Tuned Absorbers.

[gwagon]

Hi folks. I'm new to this forum. I have used the search facility but to no avail. Hopefully some one can help.

I've been asked to design a tuned absorber for a motor supported on a simply supported beam. When the motor is running at 830 rpm the system experiences resonant vibration in a vertical motion, however, at the normal running speed of 1000 rpm, the vibration is deemed too excessive.

The mass and stiffness of the tuned absorber have to be calculated so that the natural freqencies of the resulting two mass system is seperated by at least + or - 150 rpm.

I know the length, depth, breadth and Young's Modulus for the beam.

Could you put me in the right direction as to what equations I should be using, or how to derive them from fundamentals?

Any help will be greatly appreciated.

 

[Heckler]

We use material from

http://www.earsc.com/

to damp some of our systems.

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
XP Pro SP2.0 P4 3.6 GHz, 1GB RAM
NVIDIA Quadro FX 1400
o
_`\(,_
(_)/ (_)

(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right." -- George Best

 

[gwagon]

Thanks for the link. I'm looking through some of their technical papers to hopefully get a better understanding. I'm having a bit of trouble getting my head round this.

 

[GregLocock]

Have a look at the wiki

http://en.wikipedia.org/wiki/Tuned_mass_damper

your target for tuning the absorber is actually an interesting subject.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[gwagon]

Thanks Greg. That link is very heplfull.

 

[drawoh]

gwagon,

Is there any reason you cannot just make the beam stiffer? Cutting the effective length of your beam in half or making it twice as thick makes it eight times stiffer. A two by four shoved into the right place has got to be simpler than a tuned absorber.

A less satisfactory solution would be to increase the mass on your beam, shifting the natural frequency down and away from 1KHz. Increased mass would reduce the acceleration due to eccentric force, and ultimately, the magnitude of your vibration.

Can the motor sit on anti-vibration mounts? Anti-vibration mounts are very effective at 1KHz.

JHG