4 motor watts

[Ronos]

Hi, I have the Tony Nijhuis Sunderland, running the electric 4Max set up with two 3s 5200mAh lipos, one for the outer motors and the other for the inner ones,. When I put the watt meter on the inner motors and went to full throttle both motors were putting out approx 205 watts, when I put it on the outer ones it read approx 305 watts and when I hooked it up to all four motors running just the one lipo the watt meter was reading approx 460 watts. Can someone please explain the reason in the simplest way. Thanks

[Martin Harris - Moderator]

It looks as though the additional load of running all the motors from the one battery has dropped the voltage significantly. As power (W) is derived from voltage (V) x current (I) the result will be to reduce the total power.

If you connect the second battery in parallel with the first, the voltage drop will be much less and the result should equal or be very close to the sum of the two readings.

Were the readings all taken from the same battery or was one pair connected to each battery?  If so, swap the batteries and see if the difference moves with the battery.  If so, one battery was either undercharged or is not as good as the other.  Otherwise, are the motors/props identical?  Have the ESCs both been trained to your transmitter? Have you removed the red wire from one of the ESCs?

Edited By Martin Harris on 14/09/2020 23:33:16

[Ronos]

Martin Harris, what i can tell you is all 4 motors, 4 ESC, the the 4 props are identical. The two outer props are running anti clockwise and the two inner clockwise and have removed the red wire from two of the four ESC's as the diagram on the 4Max website. I want to run two lipo's , one for the outer and one for the inner, just in case if one goes down then i might have a chance of getting it back. I will charge the lipo's up again, and see what they read and do a bit of swapping about and also run them in parallel as you suggest .

[Martin Harris - Moderator]

Do you really mean that all 4 props are identical or are two of them pushers? If the latter, it might be that despite the sizes being identical, the pitches are a little different. Swapping them with the other pair and reversing rotation of the motors before measuring again would prove this.

[Chris Walby]

Why would you be running two both inner motors and outers in a different directions. As I understood you change the prop rotation on one side to reduce yaw on the take off run. I have a couple of electric (some with counter rotating props) and IC twins and to be brutally honest it does not make that much difference if you use the rudder and don't gun the throttle on take off. In a chat with George he did specifically mention that with a couple of TN multi electric motors models that counter rotating improved the in flight characteristics (turning to starboard) compared to all motors rotating in the same direction

The lower total power will be due to reduced battery voltage as a result of battery voltage sag, try it with two batteries . Don't forget longer battery/ESC/motor leads cable resistance will suffer from I squared R losses so simply high currents have significant effect with losses and volt drop. You don't have to run the batteries in parallel just run the inner ESC's of one battery and the outer on the other battery to share the load.

Which of the ESC's have the red leads attached as there might be something going on with the ESC throttle settings + I could not find a specific diagram for your 4 motor configuration...Are you using 2 UBEC's or different throttle channels on the RX. If you have plugged the set up into a servo tester you will have inadvertently connected two red wires to the ESC's together which will cause an issue.

Either a wiring diagram of your set up posted here or phone George, after all that's one of the benefits of buying from a British supplier. The problem with this forum is that there are people with opinions that contradict the manufacturer.

[FlyinBrian]

I thought the OP stated he was using two batteries

[Ronos]

Posted by Martin Harris on 15/09/2020 01:36:56:

Do you really mean that all 4 props are identical or are two of them pushers? If the latter, it might be that despite the sizes being identical, the pitches are a little different. Swapping them with the other pair and reversing rotation of the motors before measuring again would prove this.

Two are standard and two are pushers.

[Robin Colbourne]

Posted by Chris Walby on 15/09/2020 07:11:48:

Why would you be running two both inner motors and outers in a different directions.

Chris, The A400M does this. There is an aerodynamic reason:

This counter-rotation characteristic is known as Down-Between-Engines (DBE) and the A400M will be the first aircraft ever to use such a configuration. The advantages of DBE have far-reaching effects both aerodynamically and structurally. Firstly, airflow over the wings is symmetrical, improving lift characteristics and the lateral stability of the aircraft. Secondly, DBE allows for an optimum wing design by eliminating most of the effects of torque and prop-wash on each wing, concentrating the airflow over the most efficient portion of the wing located between the engines. DBE also reduces the “critical engine” effect of severe yaw in the event of an outboard engine failure. The result allows a 17% reduction in the area of the vertical tail surface.

Further aerodynamic advantages inherent in DBE have been found to give a 4% increase in lift from the wing at slow speed, which enables, for the same total lift, a simpler, lighter flap system to be employed. As a consequence of the lessening of the aerodynamic forces applied to the flaps, the surface area of the horizontal tail-plane can also be reduced by 8%.

