[kizza42]

Yep.
See here:
http://forum.rcflyingclub.com/showthread.php?tid=131&highlight=time

or here:
http://forum.rcflyingclub.com/showthread.php?tid=124&highlight=time

Or here:
http://www.ecalc.ch/indexcalc.htm

[Skidz]

Hi All,
Just a simple one. If I know the current draw of my plane and the capacity of the battery, is there a simple way to calculate flight time?

eg My plane draws 16amps, and I have a 1800mah battery, how can I calcualte how much flight time I would get?
Thanks
Mick

Mick, use the Eagletree logger I loaned you. You can plot the whole flight (or multiple flights on a single log file and separate them later). You can use Volts on the left (x) axis, Amps on the right (x) axis and cumulative mAh on the bottom (y) axis. it will also give you average Amps and average Volts. That will give you the information you need to compare against battery discharge guidance posted by Drew/Kizza.

There is no absolute answer as current draw is never linear and predicatable.

Try different flights and check out your data. You can also save the chart view as a .jpg file and post if you want others to comment on your data plots.

D.

[secant0give]

I mostly err on the conservative side. I do a rough calculation based on a throttle percentage like Drew suggested then, I set my timer for about 4 or 5 mins for the first two flights then see how the battery's cell voltage is when I charge them both back up. If it's over 3.8 V per cell then I add another minuet at a time until I get 3.7 to 3.8 V per cell after a flight. You will also get different flight times depending on how you use the throttle. You should have a feel if you've given it more or less curry in a particular flight and you should see this in the cell voltage as well when you charge them.

[dingy]

This is a very interesting article that I found some time ago.

Also remember the older a battery becomes the shorter charged time is.

Attached as a file also for reference:-



Calculating Battery Flight time
Ah x 60 / amps pulled
So, Lets see a couple examples
2000mah battery = 2ah
4000mah battery = 4ah
Lets use a 480 size motor as an example…
A standard 480 outrunner is propped around 30 amps on a 3cell battery
2ah x 60 = 120 120/30 = 4 minutes full throttle (slightly less due to servo power draw)
4ah x 60 = 240 240/30 = 8 minutes full throttle
------------------------------------------------------------------------------------------------------------
Battery C rating
This rating is considered the maximum safe (constant amp draw)
1000mah 20c pack = 1ah x 20c = 20amps
2000mah 20c pack = 2ah x 20c = 40amps
4000mah 30c pack = 4ah x 30c = 120amps
Lets use a 480 size motor as an example…
A standard 480 outrunner is propped around 30 amps on a 3cell battery
1ah 20c battery pulling 30amps = 30/1 = 30c (this is above the C rating, this will puff the battery)
2ah 20c battery pulling 30 amps = 30/2 = 15c (this is well below the max constant amp draw… This will
work good)
4ah 30c battery pulling 30amps = 30/4 = 7.5c (this is extremely good at this rate pretty much any halfway
decent cheap battery will give great results)
------------------------------------------------------------------------------------------------------------
Lets see what we get if we re-prop for a higher voltage (not all motors will allow this, but it is usually
good if it will)
Lets use a 480 size motor as an example…
A standard 480 outrunner is propped around 30 amps on a 3cell battery
Volts x amps = watts (volts times amps equals watts)
11.1v x 30a = 333watts
Now Lets use a 480 size motor on 4cell as an example… we reverse the numbers to give us the samw watts
with less amps (less amps = less heat
333 / 14.8 = 22.5amps
So if we look at a standard 480 motor we can see that we’ll get the same power with 22.5amps instead of
30amps on 3cell…. (You will prop down in size to do this)
A bit “o” confusion on battery size on changing voltage Why do people think that you’ll be heavier
with a 4cell than a 3cell , simply because they aren’t using a smaller capacity battery with the same
weight
Using the above info above we will look at a few options on batterys….
Lets use a 480 size motor as an example…
A standard 480 outrunner is propped around 30 amps on a 3cell battery
A standard 480 outrunner is propped around 22.5 amps on a 4cell battery
Lets start with a 2200mah battery on 3cell
(average weight of a cheap 2200mah 3cell pack is around 200grams)
2.2ah x 60 = 132 / 30 = 4.4 minutes full throttle flight time
(average weight of a cheap 1700mah 4cell pack is around 200grams)
1.7ah x 60 = 102 / 22.5 = 4.5 minutes full throttle flight time
So, what we have learned is that you can get the same power (333watts) out of the same (or less) weight
battey, and Pull less amps (less heat)
We must be carefull to realize though that all motors cannot just be re-proped for a higher voltage due to
motor deign or materials used in the design... and at all times you should use a good wattmeter to
determine all factors involved


Regards,

Dingy

[Kedumba]

wow, tons of really useful replies, thanks everyone, although I should have remembered that "search is my friend" and looked it all up myself, but I was in a bit of a hurry when I originally posted and didn't think. The reason for my post was that I was thinking that some of my batteries are getting a little old and maybe in need of replacing shortly and I was gonna look at different batteries for my different planes and try to work out an optimal solution (weight vs maH vs C rating) and see what gives me the best bang for my buck (perhaps not the best phrase to use when refering to Lipos!) ie can my Luton and Mini F18 share a smaller lighter battery or would i need 2 seperate ones....

