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Member postings for JA

Here is a list of all the postings JA has made in our forums. Click on a thread name to jump to the thread.

Thread: Your ideal holiday
21/08/2019 19:46:52

Venice, Melbourne, Vancouver and San Fransisco. No other cities are worth it! Not that I have visited all of them.

Posted by Mike Poole on 21/08/2019 17:46:02:

I have always fancied visiting the four points of Britain, The lizard, Lowestoft, Dunnet Head and Ardnamurchan point and a ride to the Nord Kap in Norway always appealed. Lots to do and time is running out.

Mike

The Lizard is OK, Lowestoft Ness is just a beach, I gave Dunnet Head a miss. The Ardnamurchan, including the point, is really worth the journey. The area is truly remote with stunning scenery.

To escape life, which is why I go on holiday, nothing beats Islay. At any time of the year.

JA

Thread: Are there any left?
21/08/2019 18:12:19

It is a long time ago and one’s memory can play tricks.

I think Proops were in Holborn in around 1963. They were not there in 1960 and had moved on by 1966. So had Bassick Lowke. By 1963 Proops had left the disposal market and was more like the business it is now.

JA

21/08/2019 14:19:27

I was once a Londoner and remember the shops and area (parts were dodgy).

Bassett Lowke had their shop at the west end of Holborn and I think Proops were next door. In the early 1960s the government disposal shops were split between Tottenham Court Road and Lisle/Little Newport Streets. The latter streets were infamous, the only businesses present were the disposal shops and brothels. The biggest building in Lisle Street was the London Hospital for Skin Diseases. By 1966, when I left London, the disposal shops had left Soho and later the Tottenham Court Road shops went into the HiFi market.

Occasionally I would return and by 1971 nothing was left.

JA

Just a comment, the goods stuff like HRO receivers sold for a lot of money.

Edited By JA on 21/08/2019 14:23:17

Thread: What coating/grease for long term tool storage
20/08/2019 16:22:41

If you use heavy grease like the military did remember you will have to clean the nasty muck off. OK when one has to occupy idle hands but not what you want to do on a Saturday afternoon.

In my youth we used Silkolene Sozzle, a tractor laying up fluid, to protect our bikes from the ravages of winter. When spring arrived we just washed it off with paraffin or Gunk. Like Gunk, Sozzle has long since disappeared and the old Silkolene company seems to have re-invented itself.

For protecting small steel parts I have found that Corotex corrosion inhibitor paper works a treat. However brass develops a green surface if wrapped in it for a few months. I contacted the manufacturer, MetPro Group, and they suggected using their corrosion inhibitor plastic bags. I now, happily, have a near infinite supply of their A4 plastic bags for storing small parts. They do large bags that will take a large chuck.

JA

Thread: Motorcycle General Discussion
17/08/2019 14:38:17
Posted by Ian Parkin on 17/08/2019 11:51:22:

Just seen this bike advertised on a local forum

have a look at the rear brake actuating rod..

wouldn’t want to be relying on that in a panic stop

I hope it is nowhere near me. I will probably hear it coming, though. It will drown out all the local H-Ds.

JA

Thread: Arkwright Scholarship
15/08/2019 23:36:06

Obviously your nephew is bright and unlikely to see the inside of a workshop for most of his life.

I think back to my early life. The company I did my apprenticeship with had all their engineering apprentices making oil cans etc. However if an apprentice turned up with a model to build the instructors became interested.

I would suggest a simple Stuart steam engine. He will learn a lot. However he is unlikely to finish it before finding other priorities in life. At this point he should put it in a box with the drawings and notes. Later in life he will have time, and hopefully the inclination, to finish the engine.

JA

Thread: Black Oxide coating
12/08/2019 12:58:00

I am sure there is a correct oil to use.

About a year ago I blacked a batch of small steel fixings using fresh clean Morris 32 hydraulic oil. I am more than happy with the results. The parts have been kept with a little bit of oil in a jar which is why there is a slight glint on some items in the photograph.

Blacked small steel fixings

Blacking produces an porous coating which holds oil. As long as the item is kept damp with oil it should not rust. I don't think the colour of the coating is of any importance as far as holding oil.

JA

Thread: Is your spindle bore large enough?
09/08/2019 17:55:11

Niels

How stiff is your headstock structure?

JA

Thread: Dam Solution?
07/08/2019 11:11:35
Posted by Michael Gilligan on 07/08/2019 09:11:38:

I thought I had found a helpful explanation of the syphon/siphon here: **LINK**

https://www.physicscentral.com/experiment/askaphysicist/physics-answer.cfm?uid=20080512104921

...bur I'm struggling to comprehend this statement:

[quote]

Moreover, the pressure of water in a sealed pipe decreases with altitude, so the higher you look in that pipe, the less pressure potential energy you'll find. Because of this pressure effect, the total potential energy (gravitational plus pressure) of water in a closed pipe doesn't change, even as that water rises a short distance upward inside the pipe!

