My range hood has a horizontal flap in it that is shut when the fan is not going, and opens upwards when the fan starts. The flap is of course to stop the wind coming in when the fan is not in use.

I've just made another range hood for a very confined space. Nobody makes one small enough, and I don't even want to discuss that.
But I can't make a flap valve that opens and shuts properly.
I have a 100mm ID pipe that goes from the range hood to outside, and I have cut a long rectangular hole in it and have a hinged curved flap inside. But a 40 watt fan won't open an aluminium flap. I've just made a very lightweight plastic flap, and that gets hingebound. There's just too much friction..
Perhaps I could have a circular flap inside the pipe, but unless it's much smaller than 100mm it will foul on the pipe when it opens.
Any other ideas?

"Matty F" wrote in message
...
My range hood has a horizontal flap in it that is shut when the fan is not
going, and opens upwards when the fan starts. The flap is of course to stop
the wind coming in when the fan is not in use.

I've just made another range hood for a very confined space. Nobody makes
one small enough, and I don't even want to discuss that.
But I can't make a flap valve that opens and shuts properly.
I have a 100mm ID pipe that goes from the range hood to outside, and I have
cut a long rectangular hole in it and have a hinged curved flap inside. But
a 40 watt fan won't open an aluminium flap. I've just made a very
lightweight plastic flap, and that gets hingebound. There's just too much
friction.
Perhaps I could have a circular flap inside the pipe, but unless it's much
smaller than 100mm it will foul on the pipe when it opens.
Any other ideas?


A lot of hoods don't have a flap valve. They get gummed up with deposits
anyway.
They rely on the fan and filter to limit back draughts.

On Saturday, August 17, 2013 6:57:09 PM UTC+12, harry wrote:
"Matty F" wrote in message

...

My range hood has a horizontal flap in it that is shut when the fan is not

going, and opens upwards when the fan starts. The flap is of course to stop

the wind coming in when the fan is not in use.



I've just made another range hood for a very confined space. Nobody makes

one small enough, and I don't even want to discuss that.

But I can't make a flap valve that opens and shuts properly.

I have a 100mm ID pipe that goes from the range hood to outside, and I have

cut a long rectangular hole in it and have a hinged curved flap inside. But

a 40 watt fan won't open an aluminium flap. I've just made a very

lightweight plastic flap, and that gets hingebound. There's just too much

friction.

Perhaps I could have a circular flap inside the pipe, but unless it's much

smaller than 100mm it will foul on the pipe when it opens.

Any other ideas?





A lot of hoods don't have a flap valve. They get gummed up with deposits

anyway.

They rely on the fan and filter to limit back draughts.

Well my existing range hood has a perfectly good flap valve, so I know it's possible. I have seen a horrible fan mounted in a window that has a manually operated shutter. It's horrible and I don't want that.

On 17/08/2013 06:03, Matty F wrote:
My range hood has a horizontal flap in it that is shut when the fan is not going, and opens upwards when the fan starts. The flap is of course to stop the wind coming in when the fan is not in use.

I've just made another range hood for a very confined space. Nobody makes one small enough, and I don't even want to discuss that.
But I can't make a flap valve that opens and shuts properly.
I have a 100mm ID pipe that goes from the range hood to outside, and I have cut a long rectangular hole in it and have a hinged curved flap inside. But a 40 watt fan won't open an aluminium flap. I've just made a very lightweight plastic flap, and that gets hingebound. There's just too much friction.
Perhaps I could have a circular flap inside the pipe, but unless it's much smaller than 100mm it will foul on the pipe when it opens.
Any other ideas?


You need to weight one side of the flap so it only just closes under
gravity and then the fan will open it.
Well it will until the grease and stuff sticks to it.

You could fit the spring return mechanism off a zone valve if you have
one lying about. Powered opening, spring closing.

On Saturday, August 17, 2013 7:26:14 PM UTC+12, dennis@home wrote:
On 17/08/2013 06:03, Matty F wrote:

My range hood has a horizontal flap in it that is shut when the fan is not going, and opens upwards when the fan starts. The flap is of course to stop the wind coming in when the fan is not in use.



I've just made another range hood for a very confined space. Nobody makes one small enough, and I don't even want to discuss that.

But I can't make a flap valve that opens and shuts properly.

