Impossible Battery / Motor / Main Rotor Combos? [Archive]

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SteveSFO

09-30-2007, 10:33 PM

At the risk of "beating a dead horse," I will pose the following question regarding the Logo 500 DX or 3D:

I have one desired condition: To use TP 6S ~5000mah packs

With this in mind, is it even possible to obtain a docile, cool and smooth running training / sport flying set-up, aiming at endurance (7-8+ minutes) ather than performance with the following in mind:
500mm or 530mm main rotor
Metal motor mount, mod 0.5 (212T) or mod 0 .7 (153T) main gear
Pinion with xx teeth...
ESC - Jazz 80-6-18
BEC - Western Robotics HV 5 amp
The minimum motor for the Battery/Rotor combo.... (Hacker A40-10L, Z-Power Z30-1100, Plettenberg Orbit 25-10F, Neu 1910(H)-1Y??, Tango 45-10 or other...)These all seem like powerful motors. But with a 6 cell 5000 mah battery, perhaps I have no choice. The solution may lie in the correct pinion gear selection and governor programming.

So this is my question... Can enough power management be had from the right selection of
Main rotor
Main gear mod (.5 or .7)
Pinion gearing
Governor/idle settings.I look forward to hear from someone who has been here before... There is ample set-up info in the forums, including excellent ones in this one, but they all talk about high end performance. My reason for the 6S 5000mah battery is to be able to keep them as I progress in experience (Ie to save battery dollars in future). Otherwise I could go with 5 cells and find lower powered motors...

Thanks...
Steve
-----------------------------------------
PS! Even with the following formulas, I find it somewhat daunting to obtain the necessary numbers to make an informed purchase decision...
Dana Ferguson's RPM calculator http://rceheli.com/ss/sheet as well as the following formulas:
(Rotor RPM) = (voltage) x (KV) x (gear ratio) = (1.05) x (# cells) x (KV) x (pinion teeth) / (spur gear teeth).
(Voltage [under load]) x (KV) x (motor efficiency) = (motor RPM)
(Motor RPM) x (gear ratio) = (head speed)
(Target speed) / (gear ratio) = (motor RPM)
(Motor RPM) / (voltage under load) / (motor efficiency) = KV

cptsnoopy

10-01-2007, 02:01 AM

Your question is rather vague. How much flight time do you require? I am guessing you could easily achieve 8 minutes with that battery and a low headspeed but whether or not that will provide your minum performance can only be answered by you.

MrMel

10-01-2007, 02:42 AM

Electrics arent like combustion engines where you can buy a smaller one and it will draw less gas.

You heli weighs X grams, it requires Y watts to lift, choosing a "not powerful" motor will just overstress the motor and it will pull more current because its not powerful enough.

That said, your requiment is a heavy battery for your heli, so it will be more optimal going with a lighter battery.

But for your setup I would have gotten a 1050 (Tango 45) to 1100kv motor (Z30) and a 19T pinion/212 maingear and I would have ran governor on the ESC.
I would probably have bought both 18 and 20T as spares if to try to find my optimal solution.

RPM at low load: 2123 at 22,2 volt
RPM at medium load: 1979 at 20,04 volt
RPM at full load: 1836 at 19,2 volt

You can try the configs here.
http://www.dacsa.net/heli/Calculator/Default.aspx

SteveSFO

10-01-2007, 01:12 PM

Great, thanks for the information. Fortunately I have not made any purchases yet, but am in the process of educating myself. Its rather daunting for a newbie... Thanks guys.

LITHIUMSTATIC

10-01-2007, 01:16 PM

Great, thanks for the information. Fortunately I have not made any purchases yet, but am in the process of educating myself. Its rather daunting for a newbie... Thanks guys.

Very smart researching everything. I hate to see people just start throwing money out without knowing what theyre getting.

