550E w/ Scorpion 4025-890kv head speed problem

[chrisl]

I have a 550E stretched, in a 600 rcaerodyne 500e fuse, with a Scorpion 4025-890kv motor 17t pinion 170t main, 595mm blades, 95mm tail, Talon 90 esc, the problem seems to be to low a head speed. Running -3, +5, +10 pitch. Castle link says I have it at 1600-n, 1650-1,1700-2. Is it the esc? Need a little help please! If the poles where set say to 8 instead of 10, what problem would that cause? That is one thing I found wrong that I did.

[nightflyr]

If your motor is the HKIII the specs are as follows ...

Scorpion HKIII-4025-890 Motor Specifications
Stator Diameter 40.0 mm (1.575 in)
Stator Thickness 25 mm (0.98 in)
Number of Stator Slots 12
Number of Magnet Poles 10
Motor Wind 4-4 Turn Delta Motor Wire 24-Strand 0.29mm
Motor Kv Value 890 RPM per Volt
No Load Current (Io) 2.30 Amps @ 10 Volts
Motor Resistance (Rm) per Phase 0.010 Ohms
Maximum Continuous Current 95 Amps
Max Continuous Power (8-cell Li-Po) 2700 Watts
Motor Weight 354 grams (12.49 oz.)
Outside Diameter 49.98 mm (1.97 in.)
Shaft Diameter 5.98 mm (0.24 in.)
Motor Body Length 51.8 mm (2.04 in.)
Overall Shaft Length 83.7 mm (3.30 in.)
Max LiPo Cell 8s Peak Current 110 Amps (5 seconds)
Peak Continuous Power 3750 Watts (5 seconds)
Motor Timing 5deg Drive Frequency 8kHz

On the assumption your running 6S

170 main gear * 17T pinion = GR of 10
22.2V (6S) * 890Kv = 19758
19758 / 10 = 1975.8 * ~85% eff factor = 1679.43 RPM HS

Using CC SET RPM gov mode, the numbers you post seem to be correct.

If you need to increase your HS you have to either
A) Increase your tooth count on your pinion.

B) Research the possibility of using an ALIGN 700 (164T) main gear.
Not 100% sure if your 550 can accept this or not.
If it can with your present pinion you would be looking at a max HS of ~ 1750 RPM

[Keyrigger]

I have been using a 550 with the same motor and main gear but a smaller pinion, 15t, for my CH-139 (Jet Ranger) which weighs in at 9.4 lbs. ready to fly. Your MD500 will weigh in about a pound heavier at the most (without a scale interior) and your motor will have no trouble flying that helicopter. My own preference would be to drop the pinion to a 16t, set your pole count to 10, and enter the gearing carefully. My CH-139 has no trouble picking up 2.5 pounds of water and slinging it around like a terrier with a stick. It will work fine as it is but the motor might find the shorter gearing better. Hope this helps.

Don

[chrisl]

Thanks guys, I just redid the Talon 90 w/castlelink and did a test hop. Much better, I will do more this week and weekend. Had it in a nice hoover, might have to adjust the pitch a little! Thanks again, Chris