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Other › Tango motor RPM
03-06-2008 01:57 PM  10 years agoPost 1
fergus

rrKey Veteran

Ireland

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Anyone got the numbers for max, best efficiency and best power rpm for the Kontronik Tango 45-08? Do they need to be on 10s for best performance?

Regards

Fergus

Regards

Fergus

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03-07-2008 05:24 PM  10 years agoPost 2
JKos

rrProfessor

Redondo Beach, CA

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For a given motor, the max efficiency occurs when the iron losses equal the copper losses. In simplistic terms, iron losses scale linearly with voltage and the motor's Io. Copper losses scale with current squared and linearly with the motor's Rm.

Therefore, for a given voltage, there is a power level at which the motor operates at maximum efficiency. For a given power level, there is a voltage and current at which the motor operates at maximum efficiency. A parameter (voltage, current, power) must be chosen before a max efficiency point can be found.

What cell count and/or power level are you interested in?

According to KC's Power_System_Comparison spreadsheet, the motor RPM at maximum efficiency is as follows for the Tango 45-08.

11S: 32,236
10S: 29,273
9S: 26,311
8S: 23,350

- John

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03-07-2008 06:21 PM  10 years agoPost 3
fergus

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Ireland

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Thanks for the reply. I am running 10s A123 so you could say 8s lipo on the 45-08 with a kontronik 55-10-32. I am trying to establish is it better to gear for a given headspeed through the governor mode in the ESC or mechanically by changing the gear ratio. I am aiming for a headspeed around 2300rpm. I am acheiving this on a 16tooth pinion (main is 153 tooth) and running the governor at 80%.

Wondering if going 17 tooth and lower Gov setting is a more powerfull option. As it will give the gov more headroom.

I am pulling 70amp peaks and about 20 ish in the hover. I want a good balance of power to efficiency and was wondering if my pack voltage was putting the motor in this region or not!

Regards

Fergus

Regards

Fergus

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03-07-2008 06:45 PM  10 years agoPost 4
JKos

rrProfessor

Redondo Beach, CA

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According to the spreadsheet, you will lose a few percent efficiency by going up on the pinion. This indeed follows the common rule of thumb that increasing the pinion decreases flight time even at the same headspeed.

In general, you will never gain efficiency by going up in pinion.

- John

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03-07-2008 08:08 PM  10 years agoPost 5
fergus

rrKey Veteran

Ireland

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Thanks for the detailed explanation John.

The best test of all is to go out and fly it I suppose but the weather here is terrible.

The system as is is achieving the desired headspeed but is bogging at the extremes of pitch (+12 and without cyclic) so going up a pinion is the only real option. I realise this will increase the current draw and shorten flight time. I punched the numbers in the spreadsheet and it advised a pinion of 16.5!! so its a toss up really.
I have a reasonable idea of power, voltage, current and Kv but how the governor works is a bit of a mystery to me. This is why I wondered if a lower gov setting would take the motor out of its 'ideal' rpm for power with reasonable efficiency.

The setup I'm after is something comparable to 6s lipo for power but due to the lower capacity A123 cells I was forced to go higher voltage - hence the 10s setup.

Its in a Logo 500 by the way but you probably guessed that.

Thanks again

Regards

Fergus

Regards

Fergus

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03-07-2008 08:11 PM  10 years agoPost 6
JKos

rrProfessor

Redondo Beach, CA

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Indeed, trying the 17t should be of little risk if your motor and ESC are currently doing just fine, which I would have to guess they are based on your equipment choice (cool running motor and efficient partial-throttle ESC).

BTW, what flight times are you getting?

- John

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03-07-2008 08:29 PM  10 years agoPost 7
fergus

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Ireland

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yes motor and esc are nice and cool but the system still bogs. Does that mean at 80% the esc has not got enough headroom to maintain headspeed?

