700 Conversion "Sex Change"

Ever get tired of the same old thing? Fill up your .90 with Nitro, light the flame, fly around, come home after 1 or 2 gallons of Nitro is gone and spend two hours cleaning them. Don't get me wrong, it's a wicked thrill to watch those OS 91's rip the heli through the sky.

But as I watch the YouTube videos of guys flying .90E's. I laugh as I think of the cost of batteries and not so say anything about charging them. But I always wondered. Finally after hot roding a TREX 600 with the latest in electric technology and seeing the power it had, emailing buddies of mine about the idea, I knew I was going to do an electric 90.

So here we are go! We're going to give one of my .90's a sex change and going to give her 12S poooooower!!!!!

BEFORE IMAGES:




DURING IMAGES:






ALMOST DONE:


THE SETUP (so far):
Last year's Trex 700N
Helidirect's 700E conversion kit. (You'll need 4.5 mm bolts, I cheated).
Scorpion HK4035-560 Motor
Castle Creations Phoenix HV-110 (a 110 amps yeah!!)
A123 to run the electronics

More to come as I complete the conversion, program the radio and ESC, then setup the tail. This is looking cool!!!!

Battery Placement:


MOD #1 (Give me more room on the motor mount):
A little Dremel work to give my motor shaft some more room.


MOD #2 (cut hole in back of the nose cone to run ESC wires through to the motor)




MOD #3 and #4
I lowered the boom stablization bars down to make it easier to get the battery in the back in and out. I also had a battery mount made so I can have my back battery up off the boom stablization bar in the frame. I also installed the eagle tree elogger in so I can start fine tuning this beast.


With the canopy on


First flight was a success as I flew it at 7:30PM Feb 10th 2010 by street lights. Yes, in ths dark, using the street lights to see her. I do not recommend doing your test flights by street lamp as you never know what can happen (plus I live 1 mile away from a hospital haha)

Now it's time to see how many amps she'll be pulling in flight (elogger) fine tuning her to make sure she is one wild ride. Lets see it I can get that done this weekend.

Final thoughts of the build:
I do not think I would buy a new Trex700N to do a conversion on. There are a few .90 size Helis coming out this year that are built as an Electric. I did this because I had two Trex700's, the mod form Helidirect was simple to do and very cheap. Battery placement is kind of a pain as the motor gets in the way and CG issues.


THE "Current" SETUP :
Last year's Trex 700N (over 150 flights)
Helidirect's 700E conversion kit. (You'll need 4.5 mm bolts, I cheated).
Scorpion HK4035-560 Motor
Castle Creations Phoenix HV-110 (a 110 amps yeah!!)
A123 to run the electronics
2 6S 5000mah Zippy Batteries
Stock Align 610 servos for the cyclic
Stock align 620 for the tail
Spartan DS760 Gyro
115t Mod 1 main gear from FAD
13T pinion
Cyclic Pitch 10
Elevator pitch 9

Head speed: gov at 2150.
Pitch 13+/-

For this setup I am going to go to a 11T pinion as that should get me around my 2100 HS at 75% of throttle. Details to follow.

10T Should get you around 1950.

I'll put the power consumption and adjustments made on this blog as I do them.

Change #1 - Going to need to drop the head speed a little, I knew my calculations were high with the 13t pinion but I figured I would be able to run around 80% on my throttle curve. Wrong, the head speed at 80% was 2450+. I had to lower my curver down to 60% to get 2150+ (2200). So I am going to drop down to an 11t. So back to ordering and waiting.

1st "real" flight - Other than discoverng that my headspeed was wickedly high, the flight went well. I did not expect much to happen as I did not change anything other than the propulsion system. Everything else reamined the same. Plus, I did not do anything other than hit the collective real hard and fly around. My average amps are around 21amps, high is 136 amps. So you can see the work I have to do here.

Pros:
1. Do not have to fill the tanks full of nitro (there goes my work outs).
2. I ran 2 gallons in one weekend. Do not have to pay for Nitro!!!
3. Less maintenance than the Nitro. No longer spending hours cleaning, the vibrations from the nitro motor are not there so it doesn't shake bolts out (Yes, even with Blue Loctite you'll shake parts loose.
4. Zippy 6s 5000mah 30c batteries are $65!!!
5. Cost less to maintain and keep it the air.
6. I think the motor and speed control are easier to set up that a Nitro and Gov.

Cons:
1. Charging batteries.
2. I miss the sound of the Nitro (but the electric has it's own noise).

Same:
1. I think the cost for the build is the same (OS 91, Pipe and gov as compared to a speed control and motor). Maybe the electric is a little cheaper....
2. Fun factor!!! Hell yeah!! There's nothing like flying RC helis and there's nothing like flying a .90 (Nitro or electric).

Flight Reports:
1. Great, but head speed was wicked fast.
2. Got a smaller pinion and things are better for the head speed.
3. Pinion slipped down on shaft and wasted my main gear.
4. New main gear installed. Pinion still slipping a bit.
5. Cut nice grove in shaft to stop the pinion from slipping. Works.
6. Great flight I LOVE THIS!!!
7. Great flight (waiting for new batts to come in from hobby city).
8. Wicked flight. Now it's time to start tic tocs and see if I can get that pinion to slip. I may add some support in that area and some green loctite to the pinion. I am flying it at 2050 rpms. (I would love to get it to 2300 haha)