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: What coating/grease for long term tool storage|
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.
|Thread: Motorcycle General Discussion|
I hope it is nowhere near me. I will probably hear it coming, though. It will drown out all the local H-Ds.
|Thread: Arkwright Scholarship|
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.
|Thread: Black Oxide coating|
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.
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.
|Thread: Is your spindle bore large enough?|
How stiff is your headstock structure?
|Thread: Dam Solution?|
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.
Edited By JA on 07/08/2019 11:15:11
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.
I am not sure if I am right or wrong!
Sorry, I am getting old.
Edited By JA on 05/08/2019 20:33:02
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.
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.
|Thread: Most difficult part first|
Comments deleted since they were not directly relevant.
Edited By JA on 04/08/2019 18:13:17
|Thread: Dam Solution?|
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.
Edited By JA on 04/08/2019 13:09:10
Edited By JA on 04/08/2019 13:10:32
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.
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|
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.
|Thread: Guess the Chemical?|
I drink it neat.
Edited By JA on 29/07/2019 23:36:49
The water out of my taps comes from Birmingham! Sometimes the smell of chlorine is almost overpowering.
Is drowning a health risk?
|Thread: Steam powered RC aircraft|
Writing as an ex-combustion engineer anyone who launches a "vehicle" in to the air containing uncontrolled combustion, naked flame, should be banged-up for a long time. The applies, particularly, to Chinese lanterns. The burners on a hot air balloon are obviously controlled.
Flying a model with a boiler would need quite a bit of thought. I think it would be difficult to get any insurance.
Edited By JA on 28/07/2019 15:07:38
|Thread: "I'm calling about your accident" - how does this scam work?|
I like to string them along. Some time ago I gave my name as Michael Mouse. A lot of the "scammers" who phone now want to speak to Michael.
Surely Micky Mouse is global (perhaps not in North Korea) and any one with a grain of sense or education would realise it is probably a fake name.
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