I have read the Kontronik gov calculates headspeed based on pack voltage. The A123 packs tend to settle around 33volts after charging but drop and hold 28volts under load until the pack is drained.

I can't get my head around why the headspeed bogs when the current draw is within the limits of the pack and the ESC.

Regards

Fergus

EDIT: currently 5.30 mins with a little reserve before the pack dumps.
But its hard to nail this down as my flying is a bit all over the place from circuits and loops to some heavier stuff when the nerves are up to it .. lol

Regards

Fergus

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03-07-2008 08:43 PM  10 years agoPost 8
JKos

rrProfessor

Redondo Beach, CA

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> Does that mean at 80% the esc has not got enough headroom to
> maintain headspeed?

Yes, correct.

> I can't get my head around why the headspeed bogs when the current
> draw is within the limits of the pack and the ESC.

The voltage of the pack still goes down as load increases. So, pack voltage going down as well as increased losses in the rest of the electrical system (wiring, ESC, motor) means the motor RPM must decrease once the ESC hits 100% throttle.

- John

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03-07-2008 08:45 PM  10 years agoPost 9
fergus

rrKey Veteran

Ireland

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Thanks for your help John

Regards

Fergus

Regards

Fergus

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03-07-2008 09:23 PM  10 years agoPost 10
fergus

rrKey Veteran

Ireland

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Another question if I may:
This indeed follows the common rule of thumb that increasing the pinion decreases flight time even at the same headspeed.
Does it then follow that a higher Kv motor e.g tango 45-09 and a lower pinion will give better results. The voltage will remain unchanged as will the power requirement. I knew that I must over gear with A123 cells. I am still kind of confused if overgearing with the electronics is better than gearing mechanically.

Fergus

Regards

Fergus

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03-10-2008 05:07 AM  10 years agoPost 11
JKos

rrProfessor

Redondo Beach, CA

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> Does it then follow that a higher Kv motor e.g tango 45-09 and a
> lower pinion will give better results.

Not necessarily. Each motor is a different wind and thus has different motor constants. There's certainly more to it than all this as well. All the other aspects of motor construction play part as well. Two motors with identical electrical constants can end up worlds apart in real world use.

- John

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03-18-2008 08:45 PM  10 years agoPost 12
mikeflyz

rrApprentice

Westlake Village, CA

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If staying with an inrunner, a lower pole/slot count motor with your desired Kv may do the trick. You'll have to be careful not to exceed the current limitation of the ESC. The total efficiency will go down a little as well.

Mike
MA Fury Extreme, JetCopter SX

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06-25-2008 03:49 AM  9 years agoPost 13
fergus

rrKey Veteran

Ireland

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Just as an update on the Tango in the Logo 500 with 10s A123. I went to 17tooth and lowered the governor % but I am still getting bogging on the Tango (minimum voltage is 28volts). This is especially noticable as my flying and nerve get more adventurous. Flight times are down to between 4.30 and 5 minutes.

Can anyone make a suggestion for a more powerfull motor with a similar or slightly higher Kv (currently 800)

I have just done some checking and have found the following options:

Century 650A plus (8 pole 2500watt 800Kv 340g)
Zpower Z50 A (As above)
Neu 1912H/1Y (8 pole 2500watt 825Kv 405g)

The specs for each seem very similar to the Tango. As the equivilant of 8s lipo is kind of in no mans land (most people flying 6s or 10slipo) it is hard to find info on tried and tested setups.

The other option which could be considered is going 12s A123 and using one of the 'off the shelf' 10s Logo600 lipo setups.

From what I have posted so far I would welcome suggestions to help improve power to the current setup.

Regards

Fergus

p.s heatsink will be added to the Jazz

Regards

Fergus

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07-08-2008 04:09 PM  9 years agoPost 14
Derkein

rrNovice

Cremona, Italy

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Sometimes I've used ASPA spreadsheet to choice between different configuration of battery/motor/pinion/blades.
You can find it to the following link.

Download page

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