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Tonyz
26th January 2004, 12:56 PM
this could be put elsewhere but ?
I would prefer to bend 4"PVC pipe instead of 45* elbows all over the place.
I have a memory of putting HOT sand inside the pipe and slowly bending. [ When packed inside it dose'nt allow the pipe to have 'wrinkles' on the inside of the bend ] but
1 would this be the full length of pipe and bending where
needed or
2 stuffing paper in till the required bend sot then the sand
3 How would I heat so much sand for a 4"pipe
Tony

zathras
26th January 2004, 02:39 PM
tonto, I have tried doing 25mm conduit with hot water and it's tricky to say the least. The PVC gets soft just below boiling point it seems.

With 100mm trickiness escalates methinks. Just think of how far the outer needs to stretch to accomodate the bend. I don't think you'll achieve much in compression.

Your idea though is good, but you dont really want a bend as such but a sweep over a large radius to keep a nice smooth airflow. Turbulence from abrupt angle changes will create a loss in performance.

soundman
26th January 2004, 10:59 PM
the best thing for bending pvc pipe is a heat gun.
sand is just too hard!

100mm pipe is a big ask you will need a lot of heat and some practise.

most electrical types learned this process as an aprentice (me included) 16, 20,25mm easy, 32,50mm not hard but need practise.

never done 100mm. but I can assure you it will be a hand full.

practise on something smaller first.

the plumbing pipes will be a lot less forgiving than electrical conduit.

check bil penz web site for a short discussion of the matter.
http://cnets.net/~eclectic/woodworking/PVC.html

DarrylF
26th January 2004, 11:04 PM
Life's too bloody short mate :) Just use multiple smaller angle fittings instead of a single 90 deg - like 2 x 45's etc.

Sure an abrupt 90 is going to cause a loss of suction more so than a gentle curve, but how long can you really make the curve without filling half your workshop with pipe? Is it really going to make that much of a difference?

I have a 2hp DC with a number of bends and all works fine. It would be better with 6" pipe, but haven't got around to that one yet.

Red neck
26th January 2004, 11:44 PM
Tonto

You could use flexible dust extraction hose at the bends and straight runs of PVC. With just a couple of bends the loss contributed by the flexible hose should be minimal.

Flexible hose is a different diameter to PVC but I found that by standing a piece of drain pipe on end, on the bandsaw, you could remove a slim longitudinal wedge and reglue it with PVC cement. This creates a slightly conical shaped tube (reducer) that can be cut at the correct diameter and attached to both lines.

Tonyz
27th January 2004, 05:35 AM
thanks guys, it was worth a look at, at least but 45* looks the way

soundman
27th January 2004, 11:15 PM
doing some dust pipe upgrades myself at the moment & have found a couple of tricks.

45 deg bends can be go in fem-fem and male- fem, this is very convienient.
makes an easy 90 with ability to skew as well.
the inside curve is a little smoother than a 90 but not much.

second
Get a standard 100mm bust pipe cupling & cut it in half. File a nice chamfer on the outside.
then
warm up some standard 100mm plumbing pipe with a heat gun & the cupling will (with some encouragement) slip neatly into the pipe.
If you are keen snug th joint up with a band clamp with the pipe hot.
I then pulled mine apart & glued it with pipe glue.

Same can be bone at machine outlets If a flexible connection is not needed.

my saw bench has a steel 100mm dust outlet.
I just warmed up the pipe sliped it over the port & snugged it down with a band clamp.

using these methods all standard dust pipe fittings can be made to fit 100mm drain pipe

cheers.