Clean It Up
UK Window Cleaning Forum => Window Cleaning Forum => Topic started by: davetherave on June 28, 2008, 11:15:04 pm
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I've been trying to research wfp window cleaning and i've seen people going on about baffled tanks. What is the difference between a baffled tank and a unbaffled one?
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I've been trying to research wfp window cleaning and i've seen people going on about baffled tanks. What is the difference between a baffled tank and a unbaffled one?
baffled tank stops the water moving freely, unbaffled tank = water can move freely
I will draw a quick pic so you can see what I mean..
Ian
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Hope this helps a little, if you need any more info let me know and I will do my best to help.
Ian
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If you have a tank in a van it needs to be baffled otherwise you would be likely to have an accident as the water throws the van off balance. More of a problem when you are half full. A static tank doesn't need them.
Simon.
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Hope this helps a little, if you need any more info let me know and I will do my best to help.
Ian
The picture shown is not a properly baffled tank,a propery baffled tank should look more like a box completley full of honeycomb sections from top to bottom.
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Hi, I got mine fitted by purefreedom. Go for a baffled in a van for safety reasons only!!!!!! Its a must. £50 more or a life in a wheel chair if a un baffled tank chucks your van of the road.
Mart
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Hope this helps a little, if you need any more info let me know and I will do my best to help.
Ian
The picture shown is not a properly baffled tank,a propery baffled tank should look more like a box completley full of honeycomb sections from top to bottom.
It was a quick pic NWH, and the second tank is baffled it stops the force of the water ::) you can get a lot better baffled taNKS i KNOW BUT i DID THIS SO THE GUY COULD UNDERSTAND DONT CONFUSE HIM.
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The baffles in the tank are there to prevent the water from rushing from one part of the tank to the other under cornering or braking/acceleration forces.
The diagram isn't wonderful. It only mentions cornering forces. The same is true for braking and acceleration forces. In a real tank, the baffles go both lengthways and sideways. NWH's description of the internals is perfect.
The red dot is roughly where the centre of gravity would be. You'll notice that in the unbaffled tank, it's considerably shifted whereas for the baffled tank it hardly moves at all.
(http://www.wally-the-window-washer.co.uk/tanks.gif)
The problem is that the centre of gravity moves around. If you remember your high school physics, the centre of gravity always wants to move in a straight line. This is Newton's first law. When the centre of gravity keeps on moving, the whole vehicle has to wobble in order for the centre of gravity to continue in the same line!
It might seem like quite a small effect, but as the water sloshes about, it can set up very dangerous wobbles very quickly. If you are driving close to the edge (for example, if you have to swerve violently to miss a child running into the road), this sloshing can send you over the edge without any warning.
Of course, even under normal gentle driving, you are constantly changing speed and direction. If you had an unbaffled tank the C of G would be moving forwards and backwards as well as side to side. The effect would be to change the speed of the vehicle as well as make it wobble from side to side.
Here's a similar situation that you will easily understand - imagine carrying a tray with lots of pint glasses each filled nearly to the brim with your favourite beer. You could probably balance it on one hand like a waiter in a fancy restaurant and walk round with it. Now imagine trying to do the same if you had a washing up bowl full of beer. You couldn't carry it without spilling lots of the precious stuff.
The physics is the same.
You will easily understand that all liquid-carrying tankers have the same problems. What may not be so obvious is that bulk powder carriers also have similar problems as powders can behave very much like liquids under certain conditions. Also trucks carrying meat carcasses have to be driven very carefully as the carcasses can swing from side to side as well as back and forth and cause a very similar rocking effect - although not as pronounced.
Yeah! Physics is FUN!
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
P.S. You'll notice that there are small gaps at the bottom of the baffles. They are
large enough to allow the sections to all drain properly as the tank slowly empties, but small enough so the liquid cannot rush from one section to another quickly.
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cheers guys, i understand now. ;)
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This forum is so helpful to people i wouldnt no half of what i know without it,
Chris
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Hope this helps a little, if you need any more info let me know and I will do my best to help.
Ian
The picture shown is not a properly baffled tank,a propery baffled tank should look more like a box completley full of honeycomb sections from top to bottom.
