Homemade dust extractor and RAS dust collection discussion

[Noel]

You're welcome Mike & David.
Do post how you you both get on, as I said my "calculations" weren't exactly calculated.....

 

[misterfish]

For my RAS dust collection I just have a wooden box with one of these http://www.axminster.co.uk/axminster-bi ... rod384336/ mounted horizontally below the work surface - most of the sawdust falls down and then gets sucked into the extractor ducting. It works OK providing the right blast gates are open!

Misterfish

 

[9fingers]

Interesting to find that when running a calculator over the numbers from Noel, the hose csa is 79sq cm and that of the slot is 99sq cm.
so maybe the performance is more about getting the airflow to the right place than the Venturi effect. However it works, making something along those lines is on the round -2-it list.

Bob

 

[Bluekingfisher]

MisterFish - I actually have one of those, gathering dust (pardon the pun) on a shelf. I bought it some time ago in preperation of building a collection port behind my RAS. Unfortunately I don't think it will suit my purpose now as the shape will not be suited to the space I have behind the saw. I might use it however if I ever get around to building a collection set up for my small lathe.

Thanks for the input anyway.

David

 

[adzeman]

I purchased one of those hoppers when I bought the Cam Vac. Coud not get it to work satisfactory with the R.A.S. Had sucsess with it fitted to the base of my old Bench Saw. Worked well and thought must put it onto the new table saw. Last week saw on utube two guys (think they were Canadian) had fitted one as described by Misterfish. The difference being they created a Venturi effect by fixing hardboard on the table top secures firly at the back and wedged up at the front to provide a gap.
Until I read the Moderators method this was the one I was going to try. This meant piping to the underside of my bench to which I had started. Now I am refixing the pipe/tubes to come from above.

 

[Noel]

Interesting to find that when running a calculator over the numbers from Noel, the hose csa is 79sq cm and that of the slot is 99sq cm.
so maybe the performance is more about getting the airflow to the right place than the Venturi effect. However it works, making something along those lines is on the round -2-it list.

Bob

6" hose drawn by a proper cyclone Bob would be ideal but gotta use what you brung....

Interesting figures too. I could reduce the gap somewhat but when I was mucking about with it I stopped as soon as it worked rather than trying to arrive at the optimum performance point. May make some adjustments....
Thanks.

 

[adzeman]

My completed Venturi dust extractor for my RAS and it woks

 

[Bluekingfisher]

My completed Venturi dust extractor for my RAS and it woks

Looks a nice tidy job. It's difficult to see the inner workings of your collector. Is the box just surrounding the saw or is there a sloping deflector arrangement like Noels?

Have you any pictures of inside the collector box?

 

[misterfish]

I purchased one of those hoppers when I bought the Cam Vac. Coud not get it to work satisfactory with the R.A.S. Had sucsess with it fitted to the base of my old Bench Saw. Worked well and thought must put it onto the new table saw. Last week saw on utube two guys (think they were Canadian) had fitted one as described by Misterfish. The difference being they created a Venturi effect by fixing hardboard on the table top secures firly at the back and wedged up at the front to provide a gap.
Until I read the Moderators method this was the one I was going to try. This meant piping to the underside of my bench to which I had started. Now I am refixing the pipe/tubes to come from above.

As you say it is necessary to have the extraction tubing going beneath the workbench. When I did it some years ago it just seemed the easiest method and it does seem to work.

Misterfish

 

[adzeman]

The fittings arrived today from CamVac as promised so I spent the afternoon installing the tubing.
I was slightly disapointed with the results, when I switched on it did not pull as well as it did yesterday with the temporary connection. I thought that the tubes being smoother the air flow would have improved, it had not. Dont get me wrong it still works but not better. You just have to see the dust created when the CamVac is not switched on.
Can only think it is the number of bends in the system. I have taken a pict at the junction which shows a collection of dust in the pipe. Gravity could be a cause of this and the Vac not strong enough to make it rise. A blast gate here might help? I will give that a try tonight.

This is a pict of the tubes I have installed

Here is a picture of the back prior to installing. The box only covers from the fence to the back. If you require me to enlarge my pic will do but ita all as my drawing. Have you followed my post on the Projects section?
I returned to the General Section so that Noel the moderator could see the progress (probably got his hands full just moderating one section)

 

[kirkpoore1]

Mike:

Is the vertical line going to your extractor? Or is it the one going to the right past the mortiser? If it's the vertical pipe, I'd suggest replacing that T fitting with a Y fitting and two 45 degree elbows. That will reduce friction. I'd also makes sure you're pretty much leak free elsewhere, including all your other blast gates.

Kirk

 

[adzeman]

Good advice Kirk. The vertical pipe does go to the extractor and fitting an extra Blast gate has made a difference. I have not seen any y junctions in the Cam Vac catalogue but I can ask. I am still going to look at putting in a hopper though fed by my shop Vac.

 

[Bluekingfisher]

I would definately suspect the 90 degree elbows are contributary to the dust collecting in the pipes, this will create a lot more friction. I suspose the one good thing with the clear pipe is that you can actually see any problems as far blockages are concerned and rectify accordingly.

I don't know the size of the CamVac duct work you are using or whether or not it is compatible with other pvc pipe but I'm sure you could rig up some adaptors to fit Y or 45 degree elbows.

I am encountering this problem too, with limited head height trying to make use of a 45 degree elbows meant that I had to sacrafice some space where the walls met the roof. This was the case untill someone suggested using two 45 degree bends. The result is a right angle bend but with a far smoother curve.

I haven't been following your build but I;ll try to look for it.

Unfortunately you have taken a picture of the rear of your collector, I was hoping to see how the inside looked. Is it just the box or is there a deflector on the inside directing the dust to the base for collection?

 

[adzeman]

Your bang on with your assessement, I changed to an elbow today and performance went back to when I did the temporary hok uo.

I will have to take it apart when I make an adaption so I can do a RH mitre cut and will take a pict for you but it is just a box.

Cant make my mind up if to varnish it or leave au natural. Cant use the Cam Vac at present as installing elect ducting and wiring.

 

[kirkpoore1]

Mike:

I'm glad you found the source of the problem. The Y (even if you use regular PVC, instead of clear) will get you your second line back.

As for your RAS box, I'd use a piano hinge just in front of your hookup, and let the side swing out from there when needed. That will get you your right hand 45 degree cuts again.

Kirk

 

[Bluekingfisher]

Thanks Mike, I was in the shop over the weekend, making a start on a baffle for a Thein seperator for my 200L drum. I had to make a circle cutting jig first and it worked out great. I also made a seperator for a 5 gallon drum I have linked up to my camvac. The camvac only has the 2 1/2 hose, so only really good for smaller machines.

Slowly but surely I'm winning the fight against dust. Once the duct work is all in I'll make some collector boxes for the Chopsaw and RAS.

Thanks again.

BTW - what did Kirk mean by using a piano hinge for your collector??

 

[adzeman]

Its to make a sort of tailgate so my right hand baffle can allow my RAS to turn 45 deg.

I am still doing the electrics taking longer than anticipated and have had a few distractions as well.

 

[Bluekingfisher]

Oh yes, distractions, I have one indoors too, but I love her dearly.

Thanks for clarifying the matter with the hinge.

 

[adzeman]

Look forward to seeing your pictures of your dust extraction.

 

[adzeman]

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