I know most of the home made flow benches use vacuummotors from vacuumcleaners but what about one big radial (centrifugal) fan? I know they blow quite srtongly but is their sucktion strong enough?
something like that .
sucking motor
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by 84-1074663779 » Wed Nov 03, 2004 5:55 pm
Absolutely, pressure differential is pressure differential, you will measure the same pressure difference either sucking or blowing.
I run a large diameter single stage centrifugal industrial blower and am very happy with it. As a rough guide, an eighteen inch diameter rotor running at 2,800 Rpm will get you about 15". Double that to 5,600 Rpm will get you 60" water.
Twice the Rpm will give very nearly twice the CFM, four times the pressure, but you will need EIGHT times the horsepower to drive it.
Have you considered using an old Vortech supercharger as a flowbench blower? That would make a mighty fine flowbench.
I run a large diameter single stage centrifugal industrial blower and am very happy with it. As a rough guide, an eighteen inch diameter rotor running at 2,800 Rpm will get you about 15". Double that to 5,600 Rpm will get you 60" water.
Twice the Rpm will give very nearly twice the CFM, four times the pressure, but you will need EIGHT times the horsepower to drive it.
Have you considered using an old Vortech supercharger as a flowbench blower? That would make a mighty fine flowbench.
- 84-1074663779
by gaz » Wed Nov 03, 2004 6:24 pm
Thanks Tony for the positive feedback I was hoping for. So I guess I am going to have to find a big industrial blower from somewhere. One more question how much power (kw) would a 18" rotor need to get 5600 rpm, have you any ideas. Or whats the power of your motor?
About the vortech blower i'm afraid i couldnt find this kind of a blower from anywhere around here in Estonia.
About the vortech blower i'm afraid i couldnt find this kind of a blower from anywhere around here in Estonia.
- gaz
- Posts: 21
- Joined: Thu Oct 28, 2004 6:41 pm
- Location: Estonia
by 84-1074663779 » Thu Nov 04, 2004 7:30 pm
Power required will depend on flow and blower size, as well as developed pressure, so it is not possible to give a figure.
Your best bet is to tour a few secondhand machinery graveyards and see what is available. I would suggest you look for something that has a 1Hp to 2Hp motor, with the largest possible diameter rotor. It will have a cast iron snail shaped housing, at least two feet in diameter, and the housing will be quite thin, only perhaps four inches. It will have the proportions of a biscuit !
Developed pressure will be proportional to the square of tip speed, so the largest diameter rotor you can find will be the one to get. As an example an eighteen inch rotor in a two foot scroll running at 2850 Rpm should give around 15" water pressure. A two foot rotor in a two and a half foot scroll at the same Rpm about 27" water.
The motor will have a rating plate, and the horsepower will give you some clue as to flow capability. The inlet and outlet flow areas will also be a clue as to flow capability. Do not go too big in flow ares! If you do, and you find that you need to speed up the blower, required horsepower can be extremely high.
If you speed up the blower Rpm, flow will increase in proportion to Rpm, pressure to the square of Rpm, and drive power to the cube of Rpm increase. So a bit more speed can have quite a dramatic effect on pressure and horsepower.
In my case I removed the original 1Hp motor and fitted a 10Hp motor with a 2:1 pulley drive to double Rpm. I can now easily reach 60" pressure and get double the original rated 350 CFM.
Until you actually have your blower and can test it, it is really difficult to know exactly what you have. The machinery yard may allow you to test several on an exchange basis before deciding. Something with an inlet flow "eye" diameter of three to four inches might be fairly typical. Because these blowers are so sensitive to horsepower, the original motor rating is an excellent way to judge flow capacity.
Your best bet is to tour a few secondhand machinery graveyards and see what is available. I would suggest you look for something that has a 1Hp to 2Hp motor, with the largest possible diameter rotor. It will have a cast iron snail shaped housing, at least two feet in diameter, and the housing will be quite thin, only perhaps four inches. It will have the proportions of a biscuit !
Developed pressure will be proportional to the square of tip speed, so the largest diameter rotor you can find will be the one to get. As an example an eighteen inch rotor in a two foot scroll running at 2850 Rpm should give around 15" water pressure. A two foot rotor in a two and a half foot scroll at the same Rpm about 27" water.
The motor will have a rating plate, and the horsepower will give you some clue as to flow capability. The inlet and outlet flow areas will also be a clue as to flow capability. Do not go too big in flow ares! If you do, and you find that you need to speed up the blower, required horsepower can be extremely high.
