Brilliant or Dumb idea? - Page 2 - Woodworking Talk - Woodworkers Forum
 13Likes
Reply
 
Thread Tools Display Modes
post #21 of 47 Old 06-03-2018, 01:45 PM
Senior Member
 
Join Date: Aug 2012
Location: British Columbia, Canada
Posts: 5,658
View FrankC's Photo Album My Photos
How do you justify spending the price of a 2HP dust collector on two shop vacs? Check Harbor freight and get the real thing and be done with it.

Wise men speak because they have something to say; fools because they have to say something -Plato

FrankC
http://sawdustmaking.com
http://woodworkerglossary.com
FrankC is offline  
Sponsored Links
Advertisement
 
post #22 of 47 Old 06-03-2018, 03:15 PM
Member
 
Join Date: Jun 2018
Location: Oklahoma
Posts: 35
View okbear's Photo Album My Photos
Quote:
Originally Posted by FrankC View Post
How do you justify spending the price of a 2HP dust collector on two shop vacs? Check Harbor freight and get the real thing and be done with it.
Iím not. I already have one shop vac like that. I get special pricing with Lowes so I wonít have much in another one. I did explore the HF option but Iím not crazy about the bag filter it uses. The good filters are spendy. If I do this and it doesnít work well then it wouldnít be the first time I tried something and failed. lol. My only question is what size pvc to use up high. Anybody?
okbear is offline  
post #23 of 47 Old 06-03-2018, 08:52 PM
Member
 
Join Date: Jun 2018
Location: Oklahoma
Posts: 35
View okbear's Photo Album My Photos
May have a change of plans. A buddy has three vac motors out of an old car wash. May try to do something with one or more of those.
Attached Images
File Type: jpg BBA8D6E0-6A0A-4A6F-A019-4578B3F33969.jpg (285.5 KB, 16 views)
File Type: jpg 5FFAC353-1190-4D84-8111-05571CB01379.jpg (306.5 KB, 14 views)
File Type: jpg 573C5339-4310-47A8-A161-F63A68037DD6.jpg (238.5 KB, 14 views)
File Type: jpg 5C36E90A-AAC8-4F69-B3A0-3F0EDCF34F78.jpg (281.5 KB, 14 views)
File Type: jpg F0496119-DC15-44B6-9229-6B73E6B8E963.jpg (265.0 KB, 14 views)
okbear is offline  
Sponsored Links
Advertisement
 
post #24 of 47 Old 06-03-2018, 10:04 PM
Senior Member
 
AmishElectricCo's Avatar
 
Join Date: Jan 2018
Location: Ohio
Posts: 332
View AmishElectricCo's Photo Album My Photos
I'm still stuck on the math - I wouldn't think that stacking applies to CFM, you're just using more power to move the same amount of air. Just to keep it simple:

If you have 1 motor capable of 50 CFM, adding a second identical motor isn't going to move 100 CFM...it's still going to be 50. The only advantage of a multi-motor setup is being able to section off your shop to keep runs of PVC pipe as short as possible so that you're not losing power due to long runs.

⚡ Anthony
AmishElectricCo is offline  
post #25 of 47 Old 06-03-2018, 10:15 PM
Senior Member
 
Join Date: Apr 2012
Posts: 3,025
View Quickstep's Photo Album My Photos
If two Vacs were connected to the same pipe, wouldn’t they just suck against one another?
Quickstep is online now  
post #26 of 47 Old 06-04-2018, 04:01 AM
Member
 
Join Date: Jun 2018
Location: Oklahoma
Posts: 35
View okbear's Photo Album My Photos
Quote:
Originally Posted by AmishElectricCompany View Post
I'm still stuck on the math - I wouldn't think that stacking applies to CFM, you're just using more power to move the same amount of air. Just to keep it simple:

If you have 1 motor capable of 50 CFM, adding a second identical motor isn't going to move 100 CFM...it's still going to be 50. The only advantage of a multi-motor setup is being able to section off your shop to keep runs of PVC pipe as short as possible so that you're not losing power due to long runs.
Iím confused. If you have 50 cfm being draw at each side of the Y, why would you not have >50 at the nozzle? I would think you would see ~100 at the nozzle.
okbear is offline  
post #27 of 47 Old 06-04-2018, 04:03 AM
Member
 
