Mass

[Burgerman]

Someone just ask me the difference between weight and mass. He insisted it was the same thing.
Came about because I asked him the weight of the electric delivery van. And on the chassis plate in the door it quoted mass in kg.

I told him to fill his van (delivery driver) with helium balloons. And that would incease its mass a little and decrease its weight.

Then asked him if mass and weight were the same thing. He scratched his head looked bewildered and off he went.

[biscuit]

I vaguely remember from school that 1kg is defined as the weight of 10dm³ of water at standard temperature and pressure? We have STP on the earth. So 10m³ of water would weigh less on the moon.

[LROBBINS]

Mass is the amount of material independent of acceleration (e.g. the acceleration of gravity or from movement).
Weight is the force generated by a given mass at a given gravity - we're usually talking about 1G.

Metric system: mass: Kg
force (weight): Newtons
common alternative for force (convenient, but not part of the "standard" measurements): kg-force, often just written as kg
so, for example, a chair lift may have a maximum weight capacity of 250 kg, but that's really kg-force at 1G. If on the moon, the weight limit would be 250 x (1G/moonG) so a higher numerical value.

"English" system: lb, there is no standard English system unit for mass.

To measure mass you use a balance with a unknown mass on one pan and adding known mass in increments until it balances.
To measure weight you use a "scale" - the unknown weight pushes on a spring and weight is read as displacement of the spring.
So, my little Chinese scale marked in grams is really measuring weight; 1/1000 of a kg-force not mass. As long as we're on the earth, not on the moon, on the vomit comet of off in space, numerical value of kg mass and kg-force are the same.

It happens that 1 liter of water at standard temperature etc weighs 1 kg-force, but the kg is not defined by that. Before atomic measurements, the kg was defined by comparison to a piece of metal kept in a atmosphere-controlled vault and handled with great care to which secondary standards were calibrated on an exquisitely sensitive balance.

[Burgerman]

Yes.
Or up a mountain. Or at the equator.
But its mass stays the same.

It just struck me as interesting that ADDING mass to a van, would reduce its weight. Albeit not much!

Think about a single large weather helium balloon.
Appprox Weight: minus about 4 ounces...
Approx Mass: plus 2 ounces.

[Burgerman]

It happens that 1 liter of water at standard temperature etc weighs 1 kg-force, but the kg is not defined by that.

But a litre was!

[biscuit]

oopsie, other way round! It's just as well I never needed to know during those years. Mind you, I might have been able to dredge it up, give it a shake and turn it around if I'd needed to.

[Burgerman]

Might well be the other way around. But the point being that it wasnt coincidence.
Same as boiling point and freezing point of water was 0 and 100. Not coincidence, all intended to make engineering really simple. Just like mm, cm, meters, km. All 10x bigger.

1kg / 1000 grammes, is 1 Litre volume, measures 10cm3 or a 100mm (cube), at standard temp and pressure. 0 Cent /100 Centigrade freeze and boil, All standard relatable x10 units.

For e.g in my head I can easily tell you what sized container I will need for say 2.25kg or 400 grammes of water. Or say 1.5 litres of water. And what it weighs. Everything super simple! Or I can tell you how much water you need to fill a pool from its measurements easily in my head and what that pool water will weigh. Because the metric system was designed to make stuff super simple even for me!

****************
Because god forbid we ever go back to miles, yards, inches, fractions, thousandths of inches (thou), stones, Tons, lb and ounces etc, farenheight. Because non of that stuff ever made any sense. Non of it relates to any other measurement or type of measurement, and all in multiples of some random figures you had to learn... Like weight. 16oz to a lb. 14lb to a stone. God knows how many stone to a ton but its 2200?lb... And what does a square foot of water weigh? How heavy is that? Lets say you make a 6 gallon (Real gallons!) fuel tank for a generator. What size would you make it? My brain explodes! In metric I can tell you isstantly from my head..

[biscuit]

We had only had SI (i.e. metric) in South Africa, the others were banned in about 1965, it was illegal to sell anything with any non-metric measurement markings and the schools taught metric only. So all measurement became simple, universal and logical.

Then I came to the UK. Rude awakening! This country trying to retain its individuality when it signed the Maastricht Treaty to irreversibly entangle us in the EU, but our government wasn't going to encroach on our freedom so keeping the ancient local measurements became an issue. it's like the government really hated the people. I recall seeing a newspaper article about the size of EU milk bottles - the newspapers saying vendors might rip off customers if the milk bottle size became metric. Tsk!

