Confused

[Peter]

Peter, could you give some detail on how you made your sweeps?

Sure.
I use Sketchup as follows (refer to attached drawing.
1. Draw circle of desired sweep radius (at centerline). I use 15 inches radius and the default circle with 24 segments.
2. Draw radius lines at 90? to each other.
3. Erase all but the 90? arc, add 6" extension lines. This is important.
4. Make a box so the circle tool will draw a circle in a vertical plane.
5. Hold down shift key and draw the circle at the end of one of the extension lines.
6. Select the arc and both extension lines. Using the "Follow Me" tool, click on the small circle drawn in step 5.

Hint: Turn on hidden lines and selecting the radial segments, remove smooth and soft attributes.

7. Draw a rectangle enclosing the entire structure. Right click and select intersect faces with model.
8. Erase everything but the lines on the rectangle.
9. Extend the radial lines until they intersect.

At this point, Sketchup fails--they do not have a tool that can dimension angles. YOu can use the rotate tool to see them, but only temporary. So I exported the resulting drawing into AutoCAD, and discovered the angles there. The outermost angles (at the 6" extensions) are 7.5? and the internal angles are 15? from one another.

I set my miter gage on my bandsaw to these angles, and cut segments. It REALLY helps if you draw lines along the length of the pipe that are 90? from one another, so you line them up with something on the miter gage. Otherwise, the sweep can wind up going all over the place.

Cutting PVC on the bandsaw is messy.

Using very coarse sandpaper and a rasp, I eased the cut edges. Then, aligning the linear lines, I taped the segments on the INSIDE, one at a time. I used JB Weld epoxy to join the segments.

JB Weld is messy.

I was bothered by how lousy the joints looked so I sanded them down. Don't do this. Put up with messy-looking joints. They're stronger. Once the outside was cured, I gooped JB Weld on the inside joints. This is pretty easy with 6" pipe. It could be damned near impossible with 4" pipe. I'm gonna paint mine.

The 6" extensions will fit into the bell of a pipe or a fitting.

I tried making these with foil duct tape. It works, but man, it's hard! Glue is better. I suppose if I had a plastic welder, it'd be even easier. But I need like 4 90s and a couple of 45s, so it isn't worth the investment.

Hope this is helpful...and more important: useful.  ;D

[Bulldog8]

Peter, I think that many people set up a system of 4" or 6" and are happy with it so they don't change anything. Therefore, it can be difficult to get comparative results. In my experience I have found that I have spent more money on DC accessories than the initial cost of the machine itself. (Grizzly 1029)

I first set up the system using 4" S&D pipe with a Woodstock trashcan separator lid on one of the two branches. The setup did pick up sawdust, but was quickly overwhelmed when I added a drum sander to my line of equipment. I then torn apart my first set up and added 6" metal mains, a Thien baffle top hat and a Wynn filter. The overall improvement is significant, but I can't say how the system would have worked with the 4" pipe because I changed everything at once.

In my opinion, the dust produced by woodworking is the most significant hazard in the workshop. Power tools themselves can be dangerous if used incorrectly, but brains, technique and set up mitigate those hazards. The only thing that can mitigate the fine dust hazard is equipment. So bottom line, I suggest getting the best DC system that you can reasonably afford and then use it within its capacity. Meaning if you have a machine that can only support 4" mains, fine use 4" mains and open one gate at a time. You will then get the best collection possible and honestly it's probably as good as a 2K system that supports multiple machines at one time. I'd hazard a guess and say that most people on this board (myself included) are hobby woodworkers or very small business owners.

Steve

[Peter]

Steve:

In my opinion, the dust produced by woodworking is the most significant hazard in the workshop.

With this I am in total agreement. I am a weekend/evening hobbyist. Besides being generally broke, I am also lazy. I have the bad habit of leaving the mess behind when I make something, then have to deal with that mess when I wish to make something else. I can strive to correct that habit, but that's a tough one: it's been my bane for five decades! Why the budget director stays with me is a mystery.

So I figured installing a reasonable (note I am not saying perfect or best) dust collection system would serve to keep the workspace a lot cleaner than it has been for years. And in reading here, the HF 2HP unit seemed to be well-touted, so I bought one. I am already convinced that the Thien baffle and a good filter are a must. I can build the baffle; I can save up and buy a good filter. I can build the gates and install the piping.

