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Helicopter Build - Minicopter Diabolo 700

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Helicopter Build - Minicopter Diabolo 700

Hi, I thought I would share a helicopter build with everyone. Seems like helicopters haven't had much exposure to the club, and this might be interesting for some members to see. This will be a far cry of the beautiful airplane builds on here, but hopefully you guys will enjoy! The helicopter kit is a Minicopter Diabolo 700. Minicopter a small company in Germany that makes very high quality, and very well engineered models. Even being a small company they are very well known around the world for quality, but also their involvement in Speed flying. They've held the title of the fastest R/C helicopter several times. This is not a mass produced kit so not many corners were cut. I ordered this kit 2 months ago, and after 2 weeks of transit I have finally received it today.

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There are many ways a heli can be setup. I would like to setup a lighter frame and lipo pack with a moderate powered motor. The Diabolo is a lighter air frame so I can maybe squeeze some more power in but also keep it light to keep a lower head speed for a longer flight time. I bought a tail pulley to speed up the tail for a lower headspeed and keep tail authority. With the pulley I can run up to 2000 rpm without over speeding the tail causing more problems. With this airframe you can also run from 1200 rpm to 2500 rpm headspeed so many options are open, but with experience 1900-2000 at this altitude is a good compromise. At 2000 being a little low the pitch of collective can be bumped up to make up for the lack of headspeed. Probably I'll end up starting out with 14 degrees of pitch which a high but with the lower headspeed it should speed things up, but with a demand of high power demands. The demands might be high but only for a few moments. Next up is the motor selection. I happen to have an Align 800mx Dominater that I can use as a baseline. Its a 520kv motor that can do 5100 watt(115 amps)continuous /11,000 watt(250 amp) for 2 seconds at 12s. This motor is middle of the road motor for power and efficiency. It should give me enough grunt to make up for the low headspeed and high pitch. Later I can get a higher quality and efficient motor after some test flights and tuning. The ESC is going to be a Castle Creations 160amp 50v. It will handle the motor very easily, but with the canopy design on this heli restricts air flow for heat build up. Also it will be changed later to match the motor selection later on. Lipo wise, I'll be using 2 4400 mah in series. Most 700 class helicopter use 5000 mah but usually with down sizing the packs you end up using less mah while flying. 4400's should give me close to same flight time as 5000 packs since it carries less weight. Next up is electronic selection. I chose the Jr ds8917hv cyclic servo for 2 reasons. The first reason they are high voltage so I can run a 2s lipo just for electronics for reliance. Second they are very fast with a ton of power, but still a plastic case to save weight. Most helicopter cyclic servos are aluminum cased and high consumption causing over amp draw through the flybarless controller which is not good for a reliable helicopter. For the stabilization controller I chose the Msh Brain/Ikon for many reasons. I know the unit very well, but also for its ability to take vibrations very well with out problems. Not to mention it flies well with not much tuning. Lastly, the futaba bls256hv tail servo will be installed for its unequaled performance and light weight. With most items chosen for the build one thing that has many options is the blades. In the last year many things have come out to improve performance like swept tips, and airfoils that change through out the length of the blade. I've purchased a set of Cyclone 715mm blades for several reasons. These blades have shown the can be smooth in the air , but also be very reactive when you lean into the pitch. Also I chose the 715mm blade over the 696mm version since I'm running a lower headspeed for the extra bite. I also own several different blades of various blades lengths to try. With explaining all the components that I chose the thing that really matters is the FBL controller (flybarless controller/stabilization). With this component you use a computer/tablet to program many options that is a blessing and a curse. You can tune how much pitch (up and down motion), yaw/nick (rotation of the tail), cyclic (aileron,elevator) that you can get. More importantly you and tune P(proportional)'I(integral)'D(derivative)' control which is a algorithm that sorts through errors given back through sensors info given by movement. P is the current error, I is the magnitude of the error and the duration of the error, and D is the error over time. With this you can tune out errors in the design of the helicopter, unwanted bobbles in movement from distributed weight in an airframe, speed of roll/rotation rates, expo/dual rate, and anyway you want the helicopter to react to input. Before considering an airframe you have to know what you're expecting feel in the air. Many decisions need to be decided before starting a build of a 3d helicopter of this magnitude. Things can be chosen early, but changes later will cost you lots on money. Anyway, this is my thoughts of the build of the Diabolo that I wanted to achieve. With the boring stuff decided on in the last several months the build can begin. If you are impressed by forethought then you might be interested in this build with executing an idea and making it a reality. Not necessarily making the whole airframe yourself(which is awesome) but choosing parts and pieces for a specific purpose(which takes lots of planning). Helicopters require many aspects like mechanical(will be covered later), setup(covered later), Programming(covered way later), and pilot skill(never ending). I hope to change to perspective of helicopter enthusiasts from being reckless people to a methodical hobbyist. Many things that you see in media only show the bad. Not all of the helicopter community are negative, and reckless. These are dangerous machines but with the proper guilde lines followed can be safe and intriguing. This build will take roughly a month so for the those following I hope you enjoy! [br][br]
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Helicopter Build - Minicopter Diabolo 700