[/quote]

Two nations separated by a common language ? ... or am I just being thick ?

I will have some coffee !!

MichaelG.

Micheal

I would suggest something far stronger than coffee.

In thermodynamics there is the concept of an enclosed system. Something, a device or anything, in a sealed box cannot be influenced by outside events or influence the outside. Such a concept is hypothetical but useful. It is easy for one to think of exceptions, if you do I will just redefine the sealing of the box.

In this case the pipe is the box. What ever you do to the outside will not increase the pressure.

There is another way of looking at this. The pressure of the water in the pipe is the water's internal energy. If you increase the altitude you have done nothing to the water, all one has done is to increase the potential energy of the whole system.

I hope this makes sense.

I like the photographs. I thought more pipes were being used. What I see can be quickly put on the back of some trucks and driven up the M5 and M6.

JA

Edited By JA on 07/08/2019 11:15:11

07/08/2019 08:47:29

Slowly it dawns on me the difficulties with a syphon.

You will need a large diameter rigid pipe of that runs from near the bottom of the water side of the dam to the bottom of the dry side. All the joints in the pipe above the water level in the dam must be absolutely leak free otherwise the syphon fails. The pipe work will need to be restrained to prevent movement due to change of direction of the flow (restrained using the failing dam?). The water from the dam will be exhausted at the bottom of the dam instead of any side spillway. As already mentioned priming a big syphon is not easy. The time transporting and assembling such a device would be slow compared with bringing pumps from the River Severn which can just be dumped on the ground, hoses run out and started very quickly.

JA

05/08/2019 20:29:26

I am not sure if I am right or wrong!

Sorry, I am getting old.

JA

Edited By JA on 05/08/2019 20:33:02

05/08/2019 19:10:53
Posted by Michael Gilligan on 05/08/2019 18:00:45:
Posted by Neil Wyatt on 03/08/2019 10:34:32:

I see the fire service are using pumps to drop the dam at Wahley Bridge.

I'm sure a syphon could have been prefabricated in place with a bore of about 0.5 metres and suitable cocks for priming and control that would shift a lot of water a lot faster.

Easiy and cheaply scaled as well, to match the rate of water loss to the capacity of teh river below.

Neil

.

Just returning to Neil's opening post, for a 'sanity check'

Does anyone actually believe that a "syphon [...] with a bore of about 0.5 metres [...] would shift a lot of water a lot faster." than the pumps ?

Can any of you clever chaps give a realistic estimate of the flow-rate provided by a 0.5m syphon ?

Thanks

MichaelG.

.

No offence intended; I'm just an interested neihbour

From my earlier calculations, with the water level at the top of the dam a 0.5m syphon will give a flow of 1480 gal/s (24 million litres/hr). Once the water level has dropped by 10 feet this flow will fall to 1300 gal/s.

I have tried to find the capacity of the pumps being used without success. 24 million litres/hr sounds like an awful lot. However if the bore of the pipe was 1" the flow would be 3.7 gal/s which seems sensible.

JA

05/08/2019 17:40:49
Posted by pgk pgk on 05/08/2019 16:40:30:

I recall some talk of using high molecular weight polmers to reduce friction on the boundary layer of boats (back in the 60's) to reduce drag.

pgk

Just don't get me on that one. They are used in fuel pipe lines in the States and cause havoc. They block filters and can do other horrible things.

JA

Thread: Most difficult part first
04/08/2019 18:06:08

Comments deleted since they were not directly relevant.

Sorry

Edited By JA on 04/08/2019 18:13:17

Thread: Dam Solution?
04/08/2019 13:03:55

Dave

For a siphon to work the fluid must have an appreciable density. All gasses have densities much lower than liquids so gas siphons are not met in practice. I write this knowing that someone in an obscure university lab has probably made one. As for ordinary viscous Newtonian liquids a siphon will work. However for non-Newtonian liquids such as many paints, cow muck etc all bets are off.

Your earlier point about having an understand of what is actually happening is very pertinent. My college text book of fluid mechanics describes what a fluid is in five or so pages. For the next 695 pages a fluid, liquid or gas, is treated as a continuum (that is "no part of which is perceptibly different from the adjacent parts". This model is very successful until one has large free molecular paths such as in a vacuum or hypersonics.

Siphon, or syphon which I also prefer, does not feature in the index of my text book.

Enough said, this is a long way from a dam in Derbyshire.