All my questions, then, stem from the above limitations: given the HF unit, Thien baffle, one-gate-open-at-a-time situation, future Wynn and future air cleaner, and given that I have a 10" cabinet saw, drill press, band saw, sander, jointer, planer, I need to devise a system that satisfies this:

if you have a machine that can only support 4" mains, fine use 4" mains and open one gate at a time.

I haven't found anything that says "the HF 2 HP DC can suck workshop dust through A-diameter pipes of L-length with F-number of fittings".

And the reason I am pestering you guys about this is because I don't have the time, energy or budget to do it once, discover that is insufficient, and then do it over. It is definitely easier on my wallet to install 4" pipe. But if 6" will perform better with the HF unit then I can probably swing that.

Thanks for your patience.
Peter

[Dougp28704]

Peter,

I guess I will make mine a mirror. Who knows. Can?t hurt though.

I am just going to use 4 inch for the reasons you listed.

[galerdude]

I haven't found anything that says "the HF 2 HP DC can suck workshop dust through A-diameter pipes of L-length with F-number of fittings".
Thanks for your patience.
Peter

I could be totally wrong here so please forgive me if I've missed something along the way but I don't remember reading about anyone having that information when they built their system. Most builds that I've read about have built a DC system using the available information and trying to apply it to their situation and do the best they can. And a lot of good folk try to share improvements and enhancements that they feel might help someone else. If you were to copy someone's system as in the same diameter pipe, same lengths and same fittings, would that be the system that would work for you? I know when I built my system I had to make some choices. Were they good choices? I dunno, it works.

Best,
Gale

[Peter]

I could be totally wrong here so please forgive me if I've missed something along the way but I don't remember reading about anyone having that information when they built their system. Most builds that I've read about have built a DC system using the available information and trying to apply it to their situation and do the best they can. And a lot of good folk try to share improvements and enhancements that they feel might help someone else.

Which is why I am here, pestering all you good folks.

If you were to copy someone's system as in the same diameter pipe, same lengths and same fittings, would that be the system that would work for you? I know when I built my system I had to make some choices. Were they good choices? I dunno, it works.

Obviously, it's absurd to copy someone else's system. At least, not in all details. And yeah, I appreciate that the choices you made, Gale, are specific to your situation. That the choices you made result in a system that works is super.

Now, not to say anything one way or another about anyone's choices (after all, it's the reasons you guys made those choices, that I want to copy if anything), but it seems to me that the more I inquire and gain information, the more evident it is that there is quite a bit of leeway in system design. The Woodcraft classroom shop, easily twice as large as mine, uses 4" pipe everywhere and the place was spotless. Maybe they use a super sucker fan, I dunno. I never saw it in operation. Some people here, and in other forums, use 6" PVC, 5" metal, 7" metal, and so on, with DC units that range from 1 HP to 5 HP. For the most part, everyone's system works. Rockler and Woodcraft and others, even Penn State, sell 2 1/2" systems. I don't know of anyone who uses such a thing, other than in small scale with shop vacs, but all the data I read says that it won't work.

Aerodynamically, the bumble bee can't fly. Yet there are hundreds of them every spring on the honeysuckle out front...flying.

The choices I have already made are as follows:

HF 2HP unit with Thien pre-separator.
No 90? elbow fittings and as few 45? fittings as possible.
All other "bends" made from segmented pipe sweeps with at least 2 1/2" pipe diameter radius.

The only decision that is missing, it seems, is whether to use 4" throughout, a combination of 4" and 6", or 6" as much as possible.

And, I guess, that whatever choice I make, there will still be those occasions when there will be dust and/or chips flying about the place that will have to be taken care of by the good old bench brush and dustpan.

[retired2]

It is not rocket science to calculate SP losses, velocities, and cfm for any branch of DC system where only one tool is running at a time.  You can run the calculations for 4", 5", and 6" pipe and see how the performance compares.  There are a number of resources on the web that will give you the basics.  Try Oneida Air, or Air Handling Systems. 

However, if you are starting with a HF unit, there is a very good chance that you will be missing the most basic piece of information, i.e. the true performance specs of the unit, or better yet, a fan curve.  Without that data, you are pretty much stuck with just building the system, and hoping for the best.  The truth is all three pipe sizes may work, but only one will work best.