It was a quick pic NWH, and the second tank is baffled it stops the force of the water ::) you can get a lot better baffled taNKS i KNOW BUT i DID THIS SO THE GUY COULD UNDERSTAND DONT CONFUSE HIM.
Your tank has no impact on stopping the force of water moving forward Ian at all,in those tanks the water sloshes about like a joke.Do an emergency stop with your tank and when you eventually come to a stop you`ll think your in a boat,i should know i`ve both type of tanks and would never ever have that tank again.
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anyone tried the diy land drain pipe method of baffling a tank ???
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anyone tried the diy land drain pipe method of baffling a tank ???
That`s 1 of the best ways to baffel a tank if not the best,but you try securing the pipeing after the tanks been made it`s near on impossible,this process has to be done prior to welding the tank.Omnipole use this method and the same method has been applied when making my tank the run of the mill tanks that you buy are not correctly baffeld and are not designed to hold water during transit this bloke Neil will explain all to you over the phone,it`s a real eyeopener www.plasticwatertanks.co.uk
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anyone tried the diy land drain pipe method of baffling a tank ???
Can you explain the method?
Just found this picture on the website NWH mentioned. It shows the internal baffles put in place prior to welding the top of the tank in place.
(http://www.plasticwatertanks.co.uk/sei/s/1538/118.jpg)
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i will be using an ibc ;D ......dont all start cos i dont care
wally you cut lengths of land drain pipe (semirigid with small holes along length)
insert into tank and keep going until tank is packed tight ;)
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wally that was nwh who put website up
iam talking ibc
NOT custom tanks ;D
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Hey, L.J. I really don't want to rain on your parade, but the phrase that comes into my mind is:
"It seems like a really good idea if you don't think about it too much."
Look, you can't possibly calculate the results of doing something like this. There are just too many variables.
All you can do is what Einstein called a gedanken experiment. That's just a fancy way of saying thinking it through carefully taking as much into account as possible.
Imagine carrying a washing up bowl full of water down to the bottom of the garden to water the lettuce. Yes, you're going to be sloshing water all over the place - and that's like an unbaffled tank.
Now, imagine that someone has a great idea and cuts up lengths of 2" water pipe and sticks them in the washing up bowl saying they'll act like baffles and make sure you don't spill any water. That's like your land drain pipe idea.
Run a mental video of what might happen. You'll probably notice that there isn't actually very much difference between the two scenarios.
There's still a continuous free water surface that flows around the pipes - and it's this surface that will cause the problems. You see, baffles work by breaking up a large water surface into smaller surfaces. Do a search of the free surface effect and you'll find out all about it.
That's my analysis - and it's no more than a mental video that I've run. Yours might be quite different.
Personally, I wouldn't do it.
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fair comment :)
BUT i did ask if anyone had actually tried it ;D
no offence
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just to add that you seem to have missed the point of how pipe baffle is supposed to work :(
pipe is about 6 ins in diameter(can be up to whatever size fits through lid of tank)
lengths are cut to height of tank
upend tank and insert pipes so they fill tank......tight
lay tank flat
tank is now filled with vertical pipes
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fair comment :)
BUT i did ask if anyone had actually tried it ;D
no offence
Great. And I'm absolutley sure that there's most certainly no offence intended on either side.
As I said, I've only done it as a gedanken experiment, so I have no idea if I'm right or not.
I don't want to be smarty pants about this, but I've done a lot of this stuff in my life and I have a really good "feel" for physical sciences (as well as a degree in it).
All I'm wanting to do is to share my feelings, experience and thoughts.
I can easily imagine that someone might come up with this as "a good idea", but it isn't actually that good because they don't understand the free surface effect.
I hope we're all friends just sharing whatever we can.
And that means questions as well as answers.
And as jaykie observed - we can all learn stuff from other people's Q&As.
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so why do tightly packed upright lengths of perforated pipe inside the tank not do the same thing as your diagram ???
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(i) you seem to have missed the point of how pipe baffle is supposed to work
(ii) so why do tightly packed upright lengths of perforated pipe inside the tank not do the same thing as your diagram ???
