HVLP Dust Collection

Using a furnace fan for dust collection.
I have a Delta dust collector which sits in the shed behind my shop. I am also surrounded on three sides by widder women who either go to bed with the chickens or sleep in 'til 9 am. The turbojet sound is not amusing to them. Having a squirrel cage furnace fan with an outlet of 5" by 8 1/2" that will blow your wig off, I wondered if I could use this quiet fan as an auxiliary dust and shavings collector with my lathe.
I boxed it in with some OSB (or as my brother says, SOB) and mounted a fixture on the top to attach a 4 inch flexible pipe to the cyclone. It would suck smoke, but nothing else. I realized it was not getting up to full speed with this obstruction, so I used a hole saw and made a 2 inch hole in the case. The fan turned faster but the hose suction was the same. I made 2 holes, same story.
I realized that even if it worked, the motor would be in the air stream for sanding dust and would not last long, but this was a prototype.
Conclusions: 1. This setup would only work using at least an 8 inch hose. 2. The motor would have to be outside the box for it to last. 3. The motor as supplied is too weak to overcome air-flow obstructions.
If I come into possession of a belt-driven model that I can attach a larger motor to, I will probably try again. I am intrigued by the quiet running of this type of fan.
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Gerald Ross
Cochran, GA
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I don't remember enough to answer you well, but a search on "squirrel cage blowers" may well find you something. Google, not here. There are very specific design parameters re intake loads and output loads. I've never seen a squirrel cage used for restricted flow. Developing the velocity required for DC requires considerable pressure differential, another name for restriction.
HVAC places will usually give away old blowers. A belted one makes a nice shop circulator, vapor remover, etc.
BTW, that fan is designed to have some restriction on the output. Running it open circuit will overheat the motor. With belt drive, you can control motor current by sizing the pulley, which you obviously can't do with direct drive. Buy a clamp on ammeter from HF if you really want to see what motors are doing.
You'll sure have to keep the chips out of it!
Offhand, I'd say put another DC fan unit inside and pipe it to the outside collector. Or build a sound control box for the outside unit.
Wilson

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