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Part 1 - Core
Part 2 - Tail
Part 3 - U/Carriage
Part 4 - Servos
Part 5 - Electrics
Part 6 - Flight Trials
Part 7 - Assembly
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Mil Mi-24V Hind E Helicopter - R/C Model Conversion

Part 5 - Electrics

Initially I wanted to use the standard electrical components from the donor Hummingbird. After flight test however I discovered two problems. The main motor was not providing enough lift even with a 14 tooth pinion and secondly tail rotor control was not sufficient. I believe the tail rotor problem may have been due to the power consumption of the main motor not leaving sufficient for the tail motor or possibly the combined Gyro/Mixer board as used in the latest Hummingbirds, I feel this may not be capable of adjusting to the dynamics of the model, in the Hummingbird itself it worked well.

I decided on a fully seperate, brushless setup and purchased the following components :-

  • CSM LW200 Heading Hold Gyro (lightweight uncased version)
  • 10A Pheonix Brushless Sensorless ESC for Main and Tail motors
  • Himax 2015 - 4100 brushless main motor
  • Feigao brushless tail motor

I researched carefully wiring these components together and found relevant articles on the net
 
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I had a good think about where the electrical components would all fit, the main considerations where the receiver, the two ESC's and the Gyro. I had already decided where the LiPo battery was to be positioned.

This first task is to mount the Gyro. As this is the uncased version I decided to make a cradle that would fix to the inside of the fuselage and hold the gyro with its axis of rotation parallel to the main shaft.

I made the cradle from Plasticard first making a template to make sure everything lined up. This holds the Gyro in position very effectively as the picture below shows.

I drilled a hole in the fuselage to correspond with the gain adjustment screw.
 
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The Main Electronic Speed Controller (ESC) was mounted with double sided tape against the fuselage wall adjacent to the Pitch Servo. This kept the motor wires short which I soldered and covered the joint with heat shrink tube.

All three wires to the receiver on this ESC where kept as these supply power to teh reciever via the Battery Elimination Circuit (BEC)

The receiver fits quite comfortably in the compartment to the rear of the pilots seat. I drilled a hole through the base of the fuselage and threaded through the aerial. I trimmed away some of the ceiling bulkhead to allow the routing of the cable connections.

The servo cables needed no extension and plug straight into the receiver.

 
 
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The Gyro Cradle was glued in postion with CA and checked for verticality and that it is parallel with the main shaft.

The Tail ESC was mounted with double sided tape as can be seen. The power cables to this where spliced with the main ESC and a female JST type connector fitted ready for connection to the battery. The battery cables where routed through the rear bulkhead.

Having satisfied myself that everything was in place I glued the entire chassis structure in place in one half of the fuselage, routed the cables neatly and tied off with cable ties.

Once the glue was set and everything was firmly in place I turned on the transmitter and connected the battery, both motors worked perfectly the tail rotor responding properly to any sudden changes in direction. The servos also worked correctly with no hindered movement.
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UPDATE: Having enjoyed flying the model around for a while I have become a little greedy and decided that 2/3 minutes on a 2 cell Li-Po was not good enough. E-TEC have a 3 cell 11.1v 1250 mAh battery that is 62mm x 32mm x 19mm. This is the same width as the 2 cell but longer and deeper.

I studied the model and determined that if I cut an access hatch in the bottom of the fuselage and cut away the floor of the main cabin the 3 cell Li-Po would fit and would not really spoil the appearance of the Heli.

I cut carefuly with a craft knife until I had the fitted battery free then filed the opening until the new battery fitted quite comfortably. I placed a small amount of foam on the rear bulkhead to push the battery tight against the front bulkhead to hold it in place. I also made up two hooks using 4mm brass square section to act as anchor points for an elastic band.

I am really pleased with the results, the Heli is far more responsive, tail authority absolutely precise and flight time beyond what I feel comfortable with. I did have to reset trims due to the difference in weight (only an additional 28g) and also gyro gain due to the higher voltage.

I have both lower fuselage doors closed now which gives the model a better appearance. Another plus point of this modification is better access to the main gear and motor for maintenance.

I fitted deans micro plugs to cope with the current draw from the motors as they are higher rated than the JST type connectors.
 
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