Cyclones don't suck [Dyson DC07 HEPA]

I have a workshop and a small shed, and I wanted to move my Compound Mitre Saw into the small shed. As all the machines in the workshop are currently sharing a single dust extractor, I needed to provide a second one for the saw and - prices being what they are - I thought to make use of an old cylinder vacuum cleaner which I have around. I've fitted an extra (cyclonic) cylinder in series with the main extractor, to catch most of the chips and sawdust before they fill the can, and I thought to do the same with the second unit, when it occurred to me that I could get an old broken cyclonic vacuum cleaner and use just the body for the purpose. It would undoubtedly be more efficient than my home-made one. Accordingly I scoured eBay and ended up buying a broken Dyson DC07 HEPA for 99p, being first made to understand by the seller that there was 'a tube missing' - which I could see from the photo, as it didn't seem to have the small bent duct from the base unit to the handle assembly (just visible bottom left in the photo, above the wheel).

I found someone on eBay selling the relevant spare part for a few pounds and won it just in time to collect the broken Dyson. Unfortunately, as sometimes happens, the Dyson wasn't quite as described in that the seller didn't know much about it - when I got it home the 'missing tube' was in a bag of bits and in good condition. After some consideration I asked the seller of the spare tube not to send it and to refund me only the postage costs, keeping the sale price for his trouble and being able to re-sell it. That way he got to sell it twice and I paid out less than I would have done in the end.

The next job was to see what was really wrong with the Dyson. Two things stood out - one, the motor filter was totally clogged up and two, the top of the cyclone unit (the top of the 'rocket exhaust stack') was detached, with all three mounting pillars broken off. This was a setback because the cyclone housing needs to be air-tight and also, the top incorporates a handle which is so placed as to be exactly over the centre of gravity - so is used as a lifting handle to move the machine around even if its main purpose is to lift the dust container. Which is probably why it broke! There are quite a few people selling new cyclones, or clones of them, and there must be a reason for the market - they keep breaking. Unfortunately a new cyclone top would be over £30.

The motor seemed to be fine and all the parts were now present. If I had wanted to buy a new cyclone I could have done so without buying the whole cleaner and so I wondered whether perhaps the Dyson could be resurrected and provide the whole solution - needing no filters or bags and taking up less space than my old cylinder vacuum.

I cleaned up the whole machine after disassembling it. One problem was that the dust container was full and as the release catch was on the top of the cyclone - which was detached - it couldn't be opened. I had to do a lot of judicious fiddling with long sticks to release the catch, after which it was straightforward. The filters are washable foam, and new ones are easily available anyway but these came up fine. I had to free off some of the rollers on the base which had rusted up and also clean out all the nooks and crannies and the brush rollers, but that all went fine. Turning to the broken cyclone, it was obviously a case of having to reattach the three plastic pillars which had broken off the lower part (they were still held by the screws to the upper part), but I found that I was not the first to try and they were fairly mangled and covered in superglue. Clearly simply re-gluing them was not an option - the originals were not strong enough and certainly the glued broken ones weren't. The entire weight of the machine is lifted through those three small screws.

I began by cleaning up the parts with a sharp knife and files until they were back to their normal profile although not altogether complete. At this point I wanted to use epoxy putty to mould a strong buttress round each one, but the pillars are very close to the edge of the housing and there needed to be clearance for the flange on the top part to slide down between the pillars and the outside of the housing, to provide location and a seal - so the repaired pillar had to be much the same size as the old one but stronger. On the other side, the pillars were next to the air passages out of some of the cyclone chambers, which have to be clear for the thing to work at all. The heavier debris drops out of the airstream as it comes into the side of the dust chamber, then the remaining air with the smallest particles flows up into a plenum chamber where it is distributed between the eight mini-cyclones (the 'rocket exhaust' features). Each of these speeds up its part of the airflow until the dust shoots out of the top and falls through the middle into the dust container whilst the air returns to the motor fan through another tube. This is the same action as a normal cyclonic separator but is physically upside-down on this machine. They usually point downwards. Anyway, I refixed the broken stubs together with superglue just to locate them, then wound some wire around each pillar until it provided a continuous collar up the neck a bit like the native African tribe whose womenfolk used to wear stacks of metal rings to stretch their necks. Then I coated the whole pillar with epoxy glue, warming it slightly so that it became runny and soaked between the wire coils. It was necessary to provide a reinforcing collar of some kind because the threaded screw holes had become split and would not have secured the screws for more than a few threads at most. Once all this lot was fully cured, I applied a small amount of epoxy putty (Milliput) where there were gaps and moulded it smoothly back to the original contour of the pillar, with the screws in place but well greased. When it was set the screws could be removed and left a good thread set into a metal-reinforced pillar. As a result, the cyclone housing is now secure and the machine can be lifted by its handle - although I don't do it if I don't have to, just in case.

After reassembling the cleaner it seems to work quite well although the suction is nothing like it is claimed to be in the Dyson ads. As the brushes are good and the whole cleaner is basically serviced, I have to say that there is only one thing left. Some clown has superglued the cover accessing the HEPA filter (possibly because it kept coming loose) which means I can't get into it to replace the filter. Judging by the state of the rest of the machine, this filter is probably clogged solid and is covering the whole of the air outlet from the motor, so is blocking the whole operation. Although it will work OK as a sawdust collector as it is, I think I will need to cut open the filter housing and replace the filter, securing the housing by some other method (magnets?). I'll update the blog if/when I do this. Maybe it will be of more use in the house.....but then I'll be back where I began.....but whatever the outcome, a Dyson for 99p outlay is a bargain.
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UPDATE 11 July 2014
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I eventually cracked open the HEPA filter housing without having to cut it, and the filter was indeed almost solid. Fitting a new filter and seal restored the performance expected of a Dyson and my smile is even broader. The rest of the repair has held up successfully, so far.