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I agree it does look a lot better for some reasom SMF shorten any recent posts display  :rolleyes:
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Printing 3d Forum

Vibration damping techniques

Started by teslahed, Friday,June 29, 2012, 19:31:24

Previous topic - Next topic

teslahed

I've been trying to get rid of excess vibrations affecting my flight control board because I've read it's a good way to improve quadcopter flight performance. I've found a few methods that other people may find useful.

I've been using silicon gromets 'Acousti Anti Vibration Silicone Washers' underneath my flight control board in the central stack;



http://www.ebay.co.uk/itm/280893007186?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

They are the right size to fit around the screw threads on the hexagonal spacers that most people seem to be using for their quadcopters. I screw the spacers down onto them to compress them a bit but leave some give. They seem to help but i am not sure exactly how much of an effect they really have.

Another trick I've been using is to stick a piece of that double sided foam sticky tape that is good for vibration damping underneath each of my motors. I have my motors held down tightly on to the motor mounts by cable ties so the foam is compressed beneath each motor. I'm hoping this will absorb some of the vibration from the motors and props at the source, but again I've not done much testing to be sure how much of an effect it's really having.





Other than that I've learned to balance my motors as well as my props.

I watched these two videos;





and combined them to do this;



Anyone else got any ideas worth trying?
One circlip short of a quadcopter.
 1 lobe short of an antenna.

MadMax

Very interesting post I havent really bothered to much about vibes as Im still quite new to this game and just learning, do you notice much of a difference when flying ?

teslahed

A badly balanced quadcopter makes the work of the gyros and accelerometers much harder so your flight controller wont be getting reliable information to fly the quadcopter with.

A really badly balanced quadcopter will be all over the place regardless of what you set the gyros and accelerometers to. A well balanced quadcopter will just sit stable in the hover much more easily, and i notice a difference when I'm doing maneuvers like moving in one direction whilst doing a flat spin - the quadcopter tracks more smoothly with less juddering when it's well balanced.

There are obvious benefits if you are doing aerial photography as well but I've not done much of that yet. 
One circlip short of a quadcopter.
 1 lobe short of an antenna.

MadMax

I see what your saying soif the vibes were really bad then it could maybe cause a copter to flip

Gaza07

I think the vibes would have to be pretty severe to make a copter flip, what you will find though is the vibes will upset the gyro and acc making it drift more than it would if there were no vibes at all, hold your copter out at arms length and spin it up while holding it tightly if you feel bad vibes you need to find the cause and fix it, there are other ways to detect smaller vibes like zooming in to the sensor read out in the gui  ~~

teslahed

Thursday,July 05, 2012, 14:42:36 #5 Last Edit: Thursday,July 05, 2012, 14:47:50 by teslahed
I've just ran the quadcopter with the props off using the MultiWii WinGUI to monitor vibration levels, both with and without silicon gromets. I tried to keep the scales exactly the same for all 4 runs but i had to move the quadcopter so the exact levels vary a bit - look at the relative rather than absolute values.

First without at minimum and maximum throttle;





Then with;





It's hard to say for sure but the minimum throttle level looks a fair bit smoother with the gromets than without - the maximum setting is mostly just all over the place in both so it's harder to tell.
One circlip short of a quadcopter.
 1 lobe short of an antenna.

teslahed

In my quest to improve vibration damping on my quadcopter I've found some (allegedly) better gyro tape;

http://www.ebay.co.uk/itm/160692941621?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Mine's on it's way over from Hong Kong so I'll get to try it out in a couple of weeks...
One circlip short of a quadcopter.
 1 lobe short of an antenna.

MadMax

Look forward to seeing your results it says you have to use velcro to hold it in place wont the velcro transfer vibes ?

teslahed

QuoteCut gel to the appropriate size using scissors, and place it between electronic component and mounting area. Use the (Velcro)strap for reinforcement


It's not totally obvious to me whether it's saying you have to use velcro or you should use velcro if you need reinforcement.