Join Date: Jun 2018
Location: Oklahoma
Posts: 35
View okbear's Photo Album My Photos
Quote:
Originally Posted by Quickstep View Post
If two Vacs were connected to the same pipe, wouldnít they just suck against one another?
My thinking is that they would increase suction at the nozzle.
okbear is offline  
post #28 of 47 Old 06-04-2018, 08:59 AM
Senior Member
 
Pineknot_86's Avatar
 
Join Date: Feb 2016
Posts: 1,942
View Pineknot_86's Photo Album My Photos
FWIW, I use a Shop Vac and Dust Deputy on my table saw and band saw to keep sawdust from blowing all over the floor. Other tools, I just vacuum them periodically with the SV. If it's on the floor, I use the broom and dust pan. The B&DP don't require an outlet close by and create no noise.

A diamond is how coal reacts under pressure.
Pineknot_86 is offline  
The Following User Says Thank You to Pineknot_86 For This Useful Post:
okbear (06-04-2018)
post #29 of 47 Old 06-04-2018, 12:46 PM
Senior Member
 
AmishElectricCo's Avatar
 
Join Date: Jan 2018
Location: Ohio
Posts: 332
View AmishElectricCo's Photo Album My Photos
Quote:
Originally Posted by okbear View Post
I’m confused. If you have 50 cfm being draw at each side of the Y, why would you not have >50 at the nozzle? I would think you would see ~100 at the nozzle.
CFM = Cubic Feet per Minute. It is a measure of velocity into or out of a space.

Think of it this way: You have two cars drag racing - the timer at the end is a measure of velocity, or how long it takes the cars to travel a quarter mile. If both of the cars are identical, they cross the finish line at the same time...they don't go twice as fast.

The only way to get more CFM is to add a stronger motor, not more of them. Even then, your suction is only ever going to be as strong as your single most powerful motor. Let's say you have
  • x2 motors, each rated for 100 CFM. Max CFM = 100
  • x5 motors, one is rated for 150 CFM, the other four are 100 CFM. Max CFM = 150

⚡ Anthony
AmishElectricCo is offline  
post #30 of 47 Old 06-04-2018, 01:21 PM
Member
 
Join Date: Feb 2013
Posts: 95
View Dodis's Photo Album My Photos
Caveat, pure wild guesses and thoughts...

If you want to try the dual shop vac setup, I would at least connect them both to some 4" drain PVC, for testing. I suggest going with the 4" as most of the commonly available home/hobby shop hoses, connections, and blast gates are already 4" (+/- but that is another discussion). Connecting both to a single 2-1/2" hose would just restrict the flow and not show much if any increase, except noise and electric bill. If one vac works good on a single hose, adding a second vac would require a larger diameter hose to keep the airflow moving with the increase in CFMs. And hose diameter will also affect the velocity if it is too large for the task. It's all a balancing act...

As for testing the dual vac system, once connected, google for a homemade manometer to test static pressure, and a homemade pitot tube for testing velocity. All they require are lengths of clear tubing, liquid, and a board to mount them on. Then you could generate some numbers you could compare to actual dust collection systems.

As for the actual values required, I would start out reading through Phil Thein's website as there are many discussions of real world minimum requirements to keep dust in suspension in the airflow, and tips to make the system function as efficient as possible. There were some there that did side-by-side tests of different systems with a specific length of pipe, and possibly some elbows, to get some real numbers that you could setup to test and compare.

http://www.jpthien.com/smf/index.php?PHPSESSID=eohr7cu4fe1uvq8dkod09nss62&boa rd=1.0

Once the pipes are in and the tests are run, if you don't like the results of the dual shop vacs, you can just swap them out for the HF dust collector on the now existing 4" system and be good to go, no re-piping.
okbear likes this.

Mike
Texas Gulf Coast
Weekend Wood Wrecker...
Dodis is offline  
post #31 of 47 Old 06-04-2018, 01:35 PM
Senior Member
 
Join Date: Apr 2012
Posts: 3,025
View Quickstep's Photo Album My Photos
Quote:
Originally Posted by AmishElectricCompany View Post
CFM = Cubic Feet per Minute. It is a measure of velocity into or out of a space.

Think of it this way: You have two cars drag racing - the timer at the end is a measure of velocity, or how long it takes the cars to travel a quarter mile. If both of the cars are identical, they cross the finish line at the same time...they don't go twice as fast.

