[AT] reducing noise on portable generator

charlie hill chill8 at cox.net
Thu May 19 05:04:23 PDT 2005


Hi Dean, your physics are correct but I think you have forgotten one 
important aspect of running a generator.  The generator has to run at a 
specified rpm to make the frequency correct (60 Hz) for the AC output.  Most 
run at 3600 but some at 1800 rpm input speed.
Therefore the only way to cut down on engine rpm is a larger engine run at 
slower rpm's and geared to keep the generator input speed correct.

Charlie
----- Original Message ----- 
From: "Dean VP" <deanvp at att.net>
To: "'Antique tractor email discussion group'" 
<at at lists.antique-tractor.com>
Sent: Wednesday, May 18, 2005 11:20 PM
Subject: RE: [AT] reducing noise on portable generator


> Ivan:
>
> I won't be at Portland but I understand your objective. If I remember my
> Physics theory correctly, putting a smaller pulley on the generator and
> engine will allow you to run the engine at a lower speed but it will 
> require
> more power to keep the generator outputting 2400 watts. A large pulley at
> the generator requires less engine power than a small pulley.
>
> Now if my above statement is correct, the engine will be running at a 
> lower
> RPM but it will have to work harder and you won't necessarily get a
> reduction in noise. I would think you would want to know what the power
> curve of the engine looks like at various RPM's. More power required = 
> more
> fuel used = more noise.
>
> I also suspect the generator has to be driven at some minimum RPM to be 
> able
> to achieve decent 115V regulation. I suspect with a smaller pulley it 
> would
> be more sensitive to sudden load changes as the engine would take longer 
> to
> recover.
>
>>From my perspective, I would work on trying to quiet the engine down 
>>through
> a better muffler set up first. I own a Honda generator here for back-up
> house power and paid a bit extra for it because the Honda engine was much
> quieter than other generators I looked at. I've never taken the time to
> determine if there was more to that difference other than just a better
> muffler arrangement. Maybe the Honda engine design is part of the solution
> too.
>
> Where I'm sitting right now, in my office, is directly above where the
> generator is located in the garage. When it is running at heavy load, 5000
> watts or more I can just hear a hum in the background up here. I'm about 
> 10
> feet from it vertically through an insulated floor/ceiling. Maybe the
> insulated floor is the real reason.
>
> Up close and personal it is still quite noisy, in my opinion, but a lot 
> less
> than others I have heard. Sometimes a large baffle such as a temporary 
> three
> sided wall with a top made of absorbing material such as foam rubber or
> Styrofoam can offer a significant improvement. Any sound absorbing 
> material
> would help I would think.
>
> One thing I have noticed is that as I get older it isn't quite as noisy.
> Probably has something to do with my deteriorating hearing! :-) Just park
> next to really elderly campers. They won't hear it. Hope this generates 
> (no
> pun intended) some solutions some how.
>
> Dean A. Van Peursem
> Snohomish, WA 98290
>
> I'm a walking storeroom of facts..... I've just lost the key to the
> storeroom door
>
>
> www.deerelegacy.com
>
> http://members.cox.net/classicweb/email.htm
>
>
>
> -----Original Message-----
> From: at-bounces at lists.antique-tractor.com
> [mailto:at-bounces at lists.antique-tractor.com] On Behalf Of ivan
> Sent: Tuesday, May 17, 2005 8:07 AM
> To: Antique tractor email discussion group
> Cc: sel at lists.stationary-engine.com
> Subject: [AT] reducing noise on portable generator
>
> Ok , this is for use at Portland so its on topic.  But I dont want to p***
> everyone off listening to a gen howling away .. So I put together a belt
> driven generator so we can run the ac in the camper by day  . Its chuggin
> along at 2400 rpm , with 115 under a 2400 watt load . Much better than one
> screaming at 3600 rpm .  But how to quiet it down a little more  ?
> I would like to put a smaller pulley on the gen itself so that I can lower
> the speed a little more ,target is1800 rpm and I have one of the lo tone
> mufflers from briggs  .So its a little quieter than a jet turbine .
> Suggestions ? Ivan
>
>
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