Re: Sawdust collection

[Woodspoiler]

Good link that, and congrats on building your cyclone. I followed the same route a few months ago and I still get a glow of satisfaction every time I use it.

This is an opportune moment to post an update on the pressure relief valve (mentioned in a previous thread a couple of weeks ago) to prevent the bin collapsing and eventually splitting under blockage conditions.

I made it. In fact I made two versions and tried various springs from the Screwfix compression spring kit which I ended up buying.

I was delighted with the ingenuity of them and the way I had re-purposed throwaway stuff like offcuts of copper pipe and a used decorator's filler cartridge, until I found they didn't work.

However, I now have a clear understanding of the problem and other potential pitfalls.

I have a new and completely different design that takes these into account and should work touch wood.

More details on the problem, the new design, and a load of alternative design ideas that could be made to work as soon as I've made my prototype and seen how it does. I'll probably knock up some web pages because it's quite interesting (if you're the sort of person who can get all juiced up over adventures with a home-brew pressure relief valve).

Yes, it would have been easier to fibreglass my bin or buy a steel one, but I wouldn't be having all the geeky fun and learning wot I am learning with all this.

The end product will, if it works as expected, be fairly easy to make, should work with minimal tweaking on a variety of bin desgins and vacuum strengths, and look pretty gnarly into the bargain.

W.

We've had some threads on this forum recently relating to

building

cyclones for dust collection in a workshop. I've just built a

cyclone

based upon the excellent articles posted previously, but the

one item

I had difficulty obtaining was a suitably long vacuum hose for > connecting to various workshop devices. > > I thought I would pass on the following URL for anyone who

might be

looking to acquire a vacuum cleaner hose for use in their

workshop.

I've now got a 15 metre x 38 mm hose which allows me to put the > cyclone and vacuum cleaner into the roof area of my garage,

freeing

floor area downstairs and keeping the vacuum equipment out of

the way:

> > Very helpful people, they do spares for all the major vacuum

cleaners.

The 15 metre hoses are available in both 32 mm and 38 mm,

product

codes VH1 and VH99 respectively. > > If you do order a hose don't forget you will also need hose

ends

(called 'Tool End' and 'Machine End'). I had to phone up to get

these

added to the order because they aren't on the web site. > > PoP >

[Gnube]

Don't they just, and for the total diy-er I spotted they do fans, even for the infamous kirby, and I reckon that could prove interesting, given it's reputed suck power. (I make model hovercraft too for fun, so that may well be worth a tinker with!) Thanks very much for a multiple useful link!

Take Care, Gnube {too thick for linux}

[PoP]

I've had a couple of thoughts about this collapsing bin syndrome, which go like this.....

The bin I purchased (from Homebase) was a sturdy ribbed plastic design which I thought was strong enough to withstand the pressure. My 1200w vacuum cleaner thought different, and the moment I blocked the input to the cyclone the dustbin did an instant impression of pulling its belly in to fit in a tight pair of trousers. Quite comical really, but still a problem. I haven't implemented either of the following, but I'm musing that I might try them.

The first idea I came up with was to visit a local bike shop to see if I could buy a wheel rim of the appropriate dimension which would fit snugly in the middle (vertically) of the bin. No spokes or anything, just the rim. These rims are designed to be sturdy and I don't think would crumple under the pressure.

The second idea (which I literally had last night) has the same general principle, but uses a piece of thin plastic tube (say 15mm or less) wrapped into a circle, joined together at the ends, and hot melted to the vertical centre of the bin. Sounds doable to me, the only potential issue I can think of is that the tube might not bend into that tight a circle.

With the latter it might be possible to use some 8mm or 10mm CH pipe rather than 15mm plastic to do the job.

With either of the above ideas it ought to be possible to insert multiple rings into the bin to provide strength if required.

PoP

[PoP]

Further musings on this idea.....thoughts welcome on my general ideas in case I've overlooked something obvious.

Now that I have my very long hose I can move my cyclone into the roof space of my garage/workshop, thus freeing up floor area down below. I have a spare vacuum cleaner which can be placed on permanent duty upstairs, and I can switch on/off by running its cable down.

This only leaves the issue of emptying the dustbin of sawdust. Perhaps not such a difficult task to shimmy up the ladder every so often to do that, but knowing my aptitude for laziness I'll probably overlook the emptying until the cyclone starts filling the vacuum cleaner and I hear the vacuum whining that it maybe needs emptying, exacerbating the problem with a vacuum dustbag which now also needs emptying. So I've thought of the following to solve this problem.....

I cut a large hole in the base of the dustbin - leaving a rim of perhaps an inch or so all round the base that I can use to screw the dustbin down to the loft floor (bear with me....this must sound like Heath Robinson on overtime!).

I then get a ginormous funnel, the sort you can get from Boots the Chemist for brewing beer etc. Basically the bigger this funnel is the better - and if it is transparent so much better still, because I can then see when the sawdust needs emptying without having to open anything up.

I cut a hole in the loft floor into which the funnel sits, its pointy end extending down into the workshop area. The dustbin sits over the top of the funnel, so that any dust that falls to the bottom of the dustbin automatically falls into the funnel, and thus into the workshop below. This dustbin to funnel arrangement would need to be airtight.

I close off the pointy end of the funnel with a plug, then use the cyclone. It does its thing, and any dust collected falls down into the funnel which is poking thru my workshop ceiling. Every so often when the funnel is obviously full I put a black rubbish sack around the pointy end of the funnel, release the plug and download the dust.

This approach seems to offer a possible advantage of making my cyclone dustbin that much deeper in depth. No idea what this might do to the airflow within the cyclone, but I imagine the deeper the cyclone is the better it might work.

Haven't built this yet, and I might be able to improve the design further by connecting a length of vacuum hose to the pointy end of the funnel so that I can empty the arrangement from floor level, rather than having to climb a stepladder to reach the funnel.

Anyone see an obvious problem with this design?

PoP

[Woodspoiler]

Interesting ideas PoP. I hadn't considered those. However, I see a flaw (in the case of my own bin anyway).

Any sort of strengthening rib would have to go half way down the bin as that's where I get most deflection. I don't have a problem in the upper part near the lid.

Whether the rib is horizontal (i.e. a hoop) or there are multiple vertical ribs, if they are inside the bin then they are going to interrupt the airflow in a place that is important for the functioning of the cyclone effect.

You may find that the bin still works but less efficiently. That's OK if your modification is easily reversible.

If you mount them outside the bin, any residual delfection may eventually work the bin loose of the glue holding it to the rib. Strnghtning it it in some way (self tapping screws though from the inside?) may work or you may get material fatigue after a while. Still, if the bin is only a fiver you can afford to experiment.

Interrupted air flow is why I rejected one obvious valve design: a rod attached to the outside of the inner blucket and sticking out radially so that it enters a short rigid tube (say 20mm + diameter) attached to the outer wall of the bin. If the rod ends just inside the outer mouth of the tube, then when the bin begins to collapse it will quickly emerge from it. If the mouth is covered with some sort of weakly spring-loaded cap, under normal conditions no air will be admitted, but as soon as a collpase starts the cap will be forced open by the emerging rod.

This is a visually neat and easily implementable idea that may work, but even if it does, the rod will introduce turbulence into the cyclone air flow and therefore isn't too desirable from that point of view.

My current idea is to use the initial bin deflection as a trigger, but the mechanism will be external. I have refined it down to a fiarly minimal form. All I have to do is find time to make it! Hopefully within the next week.

The advantage of a valve is that it maintains air flow through the vacuum. The motor may overheat if a blockage is allowed to persist.

W.

[Ian Clowes]

Hi

How about a few metres of 15mm Hep2O type tube wrapped in a helix with maybe 4 'wraps' from top to bottom and hot melted into place. You could put it on the outside to help with emptying the bin, ie keep the insides smooth.

IanC

[PoP]

That's a good idea.

PoP

[Owain]

"PoP" wrote | This only leaves the issue of emptying the dustbin of sawdust. | Perhaps not such a difficult task to shimmy up the ladder every | so often to do that, but knowing my aptitude for laziness I'll | probably overlook the emptying until the cyclone starts filling | the vacuum cleaner and I hear the vacuum whining that it maybe | needs emptying, exacerbating the problem with a vacuum dustbag | which now also needs emptying. So I've thought of the following | to solve this problem.....

Put an infra-red led on on side of the bin and an infra-red photocell on the other side an appoprriate distance from the bottom. It doesn't matter if they're in-line or if the photocell picks up light scattering inside the bin, because you are relying on the settled sawdust blocking the led completely. However the surface should be smooth so that 'ambient' sawdust doesn't settle on the components causing a false 'full' indication

Owain