A lot of that won't be relevant on an electric model if all four motors are driven from the same battery.

Edited By Robin Colbourne on 15/09/2020 11:59:12

[Ronos]

What I have noticed this morning is that all 4 motors are not starting at the same time. The two outer motors which are knocking out approx 305 watts are starting on a click of the throttle and the two inner motors kick in on another click. I have them on two different channels on the RX, one in the throttle channel and the other in the aux channel.

[Colin Low 2]

RONOS, "Two are standard and two are pushers". Do you really mean pushers or opposite rotation?

Why not email George at 4-max and ask him. He actually owns and flies the original Tony Nijhuis Sunderland as featured in RCME.

Sounds like cheap batteries to me and the voltage is collapsing as mentioned by Martin.

I run a Tony Nijhuis Lanc on a single 3S5000 and can get a good 15 minutes flying on a calm day, never had any problems with batteries - 4max supplied.

[Ronos]

Posted by Colin Low 2 on 15/09/2020 12:52:08:

RONOS, "Two are standard and two are pushers". Do you really mean pushers or opposite rotation?

Why not email George at 4-max and ask him. He actually owns and flies the original Tony Nijhuis Sunderland as featured in RCME.

Sounds like cheap batteries to me and the voltage is collapsing as mentioned by Martin.

I run a Tony Nijhuis Lanc on a single 3S5000 and can get a good 15 minutes flying on a calm day, never had any problems with batteries - 4max supplied.

Hi, the set up is from 4-Max, with the same 2 standard and pusher props that George recommends. I know he runs his on one lipo and like you gets a flight time.

[Ben B]

What happens if you swap the throttle channel and the aux- could it be a scaling issue or can you run them from the same rx channel to remove that variable? What happens if you swap ESCs (is it a calibration issue). All the ESCs timed the same?

I'm trying to get my head round the pusher props. Reverse motor and put on backwards to make a reverse rotation standard? Confused!

[Martin Harris - Moderator]

I think the only time you put a prop on backwards is for a pusher motor/engine i.e. the motor/engine is pointing backwards. Reversing a propeller simply makes it produce thrust in the same direction - but horribly inefficiently.

It might be worth training the ESCs on the AUX channel separately.

Edited By Martin Harris on 15/09/2020 15:36:25

[Nigel R]

"What I have noticed this morning is that all 4 motors are not starting at the same time."

Worth recalibrating the throttle range on all four ESCs, perhaps?

The lower power motors may not be getting 100% throttle, if they are not quite calibrated the same.

[Ronos]

Posted by Martin Harris on 15/09/2020 15:34:05:

I think the only time you put a prop on backwards is for a pusher motor/engine i.e. the motor/engine is pointing backwards. Reversing a propeller simply makes it produce thrust in the same direction - but horribly inefficiently.

It might be worth training the ESCs on the AUX channel separately.

Edited By Martin Harris on 15/09/2020 15:36:25

Hello, I am not putting a prop on backwards , the set requires 2x standard props and 2x pusher props

[Ronos]

[Martin Harris - Moderator]

Posted by Ronos on 15/09/2020 16:59:51:

Posted by Martin Harris on 15/09/2020 15:34:05:

I think the only time you put a prop on backwards is for a pusher motor/engine i.e. the motor/engine is pointing backwards. Reversing a propeller simply makes it produce thrust in the same direction - but horribly inefficiently.

It might be worth training the ESCs on the AUX channel separately.

Edited By Martin Harris on 15/09/2020 15:36:25

Hello, I am not putting a prop on backwards , the set requires 2x standard props and 2x pusher props

I didn't think you were - it was Ben's confusion that I was addressing...

[PeterF]

Whenever trouble shooting electric, you need to record the Volts, Amps and Watts as well at the prop rpm, all Wattmeters I have seen display Volts and Amps. On your low watt motors, is the voltage lower on the battery, if so the rpm should be lower by the dame fraction. If the lower wattage motors have full voltage but low rpm then this is probably an ESC throttle calibration issue. If you have full voltage and full rpm on the lower wattage motors then this means that the props are not as good as the other ones, check the specs are the same, you could try reversing the prop to make sure you have the props the right way around.

Watts alone is not enough information for effective troubleshooting.

[Ronos]

Fist of all, many many thanks to all your input and knowledge. I have re-programed the four ESC,s to 4-Max re-programing card ,(let's say default settings) and after a quick test and on a not fully charged lipo, the two outer and the two inner are putting out 195 watts 10.6 v on the lipo. All four connected to one lipo are putting out 390+ watts with the same voltage on the lipo.

PeterF, I will do a better check to your recommendation, when I get a bit more time. Thanks all