Obviously i wont be velcroing sensor boards down - they are too tiny - so either I'll use it without velcro if possible or else I'll add some glue if necessary.
One circlip short of a quadcopter.
 1 lobe short of an antenna.

teslahed

My new Gel based vibration absorption mat has just arrived;



I'm just going through the process of fitting some now.
One circlip short of a quadcopter.
 1 lobe short of an antenna.

teslahed

Quote from: MadMax on Saturday,July 07, 2012, 10:41:33
Look forward to seeing your results it says you have to use velcro to hold it in place wont the velcro transfer vibes ?


The stuff has an intrinsic stickyness to it very similar to those toys you throw at windows which then slide down in an amusing fashion. I tried to unstick some that i'd placed on a clean surface and found the strength of the bond quite similar to the double sided foam tape i was using before. I was a little worried that my sensors might come unstuck in flight until i tried it out for myself.
One circlip short of a quadcopter.
 1 lobe short of an antenna.

Gaza07

It looks a bit like some stuff i tried called moongel except yours looks a bit stiffer, the moongel was quite squidgy soft, and I wouldn't trust it to stick some thing in flight as it was quite easy to remove, I used it to eliminate the vibrations in a little key chain camera mount, it was made from three ply wood plates covered with cellotape to make them smooth and shiny in a moongel sandwich so the middle plate was floating on the two outer pieces of moongel, it didn't seem like it was going to hold together so I added bolts, the bolts passed through large holes in the centre plate so there was no contact between the bolts and the centre plate, the problem was when I tried to add a little pressure to the bolts to hold it all together nicely the moongel would ooze out of the sides like semi melted cheese, the mount did work and improved on the vibes but didn't totally eliminate them, I will dig the mount out and take a picture later






MadMax

Ive just been having a browse through GLB as you do  ;) and came across these http://www.goodluckbuy.com/m3-anti-vibration-rubber-tube-for-ptz-installation-x4.html
I wonder if they are any good, I didnt think rubber was that good for anti vibes and silicone was better  :-/

[attachimg=1] 

Gaza07

Nice find they might be worth a try though because they are cheap enough  ~~

teslahed

Thursday,July 19, 2012, 10:42:50 #14 Last Edit: Thursday,July 19, 2012, 10:47:13 by teslahed
The 'M3 Anti-Vibration Rubber Tube for PTZ Installation X4' are $6.89 and the 'NEW! Acousti Anti Vibration Silicone Washers Black 8 Pack' are £2.95 (so a little cheaper after conversion) and will arrive faster.

You need all 8 of the silicon grommets as you want 1 above and 1 below the flight controller in each corner.

I also had to custom make my own nylon spacers with longer screw risers. I did this by taking a female/female ended nylon spacer, cutting one of the bolt heads off a long bolt and threading that into one end of the female/female nylon spacer to make a female / male nylon spacer with an extra long male bit (lol) to give the silicon grommets something to sit on. The holes through the silicon and also the corners of the flight control board are large enough for the board to slide up and down on the extra long nylon bolt cushioned by the silicon above and below - if they stuck on this there would be no point.

It's possible that because of the way the rubber ones are designed without the nylon thread running through the vibration damping material that they would work better though - I'm presuming with the rubber ones the metal doesn't run all the way through the middle of them as that would be pointless. If you try them I'll be interested to hear of your results.

One circlip short of a quadcopter.
 1 lobe short of an antenna.

BYOD

I always find this to be an interesting topic, and I must have read 000's of ways people have tried to stop it. I have always used very well balanced props and Velcro to hold flight control boards in place and have not ever had any real issues with vibration.

The next thing I find even more interesting about the vibration on copters is...... All DJI products come with sticky pads to mount the IMU's to the frames, these sticky pads are the M3 VHB style and are less than a 1mm thick and offer no damping at all! I think that the vibration issue is like a dog running after its own tail, and to remove it all is a very hard job, I think that the people writing the code for the controllers should look to make a "compensation" for the vibrations on the copters, as I think this is what is done on the WKM, NAZA & WKH controllers do, I'm sure we have all seen the VHB pads from 3M, but if you have not used them, well it's like you have welded your flight controller to the copter, they don't come off!

