Power systems that work - READ first post

[phillipda]

Here is my brand new setup.

Hurricane 550 Pro with CF Frame and CNC head.
Z20a 980 Motor
15t pinion on motor,
42t front gear, 61t back gear.
20 OWB
Outrage 6-cell 3000 Lipo
I don't know what my head-speed is. I sure would like to know.
Gaui 75 ESC
Gaui standard BEC
Flightpower 2-cell 2150 Lipo to power the receiver and servo's
Futaba S9451 on Cyclics
GY401 Gyro with Futaba S9254 on Tail.
Gaui 500mm Carbon blades
Pitch Curve on my DX7: 34 INH 54 70 83
Throttle Curve: 0 60 75 82 90

I am only flying in Normal Mode and hovering.
I hover at three quarters hover position on radio.
I get 7 minutes of hover time and put back apx 2250 back into the Outrage pack.
I am a bit surprised with my hover time, I thought with this motor I would get a longer flight time than 7 minutes.

I figured a head-speed of something in the range of 1800-1900 would be good for me, But I have no way of telling what the head-speed is. Can't afford a Tacho.

I used this site: http://www.ezfly.se/hscalc.htm to work out my gear ratio's, according to that site with the gears I have listed I should be in the range between 1800-1900 head-speed. Am I wrong? I am only getting 7 minutes of flight time with my Outrage 6-cell 3000 Lipo. I thought with the Z20 motor I would get at least 9 maybe 10 minutes. My ESC comes down a bit warm after a flight. I am getting temps of 60 Degrees Celsius on the ESC, 45 degrees Celsius on both the Lipo and Motor.

[Mikej]

Phillip,

You don't have your set up as efficient as it could be - brushless motors prefer running at constant speeds (throttle curves) plus your throttle curve is a bit low. You would be better off running a flatter curve and at higher levels, you would obviously need a smaller pinion or a larger primary gear - I use 14/50/20/61 and a TC of 0, 95, 95, 95, 100.

Cheers,
Mike.

[phillipda]

Hi Mikej

Thanks for the advice. So I obviously have this all wrong. What flight times you getting?

I don't have a 50t front gear, but I do have a 14t pinion for the motor I could go back to and a 19 OWB. Would this work with that throttle curve you have listed? Obviously it will work, but I don't want to high a head-speed.
Also got a 16t for the motor.
I also have a 60t front gear, I don't know why I got that one instead of a 50t. If it makes that much of a difference using a 50t up the front, I will order one tomorrow

[Mikej]

I get about 7 minutes from 2 x 3S 2200 so effectively a 2200 6S battery

[mysticmead]

try using a gearing of 14/20/50/61 with that Z20... that will get you 1800-1900 at a TC of 100 flat... the motor will be cool and so will the ESC.. plus you'll get longer flight times.. on 2200mah packs I get 6 mins and still have very cool packs plus power left (my charger sucks so I have no idea how much is going back in.. but there is plenty of power left.. I just cut the flight short and be nice to my packs)

[phillipda]

I was always under the assumption that if you use 100% throttle that the motor will run hotter and use up more power, obviously I have this all wrong.

I ordered a 50t gear, as soon it arrives I will set to a throttle curve of 0 95 95 95 100.

I can't believe you guys are getting 7 minutes with a 2200 lipo. the most I get is 7 minutes with a 3300 lipo. I thought something was not right with my setup, Had no idea that if I run at 100% throttle, motor would be cooler and more efficient. Like I said before I was always under the impression that running a motor at 100% throttle will wear out and use up more energy, sure works out that way if I run my car at 100% throttle.

[kgfly]

The reason is that the way the throttle works on a brushless motor is by PWM. That is, the ESC always applies 100% of the battery voltage to the motor, it simply varies the percentage of time it is switched on. So at 50% throttle 100% voltage is applied for half the time, giving an effective average voltage of 50%. However the implications for current are significant.

Using a simplified model, imagine you had a solid 20V at the battery and the heli needs 400W to hover. At 100% throttle the motor will draw 400/20 = 20A continuous. However, at 50% throttle with only 10V average, to deliver 400W average the motor will draw 40A.
Double the current means four times the resistive losses. However since current is flowing only half the time, the total heat generated due to resistive losses is about double at 50% throttle compared to 100%

So from this simple energy transfer point of view, the system will always be more efficient at higher throttle settings than lower ones. In reality there are many other factors but in broad terms this rule still applies.