If you speed up the blower Rpm, flow will increase in proportion to Rpm, pressure to the square of Rpm, and drive power to the cube of Rpm increase. So a bit more speed can have quite a dramatic effect on pressure and horsepower.
In my case I removed the original 1Hp motor and fitted a 10Hp motor with a 2:1 pulley drive to double Rpm. I can now easily reach 60" pressure and get double the original rated 350 CFM.
Until you actually have your blower and can test it, it is really difficult to know exactly what you have. The machinery yard may allow you to test several on an exchange basis before deciding. Something with an inlet flow "eye" diameter of three to four inches might be fairly typical. Because these blowers are so sensitive to horsepower, the original motor rating is an excellent way to judge flow capacity.
- 84-1074663779
by 84-1074663779 » Thu Nov 04, 2004 7:30 pm
Power required will depend on flow and blower size, as well as developed pressure, so it is not possible to give a figure.
Your best bet is to tour a few secondhand machinery graveyards and see what is available. I would suggest you look for something that has a 1Hp to 2Hp motor, with the largest possible diameter rotor. It will have a cast iron snail shaped housing, at least two feet in diameter, and the housing will be quite thin, only perhaps four inches. It will have the proportions of a biscuit !
Developed pressure will be proportional to the square of tip speed, so the largest diameter rotor you can find will be the one to get. As an example an eighteen inch rotor in a two foot scroll running at 2850 Rpm should give around 15" water pressure. A two foot rotor in a two and a half foot scroll at the same Rpm about 27" water.
The motor will have a rating plate, and the horsepower will give you some clue as to flow capability. The inlet and outlet flow areas will also be a clue as to flow capability. Do not go too big in flow ares! If you do, and you find that you need to speed up the blower, required horsepower can be extremely high.
If you speed up the blower Rpm, flow will increase in proportion to Rpm, pressure to the square of Rpm, and drive power to the cube of Rpm increase. So a bit more speed can have quite a dramatic effect on pressure and horsepower.
In my case I removed the original 1Hp motor and fitted a 10Hp motor with a 2:1 pulley drive to double Rpm. I can now easily reach 60" pressure and get double the original rated 350 CFM.
Until you actually have your blower and can test it, it is really difficult to know exactly what you have. The machinery yard may allow you to test several on an exchange basis before deciding. Something with an inlet flow "eye" diameter of three to four inches might be fairly typical. Because these blowers are so sensitive to horsepower, the original motor rating is an excellent way to judge flow capacity.
Your best bet is to tour a few secondhand machinery graveyards and see what is available. I would suggest you look for something that has a 1Hp to 2Hp motor, with the largest possible diameter rotor. It will have a cast iron snail shaped housing, at least two feet in diameter, and the housing will be quite thin, only perhaps four inches. It will have the proportions of a biscuit !
Developed pressure will be proportional to the square of tip speed, so the largest diameter rotor you can find will be the one to get. As an example an eighteen inch rotor in a two foot scroll running at 2850 Rpm should give around 15" water pressure. A two foot rotor in a two and a half foot scroll at the same Rpm about 27" water.
The motor will have a rating plate, and the horsepower will give you some clue as to flow capability. The inlet and outlet flow areas will also be a clue as to flow capability. Do not go too big in flow ares! If you do, and you find that you need to speed up the blower, required horsepower can be extremely high.
If you speed up the blower Rpm, flow will increase in proportion to Rpm, pressure to the square of Rpm, and drive power to the cube of Rpm increase. So a bit more speed can have quite a dramatic effect on pressure and horsepower.
In my case I removed the original 1Hp motor and fitted a 10Hp motor with a 2:1 pulley drive to double Rpm. I can now easily reach 60" pressure and get double the original rated 350 CFM.
Until you actually have your blower and can test it, it is really difficult to know exactly what you have. The machinery yard may allow you to test several on an exchange basis before deciding. Something with an inlet flow "eye" diameter of three to four inches might be fairly typical. Because these blowers are so sensitive to horsepower, the original motor rating is an excellent way to judge flow capacity.
- 84-1074663779
by Rik (the Netherlands) » Wed Nov 10, 2004 4:55 pm
Hi Folks,
i am searching for more info about building my own flowbench.
I think i am going to build a bench like the one on the site:
But i only have doubts about the vacuum engine. I have one or two old vacuumcleaner motors about 1200 Watts at 220 volts. Is it enough to use such a motor? or do i have to use at least two of them ? or am i going to find some other stuff?
