Seagull 63" SparrowHawk ---- Electric conversion

Hi All,
Just starting this thread to solicit help & document my activities to get my new Seagull SparrowHawk (Electric version) to it's maiden flight and (hopefully) beyond.
This way we will hopefully supplement Beard's great Xmas build thread without contaminating it.
As a start, I hope to provide, 'wattmeter' test data from initial ESC, Battery, Prop combination ground runs over the weekend.
Thanks

Ok -- So I did my first "non-scientific" power system test measurements on the NTM PropDrive 50-50 motor in the SparrowHawk today.
Please just bear in mind that:-
1. I have never had a fixed wing aircraft/motor combo quite this big before
2. I have never used a Watt meter before, and
3. I was rather conscious that the ESC (a Pulso DLU70+ opto) might have been a bit under spec for the job in hand -- but it was biggest ESC I had available today.

As a bit of a learning experience for myself, I thought I would try three different batteries (3S, 4s & 6S) in that order.
The batteries were only at about 50% charge (3.85v/cell (storage charge)) but, as I am just a virgin at this, I thought anything that could help this go gently and safely would help.
To shakedown the test setup (& to give me a warm feeling that I was doing approximately the right thing), I decided to start with, I would perform the measurements with the prop. OFF. I guess the measured values of volts, amps and watts in this configuration are not particularly useful however, it did put me 'emotionally' in he right "ballpark" to understand the kind of RPM, vibrations and noise that I was going to encounter.

This is the Electrical Set Up used:-
Motor:- NTM ProDrive 50-50 580kv
ESC :- Pulso DLU70+
Prop:- 14x7E (still trying to work out the prop's pedigree!)
3S Battery:- Zippy Compact 2200mAh 60C series
4S Battery:- Turnigy Blue 2200mAh 35-45C
6S Battery:- Turnigy Blue 3000mAh 30-40C

So what, were the results?!!!!

Prop. OFF:-
100% Throttle
3S ---- 42w @ 3.7A & 11.48v
4S ---- 68w @ 4.5A & 15.1v
6S ---- 154w @ 5.7A & 22.84v

14x7E prop. ON:-
100% Throttle
3S ---- 269w @ 24.9A & 10.9v
4S ---- 516w @ 37.6A & 13.8v
6S ---- Dunno, I chickened out at 55% throttle!

48% Throttle
6S ---- 860w @ 40.3A & 21.1v

55% Throttle
6S ---- 1280W @ 63A & 20.5v

I could see that the current was flicking up to the high 60A's at 55% throttle stick, so I decided to call it a day there.
Additionally, although it didn't take long to do each of the measurements, the neighbours were starting to get concerned at the noise level in the garden & it was getting chilly outside which was significantly amplified in the propwash!

Well that was a bit of an eye opener for me & well worth doing.
I would now really like to try a 5S battery & agree with you guys that, with 6S battery, a bigger ESC is going to be needed.
Anybody got any suggestions for a good ESC based on this limited data?

Regards
H31

PS Garry, have you got that prop info you said I could consult?

Ok Richard, thanks for that, however prop off doesnt mean a great deal to me personally
However, with the prop on, we are getting somewhere.
Two things stand out in this test. Firstly, I wouldnt advocate doing the test with a lipo at storage level, as you will not get a true reading, however , as you havent had anything so big, I can see why.
Secondly, we do have a valuable reading here, and that is the 6 s 55% throttle. I did say that this setting would fly the model, as you are over 100 w per Lb at 1280 w. You were correct to close down as much more could have blown the ESC. You need at least an 100 A ESC, preferably 120 A to be on the safe side. A different prop would be useful as a comparison, say a 14 X6 and a 13 X 6 would pull the amps down and as you have watts to spare
I will be interested to see the full throttle test with a different ESC and prop with a full lipo. Its frightening at first, just watch the watt meter and keep your finger on the throttle stick. Wish you lived closer, cos I have plenty of 5 s lipos
I will pull the comparison chart out, and post it on this thread
www.ecalc.ch/motorcalc.php?ecalc&lang=en

Just found the one I normally use,

Garry

Are you sure you are going about this in quite the right way?
I normally decide on how many Watts I am going to need based on the plane's weight and how I expect it to fly.
Lets say you want 1200W and you want to use a 6s (nominal 22.2V) battery. This means you will be drawing 54A.
You set the 'target' Watts and for a given battery voltage it gives you your 'target' amps.
Then you make sure the specification of your LiPo, ESC and motor can handle that current with a reasonable safety 'headroom'.

As you already have the motor surely the testing is to find a prop draws your target current at full power. If a prop is clearly going to exceed your target current before you get to full power it is unsuitable for your set up and change to one with a smaller diameter and/or less pitch.

Just as an aside:
"154W with the prop off."
My 40" Petiterina goes 'unlimited vertical' with that power!

Thanks for that Q and you are quite right. Unfortunatly part of the setup was inherited ie, model and motor, so trying to work out a compromise . The motor is well overpowered for the model.. However, feel free to join in, as there is more than one way to skin a cat

Garry

The tech side of rc modelling is just as interesting as the building, thanks Q for that snippet of information, I think garry has learned something, and that's not easy at his age lol, boz

I agree on both counts Boz. When we stop learning we stop living in my book

Garry

I am sorry to say this, and also a little worried as well. This is the SECOND time I have agreed 100% with your post. Eric. Absolutely spot on in all aspects.

