A first time build, my experience, results, tips

[dustyvegas]

I built my unit with for use with a delta dust collection system (not shopvac).  I used a cnc router for some parts, so some of the things I did may not be easy to replicate.

I am finally pleased with the result, but made mistakes and have tips for others on their version.  First off, you need to understand the velocity (flow rate ) your system needs to be effective.  The following link

http://eberhardt.bz/GME_Wood_Land/GME_Woodworking_Stuff/4_Information/4_Dust_Collector_Review.pdf

is to an old wood magazine (2002 I think) review of dust collectors the key point being its discussion about flow rates and pressure drops.  One issue I have with my implementation was a serious flow rate reduction (I will get to that later).

I made the top hat with side inlet.    The general configuration is the same as referenced  elsewhere on this site.  The top and bottom are ¾ melamine with the wall being hardboard.  I use 4 inch hose on the inlet with system being portable.  The internal height is 5 inches.  Because of the cnc router I don't use the hardboard base that the original design calls for, instead I machined slots as needed into the melamine.

I didn't find other postings about using hardboard, but it is possible.  I used 1/8 inch thick, shiny on one side.  You wet (drench) the hardboard and let it sit for awhile and it becomes pliable enough to bend around circle templates.  Clamp the wet board to the template and let dry.  I did a total of 4 sections that were then laminated together.  After drying the hardboard holds about 70% of the curve you want (it springs back a little).  To laminate I used PVA glue and it was challenging.  Lot of area to glue and clamping around the circle templates was sloppy.  Do one lamination, let dry, then the next.  Next time I would try contact cement and kindof roll the laminates together.  I would also decrease it to 3 laminations.  The hardboard may be a weak link, I'm not sure how well it will wear.  My original plan was to cover the inside with aluminum sheet but I backed off after considering how difficult assembly might be.  The laminated hardboard is glued into slots in the melamine.

As mentioned, the inlet is 4 inch.  I cut a plastic dust collector connector in half and epoxied it into mdf which is then glued onto the top hat.  So it is an abrupt transition for incoming air.  It might be possible to use automotive bondo to make a smoother  inlet but I am an not sure if the incoming dust might be so abrasive that it would wear away quickly.

My dust collector is a delta with 5 inch inlet.  My original thinking was the dust collector plastic bag would be too close to the garbage can to allow me to run a straight pipe from the dust collector inlet to the top hat outlet.  I could not find 5 inch hose to allow for needed bending, so I made an adapter to connect the 4 inch hole to the 5 inch inlet.

This is when I fired everything up for the first time.  The dust collector bag was vacuumed clean so flow rate would be as good as possible.  It was obvious that the flow rate was severely reduced.   The cloth bag was actually limp there was so little airflow.  For comparison I used one the plastic cyclone type tops that cost $20-$40 and it was dramatically better.  I would say the top hat was 40-50% lower flow rate.  The top hat flow rate was too low to keep my table saw clean.

Looking at the way the garbage can sat versus the plastic collection bag, I discovered the bag wouldn't press too far onto the garbage can if I ran the straight pipe from the dust collector inlet from the top hat outlet.  I could use 5 inch ductwork.  Doing so made a dramatic improvement in flow rate.  The dust collector was now borderline  - but useable on one machine at a time (which is the way I use it by moving the flexible hose machine to machine).  If I had to do it again, I would try a 5 inch to 6 inch ductwork adapter instead of straight 5 inch pipe.  I believe it would not only flow better, but the velocity of air leaving the top hat would be reduced because of the larger diameter and that might result in more dust being left in the top hat.

Side Note:  Other posts mention using plumbing based rubber collars to connect the 5 inch pipe to the collector inlet.  The 5 inch hvac pipe (in one of the pictures) has a lip that I unfolded and pounded flat.  I use this as a slip fitting to connect the pipe to the collector.  It seems to work well although might not be airtight.  Because of the slip fit, it is easy to remove the garbage can to empty it.