Rigalo

10-01-2007, 05:03 PM

Steve,

Having seen some folk flying the 500 on 3700 6s, I would rather go for more amps, as you suggest. However, 5000 is rather a big pack. Now, considering upgrading, I would go for 4350 6s. Nope, you won't get all the flight time on the 500 as with a 5000 pack, but, with lower headspeed, you might get a decent flight/s. If you are ready to upgrade to more wingpower, I would upgrade the 500 to a 600. Now, this is where your 4350's would shine, if you put them 2 at atime in a 600. This would give you 12s with 4350's. Then, with a nice headspead of 2100, you will be looking at 9+ minutes of hard flying with a V-Stabi on it, and more power you can handle for your upgrade for a long time.

I'm currently flying the L14 with 12s, so, if I have to do a route wich will provide me ample power for and a nice upgrade route for the future, I will do without a doubt this. And it gives me some nice long flight times and a cool running setup.

One more thing, change the ESC to CC HV 85, then you will be able to do 12s in the future. Then, appart from boom, blades, etc, you only need to change to a motor like the 24-4. The CC HV 85 is a little fussy, but still worth it if you want a futur upgrade route.

Ohhh no, more ideas.....

Enjoy.

rwharrisjr

10-01-2007, 10:03 PM

Steve,

Logo 500 3D
FlightPower EVO25 5000mAh 6S1P
Motor: Hacker A40-8L-8P (1300KV)
ESC: CC85HV -Governor mode, 2200 RPM
BEC: Ultimate-BEC
Blades: 555 MAH, 85mm K&B
Mod .5 gears 212/18
Custom Heli Parts metal motor mount
Gyro: Futaba 401/9254
Servos: Futaba 9451
Spektrum DX7, AR7000
Ready to fly weight: 6.4 lbs.

I'm kind of a newbie so mostly sport flying--FFF, flips, rolls, inverted, stall turns etc.
7.5 minute flights use 72 to 75% capacity. 8 minutes pushes 80%

Love it!!

SteveSFO

10-04-2007, 01:33 AM

Good info. I know partially what threw me off - the Hacker motors seem to have the wrong KV ratings listed on their websites. When crunching numbers for the Hacker A40-10L which is listed with 500 RPM/V at http://www.hackerbrushless.com/motors_a40.shtml then the formulas just don't seem to jibe. Then when you go to http://www.fxaeromodels.com//product_info.php?cPath=94_292_225&products_id=4365 the same motor is listed with 1100 RPM/V which makes the formulas work out beautifully.

I've been advised by others that Hacker is just not posting the correct information for their motors. Amazing that the manufacturers can't even get it right. What is one to believe?

NTM

10-04-2007, 08:52 AM

Eyon

10-04-2007, 09:28 AM

I wouldn't go with hacker at all if your looking for run time, hacker's are ineffecient motors.
Kontronik tango 45-10 or a neu 1910 1y would be great setup with a 6s 5000mah battery, just keep the head speed around 2000 rpm and you'll get great flight time and power.

I wouldnt agree with that.

My Hacker A40-8L 8pole, 5 minutes of the hardest flying i can do, with 550 blades at 2350rpm. Thats a 15T mod 7 pinion. I have no doubt in my mind with a lower head speed, 8 minutes is possible. pack is a FlightPower EVO25 6s 5000

Ian

SteveSFO

10-04-2007, 12:52 PM

Getting what you pay for is an age old saying that still holds true I guess. Being a relative newbie and not wanting to have top end parts in the ship, I thought the Hacker A40-10L would be a nice cheap motor - and it sounds like it is - literally. I'll probably end up springing for the Neu. Thanks.

rwharrisjr

10-04-2007, 02:04 PM

NTM

10-04-2007, 04:00 PM

I wouldnt agree with that.

My Hacker A40-8L 8pole, 5 minutes of the hardest flying i can do, with 550 blades at 2350rpm. Thats a 15T mod 7 pinion. I have no doubt in my mind with a lower head speed, 8 minutes is possible. pack is a FlightPower EVO25 6s 5000

Ian

I'm just going by my experiences with the hacker a50 14s I used in my logo 14 on 10s 3700mah packs.
Decent motor powerwise, but the average current draw was high for the kind of power it did have. It ran quite warm. The neu motors I tried after were much better on average current draw and had more power as well.
You usually get what you pay for when it comes to motors, the hacker A series are a pretty decent bang for the buck, but not if you're concerned about maximum effeciency (which translates directly into flight time and power).