First taste of the sky

[toto]

I've just tuned back into this post as I was out at the shed.

 

I have been bust gathering data from my Watt meter for scenario's running both 4s and 6s batteries.

 

I will provide all known data with the exception of the full weight which ..... I know we need .... I have SWMBO looking out the luggage scales as we speak.

 

I am expecting a delivery from our local Indian ..... scrum scrum ..... so could be pulled away mid post at any point ...... 😄

 

In fact ...... I will post up the details with supporting images once I've eaten ... that way we are guaranteed everything ( with the exception of the weight ) on one post ..... much easier.

 

I'll be back.

 

toto 

[aidan mcatamney]

3 minutes ago, toto said:

I've just tuned back into this post as I was out at the shed.

 

I have been bust gathering data from my Watt meter for scenario's running both 4s and 6s batteries.

 

I will provide all known data with the exception of the full weight which ..... I know we need .... I have SWMBO looking out the luggage scales as we speak.

 

I am expecting a delivery from our local Indian ..... scrum scrum ..... so could be pulled away mid post at any point ...... 😄

 

In fact ...... I will post up the details with supporting images once I've eaten ... that way we are guaranteed everything ( with the exception of the weight ) on one post ..... much easier.

 

I'll be back.

 

toto 

Enjoy your Indian Toto

[David Davis 2]

6 minutes ago, aidan mcatamney said:

Enjoy your Indian Toto

 

One of the few things I miss about England, that and real ale and meat pies in pubs!

[aidan mcatamney]

9 minutes ago, David Davis 2 said:

 

One of the few things I miss about England, that and real ale and meat pies in pubs!

All good stuff David. 

[Peter Jenkins]

1 hour ago, David Davis said:

For a model like this I think you need about 80 Watts per lb.

I have to differ as 100 W/lb is a much better place to be even for a trainer.  You can always turn down the throttle stick max movement to provide a lesser power rating but then again you should learn how to use the throttle from the word go.  Full size is not taught on very low powered aircraft that are difficult to get a decent climb rate with full throttle.  The throttle is not an on/off switch although I know quite a few who treat it that way.  I hope your instructor tells you to keep both sticks under your thumbs, or finger and thumb, at all times when you are flying.

 

You won't have the noise of an IC engine to help you decide how much power you have selected.  To overcome this problem, I found that my Tx had a stick alert that allowed me to set a beep when I was at my "cruising speed" setting.  That way, you know when you are at that setting without having to look down at the Tx.

[Outrunner]

When you static test your model with a 6s lipo make sure everything is strapped down well as it will blow the contents of you shed away.

Seriously though it will be producing a lot of power so start with a small prop to take the first meter readings and increase the prop sizes to find out were the limits are.

My gut feeling is 4s should be plenty of power but you just need to increase the prop pitch to give it more speed without overloading your setup.

Remember your Wattmeter is your friend to successful electric flight.

Good luck.

[toto]

Ok .... we have ....

 

An overland thumper V3 .... 4260 / 06 500kV motor

 

 

An overlander XP2 60A ESC

 

 

A 12 x 8 prop

 

that's the constants for now 

 

test one consisted of a Voltz lipo 4s 50C 14.8 volt 5000mah battery.

 

 

When I plugged in the Watt meter ..... I got the following readings without activating the motor .....

 

00.00 A

16.66 V

185.0 W

0.0 W

 

under full power I got the following ....

 

12.24 A

15.95 V

195.9 W

 

21. wh

15.05 AP

15.85 wh

240.3 W

 

Then I set up for battery no 2 which is a Voltz lipo 6s 50C 22.2 v 4800 mah battery.

 

When I plugged in the Watt meter, I got the following readings without activating the motor .....

 

oo.oo A

24.70 V

missed this

o.oo w

 

Under full power I got the following ....

 

2.8 wh

21.23AP

0.124 ah

492.9w

 

 

I think I will do a repeat of both of these as I don't trust what I am recording here.

 

I'll be back .....

 

toto

 

 

 

[toto]

OK ..... the results are back in. Please ignore the previous. I think I have a far better recorded set this time around.