The only way to get more CFM is to add a stronger motor, not more of them. Even then, your suction is only ever going to be as strong as your single most powerful motor. Let's say you have
  • x2 motors, each rated for 100 CFM. Max CFM = 100
  • x5 motors, one is rated for 150 CFM, the other four are 100 CFM. Max CFM = 150

I'm just throwing this out there... Could it result in greater CFM if the vacuums were connected to one another in series? Kind of a multi-stage setup? Kinda like this?


I'm just throwing this out there as a crazy idea. Not suggesting in any way that it will actually work.
Attached Thumbnails
Click image for larger version

Name:	Vac.jpg
Views:	7
Size:	25.6 KB
ID:	362249  

okbear likes this.

Last edited by Quickstep; 06-04-2018 at 01:47 PM.
Quickstep is online now  
post #32 of 47 Old 06-05-2018, 07:17 PM
Member
 
Join Date: Jun 2018
Location: Oklahoma
Posts: 35
View okbear's Photo Album My Photos
Quote:
Originally Posted by Quickstep View Post
I'm just throwing this out there... Could it result in greater CFM if the vacuums were connected to one another in series? Kind of a multi-stage setup? Kinda like this?


I'm just throwing this out there as a crazy idea. Not suggesting in any way that it will actually work.
Stumpy Nubs did this with success but warned that (he was warned that) it could result in a ďturbo effectĒ and potentially result in a fire. Iím not quite that brave. I think Iím going to try the vac motors my buddy is giving me.

Andy
okbear is offline  
post #33 of 47 Old 06-05-2018, 07:26 PM
Member
 
Join Date: Jun 2018
Location: Oklahoma
Posts: 35
View okbear's Photo Album My Photos
Quote:
Originally Posted by Dodis View Post
Caveat, pure wild guesses and thoughts...

If you want to try the dual shop vac setup, I would at least connect them both to some 4" drain PVC, for testing. I suggest going with the 4" as most of the commonly available home/hobby shop hoses, connections, and blast gates are already 4" (+/- but that is another discussion). Connecting both to a single 2-1/2" hose would just restrict the flow and not show much if any increase, except noise and electric bill. If one vac works good on a single hose, adding a second vac would require a larger diameter hose to keep the airflow moving with the increase in CFMs. And hose diameter will also affect the velocity if it is too large for the task. It's all a balancing act...

As for testing the dual vac system, once connected, google for a homemade manometer to test static pressure, and a homemade pitot tube for testing velocity. All they require are lengths of clear tubing, liquid, and a board to mount them on. Then you could generate some numbers you could compare to actual dust collection systems.

As for the actual values required, I would start out reading through Phil Thein's website as there are many discussions of real world minimum requirements to keep dust in suspension in the airflow, and tips to make the system function as efficient as possible. There were some there that did side-by-side tests of different systems with a specific length of pipe, and possibly some elbows, to get some real numbers that you could setup to test and compare.

http://www.jpthien.com/smf/index.php?PHPSESSID=eohr7cu4fe1uvq8dkod09nss62&boa rd=1.0

Once the pipes are in and the tests are run, if you don't like the results of the dual shop vacs, you can just swap them out for the HF dust collector on the now existing 4" system and be good to go, no re-piping.
Thatís a great idea. Thank you. Iím planning on a 45 to 50 foot run down one side of the shop and then T off as needed and a floor sweep on that side as well. Iíll have one run to the other side of the shop for another floor sweep also. I appreciate the input!

Andy
okbear is offline  
post #34 of 47 Old 06-05-2018, 07:43 PM
Member
 
Join Date: Jun 2018
Location: Oklahoma
Posts: 35
View okbear's Photo Album My Photos
Quote:
Originally Posted by AmishElectricCompany View Post
Think of it this way: You have two cars drag racing - the timer at the end is a measure of velocity, or how long it takes the cars to travel a quarter mile. If both of the cars are identical, they cross the finish line at the same time...they don't go twice as fast.
  • x2 motors, each rated for 100 CFM. Max CFM = 100
  • x5 motors, one is rated for 150 CFM, the other four are 100 CFM. Max CFM = 150
I get what you are saying but that scenario is two solid objects under their own power in an open environment. We are dealing with a gas in a closed environment being “powered” through suction motors. So one vac is demanding X amount of air from one hose. If an identical vac is added to the same hose, how are they not demanding 2X-ish amount of air from that same hose?

