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FTFC19 TARDIS designed by HilldaFlyer

HilldaFlyer

Well-known member
#21
ArduCopter supports a couple of frame designs called SingleCopter and CoaxCopter. Boom! My mind was made up, this looks like the perfect solution.

So I set up a couple of test rigs, one sporting PixRacer board and the other with a Matek F405 Wing board. Both were flashed with ArduCopter and following two weeks of tweeking, I got both functioning (non-flight tested function) as they should.




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Here is the Matek F405 Wing setup. The FrSky XSR receiver is in a bag to decrease the range so the Taranis would stop screaming "RSSI Lost" while bench testing.

Now that all the control surfaces and motor were "working" it is time for a prototype build.
 

HilldaFlyer

Well-known member
#23
I typically plan all my cuts methodically. I threw all caution to the wind and just started hacking away on some foam. Staring with a sheet of Ross foam core, I made cuts to produce a square that is 10" on each side. The plan was to use a 9x4.5 prop, so I thought that would be about the right size.

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I just scribbled on the foam where the cuts should go and started cutting.

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I designed a 3D printed motor mount that would be held by a cross of rectangle dowels.
 

HilldaFlyer

Well-known member
#24
I made 4 mistakes cutting the control surfaces, but it was a good thing they were too long, I just hacked them in half and beveled an edge so they wouldn't contact each other when actuated.

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Believe me that just punching unplanned holes in foam made me nervous, but hey, I only made two mistakes this time. Control surfaces were mounted.
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At this point in time I was moving so quickly that I forgot to take pictures at each step. Here is the FC with the Rx hot glued to the top. It is held in place with a foam deck that just accidently happened to be the right size between the servos that I plopped down with hot glue.
 
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HilldaFlyer

Well-known member
#25
The motor mount finally finished printing, but the supporting material was too strong to remove, so I printed another without as much support.

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Here is the motor mounted on the 3D printed bracket with one rectangular dowel going through. I made a nifty little battery hanger for the under side.

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So, after a few hours of hacking and gluing, this is what it looked like.

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Connect all the wires, and I was so excited to get it done that I put on the wrong prop (pusher). Sadly I didn't discover this until I was at full throttle and it didn't take off.

After replacing the propeller, it did take off, but it crashed, crashed, crashed, crashed. Hmmm.
On the bench I discovered that the control surfaces were not activating for some reason. I haven't figured out why, but I was able to activate them once and the contraption got about 2 feet up before it tipped and didn't recover.

I think I am close to getting a working prototype. I am questioning the ability of the control surfaces inside the "thrust tube" to have enough ability to redirect the thrust. These may need to be outside the tube a bit. I noticed on Otto's landings, he usually had help, and probably because when you get close to the ground, the thrust vectoring is lost to ground effects. I am also wondering if the control surfaces are far enough away from the CG to have enough of an effect. I may need to make it longer... but that will come with more time... and when it runs, I'll get all the TIME I need.
 

HilldaFlyer

Well-known member
#27
One more thought about this test rig -
No, I did not consider, but truly should have, CG and balance. Space was tight so I just mounted the battery under the motor mount. I have yet to check, but I'll bet this thing is really top heavy. To correct this, I'm going to build a new test rig, one that is about twice as tall and has the battery in the lower half to offset the weight of the motor. I will try to put the FC near center axis which will require another set of cross supports, but I'll just print another motor mount to hold the FC for now. That will give me something to do this week besides planning a club meeting. Maybe there will be an overthrow of our current club leadership that will leave me with more time for building, but fat chance of that.
 
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PsyBorg

Wake up! Time to fly!
#31
I would think that would have to be very bottom heavy to be stable. Maybe even taper the inside like a thrust tube. I think on the prototype I would probably have the bottom skirt as the thrust vectoring mechanism vs having it all inside like that the turbulance inside would counter any kind of vectoring as the air reflects back to the surface directing it.

Maybe just slotting the lower edges around the outside where the fins are to allow air to escape and push the bottom around would even work.
 

HilldaFlyer

Well-known member
#32
I would think that would have to be very bottom heavy to be stable. Maybe even taper the inside like a thrust tube. I think on the prototype I would probably have the bottom skirt as the thrust vectoring mechanism vs having it all inside like that the turbulance inside would counter any kind of vectoring as the air reflects back to the surface directing it.

Maybe just slotting the lower edges around the outside where the fins are to allow air to escape and push the bottom around would even work.
Thanks man... I appreciate the thoughts. I've had a lot lately, and now I just need time to try them out.
 

HilldaFlyer

Well-known member
#33
Stretched the Prototype..

After all the thoughts, club meeting planning, I was able to check out the prototype. Frankly, it would never have flown. As it was configured with the battery and motor at the top, it was so top heavy that it would never have flown. It was quick and a nice way to see that the motor and control surfaces were working properly. I need to get the prototype to balance on the CG, so I have to make it taller with more weight at the bottom.


My first thought was to remove either the motor or servos and move them to a new section glued to the top or bottom. I decided to leave the current servo and motor mounts intact and just add a section in between them.


Cut the prototype in half,



Made a new section the same size as the original prototype.



Glued the new section in between the top and bottom sections.



Glued the battery cradle to the servo mount and added a support at the CG point to hold the flight controller.



This time I marked the CG and determined that the balance was just a bit top heavy. Certainly much better than the shorter one.
 

HilldaFlyer

Well-known member
#34
Parts List
  • 2 sheets of Ross foam board
  • 4 x 13g metal gear digital servos
  • Motor: NTM 28-26 1200 kv motor
  • Propeller: APC 9x4.5
  • Battery: 1300 mAh 3S
  • ESC: HobbyKing 20A
  • Flight Controller: Matek F405 Wing
  • Firmware: ArduCopter, SingleCopter
 

rockyboy

Skill Collector
Mentor
#36
Both crash and fly! :ROFLMAO::ROFLMAO::ROFLMAO:

Definitely good progress though - stabilization success - just needs a Binford 3000 to give it a little more oomph! (y)
 

HilldaFlyer

Well-known member
#39
Lots of comments on the ability to hover.
After the prototype flew, or at least demonstrated the capability to fly, it is time to design what will be the bigger version. For starters I was thinking of just making the side of the TARDIS the size of a single sheet of foam. I did some measurements of TARDIS photos and there are a lot of different sizes, so I think using the dimensions of a sheet of foam will be OK.

The dimensions are 50 cm (20" x 20") square by 76 cm (30") tall (one sheet of foam per side). 20" is a lot of space for a prop. Now to figure out what kind of power train I’ll need. I have a few motors on hand. I have built a thrust rig and tested different motor and prop combinations.





What I like to do is find the battery, propeller combination that gets within 10% of the specified amp max for the motor and select the combination that has the highest thrust to amp ratio.

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Time to build the TARDIS shell and see what the weight is going to be.
From the prototype, it looks like I’m going to need a lot more thrust than the weight of the shell.
 

Piotrsko

Well-known member
#40
My $0.02: to land you need some sort of stand off otherwise the air compresses and your controls stop working. Ok on take off because you need the compression to unstick and you aren't there long enough to tip over besides CoT is above CG. not ok on landing unless it's vertical and not tilting.

Rule of thumb: thrust = 2X weight minimum for any decent acceleration up. The nitro power people have props to 24" diameter.

Really interesting build/design.
 
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