OLH-360 maiden flight

The OLH-360 is ready!

Today I tested the 3D printed mini octocopter in my garage due to the bad weather outside.

Default APM pid settings are much to high for this octo. It caused my copter to flip at lift off. So I set the APM pid settings to LOW and did my first flight with these extreme low pid settings. Next step is to increase PID values slowly to find the best settings.

At lift off the copter start wobbling when still on the ground, when in air the wobble is gone. This is due to the fact that my current landing skid is just to flexible and to small. The gap between the electronics housing and ground is only 2 mm.

I Also need to configure some OSD settings because the OSD is displaying unwanted warnings.

So this project is not finished yet. Still some work to do:
 - pid tunning.
 - osd and other flight related configurations.
 - change landing skid.

OLH-360 update III

The delivery for all 8 DYS 1806 2300kv brushless motors took some time. Equiped with a Gemfan 5030 prop I should reach a 3 on 1 Trust to weight ratio.

The HK blueseries 12A ESC will and can deliver enough amps for this setup. Currently I have some 3 Cell 3000 mAh lipos which should provide a 10 min flighttime. But because of the 3on1 ratio I can easely mount 5k or 6k mAh lipo extending flighttime over 15min

Next step is connecting the clean (vibration free) housing with all electronics (flight controller, telemetry, fpv) to the octo frame.

list of used hardware:
- DYS BE1806-13 Brushless Motor for Multirotor (2300KV)
- HobbyKing 12A BlueSeries Brushless Speed Controller
- Hobbyking Multi-Rotor Power Distribution Board (DIY 8 x output PCB)
- Gemfan 5030 Multirotor ABS Propellers

OLH-360 update II

The installation of the electronic parts continues.

I have made a PCB on which I inserted the OSD an VTX. This to avoid a bunch of cables that is needed to interconnect these modules with each other and other the components (cam, power, apm).

This PCB groups the OSD en VTX into one module with 3 external connectors.
- 4 wire connector to camera (gnd, power, video, sound)
- 3 wire connector to APM (gnd, power, signal)
- 3 wire connector to battery (gnd, power, signal)

The FPV camera is mounted to the frame just by tape. This was the easiest and fasted option. In this setup I tried to maximize the distance (22cm) between the FPV 5.8ghz antenna and the Wifi 2.4ghz antenna to avoid interference. On one of my previous projects I had only 12cm distance which added some noise on the video signal.

list of used fpv hardware:
- ImmersionRC 5.8GHz 25mW Video Transmitter
- ImmersionRC 5.8GHz Circular Polarized SpiroNet Antenna V2
- Minim OSD v1.1
- SONY Effio-E DSP 700TVL Camera with 2.1mm lens and mic

Meanwhile I also tested a Turnigy Multistar 1704-1900Kv motor. This is a very lightweight brushless outrunner. But it does not provide enough power (thrust) to use in this project. The benchmark result can be found on this blog: http://www.multiwii.be/Turnig-Multistar-1704-1900Kv-thrust-test

I should go for an 1806 or 2204 -> 2300kv motor to reach a powerfull 3 on 1 thrust to weight ratio.

OLH-360 update I

A quick status update on the FPV 250 Style octocopter I'm currently building.


This mini octocopter called OLH-360 will have a low hung cage that is connected to the frame by anti vibration rubbers. This low hung cage will house all electronics, except the motor power circuit. (BAT, ESC, PDB)

All Power hungry electronics are mounted on top of the octocopter.
PDB (power distribution board) mounted on top in the center of the frame. Battery will be mounted on top of this PDB. ESC en motors will also be mounted on top of the arm. This will maximize the distance between the FC boards magnetometer and the EMF caused by high currents (MOTOR/ESC/BATT).


Weight is building up. When I would use 15gr brushless outrunners with 6a ESC and a 3000mAh 3cell Lipo I'll end up at 950-1000grams AUW. Depending on the performance of the motor I would get a trust to weight ratio somewhere between 2:1 and 2.5:1.

FPV 250 style OCTO-Copter (3D PRINT)

Something else now.

My next project is a small OCTO copter. Why? Because I would like to have a multirotor that is able to continue flight when one engine fails.

For this purpose I already had started my Y6 project. But I did not really like the way a Y6 flies. A Y6 is pitch sensitive when you change yaw. A second factor is the efficiency loss on the bottom motor/prop. A the last factor to discontinue my Y6 project was the size of it. I found it to be to large to fly in my backyard.


So a new project is born. This is HK FPV 250 style OCTO-Copter. This octo frame is 3D printed with PLA and weighs only 135 grams. Motor to motor distance is 36cm.