I haven't missed the point of how the pipe baffle is supposed to work. I've understood it perfectly well. And I've given it some pretty deep thought.
It's the tightness of the packing that concerns me. If
(i) they are packed perfectly tightly so there is no extended free surface at all
and
(ii) the pipes are positioned so the bottom of the pipes is in very close contact with the bottom of the tank,
it will work perfectly.
If these two conditions are not met, they will drastically reduce the effectiveness of the baffling.
The greater effect will probably be due to the free surface. For a brief discussion of the free surface effect see: en.wikipedia.org/wiki/Free_surface_effect (http://en.wikipedia.org/wiki/Free_surface_effect)
... and it's the effectiveness that I wonder about. It WILL work to some extent, sure, no question about it. It's the extent that's the question. Will it be 99% as good as a properly baffled tank or 0.2% as good? As I said earlier, too many variables to make a hard and fast prediction.
I think we need Alan Wilson to come in on this one. He's the engineer and probably very much more on top of this type of question. I'd love to hear his opinion.
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Wally .... in your washing up bowl analogy you would need to put a lid on the bowl for it to be a scaled down version of a water tank.
50mm diameter pipes in a biscuit tin with a lid fastened on is a closer analogy.
IMO
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You clot, if he'd wanted a biscuit tin in his gendanken he would have had one.Einstein very often used imagined railway carriages to explain relativity.The idea is that you pick the vehicle to get the result and biscuit tins wouldn't work. (not enough slosh).Surely this sloshing would only apply to any very small volume of water not covered by the baffles.
I use a torsion bar from the tank rear secured against the roof, because this seems a better engineering solution.
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I fear a certain amount of castigation, but I have to say that there's a touching faith in some of these posts.
"Well, if it looks like a baffle, it's a baffle, innit? Anyway. What do these professional tank-makers and science graduates know anyway? It's all theory to them, innit? Yeah. What do they know? Yeah, don't know what the real world's like, do they? All ivory towers and tweed jackets."
"Yeah. I reckon I could do a better job wif an IBC and a load of land drain. Stands to reason, dunnit? Free surface? Cor. What do they know anyway?"
"Yeah. Pack it tight enough and it'll work. I knew a guy once who made a bed frame out of scaffolding. Must've worked cos he had loads of kids."
"Yeah. It looks like a baffle, dunnit? So it's a baffle."
"Innit?"
With an unbaffled or incorrectly baffled tank, if you have to swerve and brake in a hurry, you'll roll.
Oh, for pity's sake. You cannot now claim ignorance. Buy a proper tank and do the job properly - and safely.
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Castigation?
I can see you getting the thought experiment washing up bowl over your head, and then being given a good sloshing with the biscuit tin.
Run this as a mental video and tell us how you get on.
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Yep. Works for me. I'm going to go the the next Windex
incong ingnog incnot in disguise.
Got this feeling that I might finish up with a sore head AND a length of land drain where one won't fit comfortably.
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I like the physics even if i don't fully understand it.
On the other post luke has put some really stupid shapes that are supposed to have patents. How can they help?
If what you say is true a damped sheet across the surface would be the best solution.
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Mmm...good thread...
In my van (and also in my car when I used only that) I carried my trad tools in my bucket of water.
These acted as baffles for the half filled bucket of water.
Take them out and just pulling away in the vehicle had water sloshing out of the bucket!
A washer, a sprayer, couple of squeegees and even on fairly hard breaking or cornering the water stays in the bucket.
In a WFP tank, feed in several metres of land drainage pipe so that it is curled and coiled in various different directions and you WILL have a very well baffled tank. the pipes will be fixed in position and no matter what direction the flow of force is, the water flow will be broken by the pipes and its energy dissipated.
not totally of course, but it will be dissipated.
My own tank is the standard type of baffled tank, fantastic in one direction - I've fitted mine so it is the side to side motion that is broken - but you get sea sick on front to back motion on a half tank!!!
I feel absolutely nothing on side to side, cornering and so on, even on quick changes in direction, and the baffles are exactly as shown in the first diagram!
