Needs Pictures: 0
Picture(s) thanks: 0
Results 46 to 60 of 72
Thread: Thein baffle vs Dust Deputy
-
20th February 2020, 09:45 PM #46GOLD MEMBER
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 2,645
Sure. I don't have a current clamp for my multimeter, but I do have a power meter. My setup wasn't very scientific. I just measured the motor power as I added components to the system. See the attached table. Hopefully it makes sense. I'm assuming a direct correlation between power and CFM as I have no way to accurately measure CFM. According to my readings the cyclone has twice as much effect on airflow as the 4m of 5" flexi. Which is an interesting finding as Onieda told me the cyclone is equivalent to 10ft of 5" ducting. That's not what I measured.
The flexi was laying on the garage floor. It was fairly straight, but not stretched tight.
-
20th February 2020 09:45 PM # ADSGoogle Adsense Advertisement
- Join Date
- Always
- Location
- Advertising world
- Posts
- Many
-
20th February 2020, 11:07 PM #47.
- Join Date
- Feb 2006
- Location
- Perth
- Posts
- 27,796
The problem with comparing the Oneida and your results is that we don't know their actual setups (eg naked or hooded air intakes, testing using a proper test duct or just waving an air flow meter in the vicinity of a duct opening), or at what pressures the flows were measured. If low staring flows / pressures are used this usually will result in low flow rate losses and VV. That's why on some systems folks don't see any noticeable change in flows using separators. Even the power figures are only rough estimates. The only way to really compare is with all parameters as equal as possible and then using a flow meter.
The ultimate comparision is done via fan curves (P loss V flow rates) so we know what the %losses are at all flow rates.
-
21st February 2020, 12:17 AM #48Senior Member
- Join Date
- Nov 2016
- Location
- USA, Indiana, West Lafayette
- Posts
- 188
Thank you. I did see that and forgot about it. Sorry.
One thing about comparing the makeup of the loss is that pressure drop varies with the square of the flow. Adjusting for that the loss of the cyclone is actually equivalent to about 3.6m of your flex. Note that when I say "loss" I mean the ratio of pressure drop to velocity pressure, not a flow ratio. The flow ratio, as Bob has pointed out, varies with just about everything. The pressure loss coefficient changes only slightly with flow.Dave
-
21st February 2020, 08:57 AM #49GOLD MEMBER
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 2,645
Yes, I know. A better setup would have been if I had tested the power change with each component separately. However, I don't have that much patience!
I'd love to see how you calculated that. My crude power figures suggest the cyclone is almost twice as lossy as the 4m of flex, but you're suggesting it is actually less lossy.
-
21st February 2020, 10:05 AM #50Senior Member
- Join Date
- Nov 2016
- Location
- USA, Indiana, West Lafayette
- Posts
- 188
Well, we might both get some abuse for violating the tacit "no math" forum rule, but here goes.
First step is to model the fan curve in the range of interest as P =P0 - R0 x Q^2 where P0 and R0 are the modeling constants. P is the fan pressure and Q is the flow. With the inlet open the the system pressure is P = R1 x Q^2 where R1 is the entrance loss expressed as a resistance. I that case we have P1 = R1 x Q1^2 = P0 - R0 x Q1^2. Or, P0 = (R0 + R1) x Q1^2. We can follow the same logic to get P0 = (R0 + R1 + R2) x Q2^2 = (R0 + R1 + R2 + R3) x Q3^2 = etc.... where R2 etc are the resistances of the added components.
So with R2 the resistance of the cyclone we can solve R2/(R0 + R1) = ((Q1/Q2)^2 - 1) and R3/(R0 + R1) = ((Q1/Q3)^2 -1) -R2/(R0 + R1) etc
The other assumption is that power is proportional to flow. So for your example Q1/Q2 = (1125-430)/(978-430) = 1.268 giving R2/(R0 + R1) = .608 and
R3/(R0 + R1) = .638 - .608 = .03
R4/(R0 + R1) = 1.187 - .638 = .548
So the ratio of the cyclone resistance to the hose resistance is R2/R4 = .608/.548 = 1.109
At this point I realize that in my previous post I divided instead of multiplying so the actual equivalent hose length is 4.4 not 3.6. (1.109 x 4m)
-----------------
Well, after rereading this I'm afraid it's not very coherent. Let me know if you can make any sense of it. I can try again tomorrow morning if necessary.Dave
-
21st February 2020, 04:56 PM #51GOLD MEMBER
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 2,645
Not really, but thanks anyway. My maths is pretty good, but I'm not clear on the meanings of some of the variables. I'll have another look later. No need to address this any further as it's fairly academic.
OK. Are you saying that is a good assumption? If so, would that mean power consumption would be a good indicator of filter clogging?
-
21st February 2020, 09:33 PM #52Senior Member
- Join Date
- Nov 2016
- Location
- USA, Indiana, West Lafayette
- Posts
- 188
Ah, too late. I already drew a picture. Need it or not, here it is:
The Blue line is the fan curve with entrance loss and velocity pressure baked in. That is, P = P0 - (Ro + R1) x Q^2. I've set P0 to 1 since its actual value is irrelevant here and power substitutes for flow. Again, no need for actual values, relative is all we need.
The other three parabolas represent the system curves of the three configurations you tested. Where they cross the fan curve is the values you measured. Fitting those curves is equivalent to solving for R2, R2+R3, and R2+R3+R4 as in my previous post.
To compare the individual parts we calculate the difference in pressure between adjacent curves at the same flow rate, in this case 695.
