Starting a new thread to show what I'm working on.  I'm building a new Octocopter of my own design.  The goal is to use it for Aerial Photography, lifting a mid-weight camera such as a Sony Nex5.  It will of course be using Arducopter for control.  ;)

I started off researching the various kits on the market, and starting getting analysis paralysis.  I looked at all the options such as Droidworx AD8, Cinestar, CarbonCore, and SteadiDrone.  But I just wasn't happy with the design on them, particularly for the price they ask.  Combined with the fact that I can be pretty frugal, and have a strong DIY ethic, I decided to just design my own.

The basis of the design relies on many of the Hobby King quadcopter parts.  I liked the design of the motor mounts, they are very professional looking, even compared to some of the high end machines.  And I liked that the boom mounts are blocks of aluminum instead of plastic.  Very rigid.  I also liked the look of the dome on their H.A.L. quad, but since they don't sell it seperately, I bought the whole kit, it's only $34, amazing!  I might end up using the rest of it someday, who knows?  So, I basically emptied out their stock of Talon parts, so if you need to fix your Talon quad and the parts are backordered... sorry!

Once that was settled, I set about designing the center frame.  My design required a few things, namely I want all the wiring hidden.  I don't want any spaghetti showing.  Particularly with the ESC's, while still allowing cooling airflow.  This required the center hub to be larger than is typical.  I then needed a smaller subframe to house the avionics.

You can see these plates below.  The larger one houses the HAL dome. You will notice the 3 blue anti-vibration grommets in the middle.  This is the APM1 pattern.  I did that just because.  Maybe I'll use an APM1 as a stand along gimbal controller.  The second plate had grommet mounting for an APM2.  The final plate is the top plate, and has bolt patterns for the Ublox GPS and the magnetometer.

This next photos shows the avionics frame built up with an APM2 mounted.  25mm aluminum standoffs are used. I don't like the plastic standoffs typically used.  They get loose, and lead to vibration.  They also break easily.  This structure ends up being quite rigid.

Here is the avionics frame mounted on top of the main frame.  Yes, the main frame is HUGE.  I actually don't see the point in having a tiny center frame, and then long arms.  This seems like it just leads to flex, and doesn't leave you with any real estate to mount your avionics.  

This photo shows one of my design features.  I put some cutouts on the bottom frame for weight savings, and then made matching cutouts on the top frames.  This creates some nice conduits to run wires neatly.

Here it is with the HAL dome mounted and one of the Talon arm mounts bolted in.  I'm really happy with how stiff the assembly is already.

Here it is with one of the arms mounted.  These are the short 220mm arms, I also got some of the 320mm arms.  One may wonder how I'm going to get away with such short arms and 13" props....  Astute readers will know what I'm planning already. ;)

This last photo shows one of the ESC's in position. This is a Hobby King F-40A, it's somewhat larger than typical 20A units which is partially why the frame is so big.

That's it for now.  I had the plates cut out of aluminum to start with because it's cost effective.  If it all works out, I'll probably have it redone in carbon fiber plate for the weight savings.  I was a little uncertain about the weight, but it looks like the frame will come in at 1070g all in aluminum.  That's about 300g heavier than a Droidworx AD8, but not too bad. It will drop about 1-200g if redone in CF.

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Do you mind posting the hobbyking links for the various parts you got from them. Also have you considered selling the aluminum parts?

Sure, I can do that.

I would consider selling the aluminum parts if other people are interested in them.  The only thing is they are rough when they come from the waterjet, and I'm not interested in finishing them myself.  Basically they have a bad burr on all the edges that need to be filed down.  If things scaled up enough, I'm sure I could find an automated process.

I would be interested in the aluminum parts. Rough is just fine a little finishing is easy enough. you could put me down for a couple of sets at least.

You can put me down for one set and no problem on the rough edges. You can pm me for the details.
Do you think using the standard 3dr motors would be ok? I'm thinking to use two 3300 nanotech 4S in parallel.

I like it! :-) Man the long arms really do make a difference.

I recently bought the hexa copter V1 kit from HK to build my first multirotor (I've got an extra APM, why not). But man the base plate assembly on this thing is small. I was looking at where to put the ESC's as I'm running 50 amp blue series with 3648-1450KV motors and there really isn't room without fabbing up some mounts or a new base plate assembly.

My intention is to build a variable pitch unit, a scaled up heavy lift version of the MIT quad. I tried the variable pitch units from HK and after video's to them for quality issues have received a 50% credit. The worst junk I've ever got from them. So I changed over to longer motor shafts (450 heli main shafts) and will use 600 size tail rotor heads and pitch slider assemblies instead. I should have all the parts in the next two weeks as they had to come from the global HK. I went ahead and got standard props and the long arms coming as well just to ensure I will have a flyable unit even if standard pitch.