Hgher throttle settings also mean less wear and tear on the components since the ESC FETs switch less often and the motor experiences lower currents, less heating and less vibration due to the pulsed drive voltage.

[spencer737]

Hey will the 42t front gear or the 50t front gear have more head speed?

[xodarap1]

The 42. Usually about 350 to 400 rpm more when used with the 13,14 or 15 pinion. But, the 42 will also strip easier at higher HS's.

[phillipda]

The 42 is faster than the 50.

My 50t on order has just arrived. Hopefully now this will get me some longer flight times and cooler ESC. I also ordered a set of Gaui Wooden 500mm blades. On the packaging it says not to use a head-speed faster than 1900, I was going to also try the standard combo 14/42/19/61, I worked out I would probably get a head-speed of 2150 with the standard combo on the Z20a 980 motor. Looks like I will not be able to use the cheaper wooden blades with the stock gearing.

What's these brass bushings that came with the Wooden blades? Do I have to press them into the blade holders hole on the blades?

[spencer737]

ok cool cause ya I am going to use the 500mm woodies so with 15/20/50/61 gearing I am probs going to get about 2033 hs with the Z20 980, so i may have to bring down the HS with the TC's just a smidge.

And yes those brass spacers go into the plastic blade roots

[phillipda]

That's not a bad idea, I might try out your suggestions first with the gearing. I already have the 15t and the 20 OWB on the heli, All I have to do is drop out the 42t and replace with the 50t

Do I still need to use those brass bushes with the CNC blade grips?

My 20t OWB is ##@##. The bearings have collapsed. I am going to have to use my 19t OWB.
Don't grease the OWB, this is a mistake.

[mysticmead]

the brass spacers convert the bolt hole from 4mm to 3mm... that's all they're for.. if you have CNC grips and 4mm bolts, don't worry about them... if you have 3mm bolts or the plastic grips (they only used 3mm) then insert them..

[spencer737]

Dang yeo that sucks about the OWB, how many of the spacers are you guys using between cause I tried 1 and there is just a bit of up and down play and with 2 its WAY to tight would the play have that much effect?

[mysticmead]

the OLD instructions from Gaui said to use 2.. the new instructions say to use 1.. so I used 1 :D

[mjdee14]

Dang yeo that sucks about the OWB, how many of the spacers are you guys using between cause I tried 1 and there is just a bit of up and down play and with 2 its WAY to tight would the play have that much effect?

A little play will have no affect on the operation.....you should still have full contact between the gears..... once the OWB locks up...it's not moving...

[jujiro]

I've finally found a suitable power system to my liking

Z30 1100 KV motor
Zippy 3300 Mah batteries
Mavrikk G5 Pro wide chord blades
Headspeed 1978 with 13/50/61
Only mods are a rotorworks G10 frame and T-rex 600 flybar and paddles .

to me this setup gives very good power while still allowing for 4:30 seconds of flight time. ( 2.49 AH charged back). collective was crisp and powerful and cyclics were still at a reasonable rate.

with a 14 T (2,130 HS) this setup had a lot more power at the cost of flight time, Performance wise it was a beast, and cyclics were faster

with a 15T (2,282 HS ) The Hurricane 550 was absolutely insane, it was very twitchy feeling almost as if it was a T-rex 450 on crack . Flips and rolls were incredibly fast and power moves like tick tocs were able to be done with little to no break in between as showed in this quick video . I plan on going back to the 15 T but at the time it was much to fast for my liking, plus it was hard to get used to the heli with flightimes only last 3:00.

http://www.youtube.com/watch?v=BlEx7qvE2w0

i'll have to post back in a month or so to see If I have any problems with gear stripping but so far I haven't stripped a gear which leads me to believe the better way to get more power from the 550 isn't from higher headspeed, but from longer better blades. Will continue testing with more 550 MM just to see what options are available but first I need to get some new batteries since the ones I'm testing with are quite old probably around 40-60 flights on it :)