I am trying to make a fan, how big should it be?

[vavavoom]

Hey Guys,

I want to create enough suction from a fan to send it through about 10 feet of bending hose pipes. How big should the fan be?

What sort of pressure of air are we talking, how many psi?

Lastly, where can I purchase those cogs, I think that's what you call them. You know the ones that you use to pull an object like something attached to a piece of string. I am looking for that cog that turns the rope along a track, I cannot find this from any searches I am doing, I think perhaps cogs are the wrong term to use, what's the correct name?

Many thanks in advance

 

[Richard C]

Hey Guys, I want to create enough suction from a fan to send it through about 10 feet of bending hose pipes. How big should the fan be?

What sort of pressure of air are we talking, how many psi?

This makes very little sense , what is it you’re trying to do?

Lastly, where can I purchase those cogs, I think that's what you call them. You know the ones that you use to pull an object like something attached to a piece of string. I am looking for that cog that turns the rope along a track, I cannot find this from any searches I am doing, I think perhaps cogs are the wrong term to use, what's the correct name?

Re the “cog that pulls an object like something attached to a piece of string” the only thing that comes to mind is a rope winch but, again, what are you trying to achieve? If you give a little more information, it may be easier to answer your questions!

 

[vavavoom]

Many thanks for the reply

I am trying to build a suction pump for my garden pond, I need to drain the water. I know I can buy a garden pond drainage pump, but for a long time now I have wanted to build this and would like to be able to drain the water very quickly. So I would need to be able to create a lot of pressure, how many psi do you think the pressure will be? How big should the fan be? What kind of electric engine would I need to buy?

About the rope, that's for another thing I am trying to build. I just need a mini cog, not really a winch. But something circular a little bigger than the size of my thumb. Which has a groove to hold a piece of string in place and then the idea is that I will have a battery turn that turns this cog which would then pull what ever is at the end of the string towards the cog. What do call this thing? I have seen it around a lot of places. Just don't know the name of it.

 

[freddiemercurystwin]

vavavoom, you are clearly completely crackers!!!!

 

[joe-90]

Funniest post in ages.

 

[ColJack]

the "cog" would either be a pulley or a capstain depending on what you want it to do..
moving a loop it would be a pulley.
moving a single string it would be a capstain but that requires olding tension on the other end of the string..
or a straight winch.. which winds the string onto a drum..

 

[dextrous]

Before we start looking at the drive mechanism, out of curiousity could you describe what size (diameter) fan you are intending to use, what type it is (an old room air fan, hairdrier, etc), what you intend to house it in, and how you intend to arrange the outlet from this to connect to the hose?

Then we can consider whether this will stand any chance of working, (the archimedean screw effect from this fan may work for air, but not water) and if it has then what speed of rotation will be required in order to produce the flowrate you require. From this we may be able to work out possible drive/cog arrangements and what may be appropriate electric motors that will supply sufficient torque and rotational speed.

A simpler solution may be to get several water pumps from a car scrap yard, or even washing machines and use them simultaneously to empty the pond within the time you desire.

 

[vavavoom]

the "cog" would either be a pulley or a capstain depending on what you want it to do..
moving a loop it would be a pulley.
moving a single string it would be a capstain but that requires olding tension on the other end of the string..
or a straight winch.. which winds the string onto a drum..

Many thanks for your reply

It's definitely not a pulley or a capstain. It's such a basic thing but I just forgotten the name. The cog thing is for a completely separate project.

Before we start looking at the drive mechanism, out of curiousity could you describe what size (diameter) fan you are intending to use, what type it is (an old room air fan, hairdrier, etc), what you intend to house it in, and how you intend to arrange the outlet from this to connect to the hose?

Then we can consider whether this will stand any chance of working, (the archimedean screw effect from this fan may work for air, but not water) and if it has then what speed of rotation will be required in order to produce the flowrate you require. From this we may be able to work out possible drive/cog arrangements and what may be appropriate electric motors that will supply sufficient torque and rotational speed.

A simpler solution may be to get several water pumps from a car scrap yard, or even washing machines and use them simultaneously to empty the pond within the time you desire.

Many thanks for your reply

I really don't know what fan diameter would be sufficient, I really don't know much about fans. Of course I know how they work, but I cannot say how much flowrate I require because I don't know. I know that a hairdryer fan would not work, I cannot see that being able to have much power from sucking water out of a pond. I think an estimate would be a fan the diameter of a bucket. I would say a petrol engine or battery. I would like it to be a portable battery which can be charged. But how long would such a thing be able to operate? It would need a lot of power to suck water from a pond which will drain the battery pretty quick?

I want to keep things very affordable

 

[wotan]

I think you are getting fans and pumps mixed up, you do not suck water from a pond with a fan, you use a pump.
There are several types of pumps, simplest being the centrifugal, this pump needs priming before it will work, it will pump but only to a limited head, (was going to explain, but it will take too long)
Another pump is the positive displacement pump, this will self prime and will pump to a considerable distance, and pressure.
Either of these pumps could be driven by an electric motor, or a petrol engine.

(Keep taking the medication)

Wotan

 

[Bodgeit and scarper ltd]

use a bucket

 

[dextrous]

Although using a fan to displace water should work (after all ships rely on it), the speed of rotation required to create enough pressure to force sufficent flow would be difficult to achieve.

Also, housing the fan in such a way that it remained sturdy would be difficult to achieve, especially as the drive mechanism is to be placed externally.

Also, the fan itself would have to be placed at the bottom of the pond, and it is highly unlikely that you would be able to get it to remove the vast majority of the water anyway.

I think to keep the cost down, to be honest your best bet will be to buy a sump pump.

 

[big-all]

fans are for air movement so the mechanism works on high speed as air is light
a fan designed for air movment would burn out in seconds if water was introduced thats if the electric motor was waterproof which it wont be

 

[freddiemercurystwin]

Why not get a leaf blower and try and blow the water out?

 

[dextrous]

Now then, I think you're all being a bit mean to the op here. Whatever happened to helping an enquiring mind? The op has an idea he/she wants to develop and is looking for help in how to bring it to fruition. Like you, I have my doubts as to whether it has any chance of working, but there's no need to be unpleasant about it.

For all we know, it could be a youngster looking for help from those more knowledgeable, and some of your harsh words aren't really helping him/her from trying out new ideas.

 

[ColJack]

how about a scrap motorbike engine..
the pistons would suck water into them and then discharge it through the "exhaust"