Introduction: Cheap, Crash Resistant Portable T Copter (in Apprx 200 USD)
Hello People of the world.
One fine morning, I woke up and decided to find out what is going on in the world of aeromodelling. I was surprised to see the world had been overtaken by drones. There were multirotors everywhere and everyone was making one for themselves.
So I decided to make one for myself. Being always out of cash I was hell bent to make something that was cheap. And since the only mode of transport I have is my trusty 3 yr old Honda motorcycle, it had to be portable as in backpack-able. As it goes without saying, it had to be crash resistant as this would be my first multirotor.
A portable , crash resistant T-copter seemed to be the ideal candidate for this adventure.
In this instructable I will stress on how to make the frame rather than going into the intricacies of the electronic component selection and their settings. There are a lot of websites which provide enough information on those subjects. A quick google search should do fine. (Edit : I did add basic info for the benefit of any person new to all this)
However if you are one of those lazy asses or simply want to emulate my setup, following this instructable should give a good T Copter to begin your multirotor journey.
/*Edit : added parts list*/
From local hardware shop
Zip-ties (or from HobbyKing.com)
PVC pipe 3 in or 4 in diameter
Screws/nuts/bolts ( I used 3 mm everywhere)
Cutting and soldering tools
Velcro (or from HobbyKing)
30 Minute Epoxy
Standard Props (Aerodynamic blades that actually generate lift)
Counter Rotating Props (Counter rotating props used to minimize torque due to rotation)
Motor (To spin a prop and generate lift)
ESC (This regulates the motor speed)
KK2 board to Rx wires (connects the radio control receiver to flight controller. Feeds your radio transmitter stick movements to the flight controller)
Lithium Polymer battery (power ups the whole system)
Wheel steering mounts (mechanism to make the tail rotor tiltable)
A standard Servo (I used Futaba S3003 : not available on HobbyKing) (actually tilts the tail motor mechanism)
Also you need to have a Radio control remote which you can buy from a local hobby shop. I have been using a Futaba 6EX gifted to me by my dad a decade ago. You don't need any fancy shiny stuff. A basic four/six channel radio should do the job. Turnigy 9xr is a capable and cheap radio and is recommended. You will also need a Tx module with it.
Step 1: Why a T-Copter ? and Not a Tri-copter or a Quadcopter
There is always a trade-off in the choices that you make. If you have a limited budget and want to stay cheap a T-Copter / Tri-Copter has one less motor + esc combo and hence cheaper than a Quadcopter. Also creating a portable Quadcopter is much tougher than a T-Copter / Tri-Copter (Not that it is impossible).
A Quadcopter on the other hand is more stable (not that T-Copters are bad at that) and involve less complex moving parts.
The advantage of a T-Copter over a Tri-Copter is simply in orientation. At some point of flying your multirotor you are bound to loose orientation of your craft and possibly crash. Since the T-Copter is not symmetric on its axis , the chances of this happening are lesser than a Tri-copter.
So if are a first time multirotor pilot and on a budget, stick with me.
Step 2: Choosing the T-Copter Size
The next step is to decide the size of the T Copter. The size of a multirotor is defined by the distance between its motors in mm. If you want stability and smooth flying I would suggest to go for 650 mm and above sizes. If you are looking for some adventurous zippy flying stay close to 450-550 mm.
If this is your first multirotor I would suggest to stick to the bigger sizes. Now head over to http://tcoptercalculator.co.nf . This neat little website gives you all the necessary dimension for your T-Copter. I would suggest to select the medium preset or above. I choose the medium preset for this project.
Note down your dimensions and the CG position.
Step 3: Choosing the Frame Material
Alright so you should have noted down the dimensions on the last step by now. Its time to create the frame. The obvious question that pops up is : What do I build the frame with ?
The three most famous materials, to build a multirotor in 2014 are Aluminium, Wood and Carbon Fiber. Among these three materials Carbon Fiber is the best looking material but the most costly as well. It is also the least vibration absorbing material and being the lightest of the three.
Aluminium on the other hand looks reasonably well and is cheaper than Carbon Fiber. It is slightly heavy than carbon Fiber and has good vibration absorbing characteristic.
The third material and my favorite to build you first multirotor is good old wood. It may/may not be as good looking as the other two, depending if you get processed wood or raw. It has good vibration absorbing characteristics and is most easy to work with. It is also the cheapest among the three.
So my vote for now goes to Wood. Yaay !!! The wood that I chose is called 'Lippin Patti' here in India and comes in pre-cut strips. I am not sure what it is called at your place but I am sure you will figure that out.
Step 4: Creating the Frame
This is where the instructable gets exciting. This is also the step where I do magic to trick you into believing that I took shots of all the necessary steps. If you find some odd looking and fishy pics, its time to visit your eye doctor.
I will show you the technique to build the portable, crash resistant frame. However since the wood that you get in your country will probably not have the same dimension as mine, please take into consideration the dimension changes you might need.
The most critical dimension that you must adhere to is the motor to motor distance. Any deviation in this parameter and you may end up unsuccessful. Here are the dimensions of the wood pieces I used.