I have a 100mm ID pipe that goes from the range hood to outside, and I have cut a long rectangular hole in it and have a hinged curved flap inside.. But a 40 watt fan won't open an aluminium flap. I've just made a very lightweight plastic flap, and that gets hingebound. There's just too much friction.

Perhaps I could have a circular flap inside the pipe, but unless it's much smaller than 100mm it will foul on the pipe when it opens.

Any other ideas?





You need to weight one side of the flap so it only just closes under

gravity and then the fan will open it.

You'd think so, but that doesn't work. It is impossible to make the curved flap fit the pipe completely, so air goes through the gaps and the flap doesn't open.


Well it will until the grease and stuff sticks to it.



You could fit the spring return mechanism off a zone valve if you have

one lying about. Powered opening, spring closing.

The air pressure will not open against a spring.
I need some fresh ideas.

On Saturday, August 17, 2013 8:24:47 PM UTC+12, Biggles wrote:

Any reason why you can't fit a vent with a flap on the outside?

There is a 100mm ID pipe going outside and it has a downward bend in it and an insect screen. I don't see where I could fit a flap unless it is inside the pipe, in which case a round flap will touch the pipe when it opens unless the flap is way less than 90mm and rests against an 80mm flange. That's making the pipe a bit small to carry the air out.
My existing range hood has a flap inside that lifts up perfectly and goes to the same kind of 100mm pipe.

"Matty F" wrote in message
...

My range hood has a horizontal flap in it that is shut when the fan is not
going, and opens upwards when the fan starts. The flap is of course to stop
the wind coming in when the fan is not in use.

I've just made another range hood for a very confined space. Nobody makes
one small enough, and I don't even want to discuss that.
But I can't make a flap valve that opens and shuts properly.
I have a 100mm ID pipe that goes from the range hood to outside, and I have
cut a long rectangular hole in it and have a hinged curved flap inside. But
a 40 watt fan won't open an aluminium flap. I've just made a very
lightweight plastic flap, and that gets hingebound. There's just too much
friction.
Perhaps I could have a circular flap inside the pipe, but unless it's much
smaller than 100mm it will foul on the pipe when it opens.
Any other ideas?

Maybe
http://www.bes.co.uk/products/180.asp#11382
or
http://www.fantronix.com/acatalog/Pl...t_Shutter.html
?

On Saturday, August 17, 2013 11:07:04 PM UTC+12, Richard wrote:
"Matty F" wrote in message

...



My range hood has a horizontal flap in it that is shut when the fan is not

going, and opens upwards when the fan starts. The flap is of course to stop

the wind coming in when the fan is not in use.



I've just made another range hood for a very confined space. Nobody makes

one small enough, and I don't even want to discuss that.

But I can't make a flap valve that opens and shuts properly.

I have a 100mm ID pipe that goes from the range hood to outside, and I have

cut a long rectangular hole in it and have a hinged curved flap inside. But

a 40 watt fan won't open an aluminium flap. I've just made a very

lightweight plastic flap, and that gets hingebound. There's just too much

friction.

Perhaps I could have a circular flap inside the pipe, but unless it's much

smaller than 100mm it will foul on the pipe when it opens.

Any other ideas?



Maybe

http://www.bes.co.uk/products/180.asp#11382

or

http://www.fantronix.com/acatalog/Pl...t_Shutter.html

Yes the last one might do. I had not thought of hinging it in the middle.

On 17/08/2013 11:10, Matty F wrote:

You could fit the spring return mechanism off a zone valve if you have

one lying about. Powered opening, spring closing.

The air pressure will not open against a spring.
I need some fresh ideas.


I think you misunderstand..
the power opens the flap using the motor in the zone valve mechanism,
the spring closes it when the power is removed.
You just connect the motor in parallel with the fan.

On 17/08/2013 06:03, Matty F wrote:
My range hood has a horizontal flap in it that is shut when the fan
is not going, and opens upwards when the fan starts. The flap is of
course to stop the wind coming in when the fan is not in use.

