Mini FPV Tricopter Made Out of Old PANTS???? Make Your Old Pants FLY!!

Ever looked at your old pair of denims and thought "I could make a tricopter from those"? No? Well, now you will!! And to be completely honest it isnt much more difficult to do than making a standard tricopter!!

This Instructable will be much less in depth than my fireball shooting tricopter instructable as I figured that this was a much more abstract concept so the instructable should be more focused around the whole pants thing. I also figured that if Id already written up an in depth overview of designing and building a tricopter it would be pointless going over all that again. If you do want to know exactly what Im doing at every step of this process all of the electronics are identical (a little smaller perhaps) to my fireball shooting tricopter (except for the 5v power coming from the BEC in the PDB rather than the ESC's)

For a more in depth tricopter build check out my FIREBALL SHOOTING TRICOPTER

While reading this instructable, keep in mind that much of this project was very experimental. I had a vague idea of what I wanted to do going in to it but unlike my fireball shooting tricopter (for which I probably sketched up around a dozen pages of concepts and designs), this pants tricopter was a very "trial and error" project (I only drew up one design sketch)

Id also like to mention that Banggood was pivotal in the completion of this project and I more than recommend checking them out for any electronics project not just RC.

A quick little video to show that yes, it does actually fly (with all that FPV gear also).

Heres a little review I did on the BG1104 motor trying to show all features and give my own little insights.

Yes pants! The majority of the frame of this tricopter is fabricated from my very own pair of old denim pants. We can do this by stiffening up the denim with resin to make denim micarta from which we will cut most of the frame.

Here are the plans for the tricopter frame made in adobe illustrator. The red lines are to cut, everything else are guides.

I have also included rough plans for my camera case if you are using this setup.

Note: You will have to cut a slot for the antenna if you want to use the camera case.

All electronics (apart from the battery and KK mini) can be purchased from Banggood.com

You will need:

Electronics:

Diatone PDB

Towerpro MG90S

Turnigy nano-tech 460mAh (or similar)

4x Eachine XM 10a ESC

4x Eachine BG1104 4000kv motor

Eachine 3020 props

KK mini (or similar FC such as a 6DOF rev6 Naze32)

Assorted wiring (10cm servo leads)

Assorted heat shrink

Frame:

Old denim pants

Fiberglass resin

Two large, flat, heavy boards (to act as a jig for laying up the micarta)

10x3mm aluminium strip

ZEEPTIES (all hail the mighty ziptie)

Velcro

Assorted M3 AND/OR 1/8 bolts and other hardware

Loctite (blue/medium strength)

Tools:

Assorted screwdrives/nutdrivers/wrenches/allen keys

Soldering iron

Fine toothed coping saw

File+needle files

Spray adhesive

Hotglue

Needle nose pliers

Optional:

FPV gear

The first big step for this build is to lay up the denim micarta. I prepared by cutting 13x13cm sheets of denim (more than I needed) and covering two large flat surfaces with tight clingwrap (the clingwrap will warp no matter what due to the heat produced by the reaction of the catalyst and resin but the tighter you can get it now, the less it will warp and the less you will have to clean up your micarta. Personally I didnt clean up the little creases in the micarta however and it worked just fine).

Micarta is very similar to fiberglass in the sense that it is essentially just a sheet of stiff resin, strengthened by fibres (or strong fibres held together by rigid epoxy depending on how you look at it). Micarta can pretty much be worked exactly as fibreglass would be but with cotton rather than glass fibres. Hence, we will lay up the micarta as we would fiberglass, starting with a layer of denim (in my case a 13x13cm square) thoroughly "wetted out" (meaning that the resin has penetrated all the way through the fibre). I then build upon this layer with another thoroughly "wetted out" sheet of denim. This process continues until you have reached the desired thickness. In my case this was only two layers of denim which was plenty thick enough for the frame but I ended up gluing two pieces of finished micarta (doubling the thickness) for each arm. Once the desired thickness is reached the stack can be clamped and left to set.

Once the resin has set the micarta can be pulled from the press and cleaned up. I roughly sanded both sides and cut off the excess resin

The finished micarta was grippier than fiberglass (hence why it is predominantly used in knife handles) but was much more flexible and more susceptible to fracturing. There is absolutely no reason to use micarta over carbon fibre or fibreglass but hey... its pretty freaking cool right?

Note: Dont mind the white cloth, I was originally going to layer the white cotton and denim but I figured to get a good result my micarta would have to be much too thick and heavy for a tiny tri like this so I scrapped that idea.

Heres a little timelapse of me laying up two layers of denim micarta

Cutting out the frame was relatively straight forward (compared to most of this build). I printed the patterns on standard printing paper and secured them temporarily to one side of the micarta with spray adhesive. Each piece was roughly cut out with a fine toothed coping saw (always use a fine tooth when working with laminated materials to limit the risk of delamination). The holes were then drilled (some also countersunk) and each piece was cleaned up with files and needle files. The templates were then removed with a little mineral turps.

