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Old Jun 27, 2001, 12:16 AM
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Aero-BearAZ's Avatar
Mesa, AZ USA
Joined Mar 2001
86 Posts
Motors for ME BF-110

Hi,

I didn't get any hits on this question in the Scale forum so I thought I'd try it here. Can anyone help me out here please?

I'm in need of advice on what to power my new Me-110 twin with. I don't have E-calc or Moto-calc as of yet so I don't have a way of figuring it just yet. If I give some specs can someone possibly point me in the right direction?
  • Span is 67"
  • length is 50.5"
  • area is 688 sq in
  • wing loading is 23 oz sq ft
  • weight is 105 oz

These specs are right off the box so there will be some variance in the weight and wing loading. I tend to build light tho so it should be within reason.

This is a German twin fighter/bomber design so I'd like to have scale to aerobatic performance.

Thanks in advance!

Tom Schumacher
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Old Jun 27, 2001, 01:03 AM
Rod
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Canada, BC, Kelowna
Joined Nov 1999
920 Posts
Tom, I just ran some numbers on E-Calc and it looks like 2 -Astro 05G motors connected in series would draw about 21 amps driving 9" x 6" props. This would give you 70 watts/pound. Climb rate indicated is 966'/min @ 38 degrees, or maximum climb rate of 1336i/min @27 degrees. A cheaper way (and probably just as effective), to go would be Kyosho Atomic Force or Endoplasma motors driving Master Airscrew Gear boxes. Ivan Petegrew form Chilliwack BC, Canada has done some wonderfull things with these car motors. His latest is a 12 foot span Martin Mars Flying Boat using Goldfire and Mabuchi 550 motors with MAS type gearboxes. His fleet also includes a eight foot span 4 motor Lancaster, DH Mosquito, DH Rapide (that Todd Long now owns), and a number of other multi engine models.
I hope this gives you some food for thought.
Rod
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Old Jun 27, 2001, 02:17 AM
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Brad Trent's Avatar
Canada, BC, Abbotsford
Joined Mar 1999
1,613 Posts
Tom:
I agree with Rod, any of the motors he listed would work well in series on 16 to 20 cells, depending on how much ZOOM factor you want. All of Ivan's ships use 9 cells per motor, and fly incredibly well. This past Sun. he flew the 120" Martin Mars at the RAMS electric fly-in, using a bungee launch, and shooting touch and goes on the wet grass! this is a 12 lb flying boat with no landing gear, so it's quite a feat!

I've flown a 56" span twin on 2xMag.Mayhem on 20 cells, got great results, but would probably use Atomic Force motors if I did it again, having used them in other planes since the twin,and find them better for duration at the same power level. You will need an ESC rated for at least 20 cells and 45A or more, to give a little safety factor.

Your project sounds like a winner; I should get back to work on my similar size A26 Invader, to keep the balance of power equal in the modeling world.

Brad.
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Old Jun 27, 2001, 08:49 PM
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Aero-BearAZ's Avatar
Mesa, AZ USA
Joined Mar 2001
86 Posts
Thanks guys,

I just got my copy of Ecalc, but I'm still a little unsure. I did some searching for info about the Endoplasma, I found the constants for it and plugged them into Ecalc. From the other threads on the Endo they said that it likes to run around 30 amps. Also just for the fun of it I ran an aveox 1010/2y. And also the 1010/2yP37. Here is what I got...

Code:
Plane          ME BF-110    ME BF-110    ME BF-110    ME BF-110    ME BF-110   
   Setup                                                                        
                                                                                
 Prop KRPM           9.97        10.02         9.70         7.51         8.73   
 Motor KRPM         29.92        30.06        29.10        27.79        26.19   
 Prop Watts        203          267          187          188          171      
 Motor Watts       253          311          234          218          215      
 Motor Amps         29.6         28.8         28.2         22.1         28.5    
 Motor Volts         8.5         10.8          8.3          9.9          7.5    
                                                                                
 Battery Amps       29.6         28.8         28.2         22.1         28.5    
*MAH              2050         2050         3000         2272         2272      
 Minutes             3.9          4.1          6.1          5.9          4.5    
 % Throttle        100          100          100          100          100      
 % System Eff.      69           74           66           76           67      
 % Motor Eff.       85           91           84           91           84      
                                                                                
*Prop Diameter       9.00        10.00         9.00        11.00        10.00   
*Prop Pitch          7.00         6.00         7.00         7.00         6.00   
 Pitch MPH          63           54           62           49           48      
                                                                                
*Plane oz          105          113          105          113          105      
 Wing sq.in.       688          688          688          688          688      
 Wing oz/sqft       22.0         23.7         22.0         23.7         22.0    
 Drag coeff.         0.058        0.058        0.058        0.058        0.058  
 Watts/pound        77           88           71           62           65      
                                                                                