 

First up ... under the Voltz 4s 50C 14.8V 5000 mah Lipo battery

 

The readings on start up were as follows ....

 

1. 00.00 A

2. 16.49 V

3. (a) 182.9 WP

    (b) 00.00 AH

    (c) 00.00 WH

    (d) 11.09 AP

    (e) 16.48 WM

4. 00.00W

 

The above readings are reading from left to right and top to bottom of the Watt meter

 

One initialising the motor to full throttle, the readings were as follows......

 

1. 12.24 A

2. 15.85 V

3. (a) 225.0 WP

    (b) 0.12 AH

    (c) 2.2 WH

    (d) 13.98 AP

    (e) 15.73 VM

4. 192.50 W 

 

Next up was the Voltz 6s 50C 4800mah 22.2v battery

 

The readings on start up were as follows ....

 

1. 00.00 A

2. 24.55 V

3. (a) 271.1 WP

    (b) 00.00 AH

    (c) 00.00 WH

    (d) 11.07 AP

    (e) 24.50 WM

4. 00.00W

 

One initialising the motor to full throttle, the readings were as follows......

 

1. 22.13 A

2. 22.84 V

3. (a) 534.5 WP

    (b) 0.346 AH

    (c) 5.4 WH

    (d) 22.97 AP

    (e) 22.45 VM

4. 461.7 W 

 

and there we have it  ............. hot off the press. I'm still working on getting an accurate fully loaded weight .... I'll come back as soon as I can with that.

 for the moment .... the destructions from the manufacturer give a " flying weight of between 2600 - 2800 g .... so .... 2.6 to 2.8 KG.

cheers for now

 

toto

Edited November 5, 2023 by toto

[John Muir]

460W still isn't a huge amount of power but considering you flew it on less than 200W, it's going to seem fantastic! I'd order a 12x10 prop for it which will produce a little bit more grunt and try that. You've got plenty of headroom on the setup by the looks of things.

[Philip Lewis 3]

What it really needs is a bigger prop, 4 cells is plenty for a trainer that size but would need a much larger prop, if ground clearance is as problem then you don't have much other choice than using voltage to up the RPM.

[toto]

Hi Philip,

 

using the prop that is already on, I have about an inch and a half ground clearance ..... not much so the bigger battery may have to be the way to go. 

 

I'm hoping that based on the figures that I have supplied above ..... and once I have a more accurate all in weight, that using the bigger battery wont put the motor or ESC at risk.

 

All will come out in the wash as they say.

 

cheers

 

toto

[GrumpyGnome]

4S should surely be enough for a trainer..... I had a foamy F4U about the same weight on 4S that performed extremely well.

 

Given the motor you have, seems your best option is your 6S packs....... although they'll make your plane heavier and faster.

 

In future, I'd suggest taking advice on motors from the forum, rather than a retailer (advice may well be to talk to George at 4-max...).

[Peter Jenkins]

Toto

 

Just record amps and watts.  No other figures are necessary.  Volts can be derived by dividing watts by amps.

 

For a 4 lb all up weight 400 watts is good.

500 watts for a 5 lb model etc.

If the 12x8 isn't producing the power try a 12x10 and even a 12 x 12.  Unlike an IC engine an electric motor can turn off in flight or, better still, have a very low idle rpm of say 400.  So having a high pitch prop won't cause landing difficulties as it would with an IC engine idling at 2,000+ rpm on a 40 size engine.

[toto]

Hi Peter,

 

I have just ordered some 12 x 10's so when they come I'll run the Watt Meter over the set up again. Should be mid week.

 

Cheers

 

Toto

[Philip Lewis 3]

Increasing the pitch isn't really the answer, yes it will up the amps but what it is really trying to do is increase the speed, a trainer really shouldn't be flown fast, far better to stick with the 8" pitch and increase the diameter if you can even if that means making the UC taller, you also get a bigger punch out of trouble with a lower pitched prop, a higher pitched prop at low speeds is pretty much stalled so and increase in amps yes but an increase in power not really. 

 

That said as you've ordered it try it and like as already said 6 cells is already giving you well overtwice as much power as you already flew it on which should be plenty.