Note: I later decided the arms shown were much to thin at around 1.5mm and ended up cutting new arms out of 3mm micarta later on in the build

Note: Obviously this frame could be cut out of any other material such as wood, carbon or glass fibre or even modified to be 3D printed but lets be honest, none of those materials are pants.

The rear boom is made from a length of 10x3mm aluminium and is quite simple to cut and shape, just follow the plans and photos. The bends were just done with light hammer blows (with wood between to soften the blow) whilst the aluminium was held in a vice with soft jaws.

The tail motor mount is also cut out of a 10x3mm aluminium strip in the same way as the tail boom. Remember to only slightly drill the hole in the middle of where the motor actually mounts to give room for the shaft to spin.The 2mm hole also has to be tapped to fit a 2x6mm bolt (I used the one that comes with the motor) and I just tapped it with the bolt its self as I was only tapping aluminium. Just remember to back out 1/2 a turn for ever full turn of tapping.

To get the servo to a usable state for our tricopter it has to be modded extensively.

First up is modding the housing. I chopped off the mounting bracket closest to the spline and lead then sanded that side flat, the base was then removed and the hole for the lead was expanded with needle files so that when reassembled the servo would sit flush on a surface.

Next we have to mod the servo horns. In this case, this is pretty simple. For the horn with one arm all that needs to be done is to enlarge whichever hole matches your tail motor mount to a diameter of 2mm. For any other horn the same is done but all other arms must also be removed (this isn't necessary but is more than simple enough to do and helps everything sit much more flush). I ended up using all three horns (I accidentally broke one and the other one I accidentally degraded with loctite) and all three worked fine.

Lastly we need to shorten the servo leads. There are many ways to do this including not shortening the lead and just tucking the excess away somewhere but this is the cleanest way. Cut the end off the servo lead to whatever length you fancy. Then simply desolder the rest of the wire from the servo and strip and solder the cut end of the lead back onto the servo. Simple and effective.

Note: Dont mind the ESC and tail assembly on the servo, we'll cover that all later.

Next we must prepare the arms and the electronics to go with them. The heatshrink can be removed from each ESC as can the three black wires. We can the cut the wires from the motor down to length and strip them (be extremely careful here as those wires are thin and delicate). If the wires underneath are silver (tinned) go ahead and solder them to the ESC. If not, they are most likely gold (not tinned) and most likely still have an enamel coating on them. You will want to remove this thin enamel coating by scraping the wire with a knife before tinning each wire and soldering them to the ESC.

Dont worry which wires go where at this stage. If any motor is spinning in reverse we will fix that later.

Note: At this stage of the build I am still using the original arms (once again, this was all very experimental) which were much shorter than the final arms and much thinner. The method for preparation remains the same however

To prepare the tail motor assembly the motor can be secured to the tail motor mount using the longer, 6mm, M2 bolts provided with the 1104 motors. The ESC can then be soldered to the motor as before (I didnt shorten the wires this time just left them long so that they would follow the motor as it turns on the servo. The excess was then just tucked into the heatshrink). I then attached the servo horn to the tail motor mount with a single, longer, 6mm, M2 bolt. The whole tail mount can then be pushed onto the spline of the servo (centre the servo first) and secured with the provided bolt.

The assembly is then cleaned up by securing the ESC and extra wire to the side of the servo with a length of clear heatshrink.

Note: DO NOT GET LOCTITE ON THE SERVO HORN, IT WILL DEGRADE IT (ask me how I know)

I bolted the frame together with a mix of countersunk 1/8 bolts and M3 bolts. Be sure to use medium strength loctite to secure all bolts to prevent them shaking loose from vibrations (its very hard to balance 3 inch props)

Note: Ignore the PDB already on there, its just to make sure everything is aligned properly.

Note 2: The longer bolt in the bottom left corner of the first photo is there to ziptie the antenna to later on

The tail assembly can be secured to the tail boom with a couple of zipties. Just make sure not to over tighten them as they will squeeze down on and possibly damage the ESC (conveniently mounted on the OTHER side of the servo, my bad).

I know I said I wouldnt go into too much depth in thus instructable but I didnt cover this sort of PDB in my previous instructable so Ill cover everything here.

First I cut the outside off the PDB so I was left with the inner, smaller mounting option.

In the second photo you can see how I have run the black and red wires from each ESC to its respective side of the PDB. All of the "+" pads are connected as are all of the "-" pads do when I eventually connect power to the pads all of the pads will receive power from the one battery. Do not wire the ESC with backwards as they do not have reverse polarity protection and WILL burn if you plug them in backwards.

