RatCopter - a tricopter for general purposes in every-day usage

Hi, I'd like to introduce my latest copter, the RatCopter.

My goal was to make some simple and still good enough platform for testing and having fun, without the risk of crashing expensive parts. As you'll see on the pictures, I used zip ties everywhere around. They are strong but will break on crash, avoiding other parts. (The name came from an undemanding animal… :) )

This tricopter is based on RCExplorer's idea, with some improvements and modifications. The frame is made of 1.5mm thick G10 and 1x10mm Al square tubes. Front arms can be folded back to the rear one.

First there was a solid camera mount in the front, but I realized that I'm missing the stabilization and the possibility of pitch movement. So I made a 2-axis brushless camera mount, the motors are DIY rewinded Turnigy SK3 2822 ones with EZO bearings. Now I have -90…+30 degrees of pitch range, controlled by FC, so camera can be pointed to target automatically during Mission flight.

Current setup's technical data:

  • motor to center distance: 400 mm
  • all-up weight: 1550 g
  • flight time: ~12 min
  • battery: 4000mA 4S LiPo

Parts list:

  • Custom frame
  • APM 2.6 with latest code
  • CN06 Plus GPS with MAG
  • 868 MHz telemetry module
  • NTM2830 900KV motors
  • Turnigy Plush reflashed ESCs
  • Immersion 600mW video TX with CP antenna
  • MinimOSD with latest MinimOSD extra code
  • Mobius HD camera (with live output)
  • Alexmos 2-axis BLS gimbal controller
  • RCTimer 90A current sensor
  • Turnigy TGY-306G servo on tail
  • RCExplorer's tail mechanism
  • some LED stripes and buzzer
  • FRSky TRF-4 FASST compatible receiver with PPM output
  • TS1084 12V step-down IC for video transmitter
  • 2A DC-DC 5V converter for Mobius
  • RECOM 5V DC-DC for APM
  • L7805 step-down IC for servo

Maybe you noticed the amount of DC-DC converisons, my idea is that if everything works on it's own power source, than one part can't burn out all the others. Also, any IC's connected to video systems are equipped with L-C filters, and the linear regulators are connected to the tail boom with thermal couplings. So heat dissipation is not a problem at all!

I had many issues with jello effect, so tried many variations of dampening. This current setup looks good enough for me. Also I had many small modifications between test flights. But now I have a multi-purpose copter, with the capability of FPV flying and doing some nice shots in manual/mission mode.

Here is one of my latest test videos, showing the capabilities of this small copter:

I made some photos today, I hope you'll find any details you are interrested in.

Best regards

Nhadrian

 

Views: 1101


Moderator
Comment by Graham Dyer on February 24, 2014 at 11:16am

Very nice, well thought out, very neat and lots of time/effort put in. Your equipment choices are also good advice to anyone wanting to do one too. I'm about to do something very similar just with round tubes and quite a few 3D printed parts, just waiting for the motors and a few other things to arrive.

Well done!

Comment by Hugues on February 24, 2014 at 11:33am

very nice design in a true DIY spirit!

How did you dampen the camera against vibrations/jello ?

Comment by Adrián Nagy Hinst on February 24, 2014 at 11:58am

Hi, thanks for all.

I forgot to write the prop size, 10x5 E-Prop.

And also, not only props but motors are balanced and bearings were replaced to EZO ones.

Regarding dampening, check out the third picture. Battery and camera mount are connected to a 4mm plywood plate. This plate is glued to foam plates, with plywood on the other side. And these plywood plates are screwed to lower frame plate through silicon tubes. Quite difficult, I know, but works and safe.

Best regards

Adrian

Comment by Muhammad Al-Rawi on February 24, 2014 at 12:46pm

Very clean and slick. I like it!

I found that balancing my motors in addition to my props makes all the difference. It allows me to hard mount my FC to the frame with no issues. Well done. 

I've had bearing troubles with these cheap motors. Could you talk a bit about your decision to swap out for EZO bearings? 


Moderator
Comment by Michael Pursifull on February 24, 2014 at 8:16pm
Nicely done, thank you for sharing.
Comment by Rai on February 25, 2014 at 4:47am

Adrian,

That's amazing! so smooth ... thanks for sharing. I will definitely need it for supporting research in a tough area of Bornean rainforest. Just a stupid question, do you think Y copter consume less energy than H-copter (as it has 4 motors)? Thus do you think the flight time can be extended some more minutes with Y copter? Thanks lot and I definitely will post my work and credit your knowledge.

Comment by Adrián Nagy Hinst on February 25, 2014 at 6:57am

Regarding motors, I found these efficiency enough, but the bearings are under-sized and crapy quality. Even the new motors had terrible bearing-sound... :(

The EZO bearings can be bought in our local shop, and they are japanese ones, quality products. Additionally, I'm using stainless steel bearings, they are more expensive a bit, but I don't have fo worry about humidity at all...

I don't know how efficient would be a same-sized H-copter, don't have any personal experience. I choose tri because of fast and agile tail response, I adore it.

These E-props are not the most efficient ones, but they works better in wind or hi-speed cruising compared to SF props or T-props. And the power is also ok on 4S setup!

Comment by Adrián Nagy Hinst on February 27, 2014 at 9:30pm
Comment by Rai on February 28, 2014 at 5:16am

Hi Adrian,

Thanks for sharing! That's really cool and very stable Y-copter of yours!!


Moderator
Comment by Graham Dyer on March 1, 2014 at 11:47pm

Adrian, what are your thoughts of putting the motors upside down?

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