Shop vac speed reduction

Shop vac speed reduction

This topic has 3 replies, 3 voices, and was last updated 26 January 2019 at 21:31 by Robert Atkinson 2.

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26 January 2019 at 18:57 #393130
Yngvar F
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@yngvarf
I’ve had a Nilfisk shop vac for many years. It is effective but very noisy, wich for the most part is okay as I use it with woodworking tools and use ear defenders.

The other day I noticed that reducing the speed on a sander plugged into the vac reduced the noise greatly.

Can any of you clever fellows explain how this works and maybe help me make a «quiet mode» plug?
Advert

26 January 2019 at 18:57 #26409
Yngvar F
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@yngvarf
26 January 2019 at 20:26 #393142
Dalboy
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@dalboy
With the majority of vacs, the most noise is from the exhausted air ports. You can build a purpose built cabinet but it needs to be done so that there is still enough air flow to cool the motor and baffle the exhaust coming out of the vac best to exhaust to the outside.

This has been discussed on many woodworking forums in the past but unfortunately I can't remember which one
26 January 2019 at 21:31 #393151
Robert Atkinson 2
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@robertatkinson2
The Nilfisk will have a "universal" motor (brushed). These will run from AC or DC so an easy way to reduce the speed and noise is to half wave rectify the mains. This just needs a single diode (and a switch to short it out if you want to maintain full speed capability). The diode needs to be 600V and current to suit the motor. A 6A device should be OK A P600J (or K or M) would be a good choice. just connect in series with the live. Direction does not matter.

Robert G8RPI

Edited By Robert Atkinson 2 on 26/01/2019 21:36:35
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