I've just made another range hood for a very confined space. Nobody
makes one small enough, and I don't even want to discuss that. But I
can't make a flap valve that opens and shuts properly. I have a 100mm
ID pipe that goes from the range hood to outside, and I have cut a
long rectangular hole in it and have a hinged curved flap inside. But
a 40 watt fan won't open an aluminium flap. I've just made a very
lightweight plastic flap, and that gets hingebound. There's just too
much friction. Perhaps I could have a circular flap inside the pipe,
but unless it's much smaller than 100mm it will foul on the pipe when
it opens. Any other ideas?

Could you not use a flap vent on the exit?

Like:

http://www.screwfix.com/search.do?fh...h_view_size=20




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 17/08/2013 11:19, Matty F wrote:
On Saturday, August 17, 2013 8:24:47 PM UTC+12, Biggles wrote:

Any reason why you can't fit a vent with a flap on the outside?

There is a 100mm ID pipe going outside and it has a downward bend in
it and an insect screen. I don't see where I could fit a flap unless
it is inside the pipe, in which case a round flap will touch the pipe
when it opens unless the flap is way less than 90mm and rests against
an 80mm flange. That's making the pipe a bit small to carry the air
out. My existing range hood has a flap inside that lifts up perfectly
and goes to the same kind of 100mm pipe.

How about an inline backdraft shutter:

http://www.tlc-direct.co.uk/Products/BG4BS.html




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sunday, August 18, 2013 12:04:51 AM UTC+12, John Rumm wrote:
On 17/08/2013 11:19, Matty F wrote:

On Saturday, August 17, 2013 8:24:47 PM UTC+12, Biggles wrote:



Any reason why you can't fit a vent with a flap on the outside?



There is a 100mm ID pipe going outside and it has a downward bend in

it and an insect screen. I don't see where I could fit a flap unless

it is inside the pipe, in which case a round flap will touch the pipe

when it opens unless the flap is way less than 90mm and rests against

an 80mm flange. That's making the pipe a bit small to carry the air

out. My existing range hood has a flap inside that lifts up perfectly

and goes to the same kind of 100mm pipe.



How about an inline backdraft shutter:



http://www.tlc-direct.co.uk/Products/BG4BS.html

Yes, now I know what to call it I see lots for sale!

On 17/08/2013 12:38, Matty F wrote:
On Saturday, August 17, 2013 11:07:04 PM UTC+12, Richard wrote:
"Matty F" wrote in message

...



My range hood has a horizontal flap in it that is shut when the fan is not

going, and opens upwards when the fan starts. The flap is of course to stop

the wind coming in when the fan is not in use.



I've just made another range hood for a very confined space. Nobody makes

one small enough, and I don't even want to discuss that.

But I can't make a flap valve that opens and shuts properly.

I have a 100mm ID pipe that goes from the range hood to outside, and I have

cut a long rectangular hole in it and have a hinged curved flap inside. But

a 40 watt fan won't open an aluminium flap. I've just made a very

lightweight plastic flap, and that gets hingebound. There's just too much

friction.

Perhaps I could have a circular flap inside the pipe, but unless it's much

smaller than 100mm it will foul on the pipe when it opens.

Any other ideas?



Maybe

http://www.bes.co.uk/products/180.asp#11382

or

http://www.fantronix.com/acatalog/Pl...t_Shutter.html

Yes the last one might do. I had not thought of hinging it in the middle.

Its a variation on this theme:

http://wiki.diyfaq.org.uk/index.php?...dproof_Catflap

slight variation in the areas of each side meaning it blows open from
one side and shut from the other, but is nearly balanced.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 17/08/2013 11:19, Matty F wrote:
On Saturday, August 17, 2013 8:24:47 PM UTC+12, Biggles wrote:

Any reason why you can't fit a vent with a flap on the outside?

There is a 100mm ID pipe going outside and it has a downward bend in it and an insect screen. I don't see where I could fit a flap unless it is inside the pipe, in which case a round flap will touch the pipe when it opens unless the flap is way less than 90mm and rests against an 80mm flange. That's making the pipe a bit small to carry the air out.

You can fit a butterfly back draught preventer inside a circular pipe.
The flaps can be sprung or, if the hinges are slightly inclined along
the pipe, they will close under gravity.

http://www.youtube.com/watch?v=AD2uGZYdg54

Colin Bignell

"Matty F" wrote in message
...
My range hood has a horizontal flap in it that is shut when the fan is not
going, and opens upwards when the fan starts. The flap is of course to stop
the wind coming in when the fan is not in use.