I'm sure someone will find fault with this advice:  If you don't want to get into the design math then consider using 4" pipes for dust collectors smaller than 1.5 hp.  Use 5" pipe for 1.5 HP and 6" for 2hp and larger.  There is some point at which you could use 8" pipe, but that would likely be a 3 or 5HP cyclone and not likely found in a small hobbyist workshop.  I have no personal experience with the 2hp HF unit, but my guess is that it performs more like a 1.5 HP than it does a true 2HP.  What size is the inlet port?  If it is 5", that is a pretty strong clue about what size pipe you should be using. 

If you aren't into calculations, then here is link to the best advice you are going to find on building a DC system. 

http://americanwoodworker.com/blogs/shop/archive/2010/10/25/central-dust-collection.aspx

Yes, I know, you can't buy 5" plastic pipe.  Sorry, I can't help you with that problem, but if you are contemplating 6" pipes you need to look very closely at the test data I posted in the thread on my separator build.  I went to great pains to keep SP loss in my 5" system to an absolute minimum, and I have a highly rated 1.5 HP dust collector, but when the separator was added the FPM's dropped to a level that is marginal for conveying woodworking waste.  Anything lower and the debris may start dropping out in the line.  So, when a 5" pipe is providing marginal FPM's the answer is not switching to 6" pipe.

The Thien separator is a wonderful device and it really works wonders, but it comes with a pretty high performance cost.

Regards

[Bulldog8]

If your intent is to have a spotless workshop like the Woodcraft example, you will have to get used to the idea of brooms and brushes to get rid of part of your sawdust. Using a 1.5 or 3 hp DC with 4" or 6" mains or any other size will not get all of the chips and dust with every operation. A DC system is limited not only by its design and capacity, but also the design of the tools it is connected to. Of the tools listed that you want to collect dust from you will find that the table saw will produce a fair amount of dust above the blade. This will either have to be swept up or collected above the table with an overhead device of some sort. The band saw normally has one port near the lower wheel, so what ever dust is lost before entering the lower cabinet will not be collected. The drill press, well I'm sure you can imagine the difficulty there, the material is generally large and slow moving making it harder to collect than from some other machines. I find that the jointer, planer and drum sander have the most complete collection of my tools.

None of this is meant to discourage you, but only to to interject that a DC system is only part of the clean shop arsenal. I seriously doubt that the Woodcraft guy was completely honest in implying that they simply used their system with 4" pipes and it was as clean as what you witnessed. True, it will get the majority, but I've yet to see a shop without brushes and brooms to do a second cleaning.

I do not keep my shop in a spotless or in many cases even a clean condition. I do however attempt to collect the largest amount of fine material possible with the equipment that I have. I then get rid of the rest with an occasional cleaning using a bench brush, broom and a shop vac.

Steve

[Rick T]

btw there are @ 15 pages devoted to dust collection in the FWW Winter 2011/12 Tools & Shops mag. Everything from theory, cyclones, filters, separators, shop vac tests, portable work table with shop vac incorporated.

[RonS]

Here is a pdf of the article that appeared in Wood Mag Issue182 testing 15 Under $400, 1.5 & 2 HP DCs, the HF model 45378-1VGA was included in the test. This artical has been posted many times on this site and is a good reference for those trying to decide on which unit to buy. This test includes SP vrs CFM curves for all the units teste, one of the curves shows which of the units can support 6" duct work and which can support 5" duct work.
You might find this artical very interesting
Ron

[Carpenter96]

Hi Peter. Look at the motor plate volts x amps / 746 = theoretical horse power. Example 120 volts x 15 amps/ 746 = 2.41 (perfect world) if you have a volt meter you could ckeck the voltage in your outlet, Usually around 110 volts. As far as the amps if it is 15 amps that is usually peak or start up amps, which means that your unit probably runs at less than 15 amps. And then we have line losses. So most motors that run on a 110 volt circuit are usually running at 1.5 HP. Now I have an offbrand DC that is rated at 750 cfm. and it will handle the planer, jointer or table saw individually no problem with a separator inline and 4" pipe no problem. I have upgraded to a 1 micron filter bag (much cheaper than a cartidge) and am in the process of adding a Thein Baffle. As of yet I do not know if my performance will be improved or not but from all the posts it seems like a no brainer. Regards Bob

[Peter]

Thanks Bob.

