# The Naked Scientists Forum

### Author Topic: problem with helicoids and pressure  (Read 8586 times)

#### fgt55

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##### problem with helicoids and pressure
« on: 24/03/2012 13:54:02 »
Hi,

My son are looking for systems on internet for give energy free, I know it's impossible and until now I arrive to say where is the problem but I don't find for this one ? Can I expose the system ? It's not very complicated for explain, it's only 2 wood screws and differents pressures.

Regards

#### CliffordK

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##### Re: problem with helicoids and pressure
« Reply #1 on: 24/03/2012 14:43:15 »
Hello,
You'll have to explain a bit better what the system you are discussing, and where energy is involved.

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #2 on: 24/03/2012 16:04:20 »
Ok, thanks

The system is composed with 2 wood screws (helicoids). Each screw can only turn around its longitudinal axis (translation is not possible). Screws are put closed, the thread overlap other thread. All the system is under pressure P except one screw has around itself 3P and small volumes has pressure 2P. (Small volume=interface) Small volumes are where threads overlap. Screws turn at the same rotational speed in the same direction. All volumes are constant. I tested with 2 real wood screws, effectively screws turn, I see interface move up but like the interface is composed with 2 surfaces from threads and 2 gaskets's surfaces which are in the longitudinal axis, I see nothing lost energy.

First drawing: the principle, but green area can be very small like second drawing show. Third drawing show the volume of the interface composed with 2 parts of screw and 2 gaskets.

this for find the problem easily:

1/ Screws turn at the same speed in the same direction, so they don't move up/down, it's mechanical
2/ The interface with 2P pressure put a difference of pressure which want to turn screws in the same direction. My son see screws giving energy and me too !
3/ Interface has always the volume constant.
4/ Interface is moving in translation only in the longitudinal axis
5/ Interface is composed with 2 surfaces of helicoids and 2 surfaces of gaskets. Gaskets's surfaces are are parallel to longitudinal (or can be) so zero energy is needed for move in longitudinal axis the interface.
6/ All system can be put under P pressure like that red helicoid don't need something for retain pressure.
7/ Black helicoid is under pressure 3P, this pressure can be retain by a very thin film of pressure (with a hard material and gaskets for retain pressure). The hard material is moving when the interface is coming. Like the film can be very small, this need to take off very small pressure. The volume of the black helicoid with 3P pressure is constant because the interface is moving (need to take off and need to put 3P pressure). This need zero energy in theory for me.

Sure this system need gaskets, a lot ! and a special screw for retain 3P pressure. The film of pressure can be very thin, the side must move in real time with the moving of interfaces, difficult to do in practise but in theory this can't give more energy than received !!

I need help for explain where is the problem I don't see it :)
« Last Edit: 24/03/2012 16:35:41 by fgt55 »

#### RD

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##### Re: problem with helicoids and pressure
« Reply #3 on: 24/03/2012 16:53:17 »
A mechanism like a lever or a screw can multiply force (pressure),
but does not multiply energy. Energy cannot be created or destroyed.

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #4 on: 24/03/2012 16:57:43 »
I'm sure, you're right but I don't find where is exactly the problem can you explain ?

#### CliffordK

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##### Re: problem with helicoids and pressure
« Reply #5 on: 24/03/2012 17:02:59 »
Obviously with gaskets, you get friction.

But, that aside, in a system with a pressure differential, you tend to get movement in a direction that relieves the pressure differential.  If motion doesn't relieve the pressure differential, then it would be unlikely to turn.

So, ignoring friction, the pressure would tend to try to drive the 3P screw out of whatever is holding it.  And, it would also tend to drive the 1P screw further into it.  If it is designed so that the screws don't actually move, then the turning the screws won't actually relieve pressure, and there would be nothing to drive the movement forward.

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #6 on: 24/03/2012 17:14:01 »
Yes, I'm ignoring friction.

If the screw move with longitudinal axis, screw can only turn, the axis can block the longitudinal translation I think (with bearing). Rotation is only the liberty for screw I don't know how one screw can go to another ?

#### Geezer

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##### Re: problem with helicoids and pressure
« Reply #7 on: 24/03/2012 18:28:07 »
What you have is esentially a nut and bolt.

You can multiply the force at the expense of motion, but, because of friction, you are unlikely to multiply the motion at the expense of force.