Thanks for helping me, and when you have another site or constructionplans of a better bench , that would be very helpfull.
Greetz Rik
i am searching for more info about building my own flowbench.
I think i am going to build a bench like the one on the site:
But i only have doubts about the vacuum engine. I have one or two old vacuumcleaner motors about 1200 Watts at 220 volts. Is it enough to use such a motor? or do i have to use at least two of them ? or am i going to find some other stuff?
Thanks for helping me, and when you have another site or constructionplans of a better bench , that would be very helpfull.
Greetz Rik
- Rik (the Netherlands)
- Posts: 5
- Joined: Mon Nov 15, 2004 2:01 pm
- Location: nl
by 84-1074663779 » Thu Nov 11, 2004 6:17 pm
gaz, SBC = Small Block Chevy
The proportions of that rotor look all wrong, it is far too small in diameter and far too wide. It would be much more suitable as a building ventilation fan where high CFM and very low pressure is required. If you wanted 1200 CFM at maybe five inches of water, it would probably be ideal. Despite its sad appearance a coat of paint would do wonders for it.
There are treasures out there to be found, but rotor width needs to be only about a half inch to give you all the flow you need, provided tip speed is high enough.
The rotor needs the proportions of a biscuit, large diameter and extremely thin.
The proportions of that rotor look all wrong, it is far too small in diameter and far too wide. It would be much more suitable as a building ventilation fan where high CFM and very low pressure is required. If you wanted 1200 CFM at maybe five inches of water, it would probably be ideal. Despite its sad appearance a coat of paint would do wonders for it.
There are treasures out there to be found, but rotor width needs to be only about a half inch to give you all the flow you need, provided tip speed is high enough.
The rotor needs the proportions of a biscuit, large diameter and extremely thin.
- 84-1074663779
by gaz » Fri Nov 12, 2004 4:43 am
thanks Tony, so you think this ventilator woulldn't pull the 28" pressure even if I gave it very high rpm 6000-7000? could you also give me your rotors dimensions just for an example: ID, OD, and wideness? and how much empty room there is between thr rotor and outer casing? my fan had like 3 inches, I wonder why.
- gaz
- Posts: 21
- Joined: Thu Oct 28, 2004 6:41 pm
- Location: Estonia
by 84-1074663779 » Fri Nov 12, 2004 3:52 pm
It would probably pull the pressure o/k, but that rotor looks fairly heavy, it might fly to pieces. The horsepower to turn it might be rather high as well.
What horsepower and Rpm is the existing motor ? it looks quite large in the picture. Going from 2800 Rpm to 7000 Rpm is a speed increase of 2.5 times. cubed that comes out to 15.625 times the existing drive horsepower required.
Flow could possibly end up well over 3,000 Cfm at a guess, but it might require 20 to 30 Bhp to drive it sufficiently fast to reach your required pressure. If you already have the blower, try it and see. Plot flow versus pressure and motor amps and see what you have. It would then be fairly easy to estimate flow, pressure, and horsepower at increased Rpm.
If it was me, I would clean it up and make it more presentable, and then try to do a deal at a secondhand machinery broker, try to swap it for something with more pressure and less flow.
The blower rotor I am using has a very heavy cast steel hub with a four inch air inlet eye on one side. The rotor itself is fully enclosed, in other words there are two thin steel disks front and rear completely enclosing the internal vanes. These two discs taper inwards towards the outside edge. The rotor itself is eighteen inches diameter, and only half an inch wide at the outer edge. The internal vanes themselves are very short, only a couple of inches long, located radially around the outside edge. Most of the internal volume of the rotor is empty space tapering towards the outside with a row of very short vanes around the edge. I have read that high pressure blowers are usually made this way.
This rotor spins inside a cast iron scroll that is cast in two halves. There is at least half an inch clearance between the rotor and casing everywhere. The rotating inlet eye of the rotor projects out through the cast iron housing, and there is a lip seal to completely seal off the suction side of the rotor. Because the rotor itself is fully enclosed there can be no internal leakage. The entire blower casing is pressurised at discharge pressure.
The clever thing about the rotor is that the hub is deliberately made very heavy, and the side plates and vanes very light gauge steel, so it has very good natural balance and low inertia for its size. The tapered side plates also make it extremely rigid. It runs perfectly smoothly at 6,000Rpm without any noticeable vibration or resonances.