This lousy weather may be good in a way cause I guess now I have an excuse to sit down and go over all the posted info in more detail. Again, thanks everyone for all the info
Mick

[Drew]

Here's some data that i gathered from a popular source last December. I still have the scripts and could update it if you need.

I did start another similar exercise for motors but their specs are not as easily normalised.

[Kedumba]

Hi All,

I'm having a problem with my Luton Minor. I think I may need a larger motor in it.

It currently has a Turnigy 2209 26turn 1130kv 15A Outrunner with an 18 amp ESC spinning a 9x4.5 prop. This setup seems to be a lttle under powered. I need to apply full throttle on take off and it barley lifts off the ground. Once airborn I need to keep it at pretty much WOT to keep it flying.

As an experiment I tried a 9x6 prop and it seemed to fly pretty good however the data logger that I borrowed showed that it's drawing up to 24amps which can't be healthy for the speed controller or the motor.

I have tried browsing the HK website but there is too many choices and to be honest, I'm not even sure at what I'm looking for which makes it a little difficult. Does anyone have any suggesitons as to what I can look at as a replacement for whats in there now? I think I'm just lookig for something that can turn a 9x6 prop without blowing anything up.

Also Kieran has suggested a NTM Series 35-36B 1400Kv / 495W as the motor for my Bronco, however HK is currently out of stock of these and have been for a while. Does anyone know either of an equivilent that is in stock or where I may be able to get a couple of these?

Thanks
Mick

[smuzz]

Mick - what's your Minor's take-off weight?

As for the 35XX motors - yes, "Backorder King" can't seem to help us. I got p!ssed-off with waiting about two months ago and got one from a supplier in QLD, but of course had to pay a little over twice the HK list price

[kizza42]

1) SK motors being replaced with SK3's
2) Magnet prices going up almost daily, factories are scared to invoice let alone produce magnets now.

As for ETA's
NTM: Coming through every few days, but a worker shortage on motor winding is causing delays.
G Series: Coming every few days, but not enough to fill all backorders.
SK3: Late next month all models should be in stock.

Order what you want, it will come eventually.

[Kedumba]

Mick - what's your Minor's take-off weight?

The scales show the luton at about 650 grams. Add another 130g or so for the battery to make an all up takeoff weight of around 780g. Is that any help?

Mick

[samste]

Mick i have used these guys many Times and i reckon you need this for your Machine.
I can Reccomend the emax as i was running the bl2810 in my stealth stryker to i bent the shaft by dropping the plane in the garage, so i had to swap it out till the replacement shaft comes in.

Heres the Link home page

http://www.xc-rc.com.au/


The Motor i Suggest link but heh have a look you may find something better as they have a few motors to look at.

http://www.xc-rc.com.au/index.php?main_p...oduct_info&cPath=9_97_113&products_id=391

Steve

P.s I do have motor very similar to the emax,i think it may have been a emax but the stickers gone, was running this in Island Hopper at one stage with 2200ma 3s extreme vertical.
But i'm not sure what the kv is but i'm pretty sure i ran a 9x7 prop on it.

   

[smuzz]

OK, say 800g AUW means we should be looking at about 160+ Watts, perhaps aim for a motor rated at 180~200 W for some head-room.

http://www.hobbyking.com/hobbyking/store...duct=12922 is actually in stock (shock!) and priced at about $11. With the suggested 9x6 prop it would probably do the trick on 3S.

[secant0give]

Hey that looks like a nice little motor Steve !!
I might have to get one of those my self
It looks pretty similar to what I'm running on my depron Extra
and I'm putting together another one as the poor old girl is getting a bit aged now after much
abuse.

Jason

[samste]

Hey that looks like a nice little motor Steve !!
I might have to get one of those my self
It looks pretty similar to what I'm running on my depron Extra
and I'm putting together another one as the poor old girl is getting a bit aged now after much
abuse.

Jason

If you like you can have very cheap, Can bring down field on weekend to show you as i have no use for it at the moment and was thinking of selling a couple of planes and stuff to fund a couple new projects i have going but not started.