The reason nuts do not unscrew themselves is because of friction between the nut and the bolt, although, when there is vibration, or repeated heating and cooling, a nut can creep on a bolt and lose tension.

Friction is heat energy, so if there is any friction at all (and there always is) you will get less work (mechanical energy) out than you put in.

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #8 on: 24/03/2012 18:43:49 »
Quote
What you have is esentially a nut and bolt.
Not really.

Have you read all my first message ? Have you understand all the message, if not don't hesitate to ask.

We can limit all friction but not to zero sure ! But friction can't cancel all the energy give by rotation unless you want it. Screws can't move in translation, so the interface can move up easily, gaskets and friction is only here because there is a difference of pressure.

A torque exist and rotate screws. The another thing to move is interface: 2 longitudinal surfaces, how the energy is lost ? I need an explanation for explain.

You're right friction is energy, so if screws give energy, if friction is energy where the energy is lost ? Do you think all energy give from screws are transform in heat ? Why, explain please.

Quote
is because of friction between the nut and the bolt
it's 2 wood screws like drawing show, so they can turn togeter easily.

« Last Edit: 24/03/2012 19:14:54 by fgt55 »

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #9 on: 25/03/2012 18:05:31 »
Hi,

I take time again to thinking about this problem and I don't know where friction is, if you could explain ? because when I take 2 wood screws in my hands they turn freely IF rotational speeds are the same.

For the interface, gaskets's surfaces can be hard surfaces except at junction where it's possible to use something like radial shaft seal technology for example, so the friction can be reduce I think. If not, can you explain please ?

Regards

#### Geezer

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##### Re: problem with helicoids and pressure
« Reply #10 on: 25/03/2012 18:34:26 »
Are you rotating both screws at the same time?

If you are, there never needs to be any contact between the screws so there is no force transmitted between them. If there is no force, there will be no friction.

You can get the same effect by rotating two meshed gears so that the teeth never actually make contact. Or you can put a nut on a bolt and rotate the bolt and allow the nut to rotate with the bolt.

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #11 on: 25/03/2012 19:12:30 »
Yes, I'm rotating both screws at the same time. There is always a line in contact (I used wood screw), see the drawing. One screw never block other, sure the speed must be exaclty the same. A line is not a surface but the volume of the interface is something like the yellow part in last drawing: 2 surfaces from helicoids and 2 hard surfaces which is the really the interface, these surfaces are curve but in longitudinal axis. Maybe if you have 2 wood screws this can help me to understand.

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #12 on: 25/03/2012 19:19:34 »
I add a drawing for show the real volume of interface. It's the other side of the last drawing. One screw is under P, other under 3P and interface under 2P.
« Last Edit: 25/03/2012 19:30:03 by fgt55 »

#### Geezer

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##### Re: problem with helicoids and pressure
« Reply #13 on: 25/03/2012 20:26:46 »
I really don't understand what the question is.

The two screws rotate and don't interfere with each other. A lot of things (like bearings for example) can have relative rotation without interfering each other. This isn't really any different.

Are you thinking this mechanism could be part of a pump or something?

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #14 on: 25/03/2012 21:30:24 »
Sorry. It's not a pump, all volumes are constant and pressure P, 2P, 3P never change. Red screw has around it P, black screw has around it 3P, the interface has inside 2P. Black screw see a differential pressure 3P/2P on a small part of a surface, this rotate with torque the black screw. Red screw see a differential 2P/P on a small part of a surface, this rotate (in the same direction than black screw) with torque the red screw. Interface move in longitudinal axis only but like surfaces are in longitudinal axis this don't need energy (2 surfaces of the interface is screws but screws don't move in longitudinal axis, but they turn). So if the friction for contain pressure can be small, where the energy is lost ?
« Last Edit: 25/03/2012 21:32:36 by fgt55 »

#### Geezer

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##### Re: problem with helicoids and pressure
« Reply #15 on: 25/03/2012 22:29:40 »
What you have is a type of helical gear.

http://en.wikipedia.org/wiki/Gear#Helical

However, the slope of the helix with two screws is so small that the mechanism will tend to wedge as soon as you use it to transmit torque from one screw to the other. If the screws had much steeper slopes, and you had multiple helixs on each screw, you would have two helical gears meshed, and you would be able to transmit torque.