The HF motor, made in China, has as its motor plate a rather thick coat of shiny black paint. Apparently, they don't want anyone to perform that horsepower calc.   ;D  Some years ago, I slapped a multi-meter on my electric system with regards to determining its stability for my computers. Then, I got a voltage range between 105 and 115. I doubt that has changed much in a decade. There is, on the HF unit's filter ring, a sticker that along with the 2 HP claim and 1350 CFM (which is no doubt obtained by having nothing connected to either the inlet or outlet of the impeller!), states it runs at 14 amps. So plugging that into your formula, using worst case: 105 x 14 / 746 = 1.97 HP. I do not doubt that you are correct that the real life situation is significantly less.

I did run across some useful information at WoodMagazine.com and the .pdf suggested by RonS that indicates a solution closely matching your set-up, Bob. Although that .pdf is three years old (the Grizzly model they recommend is obsolete), it contains the only fan curve data I've seen for the Central Machinery (HF) unit. Based on that data, and forms found at FreeCalc.com, it appears that a 5" metal duct is optimum (as has been said by many others and thanks to them for being right), and that 4" PVC isn't optimum, but isn't significantly worse. (I still haven't found a way to calc SP losses in a long-radius sweep, where R is 4D+)

I also just found out the cost of 5" metal (26 gauge snap lock) available locally: $2.38 per foot, $5.12 ea for a 5-segment adj. elbow. Local price for 4" ASTM D2729 PVC = $1.06 per foot. A 45?? WYE = $10.20, and a 45? L = $5.43.

Cost for my layout: Metal = $230; PVC = $140.

I reported this to the budget director and she said about the cost for metal duct, "That's not so bad, is it?" to which I replied, "Hell, no." I went on to explain that the metal is optimized for my blower and results in fewer restrictions. (A 90? turn is accomplished in PVC by two 45? Ls whereas in metal, it's two 5-segment adjustable elbows, resulting in R/D of about 4, which apparently has about the same SP loss as the equivalent length of straight pipe.)

I'll keep y'all posted.

BTW, Doug: I'm taking a look at reversing the direction in my top hat, so that rotation matches that of the impeller. I'd still use the improvements suggested by retired2: his "air straightener" and bell mouth inlet. The only problem I face is that a long straight run into the separator winds up robbing me of about 4 square feet of floor space in my DC closet. The FreeCalc.com form suggests avoiding any changes in direction within 5D of the end of the duct (or ~2 feet in 5" duct). I have JUST 2 feet from the end of the sweep to the beginning of the cyclone in the top hat. Whew.

This is hard. Are we having fun yet?
Peter

[retired2]

Hi Peter. Look at the motor plate volts x amps / 746 = theoretical horse power. Example 120 volts x 15 amps/ 746 = 2.41 (perfect world) if you have a volt meter you could ckeck the voltage in your outlet, Usually around 110 volts. As far as the amps if it is 15 amps that is usually peak or start up amps, which means that your unit probably runs at less than 15 amps. And then we have line losses. So most motors that run on a 110 volt circuit are usually running at 1.5 HP. Now I have an offbrand DC that is rated at 750 cfm. and it will handle the planer, jointer or table saw individually no problem with a separator inline and 4" pipe no problem. I have upgraded to a 1 micron filter bag (much cheaper than a cartidge) and am in the process of adding a Thein Baffle. As of yet I do not know if my performance will be improved or not but from all the posts it seems like a no brainer. Regards Bob

Bob,

Is your DC stationary and piped to each of your tools, or is it portable and you move it to each machine and connect up with a flex hose?  If it is stationary, how many feet of pipe and how many elbows to the farthest tool?

[retired2]

Thanks Bob.

The HF motor, made in China, has as its motor plate a rather thick coat of shiny black paint. Apparently, they don't want anyone to perform that horsepower calc.   ;D  Some years ago, I slapped a multi-meter on my electric system with regards to determining its stability for my computers. Then, I got a voltage range between 105 and 115. I doubt that has changed much in a decade. There is, on the HF unit's filter ring, a sticker that along with the 2 HP claim and 1350 CFM (which is no doubt obtained by having nothing connected to either the inlet or outlet of the impeller!), states it runs at 14 amps. So plugging that into your formula, using worst case: 105 x 14 / 746 = 1.97 HP. I do not doubt that you are correct that the real life situation is significantly less.

