8s - Z20 980kv on Hurri 550 ?

[duckfeather]

Motor = Z-power Z20 980kv
pinion = 13T
Main Gear = Stock 42T
One way = 20T
Pitch = -10/+10
Li-po = 8s 2200mah 25c ( 2 x 4s1p )

Throttle curve percent = 65% flat ( idle 1 ) Doing mostly -FFF, inverted hover, flips. rolls, Fig 8, etc. No 3D.
Getting 5min 15-30 sec of flight time.

Throttle curve set at 70% , gets approx. 5 min . Tach HS approx. 2000 - 2200 rpm
Temperature - finger friendly hot on motor , cool on ESC.

With every increment of higher throttle ( 80% and above ) seem to shorten flying time drastically and I dont need the crazy high HS for my type of flying. Temperature - hot motor.

Can going 16/61T combo on the gears , 90%-100% thro ( estimate HS 2100-2300rpm ) improve overall ESC/Motor's performance, better/extended the flying time ?

Any suggestion from anyone ?

[caotri]

Hi,
Which ESC youare using for 8S, CC45HV?
the stock ESC doesnot work with over 6S voltage.

[Phoinix]

Change your battery to 5S 5350 and you'll get +13 minutes with a smart setup.

8S for non 3D is a hard overkill.

[ukgroucho]

Change your battery to 5S 5350 and you'll get +13 minutes with a smart setup.

8S for non 3D is a hard overkill.

Sorry but this is just not true. I'm sure that you can get 13 mins off the 5S setup that you mention - but the 8S setup mentioned should be able to do about 8 and a half minutes WITH the same headspeed, assuming everything is running efficiently (motor in it's efficient zone). Assuming 80% maximum discharge.

5 x 5350 = 26750 MaH (1S) * 0.8 (80%) / 13 mins = 1646 MaH per min
8 x 2200 = 17600 MaH (1S) * 0.8 (80%) / 8.5 mins = 1656 MaH per min

However, whilst the 5S rig proposed has 50% more capacity than the 8S rig described I'll bet it weighs quite a bit more. So the 8S calculation is pessimistic (MaH per minute will be less at the same HS) PLUS (and this is the whole point of HV) there will be less losses in power due to efficiency issues as HV = low amps = more efficient.

The only things that duckfeather needs to do to get longer flights are to sort out the gearing so the motor and ESC are running more efficiently and (if desired) reduce HS further.

[Phoinix]

Sorry mate, but my data is true. I fly it almost every day, 13 minutes is standard.

He gave the setup, i gave the battery. You did the opposite, switched everything else and keep the battery.


What's not true is your math -> 5x 5350 or 8x 2200. mAh's as far as i know, don't add like that. You have serial connection of 4 cells, or 5, or 8 cells.

http://batteryuniversity.com/images/partone-24a.jpg


Pack capacity is 5350 at 18,5V, period. Other pack capacity is 2200mAh at 29,6V, period. Capacity stays, voltage rises. What you get with your calculation is the capacity if you keep pack voltage 3,7V.

[ukgroucho]

Phoinix.... it's all about POWER and the rate that it is consumed (i.e. how many MaH are consumed each minute). What I did in the above calculations was simplify everything back to single cell 'capacity' - and YES you can do this although it ignores efficiency gains from higher voltage so it favours the lower voltage setup.

Look at it another way. A typical Hurri running 2200 HS will consume around 400 watts in a hover.

For your 5350 5S that will mean 400 / 18.5 = 21.6 AMPS. Your pack can deliver 5350 * 0.8 = 4.28 AMPS for an hour (assumes 80% maximum drain). So at 21.6 amps in a hover you are draining your battery 21.6/4.28 = 5 times faster than the rated 'hour' value. 1/5th of an hour = 12 minutes with (e.g.) 2200 HS just hovering. I completely believe you when you say 13 minutes. With lower HS (say 2000) this is completely possible.

Now run the numbers for 8S. 400/29.6v = 13.5 amps
2200MaH pack can deliver 2200*0.8 = 1.76 AMPS for an hour.
At 13.5 amps we are draining the pack 13.5/1.76 = 7.7 times faster than the rated 'hour' value. 60 minutes / 7.7 = 7 minutes and 47 seconds.

So in this example we get 12 minutes for the 5S 5350 and just shy of 8 minutes for the 8S 2200 - ignoring efficiency gains from high voltage.
If you want to add the extra minute to the 5S calculation to make 12 into 13 then you'd add 45 seconds (it's proportional) to the 8S calculation and that gets you back to 8 and a half minutes as I stated above.

[BL]

Motor = Z-power Z20 980kv
pinion = 13T
Main Gear = Stock 42T
One way = 20T
Pitch = -10/+10
Li-po = 8s 2200mah 25c ( 2 x 4s1p )

Throttle curve percent = 65% flat ( idle 1 ) Doing mostly -FFF, inverted hover, flips. rolls, Fig 8, etc. No 3D.
Getting 5min 15-30 sec of flight time.

Throttle curve set at 70% , gets approx. 5 min . Tach HS approx. 2000 - 2200 rpm
Temperature - finger friendly hot on motor , cool on ESC.

With every increment of higher throttle ( 80% and above ) seem to shorten flying time drastically and I dont need the crazy high HS for my type of flying. Temperature - hot motor.

Can going 16/61T combo on the gears , 90%-100% thro ( estimate HS 2100-2300rpm ) improve overall ESC/Motor's performance, better/extended the flying time ?

Any suggestion from anyone ?


I would suggest you go for 16/61T setup with 8s, it will improve the overall efficiency.

I have tested 16/61T 6s 2200mAh with Z30A 1100kv, it lasts for 5.5 ~ 6mins.

[duckfeather]

Thks guys for the reply.

I am trying/getting into mild 3D and think a HS of 2000 - 2200 is about right . I think .

ukgroucho - whats your gearing recommendation for the HV 8s setup with the Z20 980kv ? Just found out there's a new 50T gear .

[ukgroucho]

duckfeather. Right now your 'front' gearing (motor pinion to front gear) is 42/13 so 3.23 turns of the motor to one turn of the front gear.

If you want to increase Throttle but keep the HS in the same range then you need to increase that ratio - say 3.5 turns of the motor for one turn of the front gear.

With the new 50t gear 50/3.5 = 14.28.
A 14t will give 3.57 to one, a 15t only gives 3.33 to one (not a big enough change IMO)

Moving from 3.23 to 3.57 is about a 10% change - so 200 RPM at your current HS.

Give that a try - get a 50t and a 14t, if you still have a lot of headroom on the throttle then you can try your existing 13t.


EDIT: Incidentally I have the same issue with my 10S setup - T curve needs to be down in the 60s to get a 2250 HS. Fortunately it's a Jazz ESC and they seem to cope with this pretty well. I am already using the RevCo 68t front gear and mod 0.6 pinions with an 18t... I've seen 17t but nothing smaller in mod 0.6. My motor (z30) is spinning at a healthy RPM (26000 or just under) so I don't think this is terribly inefficient (everything is cool / luke warm after 5 mins of flight). But I'd just like to sort it out a bit more 'cleanly'. I also want to try mod 0.8 gears as I've stripped some of the 0.6 ones. I already ordered some of the 50t front gears (and some pinions) from ReadyHeli but I also note that there appears to be a 60t front gear also....