Reply by Carl10

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Posted on Jet DC1100 Transformation ***COMPLETED***

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115 posts in 844 days

#1 posted 01-31-2018 01:50 AM

Well I don’t have a pic of what is inside my unit but this is the idea.

I took 2 pieces of flat galvanized duct material (anything stiff and flat will do) cut a slit halfway down the middle on both pieces and slid them together to make a cross. So in your case it will be 6”x5” (center tube dia. x ~5”) pieces, if you make it a hair bigger you can give it a little bend and they will stay in the tube while you tape them in place. I used foil duct tape as a temporary measure but it hasn’t budged so I left it that way.

As far as the output, you will be surprised what a difference that will make by enlarging the duct. On my old Oneida, it had an internal filter, so there was a heavy metal lattice over the blower output. I estimated that it covered almost 10 sq. in. of the output. After I removed it I measured about a 5% increase in airflow. Your 5” output is 7 sq. in bigger than a 4” duct.

To measure these changes I use a Pitot tube. Years ago I bought a small anemometer to measure airflow, and was fooled into thinking I had better performance than I really did. The anemometer is a cheap way to measure changes but not actual numbers (not even close). A Pitot tube and the accompanying Magnahelic are about $50-60 on eBay. For comparison I measured my flow with both and the anemometer was inflated by 30%. You can find a great test that RedOak did on using an anemometer here in his blog.

I know you may say that another ~5% isn’t worth the hassle, but those little things really add up. My Old Oneida started out with an internal filter and delivered ~460CFM max! After all the tweaks and adjustments I went over 750CFM. So every 5 and 10% really adds up.

Once you have your duct work setup you can do an easy test by running with the current 4” exhaust and then have someone remove it completely to see if you notice any suction differnece at your tool port. I say wait until your ducting is in becasue with no duct or exhaust you will overheat your motor (no load). If it were me I would use a 6” exhaust vent on the wall and run 6” all the way to your blower.

Hope this answers your question. Let us know what you do.


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