Help!!!! Vibration Isolation
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Posted by: dimac ® 04/10/2006, 10:39:19 Author Profile eMail author Edit

Hello, Can somebody help me with design? I have an internal combustion engine, single cylinder, two strokes. It develops 8.8 N*m torque (80 lbf*in) at 6600 RPM. It mounted on 4 vibration isolators located symmetrically around the Center of Gravity (see attachment). The natural frequency of the system (without coupling connection) is about 37 Hz. Without coupling (gear not connected), the system works perfectly, the engine oscillates around the C.G. without significant movement of the shaft (in all X, Y, Z directions). When coupling connects the shaft to the gear, after few minutes of the work at the rated speed, the system is crashes, the coupling is breaks down, and pushes down the isolators. I think that under load, the engine increases its oscillations and the coupling can't curry these axial and/or radial and/or angular misalignments and crashes. May some other coupling solve this problem? Thanks

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Re: Help!!!! Vibration Isolation
Re: Help!!!! Vibration Isolation -- dimac	Post Reply	Top of thread	Forum

Posted by: zekeman ® 04/11/2006, 00:29:01 Author Profile eMail author Edit

What kind coupling to the gear? And is the gear under any load?

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Re: Help!!!! Vibration Isolation
Re: Re: Help!!!! Vibration Isolation -- zekeman	Post Reply	Top of thread	Forum

Posted by: dimac ® 04/11/2006, 02:46:47 Author Profile eMail author Edit

The coupling is R+W Elastomer EKL/10/B (https://www.rw-couplings(DOT)com). The gear is connected rigidly to the ground.   Modified by Administrator at Tue, Apr 11, 2006, 07:59:29

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Re: Help!!!! Vibration Isolation
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Posted by: zekeman ® 04/11/2006, 14:42:18 Author Profile eMail author Edit

Do you reaally need an elastic coupling? I think this coupling plus the gear amplifies the vibration, As an experiment, try a loose nonelastic coupling just to check its behaviour. This may tell you how to proceed.

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Re: Help!!!! Vibration Isolation
Re: Re: Help!!!! Vibration Isolation -- zekeman	Post Reply	Top of thread	Forum

Posted by: dimac ® 04/16/2006, 03:06:08 Author Profile eMail author Edit

I think nonelastic coupling will not absorb vibrations from the engine and they will pass to the gear. I try to prevent this.

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Re: Help!!!! Vibration Isolation
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Posted by: rfox71 ® 04/10/2006, 13:13:46 Author Profile eMail author Edit

If your not using an allignment coupling you will most likely experience serious mechanical failure (although how quickly Im not sure). Once coupled your system is essentially fixed at that point. This changes the dynamics of the system. It will now be reacting to moments and forces created about the coupling point. I think you might need to look at changing your damping setup (i.e. location and type)...... Ill look into it more when i get the time... Very interesting... Robert

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Re: Help!!!! Vibration Isolation
Re: Re: Help!!!! Vibration Isolation -- rfox71	Post Reply	Top of thread	Forum

Posted by: dimac ® 04/11/2006, 03:09:05 Author Profile eMail author Edit

You can see above the kind of the coupling. Basically it might permit some axial, radial and angular misalignment. It seems that the coupling cancels some degrees of freedom instead of dumping the vibration. The question is is there some other type coupling that can do this work?

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