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #16 on: 25/03/2012 22:59:35 »
It's not one screw which transmit torque to another. It's the difference of pressure which create 2 torques, one for red screw and one for black screw. Screws are independant (but controlled for have same rotational speed). The slope is the slope of the pitch of the screw is not so small.

#### Geezer

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##### Re: problem with helicoids and pressure
« Reply #17 on: 25/03/2012 23:26:05 »
Yes, but you still have a helical gear : )

OK - I give up.

If both of the screws are being driven at the same speed, what does it matter whether the helixs contact each other or not, and what is the purpose of this machine?

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #18 on: 26/03/2012 00:03:00 »
My son has seen that idea on internet, I don't know where. The purpose is to give more energy than the system receive...I know it's not possible and often I find where is the problem on several systems. But here no ! Here I think the idea is to put 3 fixed pressures, 2 screws, gaskets, controlled system, etc. and recover energy from rotation of helixs (for me the translation of interface don't need energy), the rest of the system don't lost energy. I hope you don't give up ;)

We can imagine sensors with controlled system which driven at the same speed screws, it's only a technical problem (at least for me). The contact of helixs is not essential, it's the volume of interface which must be constant (for not loss energy I think). The volume of interface give a surface for each helix, the differential's pressure rotate screws and torque.

The volume of interface is not 0, see yellow part in reply #2
Maybe if you read the reply #2 you can find where an hypothesis is false ?
« Last Edit: 26/03/2012 00:09:36 by fgt55 »

#### Geezer

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##### Re: problem with helicoids and pressure
« Reply #19 on: 26/03/2012 01:03:01 »
You need to draw a box around the system and identify all the energy inputs and all the energy outputs. Total input must equal total output. If they are not equal you are overlooking something.

I can assure you that what you have is a variation of a helical gear, and there isn't a gearing system that is even 100% efficient let alone more than 100% efficient. I encourage you to study how gears work, and where they lose energy.

I'll be moving this topic to the "New Theories" forum in a little while.

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #20 on: 26/03/2012 08:24:03 »
Ok, thanks

Something important: 2 screws are motors, it's not one motor and one receptor, each give motor's torque.

I think 2 screws can be really independant, I don't see them like a gear when a screw will turn other, and maybe it's the problem. But I'm thinking about your message.

For now, maybe my misunderstood is I think the screw turn where there is a difference of pressure on a small part of surface (only one side), see drawing. Here there is ONLY one screw. One screw turn like that and give a torque ? Sure like that the sum of energy is 0 because I need to adjust the position of the red point.
« Last Edit: 26/03/2012 09:15:02 by fgt55 »

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #21 on: 26/03/2012 16:28:38 »
I think I understood your point of view, maybe you think one screw turn and give torque to the second screw ? Two Screws turns independantly and give a torque for turn 2 receptors. If you see 2 screws like motors, one screw don't give energy to other. Tell me if it's that ?
« Last Edit: 26/03/2012 17:43:10 by fgt55 »

#### Geezer

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##### Re: problem with helicoids and pressure
« Reply #22 on: 26/03/2012 19:10:10 »
Are you trying to make something like this?

http://en.wikipedia.org/wiki/Rotary_screw_compressor#Superchargers

#### fgt55

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##### Re: problem with helicoids and pressure
« Reply #23 on: 26/03/2012 19:30:18 »
It's not exatly that, more complicated and it's the contrary: pressure => torque

Please, take the reply #20, for you the screw turn and give torque ?

#### Geezer

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##### Re: problem with helicoids and pressure
« Reply #24 on: 27/03/2012 05:27:29 »
I still not sure I understand what it's supposed to do - probably a language thing.

Are you saying that fluid pressure contained by the green line will make the screws turn?

If that's it, the screws will not turn because no work is being done to make them turn. That would only happen if the volume of the 3P zone changed. The geometry of the screws ensures that the volume never changes.

If you contain high pressure gas in a cylinder with a piston, it only does work when the volume increases as the piston moves. If you look at the picture of the screw compressor I posted you can see that the helices have opposite screw directions so that work can be done on them to compress a gas. If the screws had the same direction they would rotate, but they would not compress anything.

Hope that's it!

#### The Naked Scientists Forum

##### Re: problem with helicoids and pressure
« Reply #24 on: 27/03/2012 05:27:29 »