaps, just a little wingtip rash from a crosswind gust during taxi. I may keep it around as a test bed for future ideas, or I may follow through and sell it. This is a large plane and it does occupy a fair amount of space!

Hi there,

I've got one of these (sold under Starmax's name in the UK) and I'd love a little more info on how you tamed her down, especially with regard to the axial roll.

I'm no 3D pilot: I fly a P51 foamie (Parkzone) and a balsa Spitfire (Ripmax 600 EP) regularly, and have flown a friends ST Models MX-2, all without mishap for the last whilst not an "experienced" pilot, I don't see myself as a beginner, and I thought this plane would provide a nice big platform to move on a bit.

But WOW.....she bites! I experienced all the bad points you mentioned. She has a horrible tendancy to drop the left wing in a left turn, even with the speed up. With the wing down, the nose pulls over quickly as well. As for slow flying, she just doesn't want to glide; the nose comes up, then she nose over in the stall and the left wing tucks in again.....and she doesn't want to come out of it quickly either. Landing is a 'mare....its got to be fast so she doesn't stall...but that left wing could drop at any moment anyway, so you don't want to be fast and low.....

Obviously, something is wrong in the setup. My battery is as far forward in the nose as I can reach, putting the CoG in the front half of the wing spar access cover. I'm not convinced by my thrust angle, although that could be the result of an inaccurate repair by me to the firewall / bulkhead. It is UP and right at the moment (after the last prang anyway), so that needs re-checking / fixing / adjusting down....and it seems to be VERY right. Could that cause more axial roll or should it be left like that to counter it?

I see you say that you have used radio settings to help with the axial roll; are you referring simply to DR and Expo?

She needs a little TLC at the moment before she goes up again. A good job I have loads of epoxy! I'll sort the dings out, re-set the thrust angle down and right and see what other tips you can offer before I try her again. Thanks in advance for any details you can offer.
May 12, 2011, 08:58 AM
Registered User
Got it yesterday myself and as far as I can see the motor is the same as yours, Spouny, red with 6mm shaft

After reading all this info I'm thinking of using a gyro (since i'm a heli guy) on ailerons to see how it goes....

Luke you haven't say what batteries you use.
I have a 3000mah 4S and thinking of getting a couple more of these:
Turnigy 2650mAh 4S 30C Lipo Pack

Any suggestions ? on battery and spinner and of course props
by the way where I can get a good looking spinner for 2 blade propeller?
I think I will use a 14x7

Maiden probably this weekend

any manuals with large pics anywhere???
May 12, 2011, 10:32 AM
Registered User
Using Turnigy 2200mAh 4S batteries.

Possibility for a gyro. I'm a heli guy too and I think I have a spare gyro kicking around..... hmmmm........
May 12, 2011, 11:56 AM
Capt, USAF
Roswalt's Avatar
Yeah, the first time I flew it was a pretty terrible experience. It took some revisions to get things right....

As I mentioned at the outset, this is not to be misconstrued as a 3D airplane - Despite it's title I don't see it as a viable 3D option without ditching the prop and upping the battery to 5S. With a two blade prop and a 5S 2650 battery, you will likely fly in a different class. The ESC can handle this load, but I'm not sure how long the stock motor will tolerate it.

The ailerons were programmed individually via their own servo leads; this enabled me to use flaperon/spoileron for slower landings and also enabled differential which can help your turning problem. Gyros are not needed on this plane in the slightest, IMHO. If you want to try it though, go for it.

My best battery is a 40C 2200 pack, so I used that based in the nose, but definitely not all the way forward. Battery life was more than sufficient, but I've used a 2650 pack as well and it flew fine, just a little heavier and not so light-feeling.

Can't suggest alternate props since I'm using the stock 3-blade, but I am advocating that somebody attempt the two-blade option and kick it up to a 5S batt. My suspicion is that this thing may really wake up!
May 12, 2011, 01:52 PM
Registered User
Since my first outing, I've had to replace the motor and prop anyway, so I have put a Hacker 30 in it.* The prop is a little "understated" at just an 11 x 7, but for the moment, I just want her to handle well so i can get used to her. She had bags of pull with this.

I am using the DX6i whcih seems to default to using just the one channel for ailerons.....I guess I need to read the manual to find out how to use the 6th channel as I do for my helis. The heli models default to this (for CCPM mixing its a must).

My major concern is the axial roll, in particular the roll to the left which is quite ferocious. Expo hasn't tamed it, even with half throws. I guess this is torque roll, which I get on the Spit but can hold easily with some rudder put it on throttle up. In flight it isn't an issue on the Spit, just on (hand) launch. With the MX-2 it seems to happen at random. Will sealing the aileron hinges help this?

I read on another forum that the Goldwing Mx-2 (bigger and balsa made) flew better with the CoG moved BACK. The poster there had major glide problems, with sudden nose dive stalls and moving the CoG back gave the elevator enough authority to hold it. I am wondering if that little battery sized compartment could be used after all....?

I plan to do a hand launched glide test with her before I give her another powered flight. That will give me a chance to play with the CoG. once I know she will glide, I will feel happier to fly her properly again....if it all goes wrong under power, at least then I can bring her in deadstick. As it is, there is no way to fly her deadstick, which is a worry.

* Her maiden involved a very twitchy couple of circuits in a bit of wind, but a nice landing into wind nonetheless. The second flight ended with a hard roll left, nose down from about 30ft. Full power and full back stick wouldn't move her out of this and she went in at full chat. The fuselage split in half, the firewall snapped and came loose, the spinner, back plate and prop were stuck at least 8" in the ground and pieces and the motor was ruined as being an radial mounted adaptor, it bent the motor bell! 5 minute epoxy, cocktail sticks and carbon fibr struts sorted out the structural repairs, but the motor and prop needed replacing. The ESC took a whack from the LiPo, but a new capacitor cost just 27p. The LiPo works but is dented and is now relegated to bench testing.
Last edited by Luke Warmwater; May 12, 2011 at 01:59 PM.
May 12, 2011, 02:18 PM
Registered User
Originally Posted by Luke Warmwater
I am using the DX6i whcih seems to default to using just the one channel for ailerons.....I guess I need to read the manual to find out how to use the 6th channel as I do for my helis. The heli models default to this (for CCPM mixing its a must).
Just to say, I have now spent 30 seconds in the manual and found it...ahem.....
May 12, 2011, 06:32 PM
Registered User
Sorry to hear your hard landing Luke hope it's better and stronger now

Anyone knows if the stock servos are digital ?
I try to setup the gyro (spartan quark) and I get a lot of noise.
Also I'm not really sure how to enable the gyro gain since my tx (JR 11x) don't give me GYRO SENS option because I select ACRO mode.
I use the Travel Adj. but I really don't like it because I can use only on position 1 value 0 to +150 and position 2 value 0 to -150
How am I going to switch off and on the gyro ?

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