Know How... 363

Fr. Robert and Jason Howell take you on a journey of Multi-rotor discovery with this first part in a series about the basics of building and flying these toys-become-tools!

 

 

The Challenge of flying a Quad vs. plane or a helicopter is that it doesn't have those traditional lift and control surfaces.

-- Those surfaces, combined with a propulsion unit (jet or prop) allow you to deflect enough air in the proper direction to get the desired motion.

-- A plan can also glide with the shape of its wing

 

-- In a single-rotor helicopter, a tail rotor or thrust assembly counters the rotation of the rotor

-- Adjusting the power and pitch of the large rotor allows your to rise or fall, and move in all directions

-- Adjusting the power of the tail thrust assembly lets your control yaw

 

** So how in the heck does it work?

 

The ONLY control we have over a Quad is in how we spin the motors and propellers

 

In a Quad, the motors that are diagonal from each other spin in the same direction.

-- The motors that are adjacent to each other, spin in opposite directions.

** This means that there can be a match in the amount of torque being generated by the rotors.

 

-- Increasing thrust on the remote increases Thrust on all motors... which means they're all developing the same amount of torque... which is getting cancelled out by the motors spinning in opposite directions... 

-- So the Quadcopter stays true -- we hover.

 

-- When we want to move directionally (Forward, back, left, right) we can increase the thrust from the motors on the opposite side of the movement, and decrease thrust on the side that we want to move towards.

-- In other words, we dip the Quad in the direction we want to move. 

 

-- When we want to rotate the Quad, we unbalance the torque being generated by the motors and props.

-- Let's say that the right-front and left rear motors are turning CCW

-- The left-front and right rear motors are turning CW

 

** If we increase the power going to RF&LR while decreasing power to LF&RR, then we've got more force going CCW... this makes the quad turn CW

** If we increase power going to LF&RR while decreasing power to RF&LR, then we've got more force going CW... this makes the quad turn CCW.

 

* Inrunning motors turn VERY fast, and produce little torque. Instead, they go through a reduction gearbox that spins the prop at 1/x times as fast as the motor shaft

* This means you can choose from a variety of propellers by changing the gear ratio of the gearbox. (i.e. you can make the propeller spin at its most efficient speed while not changing the RPMs of the motor.

 

-- This is the THEORETICAL number of times the motor turns for every volt it is supplied 

-- In reality, the number is slightly less because no motor is 100% efficient.

 

Turnigy 1704-1900Kv Outrunner

* When we give it 11.1 volts, it will turn 21,090 times per minute (1900 X 11.1)

 

* When we give it 11.1 volts, it will turn 11,100 times per minute

 

* When we give it 11.1 volts, it will turn 10,378.5 times per minute

 

This is a problem --- because other than the Kv, motors from different manufacturers don't really report their specs in the same way:

** Some give you thrust (like the Emax with 850g of thrust)

** Others just give you the max power (like 1740, rated for 49 watts)

** Still others will give you NOTHING

 

Dead Cat or "X-Alien" Frame $19

 

EMAX 2213-935KV (Pack of 4) $45.00

 

F-30A FIRE RED SERIES SIMONK-(RAPIDESC) ($10ea x 4) $40

 

-- OR --

 

LHI 2x 2212 920KV + 2 x SIMONK 30A ESC $63

 

POWER DISTRIBUTION BOARD 2OZ COPPER $2

 

HQ PROP 8X4.5 SF CARBON COMPOSITE PROP ($4.38 X 2) $8.76

 

KK2.1.5 Flight Controller $19

Straight Pins $3

Connectors $3.0

 

14 AWG Stranded Silicone Wire (5' + 5') $4.16

Heat Shrink Tubing $1.60

3.5mm Bullet Connectors (20 Male + 20 Female) $2.99

M3 Nylon Spacers $6.66

M3-0.5 8mm Machine Screw (Pack of 100) $7.14

 

3S Battery Charger 12.99

2200mAh 3s c5C Lipo Pack 10.99

Turnigy 9x 9 Channel Transmitter w/Receiver 49.99

 

Config 1 $236

Config 2 $214

 

Wire Cutters

Insulation Strippers

Soldering Iron + solder

Helping Hands

Screwdriver w/Phillips and Hex bits

Velcro Strapping

 

Procedure

1. Decide which arms will be fore and aft, then mark your arms #1-4 (Clockwise from front left)

2. Mount motors on arms with 8mm M3-0.5 screws, lightly covered in Locktite Blue

3. Thread Motor leads to top deck of arms

4. Mark ESC motor leads - leaving room for Bullet Connectors

5. Cut/Tin motor leads and power leads on ESCs (unless pre-cut and tinned)

6. Solder Female 3.5mm bullet connectors to the ESC motor leads

7. Solder Male 3.5mm bullet connectors on the ESC power leads

8. Insulate ends with heat shrink

10.Connect bullet connectors of ESCs to motors

11. Zip Tie ESCs to arms

12. Cut/Strip/Tin 8 x 2" lengths of 14 AWG silicone wire (4 red, 4 black)

13. Cut/Strip/Tin 2 x 5" lengths of 14 AWG silicone wire (1 red, 1 black)

14. Solder a female 2mm bullet connector to the end of each 2" wire

15. Solder both 5" lengths of wire into a Male XT60 connector

16. Insulate ends with heat shrink

17. Solder the other ends of all wires into the Power Distribution Board

18. Using nylon spacers, mount the Power Distribution board, contact points upwards to the lower frame plate

19. Attach arms to the lower frame. 

20. Run power and control leads from ESCs to interior of craft

21. Connect ESC power leads to PDB power leads

22. Mount top frame plate on arms.

23. Connect ESC leads to Flight Controller

24. Connect Receiver leads to flight controller