OK. Are you saying that is a good assumption? If so, would that mean power consumption would be a good indicator of filter clogging?
The usual method checks static pressure across the filter. Pressure is also affected by air density but since flow varies with the square root of pressure the error is reduce by half. So, a 5% density variation causes a 2.5% flow measurement error.Dave
-
23rd February 2020, 12:05 AM #53Intermediate Member
- Join Date
- Feb 2020
- Location
- Maryborough Qld
- Age
- 81
- Posts
- 25
Hi all, does anyone have dimensions for a 6" inlet /outlet Thien baffle? I need inside diameter, height and the size of the slot in the baffle. I have seen n+1 videos of builds, but dimensions are about as plentiful as rocking horse droppings. I'm going with the FM-400 and 6" reticulation.
-
23rd February 2020, 12:42 AM #54Senior Member
- Join Date
- Nov 2016
- Location
- USA, Indiana, West Lafayette
- Posts
- 188
-
23rd February 2020, 10:10 AM #55GOLD MEMBER
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 2,645
I imagine Jon is considering adding a Thein. I also assume you are referring to the cylindrical metal objects between the plastic bags and the filter bags as separators? I guess technically that is correct, but I don't think it's what most of us consider to be a separator. I may be wrong, but I reckon most people would consider a separator to be a cyclone or Thein baffle installed before the blower.
You raise an interesting point though. That is, why bother paying for all that extra hardware if you don't need it? However, at $549 I think the FM-400 is cheap enough that it doesn't matter. If Jon's Thein is good enough, those plastic bags will almost never need emptying. Later, if he wants to upgrade to better filters or move the DE outside, it would be a very simple job to modify it. I reckon it's a good DE for tweaking.
https://www.timbecon.com.au/3hp-dust-extractor
-
23rd February 2020, 10:17 AM #56GOLD MEMBER
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 2,645
Hi Jon,
I think as a start you could simply find a 4" design you like and scale it up to 6". I would just scale it up by 50%. Although the cross-sectional area of the ducting increases with the square of the diameter, so does the area of the slot and the collector bin. They look fairly simple to make, so be prepared to experiment. Don't be blinded by science!
-
23rd February 2020, 10:49 AM #57Senior Member
- Join Date
- Nov 2016
- Location
- USA, Indiana, West Lafayette
- Posts
- 188
Correct on both points. The "bag holder" is indeed a centrifugal separator, in the same family as a Thein separator or a cyclonic separator. And, yes, common language often mislabels technology.
You raise an interesting point though. That is, why bother paying for all that extra hardware if you don't need it? However, at $549 I think the FM-400 is cheap enough that it doesn't matter.
If Jon's Thein is good enough...Dave
-
23rd February 2020, 11:14 AM #58GOLD MEMBER
- Join Date
- Nov 2007
- Location
- melbourne australia
- Posts
- 2,645
Everything you say makes sense, but what's your end game? Are you suggesting Jon just buys a blower if he intends to add a Thein? These aren't readily available which is why a lot of us buy a complete DE and modify it. We've talked about how a pre-separator saves the hassle of emptying bags and how the bags are prone to developing pinholes from the circulating wood chips.
BTW, Jon has already stated money is an issue.
Do you have any suggested sizes for the Thein in a 3HP/6" system that might achieve a good compromise for both criteria? Or even sizes that will optimise each criteria? Then Jon could choose one or the other or a hybrid of both.
-
23rd February 2020, 09:15 PM #59Intermediate Member
- Join Date
- Feb 2020
- Location
- Maryborough Qld
- Age
- 81
- Posts
- 25
Hi Dave,
I'm adding it to the FM-400, or that's the intention. The reason being that I want to separate out the chips, shavings and most of the dust before the DC to save me having to be emptying those blasted plastic bags with monotonous regularity when I'm working. As has been pointed out, I'm no spring chicken and the body isn't as flexible as it was. What flexibility was left took a hit with the L3-L4-L5 fusion. If I can get the frequency of emptying down to once or twice a year, that'll suit me fine. Remounting the damned things is the killer. If I wasn't on a minuscule budget I'd look seriously at building a mini electrostatic precipitator and have that empty into a bucket like the Thien, or cyclone.
I already have an idea or two about modifying the bags to make them easier to remount by fixing an elastic band to the top of the bag to hold it in position while I wrestle the clamp back into position. Reducing the overall length of the bags won't matter, seeing that the amount they collect should be small.
-
23rd February 2020, 09:58 PM #60Woodworking mechanic
- Join Date
- Jan 2014
- Location
- Sydney Upper North Shore
- Posts
- 4,470
Mine is in a large drum.
These are the photos of mine. I cant remember the exact measurements but they came off the WEB. I can dismantle it if you like and measure the parts.
The only thing is that mine has 4" pipes, not 6"
IMG_0882.jpgIMG_0881.jpgIMG_0880.jpgIMG_0879.jpg
Similar Threads
-
Thien Baffle Dust Extractor
By HeadScratcher in forum DUST EXTRACTIONReplies: 39Last Post: 19th February 2020, 03:40 PM -
Dust Deputy
By chrisb691 in forum DUST EXTRACTIONReplies: 31Last Post: 18th February 2020, 05:50 PM -
Improving my dust collection using the Dust Commander (1/3rd price o fDust Deputy
By barrysumpter in forum HINTS & TIPSReplies: 10Last Post: 5th December 2016, 08:50 PM -
super dust deputy
By gingerbeer86 in forum DUST EXTRACTIONReplies: 9Last Post: 17th February 2012, 09:30 PM