Emax BL 3526/05 max cells

[Graham Bowers]

I have an old Emax BL 3526/05, 686 KV. One of the blue ones.

https://www.himodel.com/electric/EMAX_Outrunner_Brushless_Motor_Type_BL3526_04.html which indicates it's for 5S

 

I did used to run it on 5S however those LiPos are long gone - a consequence of not understanding the importance of storage voltage :-(

 

Fast forward and I now have a 6S setup using a Hacker A50 V4 at 365Kv and 16 inch prop in a Sebart model.

 

I'm now wondering if I can run the Emax  on my 6S Lipos, suitably propped down,  as I don't really want yet another set of 5S LiPos. It'd go into a hack Wotty.

 

If memory serves me well, 686 Kv at 22.2 Volts gives a no load speed of 15 229 rpm and 80% of that, when loaded, would be 12000 rpm as close as makes no difference. 

 

That's pretty close to the max speed allowed for a 12 inch APC electric prop, however an 11 inch would be well under.

 

APC 11x7 at 12000 rpm absorbs between 700W and 800W depending on airspeed, and at 6s (22v) that's 36 Amps max.

 

The motor weighs 250g so at 3W/g that'd be 750W so in the ball park.

 

I have a wattmeter to check the rough calculated numbers.

 

This seems do-able to me. Am I missing anything please?

 

 

 

[Shaun Walsh]

That motor is available in eCalc so I ran some numbers for a 6s battery and even with a 10 inch prop it was throwing up warnings about the voltage being too high and accompanying motor overtemperature unless the cooling arrangements are excellent in which case it might swing an 11x6 within the current limits for the motor.

 

The Motor Voltage is close or over to the Limit - please verify the max. allowed Motor Voltage / cell count Your defined Model Weight (incl. Drive) results in a All-up Weight less the sum of all you chosen components (Drive Weight). Verify your Model Weight and enter either your estimated All-up Weight (incl. Drive) or your basic weight (without Drive).

Battery Load: 13.16 C Voltage: 21.16 V Rated Voltage: 22.20 V Energy: 88.8 Wh Total Capacity: 4000 mAh Used Capacity: 3400 mAh min. Flight Time: 3.9 min Mixed Flight Time: 19.3 min Weight: 684 g   24.1 oz

Motor @ Optimum Efficiency Current: 61.82 A Voltage: 20.76 V Revolutions*: 12896 rpm electric Power: 1283.4 W mech. Power: 1123.9 W Efficiency: 87.6 %

Motor @ Maximum Current: 52.62 A Voltage: 20.97 V Revolutions*: 13172 rpm electric Power: 1103.7 W mech. Power: 963.8 W Efficiency: 87.3 % est. Temperature: 61 °C   142 °F   Wattmeter readings Current: 52.62 A Voltage: 21.16 V Power: 1113.4 W

Propeller Static Thrust: 3728 g   131.5 oz Revolutions*: 13172 rpm Stall Thrust: - g   - oz avail.Thrust @ 0 km/h: 3728 g avail.Thrust @ 0 mph: 131.5 oz Pitch Speed: 120 km/h   75 mph Tip Speed: 694 km/h   431 mph specific Thrust: 3.38 g/W   0.12 oz/W

Total Drive Drive Weight: 1143 g   40.3 oz Power-Weight: 1374 W/kg   624 W/lb Thrust-Weight: 4.39 : 1 Current @ max: 52.62 A P(in) @ max: 1168.3 W P(out) @ max: 963.8 W Efficiency @ max: 82.5 % Torque: 0.70 Nm   0.52 lbf.ft Climb Capacity: 5496 m   18031 ft

Airplane All-up Weight: 850 g   30 oz Wing Load: 17.0 g/dm²   5.6 oz/ft² Cubic Wing Load: 2.4   est. Stall Speed: 20 km/h   12 mph est. Speed (level): 103 km/h   64 mph est. Speed (vertical): 85 km/h   53 mph est. rate of climb: 23.6 m/s ( ~85...90° ) 4652 ft/min

[Shaun Walsh]

If you're going to put it in a Wot 4:

It will go like a bat out of hell.

I would greatly improve the cowl ventilation or just leave the cowl off.

[Graham Bowers]

Thanks for that @Shaun Walsh

Seems like it's not a no-no so proceeding cautiously has some potential.

If it came to pass the actual current on a test bench was over 40 Amps or so, I'd prop it down anyway, probably on pitch in order to slow it down a bit.

I bought the Wotty used and have re-purposed the Irvine 53 it came with, it didn't come with a cowl anyway ;-)

 

[Shaun Walsh]

10 minutes ago, Graham Bowers said:

Thanks for that @Shaun Walsh

Seems like it's not a no-no so proceeding cautiously has some potential.

If it came to pass the actual current on a test bench was over 40 Amps or so, I'd prop it down anyway, probably on pitch in order to slow it down a bit.

I bought the Wotty used and have re-purposed the Irvine 53 it came with, it didn't come with a cowl anyway 😉

 

If you want to keep below 40 Amps, these are the results for a 10x5 APC-E prop

Remarks:

The Motor Voltage is close or over to the Limit - please verify the max. allowed Motor Voltage / cell count Running below the Current of optimal Efficiency is inefficient. Use a smaller motor

Battery Load: 7.84 C Voltage: 21.58 V Rated Voltage: 22.20 V Energy: 88.8 Wh Total Capacity: 4000 mAh Used Capacity: 3400 mAh min. Flight Time: 6.5 min Mixed Flight Time: 12.3 min Weight: 684 g   24.1 oz

Motor @ Optimum Efficiency Current: 61.82 A Voltage: 20.76 V Revolutions*: 12896 rpm electric Power: 1283.4 W mech. Power: 1123.9 W Efficiency: 87.6 %

Motor @ Maximum Current: 31.34 A Voltage: 21.47 V Revolutions*: 13810 rpm electric Power: 673.0 W mech. Power: 563.5 W Efficiency: 83.7 % est. Temperature: 53 °C   127 °F   Wattmeter readings Current: 31.34 A Voltage: 21.58 V Power: 676.3 W

Propeller Static Thrust: 2566 g   90.5 oz Revolutions*: 13810 rpm Stall Thrust: - g   - oz avail.Thrust @ 0 km/h: 2566 g avail.Thrust @ 0 mph: 90.5 oz Pitch Speed: 105 km/h   65 mph Tip Speed: 661 km/h   411 mph specific Thrust: 3.81 g/W   0.13 oz/W

Total Drive Drive Weight: 1143 g   40.3 oz Power-Weight: 348 W/kg   158 W/lb Thrust-Weight: 1.28 : 1 Current @ max: 31.34 A P(in) @ max: 695.9 W P(out) @ max: 563.5 W Efficiency @ max: 81.0 % Torque: 0.39 Nm   0.29 lbf.ft Climb Capacity: 3562 m   11686 ft

Airplane All-up Weight: 2000 g   70.5 oz Wing Load: 40.0 g/dm²   13.1 oz/ft² Cubic Wing Load: 5.7   est. Stall Speed: 30 km/h   19 mph est. Speed (level): 88 km/h   55 mph est. Speed (vertical): 27 km/h   17 mph est. rate of climb: 9.1 m/s ( ~75...80° ) 1795 ft/min