I did run across some useful information at WoodMagazine.com and the .pdf suggested by RonS that indicates a solution closely matching your set-up, Bob. Although that .pdf is three years old (the Grizzly model they recommend is obsolete), it contains the only fan curve data I've seen for the Central Machinery (HF) unit. Based on that data, and forms found at FreeCalc.com, it appears that a 5" metal duct is optimum (as has been said by many others and thanks to them for being right), and that 4" PVC isn't optimum, but isn't significantly worse. (I still haven't found a way to calc SP losses in a long-radius sweep, where R is 4D+)

I also just found out the cost of 5" metal (26 gauge snap lock) available locally: $2.38 per foot, $5.12 ea for a 5-segment adj. elbow. Local price for 4" ASTM D2729 PVC = $1.06 per foot. A 45?? WYE = $10.20, and a 45? L = $5.43.

Cost for my layout: Metal = $230; PVC = $140.

I reported this to the budget director and she said about the cost for metal duct, "That's not so bad, is it?" to which I replied, "Hell, no." I went on to explain that the metal is optimized for my blower and results in fewer restrictions. (A 90? turn is accomplished in PVC by two 45? Ls whereas in metal, it's two 5-segment adjustable elbows, resulting in R/D of about 4, which apparently has about the same SP loss as the equivalent length of straight pipe.)

I'll keep y'all posted.

BTW, Doug: I'm taking a look at reversing the direction in my top hat, so that rotation matches that of the impeller. I'd still use the improvements suggested by retired2: his "air straightener" and bell mouth inlet. The only problem I face is that a long straight run into the separator winds up robbing me of about 4 square feet of floor space in my DC closet. The FreeCalc.com form suggests avoiding any changes in direction within 5D of the end of the duct (or ~2 feet in 5" duct). I have JUST 2 feet from the end of the sweep to the beginning of the cyclone in the top hat. Whew.

This is hard. Are we having fun yet?
Peter

Peter,

I wouldn't spend much time worrying about true HP.  Yes, there is a correlation between HP and CFM's, but as you can see from the fan curves in the test you referenced, the performance can vary quite a bit from DC's all having the same HP rating.  That is why a fan curve is far more useful than any other piece of data.

Some time back I posted information about the SP loses for 90 and 45 degree ells of varying radii.  As you might expect 1D bends like those found in plastic pipe impose very high losses.  However, increasing the bend diameter follows the law of rapidly diminishing returns, and after 2.5D the return is nearly zero.  Here is some data on equivalent length of straight pipe for 90 degree ells of varying sizes and bend radii.  You can simply halve these numbers for 45 degree ells.

                     1D         1.5D        2.0D        2.5D       

4' Pipe            12'          6'            3'             3'

5" Pipe           18'          9'            6'              5'

6" Pipe           24'         12'           7'              6'


Here are some SP losses per foot of pipe at 3500 FPM and 4000 FPM, which is most likely the range you will be operating in with a 1.5HP DC.

                       3500 FPM            4000FPM

4" Pipe             .055 in./ft.          .070 in./ft.

5" Pipe             .042 in./ft.          .055 in./ft.

6" Pipe             .035 in./ft.          .045 in./ft.


Convert all your fittings to equivalent straight length of pipe with the information above.  45 degree laterals or wye's should be treated as a 45 degree ell.  The straight leg of a wye should just be counted as straight pipe.  And of course, you need to add the actual length of straight pipe to the equivalent length of the fittings.  Then multiply the total by the losses per foot above.  Your not done.  You need to add losses for the entry port and the DC.  Assume 1" of SP loss for the tool entry port and another 1"-2" for losses at the blower.

Use the above instructions to calculate your SP loses for your worst case scenario, usually the tool farthest from the DC.  Take the SP loss to the fan curve and see if the remining SP moves enough air (CFM ) for the tool.  Most tools need 400-450 CFM.

And now for the bad news.  The above exercise does not take into consideration the losses from a Thien separator.   I took anemometer readings on my system to see how the separator affected performance.  Without the separator, I had 705 CFM at 5171 FPM, those are very good numbers.  After I installed the separator, those numbers dropped to 434 CFM at 3185 FPM.  At this level the performance is approaching speeds that are almost too low to keep the dust and dirt in suspension.

Hope this post helps.

[RonS]

Here is an artical from wood Magazine that has some of the infor and process metioned above by Retired2. It looks like this artical is dated 2007 and it is little blurry but usable. It is a process to determining your SP loses. Do a loss calc for your main run and then for each of your drops, add the main loss to each drop loss and look at your worst case run. I would use Retired2's SP loss for the Thien seperator in your main run.