Re: [CAD_CAM_EDM_DRO] My Next Router

Hi, on the noise i agree, these new upright vacs made of plastic are so
noisey!!!! cheap air fans with sharp edges help make a lotta noise. cul
brian f.

----- Original Message -----
From: "Les Watts" <leswatts@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, September 30, 2002 10:08 AM
Subject: Re: [CAD_CAM_EDM_DRO] My Next Router


> Re router noise
>
> The Porter Cable 3 1/4 hp series of routers are good machines but
notoriusly
> noisy. I use them and actually wear earplugs in the shop.
>
> There is a Hitachi router now being made that is 82 dbA at one meter.
>
> I work some with portable power tool noise reduction. I gave an
engineering
> seminar for a group of manufacturers a while back in Chicago. So I have
> some interest in quieting down routers. (I have not worked for PC but want
> to)
>
> I have not done a vector sound intensity map of the PC routers yet but
> will next time I have the stuff set up for another job. So I can only give
> educated guesses as to why it is so loud.
>
> I do not think it is the bearings.
> I think these are abec-1 electric motor grade (quiet running) conrad
> type with grease and shields that have increased internal clearance.
> Certainly the bearings make some noise, but I think not the major
> amount.
>
> I suspect two things: Brush noise (frome arcing and sparking) contributes
> a good bit. This creates a correlated harmonic series (the whine sound).
>
> But I think most of the noise is the fan system. Although the outer parts
> are a moderate subsonic mach number I think the air flow is reaching
> sonic velocity in some areas. That and vortex shedding seem to be
> making the very loud random component of the sound.
>
> This is very similar to the noise from shop vacs etc.
>
> Puting the thing in a box will certainly help, but take care not to
restrict
> air
> flow. The air ports need to be tuned absorbers.
>
> Work noise (from the tool) will always be there but the PC motor
> noise is much greater than the typical work noise as I use them.
>
> There is really no reason a router or shop vac has to be that noisy.
>
> Leslie Watts
> L M Watts Furniture
> Tiger, Georgia USA
> http://www.alltel.net/~leswatts/wattsfurniturewp.html
> engineering page:
> http://www.alltel.net/~leswatts/shop.html
>
>
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