New low vibration H quad frame

[Fettler]

Following the success of my two 720 sized prototype quads I decided to try a 450 size. The H layout allows the two motor arms to be suspended using silicone O rings. There have been many suggestions(on DIY Drones where I blogged the build)  that isolating the controller from the motors would produce undesirable flight characteristics but there has been no sign of this at all. On the contrary, the lack of vibration on the controller allows much higher tuning and very crisp handling, especially in yaw, due to the passive thrust vectoring effect.
I have flipped and rolled the previous large quads.


As the battery mass is used as ';inertia'; it is important to fix it securely in place which is why all my designs use some sort of clamp and not straps.
There is usually no sign of vibration from cameras either and the new quad features a direct mount for gopro etc.

On one of the larger quads I discovered another advantage of using the silicone bands when I had an electrical problem at 50mts. It plummeted and snapped all the bands but nothing else was broken.





I hope XmaX will pop round soon and be the test pilot after we transfer all his 450 quad bits to the new frame.
Max - Hope this will be crash resistant for the forest FPV quad race.




With this type of H quad it is important to have the motors spinning opposite to the normal X quad direction as this makes the arms tilt in the correct direction to make the yaw very fast. If you dont do this there may be yaw reversal or no yaw control at all. The APM now has a H quad frame type following my suggestion.

This vid of the first prototype should explain.
GOPR0new






This is the MK2 720 H quad.

[teslahed]

That looks very nice. I especially like all the 3D printed white plastic fittings you';ve used.

In terms of vibration damping - it is possible to have too much. If the sensors are too well isolated from the rest of the multirotor their response will lag behind real world movements and produce a ';mushy'; feeling when flying the quadcopter. I don';t think you';ll necessarily have to worry about that with your frame but if it feels a bit mushy then try tightening up your vibration dampers and see if it improves.

[nub]

aye nice frame that i quite like it, never even thought about the vibes in that way though wouldn';t have thought it would affect the way the sensors detect any tilt.

[Fettler]

In terms of vibration damping - it is possible to have too much. If the sensors are too well isolated from the rest of the multirotor their response will lag behind real world movements and produce a ';mushy'; feeling when flying the quadcopter. I don';t think you';ll necessarily have to worry about that with your frame but if it feels a bit mushy then try tightening up your vibration dampers and see if it improves.

Thanks teslahed.
Before I got the first one in the air I was swamped by theorists explaining why my machines would fly very badly, if at all. I have not seen any sign of poor control even though I tried the bands slackened right off, like in the video. I generally have them tight enough so the arms dont bottom on the frame.
Same goes for my latest octa build. Even some of the APM developers said it wouldn';t work but I think they are now convinced after the vids in this post.
http://www.multi-rotor.co.uk/index.php?topic=4294.0

[teslahed]

My own experiences of this come from an old poorly put together quadcopter i was flying over a year ago. I kept adding more and more foam insulation under the flight controller to isolate the controller and it got better and better, then worse and worse. There is definitely a sweet spot of the right amount of vibration damping and when you go beyond this point the multirotor starts to wallow in the air as if the flight controller is lagging behind the multirotor frame movements.

But as you are starting with a well setup quadcopter you wont need as much damping as i was using so you may never encounter this problem. Since you say it flies fine i can';t imagine it';s an issue with your setup. If it does start to feel a bit wallowy then you can always add a few more silicon bands to firm things up.

Do you notice a better roll response than pitch?. Your frame appears to be rigid in the roll axis but has vibration damping built in to the pitch axis which is unusual.

I look foward to some video when you get it out flying properly

[XamaX]

Looks great Mr Fettler. Count me in for a full transplant...How much Jail Ale do you think this is going to take to ensure a smooth and successful operation?? I will come prepared.

[Fettler]

After a guts transplant last night the quad has now flown.
Vibration levels are quite remarkable, even with cheapo props straight out of the packet.
The APM people suggest vibration levels above 0.5g are on the limit. A good machine will be about 0.1.
This one has 0.02g in the hover.

[XamaX]

Looks good Fettler-Will be happy to pop the RCtimer CF props on now it has survived its maiden. Would be great to get the FPV gear on and trail the autotune to see what it comes up with...Not particularly looking forward to the Tree test that you have suggested however....

[Fettler]

Tried to call. Come over.

[philtrum]

stunning design, so simple and effective
love the 3d printed parts, cant wait to get my printer built