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| 8S T-Rex 600 ESP Electric RC Helicopter FPV Project 
The this project will cover the build up of a T-Rex 600 ESP electric RC
Helicopter from the ground up without purchasing a "New In The Box"
model. I won't need the BL motor, ESC, BEC and a few other parts that
come in the complete kit.
For more power and longer flights
this heli will be run on 8 cell 8S 5000mah lipo battery pack instead of
the 6 cell 6s the stock heli uses, so the stock motor and ESC will not
be capable. The power plant this heli will use is a Scorpion Brushless
Outrunner and Castle Creations ESC which is the recommended set up for
6S to 8S lipos.
The separate parts to build a ground up 600 ESP
can be purchased on the net or a complete kit with the idea of selling
off the un-needed motor, BEC regulator and ESC to off set the cost of a
new parts. In any case we purchased a complete ESP 600 CF frame, Tail
boom, Complete rotor head, Complete tail rotor assembly, Aluminum belt
drive gears, CF main shaft (longer then ESP for 3rd bearing) , Gears,
Tail boom holder, Futaba 401 gyro, Futaba 9654 servo (tail), Spektrum
DS821 servos, Castle Creations HV 85 ESC, Scorpion 4025-890 Brushless
Outrunner, CF 600 plastic bearing blocks (for 3rd Bearing), Castle
Creations 10amp BEC, Carbon Fiber blades, Eagle Tree Systems eLogger
GPS/OSD and a few parts from FPVpilot.com like Extended landing Gear,
BSM-600 TX boom mount, AVM-100 Anti-Vibe camera mount, ET RPM sensor
mount, etc.....The wireless FPV gear I plan to use is a 900mhz 500mw
video transmitter.
With all the parts here the first thing was to drill the holes for the
new lower 3rd bearing block and removed the square indexing key on the
outside of the bearing block. This bearing block is a must for cutting
down on vibrations generated from the main shaft and the older T-rex CF/GF 600
series has them stock so I found it's a good idea to add it. After the 3rd
bearing was completed I assemble the frame and cut a larger opening for
the bigger Scorpion motor with a Dremel tool cutting wheel.
Cutting
away the frame here doesn't make it any weaker and also allows easier
installation of the motor. The 3rd bearing being added also helps
strengthen the area. With the 3rd bearing the longer CF 600 main shaft
must used instead of the short ESP main shaft. The ESP's main shaft ends
at the bottom of the gears where the longer one goes into the lower 3rd
bearing.
The aluminum main blade grips
are changed out to plastic type. These offer a little more "softness"
to the heli which is OK with FPV and AP helicopters. I installed the
complete rotor head, main shaft and the gears checking all the bolts.
I placed the 13t pinion gear on the Scorpion motor which is the
recommended size for this 890KV motor to get the longer flight times.
With the frame cut away for the larger motor installing the Scorpion
outrunner was extremely easy.
The targeted head speed is 1800
rpms with the 8S lipo and 13 tooth pinion. I also had to drill out the
top of the 13t pinion because the Scorpions motor shaft is longer then
the stock motor the gear was designed for. You can also cut the shaft
down instead but I preferred inlarging the gears bore on a lathe. This
set up should produce longer FPV flights then the stock 6S lipo battery.
Since it's using more volts with 8S lipo it will use less amps then
the stock 6S set-up creating less heat and better performance for low
"C" rated lipos. The flight times are estimated between 11-14 minutes. For
the battery packs I use one 6 cell 6S 5000mha and one 2 cell 2S 5000mah
put together in series to gain the 8 cell 8S 5000mah lipo pack. 
The
next item to be installed was the tail which has no modifications. I
went with the belt drive because of the lower cost, smoothness and in my
opinion I won't need the Torque Tube type since quicker tail response
is not a factor with my FPV/AP helis. I added a ground wire from the
tail boom to the motor mount to stop any possible static build up the
belt may induce which can ruin electronics (this is not needed on
aluminum frames). With the tail installed I moved on to the battery
area. The stock location needs to be change to the lower frame rather
then stood up like stock configuration. This allows more room for the
larger 8S lipo battery and also now the Eagle Tree data logger system
can be placed above it making it easy to attach to the power supply.
Doing this will also allow better Center of Gravity (CG) when the FPV
wireless gear is placed on the rear of the heli like video system
battery, video TX, radio RX (AR9000), radio battery, etc.... With the Battery being placed on the lower frame there is a chance that
a mis-hap like a nose in crash may ruin the expensive lipo battery so
the FPVpilot.com battery tray is used for support and a little added
protection. The battery tray also has 2 bolts that go through and
attach to the landing gear which gives even more security. The tray
also has a stopper designed into it at the motors end so the battery
can not be pushed or placed against the motor.   I installed the Castle Creations HV 85 ESC.
Once I soldered the connectors on I placed it inside the frame behind
the motor. Some suggest placing it outside the frame but since this
heli will be Over-Kill on power I don't expect it will heat up much and
if so I'll add a cooling fan on it. 
I'm using a Castle Creations 10amp BEC for powering the Spektrum AR9000
RX and DS821 servos instead of the Align regulator BEC. This heli will
require other gear and more servos to be operated other then the control
servos so the higher rated CC BEC is needed to meet the demand. Both the AR9000 and CC BEC are mounted at the rear of the 600 along with the 3S lipo battery that will power them.Note
in some cases with the older CC 10amp BEC you had to remove the orange
wire when powering a JR/Spektrum RX. This wire is easily removed and
reattached if BEC re-programing becomes needed. This issue may have been
fixed with newer CC BEC's.   With the AR9000 RX there are two external
diversity antennas so I used an extension cable and mounted one on the
tail and the other on the landing gear strut. The 900mhz
transmitter will be mounted between them mid-way on the boom. The theory
is to have the RX antennas able to receive better when surrounding the
900 mhz transmitter from the front and rear. 
With the Eagle Tree Systems eLogger, GPS and OSD being installed
onboard I used the FPVpilot.com's RPM sensor mount. The Align main gear
has a place for the magnet which triggers the sensor on every revolution
giving a 1:1 ratio for accurate Head Speed.   Even
though the Eagle Tree gear is circuit protected I like to cover the
un-used pins with servo connectors that are "dead" with the wires cut or
removed.For sensors I will use magnetic RPM sensor, temp sensor on the motor and a temp sensor on the ESC.        __________________________________________________________________________________________________________ ****Disclaimer: ****
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