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HEXA frame continues: Anti Vibration Motor Mounts

Posted by ARHEXA on April 27, 2011 at 9:54am

step by step, the HEXA frame is being constructed.

haven't worked on it for a while, but now i'm done with an interesting part:

 

 

 

I used the original arducopter motor mounts (the plates that come with the motors, which are not used on the official arducopter frame)

to be tied on the square arms, and between the mount and the motor, i've used:

*bling*bling*  RUBBER MOUNTS *bling*bling*

 

on the video you can see it works perfectly. isolating the motor from the aluminum arm.

with 6 motors working at very high throttle to keep this 4.5-5kg hexacopter, i'll need this vibration isolation to make nice and smooth videos.

 

and now, some pictures, 'coz we all like 'em !

 

 

3689403124?profile=original

 

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COMMENTS ARE WELCOME !

 

 

 

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Comments

  • Mick James May 1, 2011 at 4:29am

    After a brief think about it, I have an idea that might work for your rubber mounts. Firstly I'd like to say that's its a great idea.

    Where you have your "T" piece that the mounts are screwed into, you have 2 spare holes either side. If you were to tension some springs from the top of your motor down to these spare holes on the side, it would keep your mounts in compression. This could also work if you had a bit of rubber strap with a hole in the middle that goes from one hole, over your motor (With your shaft through the hole) and then down to the other hole. Cooling however, could become an issue as some of your front vents would be blocked.

  • Alex Lee April 28, 2011 at 5:38am

    it's 3mm thick.. the piece I purchased was 1inchx3mmx36inches long. it was about $3.49

    the plywood is hobby grade, got it from the LHS.. extremly stiff and perfectly flat.

    the frame is strong, I tried u channel tubing and skinner square tubing. the frame I have now really takes a beating. The big terminal connector is pretty light, I did make a cable that  spliced off into the individual escs but that became a bulky mess. This terminal connector fits right unter the apm board.

    i'm using the 2836 880kv motors swinging 12 x4.5 props with a 6000mah battery and I can hover for 9 min. I figure I can put about 5 lbs under it. I haven't tried it yet but i'll make a quick vid when I do. I plan to mount my nikon d90 with the 24-70 lens under it. not in a pan tilt kind of way, it'll be fixed.. pan tilt on that camera will be way too heavy.

    http://www.rcgroups.com/forums/showthread.php?p=18011985#post18011985

     

    the acrylic is 4mm and pretty strong.

     

  • ARHEXA April 27, 2011 at 10:40pm

    Brendan,

    my instincts tells you're right, but practically wrong.

    the rubber mounts will absorb the torque, the circular torque, when there is an acceleration.

    and on the video as you can see it absorbs a few degrees, less than 10 degrees, from zero throttle to 20% say.

    as the power of the system is measured by the spinning speed of the prop, it lost power by just 10 degrees (1/36 of a rotation) compared to the the hundreds of rotations per second.

     

    I agree that the rubber 'twisting' can add some latency or delay in the response of increasing throttle command, but i don't see it taking lots of power up...

     

    anyways, when i change it to 2 rubber mounts only, it will twist much less i guess...

     

    @Alex,

    what thickness is that aluminum plate? 

    Acrylic is just a bad joke, unless you fly small copters as a hobby.

    I've looked at your hexa, it's cool but there are many things i cant "afford" - weight wise.

    i'm not building the lightest or most efficient weight/strength frame ever, but i'm already at 5kg weight, and using bulky parts and methods (like your big terminal connector for the ESCs) is not possible anymore with the weight...

     

    I'll have to check if the motor mounts bends and i might add another piece of square tube in parallel at the end of the arm to make more surface...

     

  • Gord Likar April 27, 2011 at 8:30pm

    If you moved the rubber mounts to the sq. tube it would be easy to wrap a safety band around the mount and sq. tube.  AGL Hobbies had a CF mount and used grommets on the motor mount screws, but abandoned it.  Think he said it was not very effective considering the added weight. 

     

    Nice work.

  • Brendan April 27, 2011 at 7:46pm
    Some food for thought: there may be measurable efficiency lost by absorbing torque in the rubber mounts... Pedal a bike with full suspension set to full travel and you will burn many more calories than pedaling the same distance with the suspension locked up. Take any manual transmission car with stock engine mounts that absorb torque (whenever you see the engine twist as you rev it) and by minimizing this torque absorption, you'll realize more power to the wheels with same power from the engine. Since the quadcopter motors are changing RPM on a regular basis, you may experience shortened flight times with those mounts.
  • Alex Lee April 27, 2011 at 6:48pm

    oh another pic of the  aluminum mount installed on my hexa.

    3692204201?profile=original

  • Alex Lee April 27, 2011 at 6:46pm

    sure..

     

    This is the render of the mount out of aluminum.

    The files are EMachine Shop type. Just search and download the free software and then visit http://allioupe.com/hexa to get my files. 3692204302?profile=original

    I have more files in there. Exactly what I used to build my Hexa.. Just print out and tape to whatever material you want. I used plywood.

    Here is what it looks like http://www.rcgroups.com/forums/showpost.php?p=17747799&postcoun... forget about the issues, they are all resolved now.

    The ponoko file for the acrylic mounts is http://www.ponoko.com/design-your-own/products/motormount-5690

    3692204288?profile=original

    I used 4-40 machine bolts to mount.. I think the long ones are 1 and 1/4 inches and the short are 1/4 inch.. You can reuse the screws that came with the motors, just contersink the acrylic.
  • I.S. April 27, 2011 at 5:59pm

    @Alex

    could you post any picture of that?

  • Alex Lee April 27, 2011 at 5:58pm
    I have a drawing of them you can just tape on the bar stock and drill with a drill press. They do work well.
  • Alex Lee April 27, 2011 at 5:56pm
    I used those square mounts with only two bolts also and I isolated the vibration to the face that only two bolts are holding the motor and the metal used in the mount bends like tinfoil. Its really awefull. I machined my own mounts out of 1inch aluminum stock you get at the big box store and problem solved.
    I do have a piece of thin neoprene beer bottle wrap you get with the fancy logos on it and put it under the ardupilot and it pretty much does the trick.
    I also made some of the same type of mounts as the arducopter uses but fits a 3/4 inch aluminum square tube you get from the same big box store. I made them from acrylic via ponoko.com and was about 20 dollars for six mounts.
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