Going with your car scenario, let’s say you connect two identical motors to a single air intake designed for one of the motors. Would the motors not be potentially be starved of air due to a higher demand for air at the intake? Say you add more motors. Would the demand for air at the intake not be increased with each motor added?

Andy

Last edited by okbear; 06-05-2018 at 08:00 PM.
okbear is offline  
post #35 of 47 Old 06-05-2018, 07:50 PM
Senior Member
 
Brian T.'s Avatar
 
Join Date: Dec 2012
Location: McBride, BC
Posts: 2,648
View Brian T.'s Photo Album My Photos
Chronic Obstructive Pulmonary Disease will kill you. Can you afford that?
Brian T. is offline  
post #36 of 47 Old 06-05-2018, 09:03 PM
Member
 
Join Date: Jun 2018
Location: Oklahoma
Posts: 35
View okbear's Photo Album My Photos
Quote:
Originally Posted by Robson Valley View Post
Chronic Obstructive Pulmonary Disease will kill you. Can you afford that?
Little confused. Are you saying Iíll have too much vacuum pressure with a not wide enough hose?

Andy
okbear is offline  
post #37 of 47 Old 06-06-2018, 12:29 AM
Member
 
Join Date: Jun 2018
Location: Oklahoma
Posts: 35
View okbear's Photo Album My Photos
Quote:
Originally Posted by Robson Valley View Post
Chronic Obstructive Pulmonary Disease will kill you. Can you afford that?
Quote:
Originally Posted by okbear View Post
Little confused. Are you saying I’ll have too much vacuum pressure with a not wide enough hose?
Nevermind. It dawned on me what you are talking about. I was in problem solving mode and thinking you were equating flow to the human body or something. Yes of course I want the system to be right. I’m looking at the Wynn filter and thinking it may be a necessity. I’m also thinking that with the larger vac motors and 4” piping, the larger cyclone may be a necessity also.
Brian T. likes this.

Andy

Last edited by okbear; 06-06-2018 at 12:31 AM.
okbear is offline  
post #38 of 47 Old 06-06-2018, 08:05 AM
Senior Sawdust Sweeper
 
Join Date: Jan 2009
Location: Marietta, Ga. USA
Posts: 1,472
View Gary Beasley's Photo Album My Photos
Quote:
Originally Posted by Quickstep View Post
I'm just throwing this out there... Could it result in greater CFM if the vacuums were connected to one another in series? Kind of a multi-stage setup? Kinda like this?


I'm just throwing this out there as a crazy idea. Not suggesting in any way that it will actually work.
From my understanding of airflow in series you get a higher vacuum drop with not so much change in CFM. In parrallel you get higher CFM with not so much change in the vacuum drop, which is the aim in most dust collectors. You want to move as much air as possible, here vacuum drop is mainly a measure of the resistance to the airflow and you can have a high vacuum without moving much air.
Gary Beasley is offline  
post #39 of 47 Old 06-06-2018, 08:15 AM
Senior Member
 
Join Date: Aug 2017
Posts: 2,843
View Tool Agnostic's Photo Album My Photos
Quote:
Originally Posted by AmishElectricCompany View Post
CFM = Cubic Feet per Minute. It is a measure of velocity into or out of a space.

Think of it this way: You have two cars drag racing - the timer at the end is a measure of velocity, or how long it takes the cars to travel a quarter mile. If both of the cars are identical, they cross the finish line at the same time...they don't go twice as fast.

The only way to get more CFM is to add a stronger motor, not more of them. Even then, your suction is only ever going to be as strong as your single most powerful motor. Let's say you have
  • x2 motors, each rated for 100 CFM. Max CFM = 100
  • x5 motors, one is rated for 150 CFM, the other four are 100 CFM. Max CFM = 150
I have been watching this thread since it started. This post has bothered me in particular since it appeared.

I do not claim to be an air flow expert, but I know a little physics. @AmishElectricCompany is right - CFM stands for cubic feet per minute. He is incorrect about "velocity."

Cubic feet is a measure of volume. One cubic foot is a box that is 12 inches x 12 inches x 12 inches. If a shop vac can move 100 CFM, it means that it can move (suck or blow) 100 "boxes" worth of air every minute.

(Yes, let us assume a "standard temperature and pressure.")