Garry

Morning Chaps.
Thank for all you posts and advice. Some really good nuggets of gold there.
I agree with you Q that, if I was to start from 'first principles', I am NOT going about this in quite the right way but as Garry pointed out, I bought this model secondhand with the motor & Prop already fitted. I originally made the assumption that the previous owner had done the sums and selected the appropriate motor for the job, This may turn out to be true -- but then again it might not. Either way it would appear that it has more than enough 'umphhh' (efficiently or inefficiently) to do the job. So I will stick with this motor for the moment.
Unfortunately at this time, I do not have a well stocked "bits" box with a good range of props, batteries and ESC's to enable me to perform further useful tests today. I have ordered up a couple of 5S 4000mAh 30C batteries and 3 different props (14x6, 13x7 & 13x6) which I have calculated could/should help me close in on a workable solution; but I will have to wait for postie to come now.
Meanwhile I am still umming and arrhhhing over which "larger ESC" to buy.
Do I go for one which is OPTO coupled or one with an SBEC?
Should I pay for one with a data logging facility?--- I think I will find analysing that sort of info really interesting.
Should I go for a 100 or 120 Amp one?
Are some well known to be more reliable than others?
Should I think about standardising on one particular make/brand of ESC to make programming and subsequent data analysis more routine and only need one programming card &/or data download lead or Bluetooth adapter (if I really need those equipments at all!)? I do have some castle creation ESC's on my helis at the moment so I could have some synergies there but there again maybe they are a bit 'over the top' for this application.
Are there any downsides (other than cost & a little bit of weight) to having a an ESC which is a bit "overspec'd" (eg 120 or 150Amps Vs 100 Amps) for the job in hand? ...ie.. Is it worth paying a bit more now to future proof/have something a bit bigger in case I need it later on or are there problems with operational electrical inefficiencies by doing such?

I expect once I have really got the bug and ended up with a well stocked "bits" box I will have answered most of these questions, some of them will have become moot &/or purely academic and the subject of good ground & flight crew room banter.
Meanwhile have you guys got many/any views or recommendations?

Cheers
H31

As for speedo get one at least 30% bigger than you motor rating, better still 50%, get a good one
Lipos the HK Zippy compacts are good and they are cheap, I have six 5s 5ooo maybe get one and try it
I also bought 4 Thunder Power 6s 5ooo 65 c lipos they cost £150 each for the SR71 and only two survive, I would not buy TP again, but then again I know knowt

Do I go for one which is OPTO coupled or one with an SBEC?
Should I pay for one with a data logging facility?--- I think I will find analysing that sort of info

Two very good questions Richard
Go for OPTO as they are slightly cheaper and should the flight battery/ power train fail completely the radio is still powered and you can glide the model in if you have the height
If you like playing with programming go ahead and get one with data logging etc, however I use the Red Brick ones from HK, and have never had a prob.


Being a simple soul i like simple lol, but no matter which one you go for , as BB says, go a least 30% higher than you need



Garry

The 5S batteries and 3 new props have arrived so hopefully we can do some more power checks today.
The new props were not quite what I thought I ordered but nearly:
I now have:-
* 2 APC (electric 13x8E & 13x6.5E)
* 1 JXF Poly Composite Propeller 14x6
* & my original 14x7E.

I have just been checking the specs for my HK-010 "Power Analyser". I see it is rated for 50A Continuous and 100A peak (whatever that means?). I hope it is OK -- we have already seen 69A and I only stopped there because I was concerned about over doing the ESC (& also the whole affair was making quite a din in the back garden!).

I will go and charge the 5S & 6S batteries to "full capacity" and prepare the test stand (B&D workmate) whilst waiting for the sun to do its stuff --- currently minus 7 DegC. outside at the moment (no wind though).

Will report back when I have some results.....

Garry Pollard wrote: Go for OPTO as they are slightly cheaper and should the flight battery/ power train fail completely the radio is still powered and you can glide the model in if you have the height
If you like playing with programming go ahead and get one with data logging etc, however I use the Red Brick ones from HK, and have never had a prob.
....
Garry

Regarding the ESC.....
I have plumped for a YEP 120A LV(2S-6S) SBEC ESC (£50); the similar OPTO one, YEP 120A HV(4S-14S) is £129.60.
I will still have a separate power supply for the radio gear -- I will just disconnect the red wire from the ESC to the Rx should be OK.
I eventually found the Red Brick ESC's on the HobbyKing website -- took quite a bit of searching as they weren't under the separate Brand or plane indexed sections. They seem to be very cheap on price....but the one review I saw for the 200A one wasn't very complimentary at all. I am glad you have had no problems with yours Garry. Which sizes have you been using 125A, 200A?

New but related subject....
What connectors type/size/make are you chaps using on:-
a) battery to ESC interface
b) ESC to motor

.....for an installation around this size (5S or 6S, 1700 Watts, 50 to 100A) ish?

I can see I am probably opening a can of worms here, but I am genuinely interested as I can see some potential issues with the connectors currently fitted to some of my components for example:-
i) the 5S & 6S batteries have come with HXT 4mm. (I have read that 4mm should only be used for up to 50A continuous and not all 4mm are as good as each other)
ii) The Pulso 70+ ESC has individual 4mm bullets on both ends.
iii) The Wattmeter has XT60's (which I read are rated for 70A max .... but how can that be as their "bullets" are only 3.5mm Vs the 4mm which I read were rated for only 50A! ).
iv) My big 6S batteries have EC5's
v) and the new YPE ESC doesn't come with any connectors -- so I need to decide what is best to put on -

Thanks
H31

The difference in price between the ESCs you mention is down to number of cells they can handle.
The YEP 120A HV is rated for high voltage (14S). Above 6S electronics get much more expensive.