To goal is to mount the HK FPV 250 low hung kit on this frame with all electronics inside. Depending on the weight I will then choose a motor/esc/battery combination. Maximum prop size on this frame is 5 inch.

I'll call it the OLH 360 (octo low hung - 360 mm)

FPV Image quality benchmark

This is FPV250 low hung frame equiped with a fatshark fpv camera set.
The fpv camera is mounted in the clean section of this frame.

As I noticed in my previous vibration test the low hung frame performs very well on reducing vibrations. And this has a huge (positive) effect on image quality.

The movie speaks for itself. Just watch it.

Low hung clean and dirty kit

The HobbyKing "low hung clean and dirty kit" is created to reduce vibrations on fpv camera. This frame divides the quad in 2 parts. An upper deck that is dirty (vibrations) and a lower deck that is clean (no vibrations).






Hardware:
It is still the same setup. Same unbalenced props and motors. All power equipment (motors, esc, power distributor, battery) are mounted upper deck in the dirty part of this frame. The Flight controller bluetooth and receiver are mounted lower deck on the clean part. For this benchmark I don't mount any FPV gear yet.



Benchmark:

As you can see the results are really good. ACC an GYRO values (graph) are flat. This means that the clean kit is really clean and has no vibration issues. This should improve image quality or remove jello effect on a FPV cam. Even the MAG values are now a flat line. This is the result of mounting the flight controller lower deck. This makes the distance between the magnemoter and motors/esc larger and thus reducing the interference caused by EMF (high current).

DIY Solution for vibration reduction

In my first quadcopter project I already introduced some cheap and easy to build motor mounts that reduce vibration almost completely.

Downside of these motors mounts is the fact that they add 95 grams of weight to my little quad. But it really kills the vibration and the quad is flying super smooth. No shaking, no aggressive corrections, no wobble.



These motor mounts can also be made carbon fiber sheets. That will reduce the weight. With 1.5mm carbon fiber it will weigh around 45 grams (set of 4)



hardware:
It is the same setup as my previous blogpost. With same motors and the same props, nothing changed. Only added the vibration reduction motor mounts. (motors and props are still unbalanced)



benchmark:

As you can see the ACC and GYRO values (graph) is almost completely flat. The vibration reduction motor mounts do their job. This should have a positive effect on image quality when I would mount an FPV camera. But there is just not enough room on this frame to mount all that equipment (cam&tx)

FPV 250 vibration test

This is my current FPV 250 setup it does fly but it has vibration issues causing it be a little bit unstable (wobble). If I would mount FPV cam I would for sure have decreased image quality and jello effect on my fpv recordings. (motors and props are unballanced)






hardware:
- Hobbyking FPV 250 frame
- C20-1550KV brushless motors
- 6x4.5 inch TRI-blade props
- HK blueseries 12A ESC
- HK Multiwii 328P flight controller
- Live telemetry Bleutooth module
- 4CH analog 40mhz reciever
- 3000mAh 3Cell Lipo

benchmark:

because my setup has a bluetooth module I can connect my laptop over bleutooth to my quad during flight and have live telemetry. Vibrations caused by motors and prop have influence on gyro and acc values. When hovering in air these gyro en acc values should produce a nearly flat line. As you can see on my screenshot this is not case.

HK FPV250 QuadCopter introduction

The Hobbyking FPV250 multirotor frame is a very popular frame. Because it is light, strong and cheap. Currently this frame comes in 3 flavors.

HK FPV 250 basic quad frame
This is the basic and original model of this frame. Allthough it was originale designed as an FPV capable frame I advice not to use it as an FPV frame unless your motor and props are high quality and 100% balanced. It's small, light and ideal for flying in your backyard or a nearby park.




HK FPV 250L long quad frame
The long frame model was made to provide FPV users more space to mount there FPV camera, transmitter and even a second HD camera for recording. But you still need HQ, well balanced props and motors if you don't want to have that jello effect on your fpv cameras. The downside of this extension is that you can only mount 5 inch props, whereas 6 inch props could be mounted on the original frame wich makes the basic frame much more efficient.

HK FPV 250LH low hung quad frame
The 3e frame that HK released takes the benifites of the 2 previous frames. The long extension provides lots of room to mount all FPV gear and because it mounted on the bottom you can still mount 6 inch props making this an efficient frame. The extension is also attached to the frame by rubbers. HK calls this Clean-and-Dirty Kit. This should prevent jello effect cuased by vibration of motors and props.

In this blog I will investigate the vibration issue caused by motors and props. I'll compare the basic frame with the low hung frame with live telemetry output from the flight control board.