I've just made another range hood for a very confined space. Nobody makes
one small enough, and I don't even want to discuss that.
But I can't make a flap valve that opens and shuts properly.
I have a 100mm ID pipe that goes from the range hood to outside, and I have
cut a long rectangular hole in it and have a hinged curved flap inside. But
a 40 watt fan won't open an aluminium flap. I've just made a very
lightweight plastic flap, and that gets hingebound. There's just too much
friction.
Perhaps I could have a circular flap inside the pipe, but unless it's much
smaller than 100mm it will foul on the pipe when it opens.
Any other ideas?

Is the hood in position? If so you have to let air into the room to replace
what's sucked out. If not there will be no air flow through your hood.

On Sunday, August 18, 2013 12:02:10 AM UTC+12, John Rumm wrote:

Could you not use a flap vent on the exit?



Like:



http://www.screwfix.com/search.do?fh...h_view_size=20

OK, I've installed a flap vent with a single flap and it works perfectly.
But the wind causes it to bang shut every few seconds, and that makes an annoying noise. I have put some foam for it to bang against and it's quieter but not quiet enough. It needs some kind of damper, but not one that stops it opening when the fan is going.

On 26/08/2013 09:31, Matty F wrote:
On Sunday, August 18, 2013 12:02:10 AM UTC+12, John Rumm wrote:

Could you not use a flap vent on the exit?



Like:



http://www.screwfix.com/search.do?fh...h_view_size=20


OK, I've installed a flap vent with a single flap and it works
perfectly. But the wind causes it to bang shut every few seconds, and
that makes an annoying noise. I have put some foam for it to bang
against and it's quieter but not quiet enough. It needs some kind of
damper, but not one that stops it opening when the fan is going.



Put a cowl over the end to stop the wind blowing into the pipe.

Use the motor driven valve I suggested earlier.

On Tuesday, August 27, 2013 12:39:18 AM UTC+12, dennis@home wrote:
On 26/08/2013 09:31, Matty F wrote:

On Sunday, August 18, 2013 12:02:10 AM UTC+12, John Rumm wrote:



Could you not use a flap vent on the exit?







Like:







http://www.screwfix.com/search.do?fh...h_view_size=20





OK, I've installed a flap vent with a single flap and it works

perfectly. But the wind causes it to bang shut every few seconds, and

that makes an annoying noise. I have put some foam for it to bang

against and it's quieter but not quiet enough. It needs some kind of

damper, but not one that stops it opening when the fan is going.







Put a cowl over the end to stop the wind blowing into the pipe.



Use the motor driven valve I suggested earlier.

There is a cowl over the end. I'll think of something.

On Mon, 26 Aug 2013 01:31:41 -0700 (PDT), Matty F wrote:

OK, I've installed a flap vent with a single flap and it works
perfectly. But the wind causes it to bang shut every few seconds, and
that makes an annoying noise. I have put some foam for it to bang
against and it's quieter but not quiet enough. It needs some kind of
damper, but not one that stops it opening when the fan is going.

How much shove has the fan got? Would adding a bit of weight to the
bottom of the flap stop the wind opening it but still allow the fan
to? I expect that to be an AOT exercise.

If that doesn't work I think you'll have to look at a solenoid
something to force the flap open against a weight or spring that is
strong enough to stop the wind opening it.

--
Cheers
Dave.

On Tuesday, August 27, 2013 9:33:23 AM UTC+12, Dave Liquorice wrote:
On Mon, 26 Aug 2013 01:31:41 -0700 (PDT), Matty F wrote:



OK, I've installed a flap vent with a single flap and it works

perfectly. But the wind causes it to bang shut every few seconds, and

that makes an annoying noise. I have put some foam for it to bang

against and it's quieter but not quiet enough. It needs some kind of

damper, but not one that stops it opening when the fan is going.



How much shove has the fan got? Would adding a bit of weight to the

bottom of the flap stop the wind opening it but still allow the fan

to? I expect that to be an AOT exercise.



If that doesn't work I think you'll have to look at a solenoid

something to force the flap open against a weight or spring that is

strong enough to stop the wind opening it.

I've already made two flaps that the fan can't open.
I think I put put some foam at the top of the flap by the hinge. I am sure that will work.