 Climb ft/min     1287         1664         1170         1162         1049      
 Climb angle        23           31           21           21           19      
 Max ft/min       1301         1671         1193         1209         1121      
   @ angle          26           33           24           25           25      
 Max climb ft     5137         6781         7235         7085         5093      
 Cruise Minutes      8.5         10.5         12.5         12.6          9.7    
 Stall MPH          18           19           18           19           18      
 Max. MPH           60           61           59           55           53      
 Speed MPH          37           37           37           37           37      
                                                                                
 Thrust oz          58           74           54           57           50      
 Drag oz            17           17           17           17           17      
                                                                                
*Motor          Endoplasma   1010/2Y      Endoplasma   1010/2Y/P37  Endoplasma  
   Type                                                                         
*Mfr            Kyosho       AVEOX        Kyosho       AVEOX        Kyosho      
*Kv               3790         2978         3790         2978         3790      
*Rm                 22           24           22           24           22      
*Io                  2.5          0.9          2.5          0.9          2.5    
 Km                  2.40         2.90         2.40         2.90         2.40   
*Gearing             3.00         3.00         3.00         3.70         3.00   
 Motor Config.  2S           2S           2S           2S           2S          
                                                                                
*Prop           APC  9 * 7   APC  9 * 7   APC  9 * 7   APC 11 * 7   APC 10 * 6  
   Type                                                                         
*K prop              1.16         1.16         1.16         1.09         1.10   
*K pitch             0.30         0.30         0.30         0.10         0.20   
 K eff               1.00         1.00         1.00         1.00         1.00   
                                                                                
*Cell Type      RC-2000*     RC-2000*     =3000mAH     CP-2400SCR   CP-2400SCR  
*Cell Count         16           20           16           20           16      
 Pack Wgt oz        32.8         41.0         32.8         41.0         32.8    
*Cell Volts          1.25         1.25         1.25         1.12         1.12   
*Cell mohm           5.2          5.2          6.6          5.3          5.3    
 ESC mohm           15           15           15           15           15      
                                                                                
 ElectriCalc  06-27-2001    02:36:43
I'm thinking that with the Endo I might use a Modelairtech belt drive unit. Are they any good?

*If* these figures look acurate to you the only question I have is what ESC should I use that will handle close to 60 amps cont? I was thinking maybe Jeti 60 or 80. What do you think?
Also, what would be the maximum watts for this aveox?

Tom
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Old Jun 28, 2001, 12:30 AM
Rod
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Canada, BC, Kelowna
Joined Nov 1999
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Tom, Why would you want a 60 amp+ ESC? If you run the motors in series (the only way for anything larger than a 400), your battery draw is approximately 30 amps. A 35 or 40 amp ESC would seem to fill the bill. With the Endoplasma you may want to go to a higher gear Ratio. The GP box with a 10 tooth pinion would give you a 4.6:1 ratio. Or the MEC boxes will give you 6:1 or higher. Try the Atomic Force, it will work with a lower gear ratio than the Endoplasma.
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Old Jun 28, 2001, 01:09 AM
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Aero-BearAZ's Avatar
Mesa, AZ USA
Joined Mar 2001
86 Posts
Rod,

You're right, I forgot the motors were in series. I'm still new to this electric stuff so sometimes I'm a little "thick headed". Having said that you're going to have to forgive me here for asking this next question...

Why would I need such a large gear reduction? From what I can see in Ecalc, if I plug in a gear reduction of 4.6:1 (or higher), in order to get my watts per pound up to an acceptable level I need to be swinging a 12" (or larger) prop. The max that I can swing will be 11" because of clearance issues with the prop and fuse. Am I missing something here?

Do you know what the numbers are for the Atomic Force motor?

thanks again

Tom
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Old Jun 28, 2001, 01:59 AM
Rod
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Canada, BC, Kelowna
Joined Nov 1999
920 Posts
The Atomic Force numbers are:
RPM/v 3535
Io 2.5
Rm (mohm) 25
As a general statement motors with a lower RPM/v have more torque and therefore handle a lower ratio gear box. High RPM/v (or low wind motors) have less torque and therefore need a higher gear ratio box to develope sufficient power. Try it out on eCalc An Atomic Force will draw the same amps driving the same prop using a 6:1 box as the Endoplasma will draw using a 6.5:1 box.
Lower wind motors are "Hotter" that high wind motors. They draw a high current and generally use a gearbox, wheresas high wind motors draw a lower current (with the same cell count), and are more suitable for direct drive or a lower ratio gearbox. You can see this on the Astro Flight site. Their FAI motors are low wind motors,and draw high currents, wheras their sport motors are higher wind and work at lower currents. One issue to look out for, is the current that any combination of motor/gear ratio/cell count/ prop size will draw. Motors are only able to run at a maximum amp draw, otherwise the smoke will release and its repair time. So watch out for the maximum current -- Astro 05 Sport are spected at 30 amp Max. (they are rugged and will take more), whereas a can 600 maximum is 25 amps. A Speed 400 should be set up to run at about 10 amp max. -- static. And so on--.
Hope I have not confused you too much.
Rod

[This message has been edited by Rod (edited 06-28-2001).]
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