The science being spoken may be all very accurate, but in practical terms, land drainage pipes really do work, and of course standard downpipes wedged in are also first rate...but a whole lot more expensive! those things are really pricey!
Ian
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It's OK. The knickers are no longer resembling a Moibus strip. Just off for a bit of self-flaggelation before boring No 1 son to sleep with tales of superconductivity and moments of inertia. (Poor little butter
Sp has an end of term physics test in a couple of days!)
I love this physics stuff. Sorry!!!
Can't see a scientific error without losing my grip on what really matters and flying off into realms of quantum mechanics and multiverses. Richard Feynman has a LOT to answer for. Quantum magnetohydrodynamics indeed!!!
And don't get me started on Hawking.
I really wanted to be ....
Oh, sod it.
Goodnight, world.
PS "moments of inertia" - that was a physics joke.
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I fear a certain amount of castigation, but I have to say that there's a touching faith in some of these posts.
"Well, if it looks like a baffle, it's a baffle, innit? Anyway. What do these professional tank-makers and science graduates know anyway? It's all theory to them, innit? Yeah. What do they know? Yeah, don't know what the real world's like, do they? All ivory towers and tweed jackets."
"Yeah. I reckon I could do a better job wif an IBC and a load of land drain. Stands to reason, dunnit? Free surface? Cor. What do they know anyway?"
"Yeah. Pack it tight enough and it'll work. I knew a guy once who made a bed frame out of scaffolding. Must've worked cos he had loads of kids."
"Yeah. It looks like a baffle, dunnit? So it's a baffle."
"Innit?"
With an unbaffled or incorrectly baffled tank, if you have to swerve and brake in a hurry, you'll roll.
Oh, for pity's sake. You cannot now claim ignorance. Buy a proper tank and do the job properly - and safely.
patronising little muppet aren't you
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I fear a certain amount of castigation, but I have to say that there's a touching faith in some of these posts.
"Well, if it looks like a baffle, it's a baffle, innit? Anyway. What do these professional tank-makers and science graduates know anyway? It's all theory to them, innit? Yeah. What do they know? Yeah, don't know what the real world's like, do they? All ivory towers and tweed jackets."
"Yeah. I reckon I could do a better job wif an IBC and a load of land drain. Stands to reason, dunnit? Free surface? Cor. What do they know anyway?"
"Yeah. Pack it tight enough and it'll work. I knew a guy once who made a bed frame out of scaffolding. Must've worked cos he had loads of kids."
"Yeah. It looks like a baffle, dunnit? So it's a baffle."
"Innit?"
With an unbaffled or incorrectly baffled tank, if you have to swerve and brake in a hurry, you'll roll.
Oh, for pity's sake. You cannot now claim ignorance. Buy a proper tank and do the job properly - and safely.
patronising little muppet aren't you
Castigation - probably well-deserved, though.
I'm truly sorry if you feel offended. I hadn't intended that to happen. It was written tongue very firmly in cheek.
Having said that, if I were in your shoes, I'd feel cross as well.
But I still feel that I have to say that just because it looks like a baffle doesn't mean that it IS a baffle - and that's the whole point.
These things are carefully designed by certified and qualified engineers and then checked by other engineers. They have to do all sorts of calculations to make sure that the liquid flowing under the baffles won't go at a frequency to set up a resonance which will make everything fall apart. They are made by skilled men using correct tools and out of certified materials and then, finally, inspected by miserable, but highly skilled, old codgers like my next door neighbour.
Baffled tanks are NOT thrown together in a garage out of recycled bits gleaned from farms and factories.
And there are perfectly sound reasons for that. And I want my kids to be able to play in the street without the fear of them being crushed to death because some window cleaner decides to do a flick roll in a badly loaded van instead of doing a safe emergency stop.
I'm becoming quite cross, I'm afaid, and I don't care for being cross.
My contribution to this debate is now over.
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You can't withdraw from the debate because you didn't take part. You stated some information and your opinion.
Then Ian gave a real life counter example with his bucket, and stated from practical experience and empirical observation that land drainage pipes work as baffles.
In a debate you would have addressed this point instead of defending and justifying yourself.(irrelevant)
If you are going to be an intellectual bully at least be a good one.