Edited November 5, 2023 by Philip Lewis 3

[Learner]

 Just buy the right motor to run on 4 cells with a 12 x 8 prop.

[David Davis 2]

So, ignoring for the moment the differing points of view offered here, the facts are as follows. Your existing power train produced 192.5 watts at full power on a 4S LiPo. Given that your model weighs between 2.6 and 2.8kgs that is about 6lbs in Imperial measurements.

 

Divide 192.5 by 6 and the result is 32.083, so your existing set-up is producing 32 watts per lbs. This is significantly less than my advised 80 watts per lb or Peter Jenkins 100 watts per lb, in fact I'm surprised it flew at all on so little power when 50 watts per lb is generally recommended for slow-flying vintage models! If my calculations are incorrect, doubtless I will be advised by those for whom mathematics is a more comfortable subject!

 

Given that my Telemaster 40s which were larger trainers and the same weight as your Domino flew on 4S, there's no reason why your model should not fly on a 4S LiPo, you just need a larger prop to get the the power you require. You've ordered some 12 x 10s which will make a difference. I will be interested to see the results.

Edited November 6, 2023 by David Davis 2

[leccyflyer]

The motor that  Toto pictured has printed on it- props from 15". The limiting factor in this set-up is the available prop clearance. If that set up could take a 14"x7" prop it would likely be perfect with the 4s1p 5000mah battery, but that isn't an option, due to the limited prop clearance as described. I'm surprised that the model flew as well as Toto described, given the 200 watts that the motor was producing, but clearly it did fly, multiple times.

 

You don't actually need 100w/lb for a high wing trainer , back in the day that the rule of thumb was made that was sufficient power to fly most sports models and you could manage with considerably less than that for the job a trainer needs to do. 500w ought to be able to fly a 6lb trainer nicely. Bottom line is that the motor, with that low kv, is not being worked anywhere near optimally with that 12x8" prop on a 4s1p pack-it is intended to use a larger diameter prop. I dare say this is yet another case where a much less popular 5s1p 5000mah pack would be the sweet spot for a battery, with a 13x8" prop, though the prop clearance would be a concern. 

[toto]

So,

 

Would the increase in power from my 6s put the motor or ESC at risk ? Maybe couples with a smaller prop?

Edited November 6, 2023 by toto

[leccyflyer]

You have lots of headroom with a current draw of just 22amps using your 6s1p 4800mah pack and that 60amp ESC - it should be good for at least 50amps. The last thing you need here though is a smaller prop 🙂.

Edited November 6, 2023 by leccyflyer

[toto]

Ok .... so leave the prop as it is and use the 6s.

 

The current prop only has one and a half inch ground clearance so I think that is maxed out on prop size. The change to the 6s makes more sense as long as there is no risk of the magic blue smoke. 

 

I get that this 6s is giving twice the power but my throttle can go down as well as up ........ otherwise it would be off like a scalded cat.

 

Thanks to all the above in responding to this. It's really appreciated. 

[leccyflyer]

For the equipment you have -given that most important physical restriction on prop size - your best bet to to try the model on your 6s1p 4800mah packs with the existing prop. The more usual method of optimising your power train would be to experiment with larger diameter props, which is an option that isn't really open to you. Try it with what you have before going to the expense of swapping motors, but by all means experiment with pitchier props, within the prop diameter constraint that you have - be aware though that a 12x10" might give more watts, but it will be more about increasing the top speed of the model and a less pitchy prop is somewhat nice to have for the take off run.

[leccyflyer]

Of course it's vital that you check and ensure that the model is balanced correctly with the larger pack - that should go without saying.

[Learner]

Whats the weight difference between the 4s and 6s batteries?

[toto]

Hi Learner ..... no idea but I'll weight them tonight when I'm back in the shed. I have a set of electrical scales.

 

I'd be surprised if there is much of a difference as the physical size is there or there about. They both weigh the size of your average small family car ....

 

Just to clarify .... which part of the prop number ..... 12 x 10 ...refers to pitch again. I'm assuming the 12 bit refers to the length ?

 

Cheers

 

Toto