[L.J.Thorpe]

so why do tightly packed upright lengths of perforated pipe inside the tank not do the same thing as your diagram

[michael papworth]

(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

... 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.

[AuRavelling79]

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

[Clive McDonald]

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.

[michael papworth]

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.

[Clive McDonald]

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.

[michael papworth]

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.

[Clive McDonald]

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.

[Ian_Giles]

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

[michael papworth]

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.

[L.J.Thorpe]

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

[michael papworth]

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.

[Clive McDonald]

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.