DC Overkill

[Doug Shepard]

I need to have removable DC downtubes for when the GaShop has a vehicle inside. So I'm telling my buddy Mr. Goldberg - "Rube, I know you can just plug some PVC into a bell end, but there's just something about not having a seal there that really bugs me". So Rube gets to work sketching something and hands it to me. Hmmmm sez I, maybe this could work. So here's the Rube Goldberg invention.

There are 4 plates mounted on the bottom of the rafters where the PVC ducts terminate. Each has a 14 ga galvanized ring, and a 1/4" rubber gasket. The plates and the mating ones on the down-tubes are recessed in so that the gasket seals up at the same point where the rare earth mags on the down-tubes contact the metal ring above.
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This attaches lickety-split and can be moved from one duct to another in about 3 seconds. This first one will get used on the disc/belt combo, but is probably the same one I'll use for the router table but stuck on at a different location.
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I still have 3 more down-tubes to finish, another with a 6"-4" change but a little longer for the DP. Then 2 more mostly for the TS and BS which will stay 6". Then I'll tackle the flex hose machine/down-tube portion. Starting to see some daylight at the end of the tunnel.

[Brent Grooms]

Doug, my friend, you might have just saved me a BUNCH of grief for my future installation. Brilliant thinking! I wouldnt have thought to use RE magnets for the quick disconnect!

[Doug Shepard]

Doug, my friend, you might have just saved me a BUNCH of grief for my future installation. Brilliant thinking! I wouldnt have thought to use RE magnets for the quick disconnect!

I'm hoping to have the other 3 plus the 1 remaining "remote" blastgate hookup done by next weekend. Not sure if I'll have flex hose connectable from machines to the downtubes at that point, but at least enough I can fire the unit up. You're welcome to stop by and check out the tubes to see what you think as well as look over the electric stuff you had questions on earlier. Drop me a PM if you want.

[Don Bullock]

That sure looks like a fantastic solution to the problem to me. I hope you've sent in your design as a tip to one of the woodworking mags.

[Jim Becker]

Very innovative, Doug!

[Michael Weber]

Cool! Whats the holding power of the re magnets?

[Doug Shepard]

Mike

I'm using 2 different sizes here. Here's the specs info.
http://www.kjmagnetics.com/proddetail.asp?prod=MM%2DA%2D25
http://www.kjmagnetics.com/proddetail.asp?prod=MM%2DA%2D20
I first ordered the 25mm, but when I tried one on a piece of the 14ga steel I got for the rings, I thought - Holy #### that's way too strong. I then ordered the 20mm ones but hadn't got around to returning the 25mm yet.

I attached these for the first time the other day and it was sticking, but didnt have enough grip to suit me. I think there are a couple of reasons for this. That PVC flange I heat flattened and cut out for gluing on the tube end isn't 100% dead flat. Close but no cigar. I think I've also got varying thicknesses in the layer of epoxy thats holding the 1/4" rubber gasket on the PVC flange on the top plates. This all ends up in a non-scientific slop factor that's resisting letting the mags make as direct a contact as they would like. It makes for a nice snug closeup on the gasket but is conspiring to try to resist closing up on the mags a bit. So I decided to re-drill for the larger mags and try that. I figured I'd just plug the smaller holes but before even trying the 25mm mags alone I decided to just leave the 20mm mags in as well to see what happened. To my surprise the setup felt just right. So there's a whopping combined pull with the mags of 132 Lbs. I'm sure my manufacturing technique with the PVC could be improved and this whole affair fine-tuned better. I dont really want to deepen the recesses out too much more to allow some of this non-flatness or glue thickness or I wont have as much screw holding depth on the flanges. So my plan on each of the next 3 it to first try only mounting the 3 25mm. If it feels like that particular tube needs it, I'll add the other 3 20mm though in hindsight, I think I'd space them at 60 degree intervals this time rather than double groups at 120 degrees.

[Jim C Bradley]

Hi,

That is REALLY clever!

Isn't it great when you get a Rube Goldberg and it hits ole Murphy on the head.

I'll bet a ton of WWs that read your thread don't even know about the origin of Rube---or to put it another way, Dearie, I'm much older than you.

Enjoy,
Jim

[Doug Shepard]

Just an update for anyone contemplating this. I got the first 2 shorter tubes done that are using 3-25mm and 3-20mm and no problems there. I got the longest one done today and hung. It's 6" all the way and runs to about 20" off the floor (IIRC the length was around 76"). While it hangs just fine, I'm not comfortable enough with the grip so I'm going with all 6 mags at 25mm for a total pull of 186 Lbs. The only issue here that I'm not happy with is the longer moment arm means it's easier to knock the mags free if bumped into down low. So I'm beefing up the pull on the longer tubes. I'll have to order a few more 25mm mags for the last tube, but will get the longest one beefed up tonight.

[Mike Heidrick]

So one idea I was thinking about when I read this thread.

What if you had some support/guide dowles (3/4" or 1" maybe) that the wooden flange fit over - maybe three or so spaced around the flange. It might help with lateral movement and reduce the chance of it knocking loose when pressure is applied down low.

Does this idea make sense???

Thanks for this thread. You really have me thinking now. Great idea.

[Doug Shepard]

Now why didn't I think of that. I did get the big one redrilled for the other 3 bigger mags and re-hung. It's feels a bunch more secure now. You'd really have to bump it pretty hard now to have it torque one side (followed by the others) free. I'm going to leave it alone for now, mainly because I'm SICK of working on DC installation stuff and want to get back to woodworking. But if this still ends up being an issue, I think your idea wood help that problem. The only big downside, is that right now I can spin the tubes in any orientation. I've got 45's on the ends of the tubes to sort of help angle flex hose toward machines. I can turn the whole tube right now to point it wherever I happen to roll a machine out. The pins would force me to pick some locations, install the pins for those, and then have to roll the machines out to fairly fixed locations. But if it's a choice between that and having them be too iffy, I'd take the pins.

Anyway here's the outcome. Cant do the 4th tube until I get some more 25mm mags. It's going to be a bit shorter than the big one, sized primarily for use on the bandsaw.
Here's Number #2 - same layout as Number #1 but a little longer. Mostly for use on the drill press but could also be put to use on router table or maybe even a benchtop planer if raised up.
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Number #3 is the tallest one. Mostly for TS use.
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Edit:
Did I mention that the whole place is in such disarry primarily due to this whole DC install?