Steve

[Kedumba]

I remember that Island hopper If jason doesn't take the motor I may, depending on price, although I'll need a new ESC to go with it. If Jason does want it, I might try the HK one the other steve suggested. I'm sure all I need is just a little more power. While I'm on the subject, anyone know of a reasonable 20 - 25amp ESC? I was thinking of grabbing a cheap turnigy one.....
Mick

[smuzz]

The 18A ESC you say you already have would be alright with the motor I was suggesting Mick. I know it says 25A ESC on the page that describes the motor, but the motor itself is rated 20A max anyway and on that little plane you would rarely need to put 180W through to the motor (10V on 3S under load and 18A).
Anyway, HK does have a stock of these http://www.hobbyking.com/hobbyking/store...oduct=6458 which would up-rate your current ESC ( ..... get it? ... "current" ESC!)

[samste]

I have some brand new 25 amp esc's 3s only that i removed from the A-10 when i bought it as i fitted new two new 25 amp esc in the A-10 that are 4s capable instead as i run 4s in the a-10 for grunt.

Cheap as $10 if you like.

Steve

P.s Don't know Brand of Esc as it Came out of the My Old Gws A-10 Frame ARF that i use to play with.

[Kedumba]

I was gonna put in an order for a http://www.hobbyking.com/hobbyking/store...duct=12922 motor from HK and wanted a 20 - 25 amp ESC for that as a replacement in my Luton Minor. Would prefer the larger one for a safty margin. I spent too much time building it to loose it to an ESC that burns out on me....

I am also looking for another power setup for my giant Mugi Evo that I'm building as a slow flyer (at least I hope it will..... fly slow that is..) which is why I was thinking about that motor of steve's...although the HK one would probbly work as well. Although...thinking about it, maybe I should look at a higher KV and smaller prop aka stryker/funjet type setup...

I have built a standard size 800mm Evo which I put my EDF on (the one that threw a blade last weekend) as my fast one but the new one has a 1200mm wingspan and I hope will be more of a glider.....maybe .... the joy of SPAD.. I could really get into this...

Oh, also, would the Turnigy Speed Controller Programming Card be able to program the Hobbyking SS Series 25-30A ESC??? Thanks


Mick

[smuzz]

Oh, also, would the Turnigy Speed Controller Programming Card be able to program the Hobbyking SS Series 25-30A ESC???

Dunno - the ESC page says that it's compatible with the "Turnigy" programming card, but the page for the card indicates three different types of ESC without mentioning the "SS" series ???
I've used that ESC before, but haven't programmed it as it's default settings were fine for my purposes.

[samste]

http://shop.ebay.com.au/sis.html?_nkw=Em...15+25+T214

lots of motors on ebay too

[Kedumba]

Hi All,
Looking for some help or suggestions to fix/replace my EDF unit. Last weekend after a not so sucessful launch of my Mugi Evo, my EDF choked on it's own fan blades.

This little EDF has had a mixed history. It initially started life in a HK Flycat which shows it to be a 56mm EDF. After the Flycat was involuntarily retired after an unfortunate meeting with the ground, I stripped out the EDF and had it sitting around in the shed until I recently found the plans for the Mugi Evo and decided to resurrect it as the powerplant.

After seaching with internet for a while I couldn't a replacemet fan so I thought I could replace the who unit to something thats a bit more common and has easily available spares.

I ordered from Sydney RC Jets a 64mm EDF unit thinking that I could just transplant the motor from the old 56mm edf to the new one. Seems that the 64mm EDF unit will only fit a smaller diameter motor (~20mm) whereas the motor that come out of the 56mm EDF is 24mm diameter.

Ok, so now I'm stuck and I'm looking for pointers/links/suggestions/offers. I'm thinking I'd like to have an edf maybe somewhere between 55mm to maybe 64mm but it must be cheap, easily available and fit my 24mm diameter motor, which could be the tricky part cause no-one seems to detail the motor diameter in their listings....

Thanks
Mick

[~KevJ~]

not sure what you want to spend but in my opinion the best 64mm option is this one..

http://www.extremerc.com.au/estore/index...page=index&cPath=146_11_195_251

its a machined down 70mm aluminium wemo rotor in a 64mm plastic housing able to hold motors up to 28mm.. which means very flexible from low power setups up to fairly fast setups, the rotor is quality for 64mm i reckon.. 50 bucks tho not sure if that fits the bill..
as far as performance goes well following video shows 4s results.. its pretty quick for a little sucker..

http://www.youtube.com/watch?v=i1Ql_hW-ZRA&feature=channel_video_title

[Kedumba]

Does anyone have a prop balancer that I could beg/borrow/steal/rent or otherwise gain use of? I have a couple of props and an EDF fan I'd like to balance..

thanks
Mick

[Kedumba]

Wow, my very own thread of all my really annoying questions I'm not sure whether to feel privileged or embarrised!!!

[kizza42]

Forum cleanup... Im deleting everything else. Feel privileged!