If you attach two 100 CFM shop vacs to a system, they will try to suck 200 CFM. That's when turbulence comes into play. Air has viscosity and other properties that affect how it flows in a system. The shop vac filters will slow some of the flow, too. Car engine designers think a lot about this problem - How do you get a lot of gas and air to flow and distribute very quickly into a small chamber before you light the spark?

Just because you have 200 CFM of capacity in your two shop vacs doesn't mean that the shop vacs will be able to suck the entire 200 CFM of air. For a lot of reasons.

You can move your 100 CFM of air by pushing a 12 x 12 box of air forward one foot every 0.6 seconds:

* Imagine a 12 x 12 box with a flat 12 x 12 piston inside, with the 12x12 piston pushing forward 1 foot. That's one cubic foot. If you do that every 0.6 seconds for one minute, you will get 100 CFM (cubic feet per minute).

* Imagine a 4 x 4 box with a flat 4 x 4 piston inside, but this time with the 4x4 piston pushing forward 9 feet to get one cubit foot of air. If you do that every 0.6 seconds for one minute, you will get 100 CFM.

Note the air speed in the two examples. The air in the 4x4 example must move 9 times faster than the air in the 12x12 example to achieve the same 100 cubic feet per minute. To get the air to move faster, you must increase the air pressure.

I hope you understand the point above. You can get 100 CFM from a wide opening with low pressure (low air speed), or a narrow opening with high pressure (higher air speed). Note the popularity of HVLP "high volume low pressure" sprayers - they give you a lot of CFM because the hose is big. My air compressor is far more powerful. One reason it can't deliver the same CFM as an HVLP sprayer is because it pushes the air through a much smaller hose. It can't build up enough pressure in the tank to push the air that fast. It would explode first.

Turbulence and filters interfere with air flow too. That is one factor that makes it difficult to analyze @mhhickma's system.

The question has come up about what happens if you gang the two shop vacs together in series. I don't know. What I do know is that there are multi-stage systems that do exactly that. You can buy 2, 3, 4, and even 5 stage HVLP sprayers for example, which move more air as you add stages. The stages are arranged in series, with the output of one feeding the input of the next. The output of one stage is higher pressure air, which is then compressed by the next stage into even higher pressure air, etc. The design of the air flow between the stages is important - they don't simply feed one directly into the next.

Bottom line prediction:

If mhhickma attaches two shop vacs to his dust collection system, it should draw more air than a single shop vac. How much more air will actually move is too hard to determine. The system may cause the shop vacs to work harder, increasing wear. You know that sound when the motor works harder because the hose is partially blocked. The noise would bother me. Even with ear protection, my shop vac is annoying.

Last edited by Tool Agnostic; 06-06-2018 at 08:20 AM.
Tool Agnostic is online now  
post #40 of 47 Old 06-06-2018, 08:31 AM
Senior Member
 
Ron_J's Avatar
 
Join Date: Sep 2014
Location: Central PA
Posts: 447
View Ron_J's Photo Album My Photos
Quote:
Originally Posted by AmishElectricCompany View Post
CFM = Cubic Feet per Minute. It is a measure of velocity into or out of a space.

Think of it this way: You have two cars drag racing - the timer at the end is a measure of velocity, or how long it takes the cars to travel a quarter mile. If both of the cars are identical, they cross the finish line at the same time...they don't go twice as fast.

The only way to get more CFM is to add a stronger motor, not more of them. Even then, your suction is only ever going to be as strong as your single most powerful motor. Let's say you have
  • x2 motors, each rated for 100 CFM. Max CFM = 100
  • x5 motors, one is rated for 150 CFM, the other four are 100 CFM. Max CFM = 150
Sorry, but Yeah-Yeah, Squints and the boys already proved otherwise with their moms vacuum cleaners. And it would have worked, had the Beast not pinched the end shut.
Ron_J is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Woodworking Talk - Woodworkers Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Work Tables, stations, etc. an idea StampBear General Woodworking Discussion 15 03-15-2017 04:11 PM
Work station idea...will it work? OutdoorSeeker Design & Plans 0 01-19-2017 08:34 PM
Need clever idea to keep stuff out from under furniture Sleeper General Woodworking Discussion 8 09-19-2016 10:11 AM
Feel free to steal my idea! Masterofnone General Woodworking Discussion 6 04-10-2016 06:41 AM
having a design idea i need your help shayvidas General Woodworking Discussion 8 03-03-2016 08:42 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome