J. Phil Thien's Projects

Sorry about the bad link. I hope I have it right now:

http://www.jpthien.com/smf/index.php?topic=1157.msg6542#msg6542

You can bash your own from some pipe. See here:


http://www.jpthien.com/smf/index.php?board=1.0

Its very easy. Good luck and let us know how you get on.

I almost died as a child because of allergies to dust, danders and pollens so the subject has been, shall we say - interesting for me. The fact is all dust is dangerous. The finer it is the greater the hazard partly because these penetrate further into the lung tissue.

Dust from MDF is extremely fine and has traces of formaldehyde so it is recomended that the exposure to this should be zero. My friend was a navy carpenter and worked wood all his life without dust extraction. He is now very ill, cannot work wood and had to sell all his wood work equpment. No need to go OTT but reasonable precautions need to be taken.

It is this danger that makes me very reluctant to pump dust laden air outside into the environment. If I do not want to breath it why should I expose other people to it?

A well made practical solution. How is the can guided by the "C" shaped piece?

My Thien is a crude lash-up with the baffle pushed down into a plastic waste bin. The baffle is held in place by the slight downward taper and the spring in the walls. This bin has a series of indentations down the side to stiffen the thin and otherwise flexible plastic walls. Hence the air stream is forced against the wall and bumps along againsts this "rough" surface.

I have noticed that very fine dust ends up in the bottom of the collector. I have been so ashamed of my lazy build that I not mentioned this before. I checked today and indeed the very fine dust has been extracted. It looks as though this unintended structure might work for your sanding dust. The indentation are about an inch wide and 3/16 of an inch deep separated by a 1" wide smooth wall.

I do not think it is too narrow but I would prefer to use a longer transition. This one looks as though it is less than 4" long and I think the air flow will exit it still more or less circular. 8" would be better and I have seen three time the diameter of the pipe quoted and that would make it 12" long. These are easy to make. Take a rectangular block of wood the width you want and the other dimension slightly more than the id of the pipe you are using. So 3 1/2" by perhaps 41/2" in this case.  Squeeeze the pipe until you can put the block inside the pipe and hammer the pipe down until it is a rectangle the width you wanted at its mouth and as smoothly faired back to the round section as you can get it. Job done. A few minutes work.

r2 suggests the area of the rectangle should be (I think he said) 10% greater than the cross sectional area of the pipe and although you could still make this, it is probably not worth the extra effort unless you are a skilled sheet metal worker.

I am sure a Thien baffle will sort out the scrubbing. Can you give us a link to to the "U" tube build?

I would love to b test but I am not able to do so at the moment. I am very interested to learn of the readings you get in your shop under various conditions. Looks fascinating.

You are in the right place. Build a top hat as described at the top of this thread. Most people seem to use the Brute trash can. Use polycarbon sheet instead of acrylic (Perspex). You can leave out the elliptical bell mouth to the exit pipe and add it later if you want.

I do not know why the thin baffle works best or if a bevel on the edge of thicker material will work. It is so easy to make it from 1/4" tempered hardboard that most just make it that way. It probably does not need much support but you might as well add it while you are at it.

Please ask if you have more question and cannot find them easily - though the search fuction usually brings up the asnswer. Let us know how you get on. Probably best to start a new thread if you do - as this one is getting too long.

I have had success with a powerful shop vacuum. It has a 2 1/2" diameter hose and worked quite well with a 3' length of hose connected to a 3' length of 2 1/2" plastic pipe manifold, complete with blast gates to extract from 12" site thicknesser, or a jointer or a belt  sander. One downside was that all that busy motor made a lot of noise. If you are aligning your inlet to the circumference of your trash can so the air and wood debri spin around the inside walll try it without a baffle first. I found that the fine filter in the vacuum cleaner did not block all that often even without a baffle. It was not perfect but worked OK.

I have built several separators that take out the heavy wood debris by spinning the air stream against the wall of the bin. They work well but do not take out the fine dust. If you are re-circulating air back into your shop you need, as you say to fit a fine pleated filter. This will get blocked and performance will drop until you are forced to clean out the filter. This is a royal pain so is to be avoided. Using a Thien baffle in a top hat avoids the need. I would urge you to build a top hat. It is not much more work indeed easier work than fitting pipes to barrels. My hand tool soul cries, but a day with an electric router should see much of it completed. The best build is here:

http://www.jpthien.com/smf/index.php?topic=563.msg3034;topicseen#msg3034

However do not use acrylic because it is too brittle, think plastic glass. Use polycarbonate instead it is ideal and should be cheaper. Please let us know what you decide.

Best top hat design is here:

http://www.jpthien.com/smf/index.php?topic=563.msg3034;topicseen#msg3034

Its a fairly long post but gives almost everything you need to know. However do not use acrylic for the walls as it does not like being bent, think of it as plastic glass. Use polycarbonate instead as it is ideal for this job and should be cheaper.

Please let us know how you get on and if you can measure anything that would be helpful.

The reason you had problems bending acrylic is that it is too hard to be used as a flexible material. Think of it as plastic glass. Polycarbonate is ideal for bending and is much more scratch resistant.

Thien separators work very well and are very practical.

I am not quite sure how you are using your 4kw blower? It sounds as though you are sucking from the planer and pushing the shavings and dust out through a pipe system? I do not think that would work. The usual way is to use a pipe system to suck from the machines, pass that loaded airflow through the separator and then into the DC. All suck - not push.

Your blower may not be suitable to make your own DC. It depends on the pressure/flow curves. Unless the blower is specifically designed for this use it will probably not have the right specifications.

If you had a DC with that much power it should be able to handle 150mm (6") pipework with ease. Even so keep all pipework as short as possible, use slow bends, ie with radius twice or thrice the diameter of the pipe or two 45 degree bends instead of one 90 degree. Use "Y" junctions with the incoming branch set at 45 degrees to the main flow instead of "T" junctions. Maintain the 150mm to as close as possible to the machines then neck down to 100mm (4") ot whatever size is on the machine. Keep any hoses to the absolute minimum as they will eat into performance.

Make a top hat separator as here except use polycarbonate sheet and not acrylic for the walls:

http://www.jpthien.com/smf/index.php?topic=563.msg3034;topicseen#msg3034

Close-couple the DC fan to the top hat with an air straightener section.

It is well worth having the DC  and separator in a separate walled room or chamber so that the noise of the former and the dust when emptying the latter is kept well away from the shop. You should fit a control system so that your wood working machines cannot be switched on unless the DC is already on. If you are as lazy as me it is all too easy to "forget" to turn on the shaving shifting system.

Consider if it is safe to vent outside! You are collecting shavings for your convenience and dust so that it does not damage your lungs. The most dangerous very fine dust will travel on the wind a surprising distance. Where will it end up and who might unknowingly breath it? If you cannot be certain then fit a fine dust pleated filter. It may even be illegal in your area for you to vent dangerous dust into the atmosphere.

r2, I was not being critical of your posts. I think it would be great is your input could be somehow drawn together as an entity and "pinned" (If that is the right word) to the start of the blog. At the very least something pinned at the head of the blog so that newly interested readers could be directed to the start of your build. I also think that it should be locked to prevent it becoming even longer.

BTW it would be helpfull if an inexpensive method could be agreed to give a consistent set of measurements so that small design changes could be quantified by TH builders. UnfortunatlyI do not have enough knowledge of fluid dynamics to do this myself.

We had some great input with a contributor making a mathematical model of a TH. I feel I shot this down somewhat by insisting it should at least be able to replicate your real word results. Could this be one reason that posts have dried up or is it that we have given the impression that nothing is sufficiently resolved to ensure that a build is worth doing?