JA

Edited By JA on 04/08/2019 13:09:10

Edited By JA on 04/08/2019 13:10:32

03/08/2019 18:53:55
Posted by SillyOldDuffer on 03/08/2019 18:14:45:
Posted by JA on 03/08/2019 11:57:00:
Posted by SillyOldDuffer on 03/08/2019 11:21:54:
Posted by Bazyle on 03/08/2019 10:49:03:

Maybe not. A syphon can only apply one atmosphere to overcome the friction per 30 ft pipe...

Or maybe that's wrong too!

I think I'm correct in saying that no-one understands how siphons work. ...

Dave

Sorry, siphons are simple. A bit of fluid dynamics -

...

Unfortunately not. Have a read of the Wikipedia article on Siphons. While it agrees Bernoulli equations provide a 'fair approximation' of the flow, the section on 'Modern Research doesn't come to a solid conclusion as to how Siphons actually work. At least not the way I read it.

It's been shown that siphons do not depend on atmospheric pressure because they work in a vacuum. Operation looks to be more to do with gravity and molecular cohesion. I wonder if anyone has tried to eliminate gravity by siphoning liquids in outer space?

The latest research - Hughes and Gurung, Queensland University of Technology, 2014 - concluded "It follows from the above analysis that there must be a direct cohesive connection between water molecules flowing in and out of a siphon. This is true at all atmospheric pressures in which the pressure in the apex of the siphon is above the vapour pressure of water, an exception being ionic liquids." Why are ionic liquids exceptional? Of course being Australian they were upside down when they tried the experiment...

Dave

Edited By SillyOldDuffer on 03/08/2019 18:17:16

Dave

I have just had a look at Wikipedia. I treat Wikipedia as a thoughly untrustworthy source of information. It has a vast amount about what is generally a very simple hydraulic device, a lot of it seems to be grounded in mumbo-jumbo. Away from problems due to pressure approaching a vacuum at the top of the siphon Bernoulli’s equation applies. When the height of the siphon is around 30ft the water starts to boil and the simple Bernoulli analysis fails. The modern studies referred to in Wikipedia concern these low pressure conditions.

JA

03/08/2019 11:57:00
Posted by SillyOldDuffer on 03/08/2019 11:21:54:
Posted by Bazyle on 03/08/2019 10:49:03:

Maybe not. A syphon can only apply one atmosphere to overcome the friction per 30 ft pipe...

 

Or maybe that's wrong too!

I think I'm correct in saying that no-one understands how siphons work. Air-pressure might have some effect, but can't be the main mover because siphons work in a vacuum. Another hypothesis suggests gravity provides the force rather as the weight of a length of chain pulled over a lip might cause the rest to follow. But this requires us to believe that water is strong enough to pull a large mass of water along behind it, and water has almost no tensile strength. Hmmm.

I wonder if the Fire Brigade are siphoning already? The press aren't noted for technical accuracy, and they might assume that a siphon started by a fire engine pump was still being mechanically pumped. Dunno.

Dave

Sorry, siphons are simple. A bit of fluid dynamics -

Looking at the BBC news site the dam is about 45 ft. Let us have a siphon pipe, 1 foot diameter, full of water from and to the bottom of either side of the dam. With the dam full the water pressure difference between the leak surface and bottom of the dam is

                    height of water x density of water = 45 x 62.4 [lb/ft^3] = 2808 [lbf/ft^2] = 19.2 [lbf/in^2]

This drive the flow of water whose velocity can be calculated using Bernoulli's equation (really conservation of energy). The velocity in the pipe is

                   square root of (2 x pressure difference / water density) = (32.2 x 2 x 2808 / 62.4)^0.5 = 54 ft/s

                  [the 32.2 is required because imperial units  gets into a bits of a mess when handling mass and force]

 The water flow rate can then be calculated for the full reservoir

                   water velocity x pipe cross sectional area = 54 x 3.1415/2 x 1^2 = 85 ft^3/s = 530 gallons/s

This flow will reduced as the water falls and as already pointed out will cease when the water pressure at the top of the siphon approaches a vacuum.

I am sure that some one has posted a similar reply during the twenty minutes it has taken me to post this.

Edited By JA on 03/08/2019 12:27:02

Thread: Another scam
30/07/2019 17:47:58

I have always assumed that if you pressed 1, or any other number, with one of these calls you would be charged a lot of money. A couple of months ago I let one of these calls run on without pressing anything. After about ten seconds I got an actual voice on the line so I tried to string her along. To me this suggests that pressing 1 or anything does not do anything.

Confused.

JA

Thread: Guess the Chemical?
29/07/2019 23:34:56
Posted by Howard Lewis on 29/07/2019 22:37:46:

water is safe if drunk in accordance with the safety instructions, and in the right spirit, I am told.

Howard

Whisky?

I drink it neat.

Edited By JA on 29/07/2019 23:36:49

29/07/2019 19:12:09

The water out of my taps comes from Birmingham! Sometimes the smell of chlorine is almost overpowering.

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