Although the flow rate was adequate, it was far from optimum.  Normally you would not run 2 dust collectors in series.  Because the top hat was acting as a restriction, it made sense to try and put a "booster" pump in front of the top hat.  I found a used HF 1 hp unit, it made a huge difference.  The setup now flows great and so far a 20 amp fuse has not popped when running both motors on the same circuit.

The next time I build one of these:

I have seen comments in other posting about using a bell mouth on the top hat exit.  I found a few articles that imply the flow rate could improve 20%.  On the next version I would make that addition, even if it was made by sanding the shape from MDF.

It might be possible to make a 2 part separator.   Instead of having the base attached to the side walls, the base could be mounted to legs that sit inside the garbage can.  The slot would increase to 360 degrees, which might not be desirable but there are probably ways to adapt something.  This would make cleaning jams easy and construction might be simpler. 

[retired2]

There are quite a few builds on this forum using the Delata 50-760 DC, including my own.  This model dust collector does pose a bit of an alignment problem between the separator and DC inlet port, and it has been tackled several different ways.  Like you, I ditched the wheeled cart that came with the separator so I could create some more working space under the unit.  My separator appears a bit larger than yours, but I was still able to fit it under the inlet port without any offsets in the connecting duct, or without interfering with the plastic discharge bag.

By now you should see the plastic bag really doesn't do much other than capture a very small amount of by-pass waste.  So, the bag could easily tolerate a great deal of interference with a larger separator, and it would still work just fine.

By the way there is link to a newer test of DC's that has been posted here several times.  Unfortunatley, it is still four or five years old, but it does include the Delta 50-760.

I'm not sure if I've seen anyone hook-up two blowers in tandem.  I'd love to try that myself, but I see a number of problems it would create for me.  First, I'm not sure I could tolerate the noise level in my basement shop.  Have you taken any sound level readings with two versus one DC's in operation?  Secondly, I might need to do some rewiring.  I have two 20 amp circuits in my shop for stationary tools.  One of those is shared with the DC.  Another DC on that circuit would almost surely trip the breaker during starting because I have my blast gates wired to remotely turn on the DC.  So, imagine turning on a power tool and two DC's simultaneously on the same 20 amp circuit.

Keep us posted if you make any modifications.

[dustyvegas]

I have seen the link to newer tests on the dust collectors, but couldn't find it when writing this up.  The point I wanted to emphasize with the link was how pressure drop really affects flow rate and the importance of flow rate in making effective dust control.  The article you reference, I think the author mentions making a bell mouth type adapter out of MDF to use when connecting to a jointer and he saw a big improvement in air velocity.

As for noise running the two in series does not double the volume.  If you think about it, when any dust collector is running you have noise from two sources - the motor itself and then the air/debris moving through the ductwork.  With my setup the ductwork noise is only moderately increased because of the higher flow rate and the noise from a motor spinning isn't very much.  So my system is about 10-20% more noise than with just the delta running alone.

For reference a router running in the 18K or 21K speed is much louder than the dust system with both motors on.  My delta table saw is quieter.

I like the series setup but I do take caution to start the delta, let it get up to speed and then start the secondary blower.  The idea is that the start is where the motor will spike the amps, staggering the starts keeps me under my breaker.  Also I want vacuum pressure in/on the garbage can /top hat and if somehow the secondary blower spun up faster it would put positive pressure in there.

I had doubts about the setup, which is why I got the used HF unit to experiement with.
http://www.harborfreight.com/13-gallon-industrial-portable-dust-collector-31810.html
I figured if it didn't work I could get my money back reselling it.  They make a slightly smaller unit that  should work too.

Keeping in mind that I got mine used but it looked to be in good shape, I had to seal some of the seams in the housing and add thick sealing tape to the exit attachment.  I removed both the inlet and outlet screens, they seemed ripe to clog up.

If you look inside the unit I was suprised at how much space there is around the impeller.  The upside to this is that I can run my system with the just the delta on and still get decent flow.  I use this when cleaning up dust on the floor or using sanders.  I suspect that in those situations the lower flow rate might aid in keeping the finer dust in the top hat.