[Burgerman]

Well in engineering, threads, metal sizes, quantities of fuels, gas like propane etc, money, measurement, raw materials (like wood, etc) tiles, slabs, drink bottles and glues, temperatures, and more we are allmost completely metric. I have huge collections of tools, drills, threading equipment, metals, and so on. Carpet, tiles, etc all square meters. Even bricks are now metric.
If you buy any car, wheelchair etc it is all completely metric.

All true, anywhere other than in the USA.
Finding imperial measurements here is very hard as they are not really used other than for matching old legacy items or tradition (beer) by way of example.

Beer (pints) and a few things that must "match" such as bathtubs, wheel diameters (but not tyre widths!) because they must fit in a space or replace older existing. And car speeds and miles on roadsigns we still use antiquated imperial measurements. Which is definitey odd.

[LROBBINS]

The other exception that I know of is threaded plumbing fittings. Those are given in inches, not of the real pipe but of the diameter of an equivalent pipe with laminar flow so the flow rate will be the same whether the pipe is rough (e.g. cast iron), smooth (e.g. copper), thick or thin walled. Even so, there is a difference between U.S. and European fittings. U.S. have a tapered thread so need very little sealant to be leak free, European have a straight thread so need lots of sealant (e.g. 10 turns, or more depending on fitting size, of teflon tape). I learned that the hard way when I moved here and fitted a shut off valve with 2 turns of tape as would have been fine in the U.S. Soaked me a bit.

[Burgerman]

Taper threads and parallel threads in UK. Depends what we are doing and with what. Ex plumber here!

But again that because theres millions of pipes in factories, homes etc and changing to metric here would now be extremely difficult as nothing would fit... So in this case we are stuck with legacy nonsense.

[Burgerman]

Also, real plumbers hate PTFE tape and consider it a DIY bodge.

We use (used) hemp (fine flax fibres) and stuff called "boss white". A mix of linseed oil and clays etc. Smells great! Just as quick really once you are used to it. But way better long term.
Today I am lazy, and resort to the DIY PTFE bodgery... But they come loose or move. Soft stuff and slippy. It feels like an unsafe joint to me.

If I want something solid now, I resort to a coat of oil based gloss paint on taper threads instead of either.

Taper threads BSP (British Standard Pipe - not taper)came first but people now add a T to differetiate and are meant to be TIGHT by design to seal!
Parallel threads BSPP (British Standard Pipe Parallel) are meant to use end washers, fibre washers, Hat shaped connectors etc and not really meant for thread sealing. But you can at a push. Its hard to make the sealer/hep/ptfe to be drawn into a joint. That too is a bodge. And leak later. And likely have thread damaged by running past the end of a thread as you tighten as thats is the only way to get it tight.

Wrap the flax hemp fibres in the same correct direction as PTFE. Smear BossWhite on it. Assemble. Its much tighter and less "slippy" than PTFE and it never leaks or moves because of that ptfe softness or slippy-ness later on... And it sets rock hard over time. So dissassembly needs heat usually.

[biscuit]

I have random boxes of plumbing stuff that is never quite what I need but I keep it anyway just in case. And not quite what I need leaks like a sieve. There are too many thread types. So I endure annoying old taps, mainly.

[LROBBINS]

In Italy, hemp was also traditionally used, but even the pros now use teflon tape. Lot's of turns in the right direction and it seals quite permanently. Straight-thread tube fittings (mm sized) also use washers, but the straight-thread inch-sized pipe fittings use hemp or teflon and no washers. I've yet to have a taped fitting leak (in >20 years use), but maybe I've just been lucky.

With tapered fittings, I used teflon tape when I wanted it to be easily removable, and oil based paint when I wanted a "hidden" connection (such as behind a dishwasher) to be "forever".

I still don't really understand why we use inch-sized pipe fittings here when the metric system was adopted centuries before there was indoor plumbing.

[Burgerman]

Old normal taps are always parallel threads. 1/2 or 3/4 bspp threads. Sealed with a thin fibre washer on the tap connector. Those expand when wet. And the only thing on a thread there should be a tiny drop of oil.

[martin007]

In Spain the use of teflon is the majority.
However, there are still plumbers who love hemp.
The plumber in my area uses hemp dipped in "minium paint"; he is a great professional.

