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HomeScaleAircraftHelicopterScale Model RC Helicopters › A little head speed help please
10-09-2012 02:10 AM  5 years agoPost 1
Ron Novak

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Fayette County, Pa.

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T-Rex500 stock motor and ESC using Align 4-blade head. What head speed / pinion gear should I use for sport flying.

Ron

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10-09-2012 02:57 AM  5 years agoPost 2
JoseReyes

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Steilacoom, WA USA

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You can start with 82% to 85% throttle about 2000 to 2200 rpm's with a 11T to 12t pinion but in all honesty the stock motor will not last long with the 4 blade head. I had to go down to a 1210kv and 13T pinion to keep the ESC and motor from burning up... Hyperion 1210kv as they do not need oiling like the Scorpion motors...

It's just a suggestion, however, keep an eye on the temps on the ESC and motor, sooner or later you will have issues with heat...

Best scenario would be 1000kv or 1210kv with a 13T pinion for 85% efficiency and a estimated head speed of 1900 to 2100 give or take depending on how heavy...

Jose

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10-10-2012 03:11 PM  5 years agoPost 3
Ron Novak

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Fayette County, Pa.

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Thanks Jose. This is the info I was interseted in. I wonder if the guys that build this as a scale project using the Align bodies are up against these same issues?

Ron

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10-10-2012 08:29 PM  5 years agoPost 4
JoseReyes

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Steilacoom, WA USA

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Heliman
Fayette County, Pa.
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Thanks Jose. This is the info I was interseted in. I wonder if the guys that build this as a scale project using the Align bodies are up against these same issues?

Using the stock align motor for scale heli's using two blades is not an issue. The issue comes when changing from two blades to either three, four, or five blades...

if you have to go below 80% on your throttle curve, then you either have a motor that is too fast for the setup and or wrong pinion setup...

For multiblade setups you need a motor with more torque not more speed, hence, a lower kv motor. you want to keep the power output of the motor
between in the high 90's 80 being borderline too low...

The key is to have a motor kv just fast enough to give you your desired head speed with optimum performance. Any time you have to take the ESC below let's say 85% you are asking for trouble sooner or later. Maybe not right away under cooler temperatures, but as the temperature outside gets hotter, you will start seeing the ESC overheating.

Forexample:

Motor 1210kv, pinion 13T, Main Gear 162T mode .6, 3300mah lipo 6s 40c
at 85% throttle curve, you would be getting an estimated give a 50-100 rpms difference...

Head speed is around 1832, again +- margin of 100rpm's

With this setup I can fly comfortable 8 minutes constant...

You must realize that total weight of the heli also plays into these numbers, type of blades, etc...

BO-105 500 size, total weight 6.5 lb, 4 blade head, scale blades, 600 size tail blades 8-9 minutes on a 3300mah 40c 6s lipo
HH-60J Jayhawk 500 size, total weight, 9.5 -10 lbs, including all external accessories (external tanks, engineer at door) flies around 8 - 10 minutes... except this one uses two 2600mah 25C 6s lipo's in parallel. Why? to offset the CG of the heli. Jaywalk being very tail heavy needs a bast amount of ballast in front to correct the CG, I chose to use useful weight

Jose

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