No problem on the questions Dan, but most of those links are not opening up to anything.
A shop vac as you know is designed to vacuum up dust, or to deliver the much smaller volume of air movement required by a hand tool like a router. It's not going to shift enough to collect much from a floor machine - as before that only happens when there's enough air moving to create a decent sized low pressure volume around the source of dust.
Going the DIY route is going to be significantly cheaper, but it does require some study and getting stuck into the (basic) numbers so you don't boob in selecting the bits needed to sort out a properly functional design. There's lots of info on the Pentz pages, albeit it takes a lot of ploughing through.
A very superficial sequence to pull together the elements of a DIY unit might be more or less as follows:
1. Scavenge an LP fan/blower of the right type (whether part of a stock bit of kit or not - they are used in industry too) that's likely to shift enough air. The minimum if you are going to go a mobile unit serving one machine at a time with say 2m of 6in flexible is probably around 2HP. Ideally a bit larger, say 2kW plus if you don't want to be too hobbled on duct length. Go for the higher number if you plan the extra duct length needed to give the option of exhausting outside. It's not an exact indication of likely fan capability, but HP is at least a very solid indicator.
This is the type of impeller found on these LP fans, they are used all over the place in industry. It's important to get the right type. The size shown needs around 5hp so its bigger than the minimum needed here:
http://www.clearvuecyclones.com/index.p ... ucts_id=11
Bill Pentz lists good data on fan types, sizes and sources on his basics page.
2. The blowers on some recent dust collection units are types that generate more suction, and the resulting greater pressure drop seems to allow smaller duct/hose sizes (at the expense of higher air velocities and all that entails) than those found on your typical LP fan/ bag filter/dust system. e.g. some of the recent Record Power units. Even so roughly the same sort HP is going to be required.
I don't know how good a basis for an effective system these are. As before the others may be able to comment on how these do in practice, and what sort of ducting options they can run.
3. Source some flex hose/ducting in the right size. i.e 6in in the case of a low pressure radial fan, probably smaller in the case of the above higher pressure/higher velocity units above if its confirmed they actually do shift enough air to properly gather in fine dust (and not just chips) at a machine.
Make sure that this cross section of duct runs clear through to the cutting area - including through the machine hoods which may need modification.
Flex hose is not too expensive at from memory around £12/m from most woodworking machinery places, and EBay. Rigid galvanised ducting is cheapest in spiral wound form from an industrial ducting supplier - it's again very cheap.
4. As before more HP is required if you want to install a system with longer ducting runs in a larger shop- the Pentz link I posted before shows a very easily understandable table listing HP/acceptable cfm/length of duct run.
5. Select a suitable cartridge filter - to at least HEPA 15 efficiency. Mine has two 262-5001 cartridges from Donaldson Filtration's UK branch in Leicester. I paid about €98 each (exc VAT), but I think there are some better priced and more small order friendly suppliers of industrial filters than that. Somebody posted the name of a web shop doing industrial HEPA standard filters in the UK in the past year I think.
6. Get a cyclone built to the Pentz dimensions. It cost me about €120 locally to have one rolled and seamed (I'm fitting the inlet) in something like 22G galvanised steel by a local ductwork establishment.
7. There will be some other bits needed as well like a chip collection drum, some sort of framework, hose clips and so on.
That's roughly one DIY route to a low cost minimal one machine at a time mobile version of a fan/cyclone/filter/chip collection unit based on the Pentz principles (mobile because it keeps the hose short enough) - but it'd at least be one delivering enough puff to do a good job
If DIY isn't attractive for whatever reason you can buy buy something that seems very like it (Bill has had a big influence on the suppliers of commercial systems I think) in the form of one of these ready made mobile filter and cyclone units from Axminster Tools:
http://www.axminster.co.uk/axminster-pl ... rod795045/
Stuff like fan/motor spec, filter spec, filter life, spare filter costs and so on on these would need careful checking out. The cyclone looks a little short and dumpy compared to the Pentz format, and it mightn't be the plan to try to run more than one machine at a time from the bigger one one despite the forked hose connection fitted to it - but the chances are that one or the other would do a very decent job.
