Shorten My DC3000/DC6000

[dusty]

Because of limited shortage I am considering a modification to my Shopsmith Dust Collector. If I do this, it will allow me to position the dust collector beneath a shelf and still use the DC (with 24" filter hood).

To do this, I would reduce the height of the two metal side supports. Doing so would reduce the height of the dust collector bag and this is what makes me hesitate. Will reducing the size of the dust collector bag adversely effect dust collection efficiency. Yes, I will have to change bags more frequently - a task that I deplore because of how large and clumsy the bags are.

[RFGuy]

Dusty,

I am no expert, but I do a lot of research and dust collection has been a definite interest of mine for some time now. As far as I understand it, the collection bag and filter hood present "back pressure" to the blower fan of the dust collector. I believe if you shortened the stand height, making the dust collection bag smaller it would increase back pressure on the blower and could result in lower airflow measured at the inlet (less suction). In other words your collection efficiency would decrease, but by how much I couldn't say. Also, leaving the 24" filter bag unchanged, but making the collection bag smaller may just shift more of the blower outlet airflow to just exit out the filter bag instead. Assuming the increased flow rate through the filter bag isn't beyond the filter bag specs (causing too much cake to dislodge and exit through filter bag pores), the increased airflow through the filter bag may just compensate enough letting you shorten the collection bag without affecting overall performance. In other words, it might be "okay" and just force more air out of the filter bag quicker. IF your computer fan test meter that you built before was still working, I would suggest just making the collection bag smaller by choking off half of it and running a test both ways to compare. This would let you try it out before committing to the shortened frame just yet. It is an interesting idea...I never liked the filter bags to begin with and would prefer a bucket underneath for dust collection. If you shorten it, you might want to consider further modifications to insert a bucket or drum for dust collection. A 17 gallon steel drum is a good size and probably short enough for your application.

https://www.stanmech.com/articles/under ... f-a-system

[dusty]

Dusty,

I am no expert, but I do a lot of research and dust collection has been a definite interest of mine for some time now. As far as I understand it, the collection bag and filter hood present "back pressure" to the blower fan of the dust collector. I believe if you shortened the stand height, making the dust collection bag smaller it would increase back pressure on the blower and could result in lower airflow measured at the inlet (less suction). In other words your collection efficiency would decrease, but by how much I couldn't say. Also, leaving the 24" filter bag unchanged, but making the collection bag smaller may just shift more of the blower outlet airflow to just exit out the filter bag instead. Assuming the increased flow rate through the filter bag isn't beyond the filter bag specs (causing too much cake to dislodge and exit through filter bag pores), the increased airflow through the filter bag may just compensate enough letting you shorten the collection bag without affecting overall performance. In other words, it might be "okay" and just force more air out of the filter bag quicker. IF your computer fan test meter that you built before was still working, I would suggest just making the collection bag smaller by choking off half of it and running a test both ways to compare. This would let you try it out before committing to the shortened frame just yet. It is an interesting idea...I never liked the filter bags to begin with and would prefer a bucket underneath for dust collection. If you shorten it, you might want to consider further modifications to insert a bucket or drum for dust collection. A 17 gallon steel drum is a good size and probably short enough for your application.

https://www.stanmech.com/articles/under ... f-a-system

I can simulate this. If I set some sort of platform under the dust collection bag and pull all of the excess bag up (make a shorter bag) it would have the same effect. Thanks for the comments that gave me that thought.

I still have the fan box that I made for these tests. I'll just have to buy another fan and try not dropping this ome. Unfortunately the numbers will likely be different (different fan) so comparisons could be misleading. Simply won't be able to draw comparisons with a DC3000.

[RFGuy]

I can simulate this. If I set some sort of platform under the dust collection bag and pull all of the excess bag up (make a shorter bag) it would have the same effect. Thanks for the comments that gave me that thought.

I still have the fan box that I made for these tests. I'll just have to buy another fan and try not dropping this ome. Unfortunately the numbers will likely be different (different fan) so comparisons could be misleading. Simply won't be able to draw comparisons with a DC3000.

Dusty,

Sounds good. Yeah, I would definitely want to try to test it before doing the cutting if I was doing this myself. Yeah, I wouldn't worry about the "actual" airflow numbers, but just getting a comparison of before and after (A/B testing) should be sufficient. IF you see it drop by 50% then you know it probably isn't a good idea, but if it doesn't change or only a little then it should give more confidence. Let us know how it goes with this...good luck.