The standing piece in the 'T' frame :
Length : 523mm
Width : 40mm
All other wood pieces :
Height : 15mm
Width : 20mm
Length : According to requirement.
The wood pieces required are clearly shown in the pic above which I did digitally manipulate to look like an illustration.
Step 5: The Folding Mechanism
Take the main wood strip and mark two points 519 mm apart and at the center point along the width (20mm in my case). Leave 20 mm from both edges as a margin of error. At one of these point will come the tail motor and the folding mechanism at the other.
Lets complete the folding mechanism in this step. The tail motor will be done in a later step. Mark the center lines on the folding mechanism wood pieces and use epoxy to glue these pieces to the main wood piece: one on top and one at the bottom. After the two pieces have dried use a cotton thread to wrap around the joint and simultaneously ask a colleague to apply CA glue to it. Let the CA dry. This will create a strong joint.
Since the height of the main wood is 10 mm and that of the folding arms are 15 mm, I had to grind 2.5 mm from both sides of the folding arms. You can avoid this if you choose the wood wisely.
Insert the folding arm into the folding mechanism and temporarily use tape or rubber bands to secure it. Leave a clearance of 10 mm from the main wood strip. Then drill two holes (3 mm in my case as I used 3 mm nut/bolt) through the assembly.
One hole will have a nut and bold to allow the arms to swivel around it. The second hole will be used to fix the open position of the arms using zip-ties.
The pictures should make the process ample clear.
Step 6: Mounting the Motor on Folding Arms
The motor that I have used is the Turnigy 2830/11 1100 kv motor available at hobbyking.com . The esc used is 20 amp multistar esc again available at hobbyking.com .
Dry fit both the folding arms and mark the two points 600 mm apart and being symmetric about the main wood strip. Trace the motor mounting template. We will be using zip-ties to mount the motor. This helps prevent any damage to the motor in case of a crash as all the impact is taken by the zip-tie and it snaps.
Refer the pics.
Step 7: Mounting the ESC
Similary use the zip-ties to mount the esc's on the folding arm as shown.
We will be using both standard rotation and counter-clockwise props in our T-Copter. This helps counter the torque generated, due to the spinning mass of motor as well as propellers, to cancel out each other a bit.
If you view your T-Copter from above, the tail prop and the left arm prop should be rotating in clockwise direction. The motor on the right arm should rotate counter clockwise. Needless to say order more standard rotating props thatn counter-clockwise rotation ones.
The rotation on the motor can easily be changed by swapping any one wire that connects it to the ESC.
Step 8: Creating a Custom Wire Harness
Since a single Lithium Polymer battery will power all the three motors, you can either get a power distribution board or go the cheaper way of fabricating a custom wire harness as shown in the pic. This will require some soldering skills.
Step 9: Tail Yaw Mechanism
A T-Copter or a Tri-Copter move on the yaw axis by tilting the tail motor and hence directing the thrust sideways. This yaw mechanism can achieved by using a servo motor and nose wheel steering assembly. It is not necessary for you to use the same mechanism. You can google Tri-Copter yaw mechanisms to find other methods.
This yaw mechanism is one used by David on his tricopter and explained beautifully here.
Use zip-ties to secure the mechanism.
Step 10: Mounting the KK Board and Reciever
Used a plastic lunch box to protect the flight controller board ( KK original board) and the receiver. Use a soldering iron to melt holes in the plastic and zip-ties to secure it to the frame. Place the box as close to the T joint as possible. We will balance the T-Copter by the counterweight of the Lipo battery.
The KK board was put inside the original foam case it came in and was glued using hot glue. The connections made with the receiver and wires routed appropriately. Be sure to read the KK2 installation manual and connect the board correctly with the Rx and the esc's.
Step 11: Adding a Landing Gear
The best landing gear that I found for multirotors is PVC pipe. I used 4 inch diameter pipe and cut out three pieces of 20 mm thickness. Use zip-ties to attach to the wood frame.
Step 12: Placing the Battery
Use a minimum of 2200 mah lipo with atleast 20c rating. Place your lipo on top of the main wood tail strip and try to balance out the T-Copter about the CG point as shown in the step where the frame size is calculated. Use velcro strap to fix the battery.
Step 13: Fold Up Your T-Copter and Go to Your Flying Field
Step 14: Flight and Crash Resistance
The only thing you will ever break on this multirotor are the Propellers and the Zip-ties. So get spares for these and enjoy flying your T-Copter.
Flight Time 7-8 minutes
The videos are a testimony to that. The first video shows a fellow aeromodeller flying his newly built T-Copter for the second or third time.
In the second video I was flying this T-Copter in over 60 Km/hr winds on a hill cliff. Suddenly a prop simply decides to disintegrate in mid air. The T-Copter plunges straight from around 10 m height. All I broke was zip-ties and the single prop of-course.
The third video shows the close up of the T-Copter after the crash.
The fourth video shows my friend doing some cool aerobatics on his T-Copter.
If you have any comments or question you are welcome on my website :
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