Bang Buck Quad

$170 and lots of bang for your buck.

I call it the Bang Buck Quad because its relatively cheap, it goes like a skinned cat* and it is made in China.

I did a lot of homework on the forums before deciding which parts to buy. Its has survived numerous crashes already with just broken props and zip-ties. I get about 12 minutes flight time out of a 3S 2650mAh battery and about 10min with a 2200mAh. It will carry a GoPro with ease. Most importantly, with the Simon K firmware it is rock solid stable, fast and highly maneuverable. It is also suitable for beginners if you dial down the sensitivity. 

Here is a video of it in action.

Materials list:

Including postage your looking at about $170.

I have not included a receiver in here.

The build notes.

Most of the work here is connecting up the Frame, ESC's and motor. The Frame itself is easy to assemble. Rather than do step by step I am going to go with a non linear approach to the build log.

Motor mounts. Three zip ties are all you need. I used three on each mount. Mount all three loose first then tighten each a little bit at a time to keep the mount centered.

I managed to get it centered without drilling any extra holes.

Advantage of the zip ties is that they absorb the impact of any crashes. The ones I have tend to stretch rather than break. If you don't cut them down too much you can just re-tighten them. Though I have not proven it, they might just absorb some vibration as well.

I have not tried this yet but you could also replace all the metal screws with nylon ones. They are cheap and it would help protect your frame in extreme crashes.

You will need a nice big hot soldering iron for the wiring and connections to the frame. A cheapo 15W will simply not cut it. I use a 120W Truper trigger type iron that I got from our local Kiwi hardware for around $70, its a cheap brand and overpriced but I am more than happy with it.

These things only heat up when you have the trigger on and some have a two stage trigger and even a light. With a bit of practice you can get the temperature just right. They are also good for heating heat shrink.

I did do some homework on getting one from Amazon but I had to buy local as they do not deliver to Ecuador. I cannot guarantee that these are any good but there is not much to them (just a transformer and a switch) so I would say any brand is a a safe bet. Quality might vary on the tips but you can get them easily.

Here are some options if you are in the states or on 110 volts:

I have diverged a bit here I might make a DIY Soldering tips page later on.

Moving on.. Lets start with the hardest soldering, the battery connector.

I did not have anything thicker than 16AWG so I decided to double it up.

Split the strands into two.

Then twist together and give it a good tinning. A tip from you can also wrap a single thread of wire around it to hold while soldering.

Having another plug without the battery connected in the other side helps the pins to stop moving and the plug deforming when you heat it up. Plenty of flux and a good hot iron before you make contact is essential. Here I didn't tin the plug first but that also helps.

Not the best job but it will work.

The 5mm heat shrink needed a bit of stretching before it could fit over both wires.

Tin the pads and the wire before soldering, I have flux in a pot as the solder here does not come with flux. Lots of heat and lots of flux.

Here is my quad sitting in my flux pot, the joys of a cluttered table.

Before you put them in you might like to flash your ESC's. While you are at it you may as well balance your motors as well. I first went with the HK Blue Series 20A but I completely muffed the soldering which overheated a few of the FET's. It was all together and I found that two of the motors were cogging. I pulled the covering off them checked all the connections, all OK. I then tried it without the heat sink on (normally you can do this no problems at low speed) and I had flames.

Good thing I had a bunch of HK F20-A ESCs which were intended for a hexacopter frame that is now gathering dust. Although these are heavier they are much easier to flash and the wires are long enough not to need any extensions.

Here are some pictures of how I fitted the HK F20-A ESCs.

Motor is soldered and heat shrinked directly to the ESC, No extensions needed.

Probably best to do these connections last and test your motor direction first.

The wires are long enough to reach the frame, I think I even trimmed them off a bit.

Note the use of zip ties and the exposed pads so it is easy to flash later.

I chose not to put in bullet connectors simply because they are a pain in the bum to solder. If you are planning more airframes it might be an idea but I am not sure it is worth the hit on resistance, weight and reliability.

Also without the bullet connectors you have to make sure that your wiring is correct for each motors rotation. The other option is to re-flash with the reverse version of SimonKs firmware

The soldering was done with the top of the frame removed.

Top view with the controller mounted. I mounted it with double sided tape. I offset mine so I had room to mount my GoPro. It may not seem intuitive but you can mount the board anywhere on the frame as long as it is flat and pointing to the front. These boards only measure angular acceleration which is the same for any point on a rigid body. If you have a KK2 board and want to use the self leveling features you will have to mount it at the center of gravity as it also measures linear acceleration.

That said, the is the least amount of linear vibration at the center so it is best to place it as close as possible.

View from the front. Receiver is held on with velcro.

View from the back, the lipo alarm is essential for a quad and good for your batteries. Again it is stuck with velcro and it must be removed to fit the battery. I like this because it reminds me to connect it.

Furry side on the batteries so they don't pick up so much grass and pubes.

No battery strap is needed as by design the quad can only accelerate in one direction (up). Dont throw it away though as you might choose to mount the battery on the bottom later and fill this space with FPV gear.

On that if you are planning on doing FPV with one of these it might be better going for the non PCB frame as there are large slabs of copper here.

Bottom view. I drilled two holes and made to notches so I could attach strings and test the roll and pitch axis indoors.

Before you attach your props its time to setup the controller board and make sure that everything is working.

I'm feeling lazy and Josh has two great videos on programming and then setting up your controller. He is using the HK 3.0 controller which is the same as the HK v2.1 except with more memory. Don't worry the other Josh is not in these videos. :)

Calibrating using the SimonK firmware is done exactly as Josh shows, the only difference is that you will hear only 1 beep at full throttle and then 2 beeps at zero throttle followed by one long beep indicating that the ESCs are armed.

Last thing to do is mount the props.

Cut these off so the nut makes a nice fit. I have also drilled out the hole to 4mm. You can if you like balance the props but for non camera work I don't bother. I found that even with chunks missing out of the props it still flies fine.

Before cutting I added two extra nuts to have a reference. It also helps to repair the thread when they are removed.

Dremels are cool, you can also use a hacksaw.

A few drops of locktite means you dont have to tighten the nut as much. If you tighten too much the shaft can move in the bell and you will add unnecessary friction.

I highly recommend sanding the knife edge off the props. I used a fine sandpaper very lightly to round the leading edge slightly. As well as saving your fingers this might just improve the aerodynamics of the props given the dodgy moldings. Don't go too crazy you just need to be able to feel the difference with your fingers rather than see it. Remember this will not make your quad idiot proof but it will reduce the risk. Unlike Bruce's Lady Bird this thing could kill your cat.

Thats it. You are ready to fly.

A lid to protect your electronics is also a good idea. The round lid from a pack of DVDs is ideal. A few holes and some zip ties and you are done.

I tried a 50 stack one for a bit and it changed the aerodynamics quite a bit. It looked stupid but it just felt like it flew better. I would say it was smoothing the airflow through the rotors reducing the vortex ring state. Of topic a bit but if you are interested in helicopter physics like I am check out these videos. The guy is a bit of a dork but the content is great.

Some tips for newbies, take baby steps. Start off hovering and practice till you are good at it. Then practice hovering with it facing you, then to each side. I went through 10 charges on my first heli before I started doing turns, and that was after hours on a simulator. This helps to wire up your eyes, brain and thumbs so when you do start flying forwards and doing turns you will not make so many mistakes. 

Have fun.