[dusty]

Anybody got an old DC3000 that has been permanently retired from service and is willing to part it out. I could use the legs. PM me if you do.

[jsburger]

Please excuse my ignorance but, since the collection bag is plastic and no air goes through it how can the size of the plastic bag effect the performance? All the air goes through the filter on top regardless.

My ClearVue cyclone DC had a 30 GAL collection drum under it. If I put a 45 GAL drum under it instead I would not expect any difference in the collection ability.

[HopefulSSer]

If you were to shorten it, say 5", wouldn't that be the functional equivalent it being the normal height and having 5" of collected material in the bottom of the bag?

[DLB]

Because of limited shortage I am considering a modification to my Shopsmith Dust Collector. If I do this, it will allow me to position the dust collector beneath a shelf and still use the DC (with 24" filter hood).

Mine is a 42" hood, so perhaps some difference, but one difference I see between DC-3300 and DC-6000 is that the 6000 keeps A LOT more material in the air inside while running. I attribute that to three major differences: more flow, concentrated flow at exit, and exit location is lower. Shortening the machine will lower that exit further, closer to the accumulated debris. Not a deal breaker, but something to consider.

How much do you need to shorten it? I'm not a huge fan of the 12" hood, but it might be the lesser of two evils.

- David

[dusty]

Because of limited shortage I am considering a modification to my Shopsmith Dust Collector. If I do this, it will allow me to position the dust collector beneath a shelf and still use the DC (with 24" filter hood).

Mine is a 42" hood, so perhaps some difference, but one difference I see between DC-3300 and DC-6000 is that the 6000 keeps A LOT more material in the air inside while running. I attribute that to three major differences: more flow, concentrated flow at exit, and exit location is lower. Shortening the machine will lower that exit further, closer to the accumulated debris. Not a deal breaker, but something to consider.

How much do you need to shorten it? I'm not a huge fan of the 12" hood, but it might be the lesser of two evils.

- David

My DC 3000 came with the 12" hood but when I changed to the 24" I saw so much improvement that I don't want to go back. However, that might be a solution and since I do so much less woodworking now that might be the smart solution.

I'm totally undecided!

[RFGuy]

My DC 3000 came with the 12" hood but when I changed to the 24" I saw so much improvement that I don't want to go back. However, that might be a solution and since I do so much less woodworking now that might be the smart solution.

I'm totally undecided!

Dusty,

It cooled up enough this past weekend for me to get up in the attic to take some measurements on my DC-3300. Hopefully this datapoint will help you. So, my DC-3300 is not upgraded and has the 42" filter hood on it. I moved it to the attic because I don't use it anymore, though I hope in the future to get a Shark Guard so the intent was to someday use the DC-3300 for above table dust collection up into the attic. As a reminder, the max airflow that I can get through 1 port of my DC-3300 is only 142.7 CFM (viewtopic.php?p=285543#p285543). I should also point out that before moving the DC-3300 up into the attic that I cleaned it fairly good (cake build-up should be minimal) and the bag is almost completely empty.

What I did is that I first confirmed that I was getting similar/same airflow as what I measured before from 1 port. Close...it was like 141.7 CFM, but good enough. Then I took a bungie cord and wrapped it around the collection bag several times to close off the bottom half of the bag. I did this at half way up the bag so it should reflect the bag height being cut in half, similar to you shortening yours. What I measured was 129.7 CFM (1 port only). So, it is like an 8.5% drop in airflow for my DC-3300 in doing this. As I suggested previously, ANY change in back pressure can and will affect the airflow because it shifts the blower fan curve. Granted this is only a slight shift (<10%), but it is a shift. Keep in mind that you have a different filter hood which will also affect your performance a bit. In addition, I believe you intend to do this on your upgraded DC-3300 which has the new blower fan from SS. This new blower fan will have a totally different blower fan curve compared to the original DC-3300 design so you may see a much smaller drop in airflow with it, but I can't say for sure. I doubt you will see more than a 10% drop in performance by shortening your upgraded DC-3300. In any event, the decision is yours, but I just wanted to give you some data on my original DC-3300 to hopefully help. Good luck.