I know we are supposed to leave straight pipe on the last 3 feet of duct run to the cyclone. I have a brand new cv1800 with the 6inch s&d inlet. I've been told that I will benefit from running my main trunk line in 7" duct ( I'm running thick gauge metal pipe ) however I'm concerned that running the 7inch and reducing at the inlet will cause too much turbulence and reduce the amount of separation capability. Am I being too worrisome ? Any advice including speculation is helpful. Thank you all so much and may you be safe in this trying time.
Reduce Duct 7-6 at cyclone ?
- Thread starter Carswell
- Start date
I'll speculate that a long smooth transition will minimize turbulence to the point of not being a factor. Ideally the transition taking place over the 3' or more of straight length before the cyclone. If you look at 10C page 67 of http://www.lorencook.com/PDFs/Catalogs/Cookbook_Catalog.pdf you'll see that the equivalent drag of the shallow angle transition is 6' of straight pipe and that is a 2 to 1 constriction. With a 1" diameter change it shouldn't even be a factor. So if you can find a long transition or have it custom made to fit you should be golden. 
If you can only get a short transition it might be better having it at the start of the 3' section.
Pete
If you can only get a short transition it might be better having it at the start of the 3' section.Pete