Larry3215

My Feedback: (2)

I recently purchaced a Mega 22/45/3 and was disapointed to find that MotoCalc's predictions for current draw and prop RPM are not even close. It turns out that MotoCalc has the RPM/Volt numbers based on a 22/45/3E (energy star version). And then they changed those numbers based on test data from the guys at Modelair-Tech http://www.modelairtech.com/combos.html .

I have a Super Watt meter and can measure battery volts, current draw and prop RMP reasonably close.

MotoCalc predictions with motor constant of 720 (modified constant)
12 cells, direct drive, 11x7 APC E prop - 23.2 A 8388 RPM
12 cells, direct drive, 12X8 APC E prop - 31.1 A 7680 RPM

MotoCalc predictions with Mega's stated constant of 1000
12 cells, direct drive, 11x7 APC E prop - 40.2 A 9460 RPM
12 cells, direct drive, 12X8 APC E prop - 48.9 A 8214 RPM

My tests: (after aprox 30 seconds of running on fresh charge)
12 cells, direct drive, 11x7 APC E prop - 33.1 A 9000 RPM
12 cells, direct drive, 12X8 APC E prop - 40.5 A 8000 RPM

I don't have a good way to measure no load rmp or very low resistance. I'll have to try to think of a way. I am going to play with the constants in MotoCalc and see if I can get the predictions closer to reality. I also have a gear drive from Model Electronics corp. I am going to put it on and test three bigger props - 15x10, 17x10 and 20x13 with 12 and 18 cell packs. If any one is interested I'll post the data.

Has anyone run these number on Electra Calc ( or what ever the other software package is)?

Larry

realwiz

My Feedback: (9)

I have a Mega 22/45/3 as well. Currently it's in a Eagle 2 Trainer. I was wondering what plane you have your motor in. I'm looking to find a hotter plane to put it in. If you want I can run some numbers for you on mine with a gearbox.

Larry3215

My Feedback: (2)

I would love to see some more real world numbers. I've used mine in two scratch built planes so far.

A 54" span delta wing (made from all blue fan fold foam) with an all up weight just over 4 lbs, direct drive on 12 3000 ma sc cells. Flies prety well. Short take offs, 8 to 10 minutes if I dink around with a few touch n goes and 5 to 6 at close to full throttle with good verticle.

The other plane WAS an all coroplast SPAD biplane. 54" span, 11 lbs all up, 18 cells, 3.4/1 ratio with 20x13 prop. Only got to go once around the patern befor I crashed it. I hit the flap knob while fumbling with a trim change and couldn't pull out of the dive soon enough. Fuse broke in half behind the battery pack. Take off was very short with strong climb out. Didn't get any other numbers tho.

I am building a new 48" span blue foam 3D type machine now. When I get the motor mounted I'll run some more test with different props and ratios and post the data. I'm planning on using 18 to 20 cells and hope to be able to hover.

I wonder if ElectriCalc is any better than MotoCalc on its predictions?

Larry

realwiz

My Feedback: (9)

I haven't used Electricalc, and really haven't spent much time with Motocalc either. I flew my plane today and recorded some numbers.

22/45/3 TMM 40amp esc w/ 1.7:1 superbox 16 x 2400mah cells

12x8 APC-E prop 8200rpm at 25amps

13x8 APC prop 8000rpm (didn't record amps)

According to ThrustHP Calculator the 12x8 prop should give 4.18lbs of thrust at 62mph while the 13x8 should give 5.48lbs at 60mph. I did notice the plane had more authority with the 13x8. I'm still looking for more, especially since this motor can handle a lot more amperage. I'd like to go to a larger prop, but I don't have the clearance, so I'm looking to go to a three bladed prop, but haven't figured out which prop to use.

Let me know how your 3d foam plane works out.