You will also notice in the second photo that I have a couple of other wires running off. The red and brown wires sticking out from the front and back of the PDB are connected to their respective pads of the 5v BEC output. These will eventually go off to power the receiver and KK board and the other to the rail of the KK board (again, if you dont understand, check out my fireball shooting tricopter instructable). The orange wire coming out the right of the copter will go to the voltage checker on the KK mini.

In the last photo I have secured the tail assembly to the tail boom and have wired up the tail ESC to the pads the same way I did the others. I also soldered a female JST connector to one of the 12v pads (powering ALL of the 12v pads and the 5v pads)

Note: You wil notice in some later photos there is also a black and white wire coming off the PDB, this is to connect to the FPV gear later and is entirely optional and dependent on what FPV you use. In my case, my FPV backpack runs off 12v so I hooked it directly to a 12v pad but in many cases your FPV gear will run off 5v, in which case you would connect it to a 5v pad. I understand that not isolating all this will cause lots of interference especially without a filter but there is simply no room on a tri this size to be messing around with filters or external BEC's.

I decided the arm was a little too fragile and thin at only 1.5mm thick (the original arms were also a little too short) so I epoxied two sheets of micarta together and cut new arms out of my new 3mm micarta.

The receiver was secured on top of the PDB with a couple of zipties. Notice that I have already connected 10cm servo extension leads to the receiver (if you dont understand the receiver wiring, you guessed it, check out my other instructable). Also notice that I have connected the receiver to one of the 5v outputs from the PDB's BEC. This will obviously power the receiver but will also power the KK board (check my other instructable)

Note: Notice the nuts halfway up the bolts. These have been loctited on and will give the KK somewhere level to rest in the next step

Next the KK mini was bolted onto the frame resting on the nuts mention in the previous step (I only used extra nuts on two of the bolts to secure the KK as it will already be held very tightly in place by the wiring).

Note: Notice that here I have also ziptied the antenna to the longer bolt

In this step all of the wires to the KK board can be connected.

The right rail (closer to the top of the image): The ESC's as well as the servo lead are connected to their respective outputs (signal wire closest to the screen). The remaining 5v output from the BEC is connected to the far right rail to power the servo and all ESC's (apart from ESC 1). The orange wire from the 12v pad of the PDB can also be hooked up the the battery voltage checker on the KK so we can monitor our batteries voltage.

The left rail (closer to the bottom): The 10cm servo wires from the receiver are hooked up to their respective inputs on the KK. Ignore the 2x3 array of pins, this is used for flashing the KK later on if you want.

Note: once again, for more on how to wire up a KK check out my fireball shooting tricopter

You may have noticed the velcro in the previous steps. This is to secure the battery to the frame. The front velcro was hotglued to the bottom of the frame and the back velcro was threaded between the PDB and the frame.

Plug in the battery and check for smoke... sniff the board... nothing? Okay, your good to go!

Before throttling up go into the KK2 menu and select receiver test then make sure all readings are 0 (or close to it) then make sure bumping the sticks left, right, up or down causes the screen to read left, right, up or down for its respective channel (the readings should max at around 90-100). Next load the tricopter layout, and calibrate the KK2 sensors (more info)

Arm the KK2 by lowering the throttle to 0 and pushing the YAW all the way to the right. Now throttle up a little and pick up the tri. Check the direction that the two front motors are spinning, if they are spinning opposite directions you are fine, if not you will have to reverse one motor by swapping two wires going to the motor (a little more soldering, I know, but hang in there! Its almost flying!!). Now turn the tri left and right and check that the tail motor tries to stay in one place (more info). If not, reverse your YAW in the mixer editor.

Attach your props and try to fly. Its a lot easier to get off the ground if you really punch up on the throttle (I know it seems counter intuitive) and with a tri this size you wont really do much damage if something goes wrong. Check out flitetests tutorial for more info on HOW to fly.

Check out this handy guide on how to tune your PIDs on a KK. The tutorial uses a KK2 but the process is the same for the KK mini.

My PIDS ended up being around:

Pitch:

P gain: 14

P limit: 100

I gain: 16

I limit: 20

Roll:

P gain: 14

P limit: 100

I gain: 16

I limit: 20

Yaw:

P gain: 10

P limit: 10

I gain: 20

I limit:20

Note:

These numbers are far from perfect but they are stable enough for you to get off the ground and start playing around with settings yourself.

I secured my FPV backpack to the frame with some velcro and a rubberband. I then wired up the backpack to 12v off my PDB (not filtered, I know). Of course this could be done in many ways this just seemed to be the best way for me. This step is completely optional and the tri does fly better and longer without that extra (in my case) 40g of weight but it is pretty bloody cool!!