Originally Posted by
Ellsworth LeDrew
I currently have a 2 HP General with 4 inch tubing that is about 12 years old. I use the garbage can and Lee Valley dual port lid as a first stage to collect chips. The Padauk highlights how much leakage there is from this, even with insulation striping between the lid and the can. Otherwise it removes much of the heavy material. There is some leakage around the General bags. My understanding is that this is characterized as a chip removal system. With measurements of air flow with an anemometer and some basic math, I measure the throughput at the machine to be about 755 cfm and at a nearby jointer it is 707 cfm.
A 2hp extractor will not flow 750 CFM even downhill with all sails up and a 4" pipe will not flow anywhere near that either at the low pressure a dust collector works at. Anemometers cannot be used to measure air flow but everyone persists in using them despite many posts here saying don't bother. The reason the air speed means nothing are several fold, air speed into the duct varies across it due to turbulence created at the entry and within the duct air flow varies due to the air speed being affected by the duct wall so the air in the centre of the duct is faster than the air closer to the walls.
Chris
Everything I like is either illegal, immoral or fattening