I've decided to bite the bullet and run an extraction duct down the length of my woodwork shop using standard 110 mm underground drain pipe mounted up in the roof. There will be a drop down to my extractor about 1/3rd of the way from one end, and drops to the various machines in 125 mm, 100 mm , and 80 mm as appropriate to the machine. There will also be a 'floor sweeping' port that shavings can be swept into. Each inlet will have a plate valve to enable it to be shut off.
Now I've had the 110 mm pipe, the plate valves, and various bits of flexible pipe for some time, but the 'round tuit' hasn't happened.
One hold up is the realisation that the extractor, (the source of the suck) will be connected midway along the duct requiring a straight 90 degree Tee fitting and these are not available in 110 mm drainage style, as all Tees have a degree of flow management - so a 90 degree Tee is really an 87.5 degree Tee with markedly swept internal shape to encourage flow in one direction. So no use to me
Well we are Mad Modders aren't we - MAKE a 90 degree Tee - so that was this mornings job.
I took the stub end of a pipe that had a female socket incorporated, and projected the required shape of cut out onto it by holding another pipe at 90 degrees and drawing round it.
A bit of Jig Sawing, a bit more marking, a bit more jig sawing . . . .well you get my drift . . .an iterative process . . and we ended up with a hole in the pipe that I could push the other pipe into, draw round, cut out the 'birds mouth' and glue it all together. Seems to have worked OK - see how strong it is tomorrow before I commit to using it. Meanwhile clips and 87.5 degree Tees on order so I'll update this thread as the build continues.