What horsepower and Rpm is the existing motor ? it looks quite large in the picture. Going from 2800 Rpm to 7000 Rpm is a speed increase of 2.5 times. cubed that comes out to 15.625 times the existing drive horsepower required.
Flow could possibly end up well over 3,000 Cfm at a guess, but it might require 20 to 30 Bhp to drive it sufficiently fast to reach your required pressure. If you already have the blower, try it and see. Plot flow versus pressure and motor amps and see what you have. It would then be fairly easy to estimate flow, pressure, and horsepower at increased Rpm.
If it was me, I would clean it up and make it more presentable, and then try to do a deal at a secondhand machinery broker, try to swap it for something with more pressure and less flow.
The blower rotor I am using has a very heavy cast steel hub with a four inch air inlet eye on one side. The rotor itself is fully enclosed, in other words there are two thin steel disks front and rear completely enclosing the internal vanes. These two discs taper inwards towards the outside edge. The rotor itself is eighteen inches diameter, and only half an inch wide at the outer edge. The internal vanes themselves are very short, only a couple of inches long, located radially around the outside edge. Most of the internal volume of the rotor is empty space tapering towards the outside with a row of very short vanes around the edge. I have read that high pressure blowers are usually made this way.
This rotor spins inside a cast iron scroll that is cast in two halves. There is at least half an inch clearance between the rotor and casing everywhere. The rotating inlet eye of the rotor projects out through the cast iron housing, and there is a lip seal to completely seal off the suction side of the rotor. Because the rotor itself is fully enclosed there can be no internal leakage. The entire blower casing is pressurised at discharge pressure.
The clever thing about the rotor is that the hub is deliberately made very heavy, and the side plates and vanes very light gauge steel, so it has very good natural balance and low inertia for its size. The tapered side plates also make it extremely rigid. It runs perfectly smoothly at 6,000Rpm without any noticeable vibration or resonances.
- 84-1074663779
by gaz » Sat Nov 13, 2004 10:07 am
Thank you Tony for the long description. Unfortunately I can't tell you the hp of my motor because the metal plate has been removed from it. Nor can I tell you the CFM the ventilator deliveres.
Where are your type of ventilators used anyway? In which field of industry should I be looking for it?
I put some pictures from another rotor on . Would the necessary rotor look something like that?
Thanks in advance
Where are your type of ventilators used anyway? In which field of industry should I be looking for it?
I put some pictures from another rotor on . Would the necessary rotor look something like that?
Thanks in advance
- gaz
- Posts: 21
- Joined: Thu Oct 28, 2004 6:41 pm
- Location: Estonia
by Mouse » Sat Nov 13, 2004 3:54 pm
Tony,
How would one of those carpet drying blowers work. You can rent them to pump air under a wet carpet to dry them out.
One on the Home Depot (shop vacs) web site advertises 2500cfm.
Do you think I could get perhaps 350 cfm @ 28" from that?
John
How would one of those carpet drying blowers work. You can rent them to pump air under a wet carpet to dry them out.
One on the Home Depot (shop vacs) web site advertises 2500cfm.
Do you think I could get perhaps 350 cfm @ 28" from that?
John
- Mouse
- Posts: 308
- Joined: Wed Jan 21, 2004 8:45 pm
by 84-1074663779 » Sat Nov 13, 2004 6:20 pm
Mouse, I am not familiar with that type of blower, but I would imagine anything that could generate 28" or 1Psi, (144 Lbs/sq Foot) would rip a carpet right off the floor.
These are more the sort of blowers you might be able to find secondhand.
Note from the pictures, that they are all very large diameter, and have very thin narrow rotor housings, and relatively small intake and exhaust flow areas. Those are the sort of physical proportions to look for. Get the largest diameter you can find ! That will get you high pressure capability.
Click on "Air Handling Centrifugal "(top right)
Then click on "Pressure Blowers"
Note the high horsepower requirements for high pressures and flows.
.
These are more the sort of blowers you might be able to find secondhand.
Note from the pictures, that they are all very large diameter, and have very thin narrow rotor housings, and relatively small intake and exhaust flow areas. Those are the sort of physical proportions to look for. Get the largest diameter you can find ! That will get you high pressure capability.
Click on "Air Handling Centrifugal "(top right)
Then click on "Pressure Blowers"
Note the high horsepower requirements for high pressures and flows.
.
- 84-1074663779
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