This will be what the model will look like complete. Everything is specified when ordered and built to your specs.[br][br][br][br]
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Helicopter Build - Minicopter Diabolo 700

This isn't this specific model, but the speed version that hold many speed records of nearly 200 mph. The difference between this model is a carbon fiber fuselage, lower frame (battery holding frame, fuselage, and other small components.[br][br]
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Helicopter Build - Minicopter Diabolo 700

A speed run competition in Germany last year. Many advancements have been make since. https://www.youtube.com/watch?v=R2qXX7iCScI Also a video of a diabolo 3d https://www.youtube.com/watch?v=J5af0t9rLCo
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Helicopter Build - Minicopter Diabolo 700

Wow, that was incredible! You will most definitely set this association on fire with this helicopter. Congratulations.

Onward and Upward.
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Helicopter Build - Minicopter Diabolo 700

Nice job

MMAA President
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Helicopter Build - Minicopter Diabolo 700

Never been a heli freak, but am looking forward to seeing how this goes. I can't believe how much planning you put into this up front. So what exactly is head speed, and what's it got to do with anything?
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Helicopter Build - Minicopter Diabolo 700

Thank you for the kind words. Helicopters have many things that come into play in how they fly. RRMerlin, headspeed is how fast the main blades spin and have a lot to do how the helicopter flies. Say you have 2 set ups. One with 2200 rpm and another at 1800 rpm. As the 2 blades spin around they are one place at a time. The faster they spin the faster they can add lift all the way around the rotor disk. End result is more stability, and a more responsive helicopter. If you were to give 10 degrees of pitch to each setup you would see that the 2200 rpm setup has a lot more lift than 1800 rpm setup. A bad result of a higher headspeed is the energy needed to maintain than a lower headspeed. Just like an airplane if you have it at full thottle it going to use more fuel than at half throttle. With this 700mm blade helicopter its more exaggerated than an airplane prop. For a 100 extra rpms you go up you can be taking a minute or more off your flight time. With the diabolo being light the amount of lift should be less so I can lower the head speed and still be as fast as a heavier helicopter. If you take it a little further and add more pitch than normal it can help with the stability and lift a little more. End result is a responsive helicopter with less energy used. Keep in mind an average flight time is around 4 minutes which isn't long.
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Helicopter Build - Minicopter Diabolo 700

Ok, tonight I got to sit down a little and start digging in. Checking out the contents of all the parts in the kit, and the pictures does this no justice at all. Probably can tell there are a few small parts in the bags. Almost all the bags are marked for each step in the manual. So up to this post I'm up to step three. I've noticed that the manual has no wording probably because of a language barrier between country's its sold in. So I'll go through what I've done so far. 1. The first step in the manual wants you to sand down the carbon fiber parts edges. Its important later on because you don't want your wiring to rub on the sharp edges of the carbon fiber and cause a short. Trust me the cut edges are sharp! Another thing that I've found after building many helicopters ranging from cheap to very high end is the quality of fasteners. I've found that cheap hex head screws fit loosely on a driver, and require a very high quality drive not to strip out. Another thing is that the screws are filthy with grease and oil. This is really bad because you need to locktite all the screws, and locktite doesn't stick well to a filthy fastener. I use rubbing alcohol on each screw to clean them up. I found in this high end kit that the screws were really clean. Although, I noticed that any black screw/set screw where pretty dirty. Luckily only the set screws were these black style fastener. Other than that the fasteners where top notch which will pay off later after many flights and maintenance. * I want to add something here. A quality kit doesn't mean a monkey can put it together and have a fine running heli. There are definitely key things to know mechanically, and looking to many things to have problem free model. 2/3. These steps cover the 2 stage gear system to the main rotor. By this I mean there is 2 stages of gear reduction from the motor to the rotor. This is done to keep the helicopter slender mostly for aerodynamics, and keeping the frame side closer together for a stiff frame. The gears are smaller but can cause problems with concentrated forces making it weak. You would have to see in person but the gear system is very beefy to handle the extra forces. Most other helicopters have 1 stage that consists of one gear on the motor and a main gear that drives the rotor. This way you have a large gear on the rotor side which can end up pretty large making the frame wide to get the gear reduction needed. Even with a low KV rated motor a 10:1 is required to get a workable rotor rpm so the rotor gear can get pretty big. Something to notice that these gears are not molded like most. These gears are machined either out a special polymer, or steel for precision. This step of assembly is important to keep an eye on mesh because of the forces cause heat that actually melt these from massive amounts of pressure applied. I'm running a 14 hp motor running a rotor that is over 5 feet wide running 26,000 rpm motor reduced to 2000 rpm so the forces are very high in the gear train. (If you're paying attention you'll notice that the math doesn't work out for the 10:1 ratio, but I'll go over that later). After assembly the precision came through that I didn't have to do much to get the gear mesh right on the money which experience lets you see and feel. As you can see in the pictures I'm only assembling one side of the frame and leaving the other side off. This has to be done to watch the gears meshing together and to line up correctly. You can see the belt that will traveling to the tail of the helicopter off the pulley at the bottom. Its hard to tell right now but the motor will be running the bottom left gear in the pictures below. 4. I only started this step tonight, and I pooped out. This step will include mounting the tail boom onto the one frame side. I ran into an issue with sliding pieces together with the tight tolerances kept in the kit, but it might have been my tired hands. I'll show pictures later but I had to reveal the metal of the tail boom to an aluminum clamp. This is another important step because of a helicopters biggest enemy… Static. Everyone has felt the wrath of someone dragging their feet on carpet and touching someone, right? Same thing happens when a belt driven tail is ran through a metal tube to the tail. A static will build up and discharge out. This is bad as we know for our transmitters to cause a brown out, and crash. The theory behind it is if there is continuity from the boom where the static charges up can flow through the boom, to the frame(carbon fiber is conductive), to the motor, back to the negative side of the battery, and safely dissipate the charge. I'll see how this goes but I might feel better drilling and tapping into the tail boom and physically bonding the tail to the motor. This way I can control the impedance in the path to the negative side the lipo, and know that I don't have anything to worry about. Well, thats it for today. Thanks for reading, and I hope to get a little further this weekend. Its late and see how this build thread is going to get long, and tons of work. Anthony [br][br][br][br][br][br][br][br]
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Helicopter Build - Minicopter Diabolo 700

Hey! I forgot to mention a few things in my last post! I wanted to add a few things but maybe I'll be the only one to care. To get things straight, carbon fiber is the new bling! I would like to point out that I ordered a few upgrades with this kit. If you see in the first pic with all the bags of parts you can see a few parts with blue tags on them. These items are 1. carbon fiber skids (never seen these before, and should save some weight!), carbon fiber landing gear laminated into a bow (even more weight, and look cool too), quick release canopy mounts(which make it fast/easy to get ready to fly), and extra main rotor dampers that I'll explain later! Notice the cresent wrench included in the kit? Never seen that before either. One last thing I noticed. The canopy came with the decals (not cheap ones, but professional kind) applied. Which is a big project in its self! And!, it came with a carbon fiber windshield on it which is 60$ option that I didn't buy! I'll post pictures tomorrow! Anthony[br][br]
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Helicopter Build - Minicopter Diabolo 700

Holy cow that's a bunch of parts! No wonder helicopters take so much more maintenance than fixed wing airplanes. I'm looking forward to following this project. I'm a sailplane sort, but there's always something to be learned in this hobby.
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Helicopter Build - Minicopter Diabolo 700

Merlin, yeah it has a ton of small parts. The actual air frame goes fairly fast though. Its also interesting to see and learn from all of you guys too. I actually bought a foam biplane to start getting into planes a bit too.
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Helicopter Build - Minicopter Diabolo 700

Ok, I had a busy day working on the Diabolo today. Digging in Boom Mounting - I left off last night trying to get the boom clamps onto the boom but had a hard time. Come to find out there was a outer sleeve that I didn't notice due to lack of sleep. I forgot to take a picture but I filed down each end of the boom to reveal bare metal. So in the picture you can see the boom is attached with the 2 square boom clamps and below the one closest to the front is where the metal is exposed so the static will have a path to negative on the motor. I mentioned before that I wanted to do a bond jumper from the boom to the motor but after reading up on what others have experienced I think its unnecessary. Next was working on the tail box. After sliding the tail box on and fishing out the belt I slid in the tail pulley. Key thing in this step is the the twist of the belt coming down boom has to be correct. Commonly the main rotor spins clockwise while the tail spins counter clockwise, and for good reason on real helicopters. As the main rotor pushes air downward the advancing tail blade will be coming up into the downward air from the rotor. This isn't really always the case with a RC 3D helicopter that flies upside down, but has become common in design. So now the belt has the correct twist going from horizontal (off the main rotor) to vertical to the tail pulley. The tail pulley is slid into place, and the shaft is inserted into place. One last item to look is the red tail pulley. This is a smaller than stock pulley to speed up the tail for the lower main rotor headspeed that I'll be running. It has a maximum of 2000 rpm headspeed or a risk of over speeding the tail. If the tail blades spin too fast then the tail will pushed beyond its limits and fail. I think this will do for now… Time to rest up a little. [br][br][br][br][br][br][br][br]
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Helicopter Build - Minicopter Diabolo 700

Ok, so by now the air frame is getting closer to completion, and I need to catch up on the build notes! Let me tell you this thing is pretty rigid, and more so than anything else I've set my hands on. I really want to post a picture of where its out right now which is impressive, but I'm going to show the progression of the build. Don't think this build is over though! The first portion is going to be mechanical and its the fast/easy part. Setup, and then tuning is the part that takes time. I Put in about 12 hours on it today, and I have to say that the mechanical part is fairly technical since this is an advanced helicopter, and there isn't much guidance from the manual. Lets get started… So now the tail is set into place for now for later adjustment. Now onto the rest of the bracing for the gear train Gear train and belt tension er - I accidentally left a teaser at the end of my last post showing the parts with the shock absorber. These are the parts for the this step. First item on the to do list is the x brace. The x brace is installed to connect the left and right side of the frame to add stiffness to the frame for the motor torque which is a huge help. Without this brace you would find carbon fiber marks on the motor as the torque contorts the frame under large loads. The you also see the 2 large aluminum black anodized plates giving even more rigidity to the frame, and between these three pieces it makes this drive train almost indestructible. The only weakness here is going to be melting of the gears(I'll get to this later too). You'll also see the aluminum pieces to mount the upper half of the cyclic (aileron) servos. The rest of the parts are for the belt tensioner and canopy mount. In the picture below you see the 2 aluminum black anodized plates installed and the X brace with the belt around the tail drive pulley. When the other side of the carbon fiber frame side goes on this thing is going to be stiff! You can see how x,y,z axis of the torsion stresses are covered quite well. By this point my wrist is getting tired, and starting to need a small power driver to install all the screws. Also note the nice aluminum parts in there, and these are probably the nicest I've seen before. Tensioner - This part raises my interest the most with integration of a oil filled shock absorber for a belt a tensioner. The abuse the tail can take during a flight can be through the roof, and its up to the tensioner to keep things from slipping. A tail rotor is almost one foot in diameter with variable pitch and running crazy high speeds can be very powerful. Don't be fooled how much power the tail really has! These helicopters can go left/right at 60 mph or more and still hold with a lot of power to spare. Also fast pirouette speeds to a stop, and then change of direction in the opposite direction can hammer the mechanics of the tail. So in the next picture you can see how the tensions are set in frame. There is one idler pulley with another pulley on a lever arm that extends out of the frame side that hasn't been installed yet. Both are equipped with stacked bearings with grease shields, and with very tight tolerances. Gear Lube - Every thing is in place to install the left frame side now but you will see how enclosed the frames when everything is together. This will be a good time to give the gears some lubricant, and a fighting chance to hold up to the punishment of flight. The gears are very smooth before, but after the lube is applied to the gear the difference is very noticeable. With this lube you apply it and wait 15 minutes for it to dry. Then its sticks and then you have a very slippery gear that doesn't fling grease all over the place. I use this stuff on all my helicopters and it keeps things very quite and cool. Good stuff! [br][br][br][br][br][br][br][br]
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Helicopter Build - Minicopter Diabolo 700

Ok, now its time to install the second frame side on, and the shock for the belt tensioner. Not much to cover here, but ton of screws to install the the left aileron upper servo mount. I just set the shock in the mid way point, but will probably be changed later. The thing about the mechanical build is that things will change later after everything is set, and ready to be tuned. With the side frame on you can see the everything is closed off, but held very tight to make a tough frame! Lower Frame - Not much to cover here either. This is where the lipo batteries will be held, and are separate for a reason. In an event of a crash the lower frames can be changed without tampering with the upper frame where all the technical parts are. This keeps things cheaper and easier to fix. Just a few screws and the frame is starting to look like a real helicpter. You can see at the bottom you can see where the skids will attach. This is a Version 2 so more will be added to the lower frame to accommodate a sliding batter tray, but I haven't seen the parts for it yet. Also the rear canopy mounts are installed.[br][br][br][br][br][br][br][br][br][br][br][br]
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