Regards

Martin.

teslahed

Wednesday,August 01, 2012, 08:45:31 #16 Last Edit: Wednesday,August 01, 2012, 08:59:58 by teslahed
It is a tricky one. My idea of mounting the motors using the foam pads has not worked at all well and has been abandoned (feel free to give it a try but i don't recommend it). It introduced more vibrations by allowing the motors to wobble slightly rather than less by absorbing them.

The silicon grommets seem to do at least a little good though and i would guess the sticky jell stuff that i have for sticking down the sensor boards also works quite well, going by flight performance (and i used in on my camera too).

I've yet to buy a prop balancer that works properly though :-/
One circlip short of a quadcopter.
 1 lobe short of an antenna.

teslahed

Sunday,September 09, 2012, 19:06:27 #17 Last Edit: Sunday,September 09, 2012, 19:08:37 by teslahed
Maplins are a cheaper source of the silicon anti-vibration grommets than anywhere else found so far;

http://www.maplin.co.uk/silicon-washers-99272
One circlip short of a quadcopter.
 1 lobe short of an antenna.

icedfusion

I bought some of these gel mounts:

http://www.gelmec.co.uk/



However, they are pretty expensive for 4 of them (around £20), but they are supposed to do an excellent job of taking away vibrations. I haven't used them yet as I haven't really found a frame to use them on yet.

ice.

icedfusion

Any news on how that gel performs teslahed?

ice.

teslahed

I'm still flying using the gel and it seems to be working well, but I've changed so many things on my quadcopter to try and improve it that i can't be sure how much of a difference the gel actually makes.

It's certainly worth a try though.
One circlip short of a quadcopter.
 1 lobe short of an antenna.


sausageroll

Ive  not seen any vibration on the quad or hex, using the naza. After the first crash, I replaced the naza onto the new chassis, didnt have any of the included tape so I used jelly tape, which is a thick squashy strip. I havn't noticed it get better or worse, but its stuck fine and it works fine as well...

The hex has zero effort to stop vibration apart from using decent props which are were ready balanced.


teslahed



Interesting video comparing different vibration damping materials.
One circlip short of a quadcopter.
 1 lobe short of an antenna.

rickp

I';ve had very good results with my APM 2.5 board between 2 layers of foam (the sort that hard-drives are packed in - as thats what I had to hand), but I think I can do better.

I';m going to try the ';earplug'; mount. I';ve got some copper plates I can use for the base. Should get it done by the weekend - will report back once I';ve test flown it.

Balders

I bought some moongel ages ago when I was first getting into fpv and aerial video.  I think I bought it after seeing it on rcexplorer';s website actually...
Growing old is mandatory...Growing up is optional

FPV Guru
BNUC-S qualified
Sbaps.co.uk

Vidal

This is how ive mounted mine.
Cut out some copper plated board larger than the FC. Put a nut and bolt in each corner. Then used O-rings to suspend it between the bolts.
Used moongel to fix the board to the quad.

rickp

Quote from: Vidal on Thursday,March 07, 2013, 07:29:01
This is how ive mounted mine.
Cut out some copper plated board larger than the FC. Put a nut and bolt in each corner. Then used O-rings to suspend it between the bolts.
Used moongel to fix the board to the quad.


Looks good - but I';d be worried about the copper shorting the ESC connections, even though there looks to be plenty of clearence...

teslahed

i think it looks very good - but I';ve seen other people suspend flight controllers with o-rings in the corners like that as well as put them on gel before. I wonder if there is any risk you';d set up a system that could oscillate backwards and forwards and ';ring'; or wobble as if it was on springs? Have you tested the flight performance  both with the O-rings and without? Is there any noticeable difference.

I';ve never heard of anyone having problems with this type of setup - it';s just the thing I';d be worried about - possibly unnecessarily.

Great stuff posting the details, thanks!
One circlip short of a quadcopter.
 1 lobe short of an antenna.