I'll be watching intently :-)


P.s. aren't those base mounts up side down?

Jeff, you prefer the long arms?  I think they're too long and spindly.  If I cut-em in half, it'll look like a dwarf octo, but I think it will be better for a lot of reasons.

Yeah,  the base plate on those is ridiculously small.  I really don't understand why this type of design is typical.  It leaves no room to mount anything.  For sure the ESC's on that design would have to go on the arms. 

So you put 450 main shafts into a 3648 motor?  I know the 600 tail hubs fit on the 450 main shafts, but hadn't seen a motor to match.  Who's motor?  I'm really interested in this because I want to do a direct-drive VP tail for my 600.  Get rid of the belt and all that junk.  Much better than AP.  I'd love to have any info you have on this.

Who's mounts upside-down?  Mine? Yeah I guess they are, but I don't really see a "right side up".

Huh, interesting.  Well, I can do that.  It's not a big deal.  Takes about a week.  Would you guys be interested in CF plates instead?  I want to get some done in CF, and having a batch of 3 done makes it cheaper.

In either case, you also will be needing some hardware to bolt it all together.  I can also put that together for you.

Basically I could supply a kit, and you get the rest from Hobby King.

I just checked eCalc, it should fly no problem with the 2830-880 motors and 10-4.7 props.  You wont have quite as much power as mine with the bigger motors, but it'll work fine I think.

Actually, I'm kind of surprised at how good the numbers look. 

I haven't received the 450 shafts w/ collars yet (part of two orders coming, they made it through customs but not to me till next week). The motors are the Turnigy units here, they were the only in stock units they had that were actually labeled for 6S in a KV that would max out the variable pitch unit's 28,000 rpm limit with 20% overhead. They have 5mm shafts and I'll have to enlarge the Talon motor mount plate where the motor shaft goes through to fit the 450 (V1) shaft collar as it is larger than the hole, but it's not a very technical mod. I plan to use some DS929HV micro servo's with custom arms directly on the pitch sliders to eliminate any linkage slop. I still have to sort out how to mount the servo's on the motor mount brackets, but it's hard to see until all the parts are present.


I couldn't fit it in the budget yet but the 3 bearing 600 tail rotor assembly from Heli Option looks like it would take a much better load and hold up forever. For now I just went with the HK 550 tail set.

I've got 6 sets of 9" variable pitch blades that I may use, I've got 11x7 three blade props and 105mm tail rotor blades on the way, and am considering either 250mm main rotor blades or some 142mm CF main blades depending on the performance efficiency I get on the bench.

On the long arm front I am not sure (so I bought em cause they are CHEAP), the CF tubes I think would handle the torque OK but the mounts I may have to double up on, if I do a custom base. Not really sure until I can sort out what the ideal blade/rpm/thrust/amps combination is. Then I can static load the assembly to see if I get deflection in the mounts and plates. I was considering using the Talon V1 main tubes to reinforce the larger V2 tubes if necessary, epoxy a few short sections inside the V2 tube at the motor mount and base mount areas. From what I read the difference in size is correct to insert one into the other.

So it 5mm the shaft size of the 600 tail?  This is great news!

I was trying to figure out how to mount a motor to the tail gearbox, and then have a shaft coupling going to the standard tail drive gear.  Just sticking a long shaft in the motor is WAY less of a cludge!  Wow, I'm super excited about this now.  It's so simple! I wonder if I could use one of the turnigy multi-rotor mounts, and just drill it out to bolt onto the tail drive gearbox?

I notice quite a number of the NTM motors have a 5mm shaft.  Like the 3548's.  I want to run it on 3S I think.  I'd need a 1000kV, which is totally doable!

Do you need to cut a c-clip groove in the shaft though?

The only issue is they are talking about needing 60A ESC's which is a bit crazy!  I'm only using 100A for the whole heli.

The 3648 is propably a bit overkill for the tail, it's HEAVY! I think you'd have issues balancing it.
The "Donkey" type motors might be a better option. 800kv on 6S might not give you good overhead on RPM, IIRC the tail on my 600 does ~16k RPM, but you could spin it faster and use a less torquey motor to save weight. If the diameter of the tail boom is correct it would make a sweet mod to use the Talon mount and a left over Talon tube of any length you want?

Start measuring! LoL :-)

No cutting groves for clips, that is why I got the V1 450 shafts, adjustable lock collar ;-) just grinding flats for the motor bell set screw and tail rotor head set screw. I just hope the HK shafts are straight and hardened. Will know next week...

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