[biscuit]

Are PTFE and teflon the same thing? And thread lock like loctite? And the thread lock I put down the hinges of my spectacles? Which is loctite, one of the loctites anyway.

[martin007]

Loctite is cyanocrylate.
In the short term cyanocrylate in contact with water or moisture degrades.

[Burgerman]

Teflon is a brand name for the stuff called PTFE or PolyVinylFlourEthlene. Or similar...

PTFE is the same chemical on non stick pans, also used as low friction blocks and parts in engineering etc. And a thin tape used as a pipe seal for threads.

Loctite (best used with hardner spray) can be loads of different types. Theres about 70.

I ontly use 3 different ones.
I use a RED one, which you dab on a thread if you want something that cant be removed... Like wheel mount studs, (not the bolts or nuts you undo to remove a wheel. Or exhaust mount studs. Unless you heat it and then it lets go. Done properly it cant be undone with hand tools usually unless you heat it a few secs with a propane toch.

A BLUE one that grabs threads very well. Stops anything coming undone unless you lean on it a bit... Or heat it a bit. I use it all the time. It has another advantage. That is that threads also dont corrode. I dont use this on things like bolts into an aluminium casing. Those I grease!

And a bearing lock to stop them creaking and fretting in a wheel etc. These are quite easy to remove when you want to do so.

[martin007]

Are you saying that the nut lock glue is cyanoacrylate with color?

[Burgerman]

There are many types of glues. Henkel (Loctite) make cynoacrolate glues like superglue too.

But you cant just use superglue in place of threadlock glues like say the blue and red loctite I use. Its not oil or waterproof and corrodes metals for a start. And not strong enough. Henkel chemicals make many products.

https://www.henkel-adhesives.com/uk/en/ ... ckers.html

[biscuit]

My little red bottle of blue gunk that I put on my glasses said it is a thixatropic paste. I think it means the slurry is liquid until you stir it (cook) or turn the bolt (mechanic), then it's solid. I hope it holds, it is my last pair of specs and I am tired of hunting for miniature bolts.

Umm. Thixatropic paste is for cooks. Loctite tastes horrible.

[martin007]

That is more logic.

[Burgerman]

50ml sizes but this stuff is basically fit once! Hope you never need to dissasemble. For things you never want to come apart!

https://www.threadlockeruk.com/products ... e-272-50ml
Add 450C heat makes it let go.

This blue one, also available 50ml, as well. I use the blue one for loads of things. You CAN undo stuff you use this on, but it certainly grabs... And stops corrosion etc. Mines 50ml...

https://www.threadlockeruk.com/products ... e-243-50ml

Theres many others. These are all you need.
These two both work without activator. But a hell of a lot better with it. Esp the red one. Use the red one on clean threads and its like its welded on!

[martin007]

If I'm being honest, I've never used a similar glue.
So far I manage with self-locking nuts, fluted washers and pressure washers.


P.S. I have plus 40 years.

[Burgerman]

Well I built a lot of hobby stuff, drag race engines and the like. When building race engines its pretty much essential in some places. or they fail! And some places even the engin manuals specify it on say exhaust studs, or main engine drive chair sprockets and nuts etc.

And IF I flew helicopters I personally would insist the jesus nut used it!

[Burgerman]

Loctite is cyanocrylate.
In the short term cyanocrylate in contact with water or moisture degrades.

No. And they dont stick your fingers together, and are waterproof, and not cynoacrylate.
Loctite is the brand name used by Henkel chemicals for many houshold glues and that includes superglue as well as industrial glues that are non cynoacrylate and are metholyacrolate and other types mostly thread and bearing lockers. Theres around 50. Some are temp proof, some can be used on wet or oily surfaces, some for different metals, some for all metals, some are anti corrosion, some can be dissassembled easily, some need heating to 450C first, some for shafts, some for bearingss, some for threads that are small, some for large threads, etc.

50ml sizes but this stuff is basically fit once! Hope you never need to dissasemble. For things you never want to come apart!

https://www.threadlockeruk.com/products ... e-272-50ml
Add 450C heat makes it let go.

This blue one, also available 50ml, as well. I use the blue one for loads of things. You CAN undo stuff you use this on, but it certainly grabs... And stops corrosion etc. Mines 50ml...

https://www.threadlockeruk.com/products ... e-243-50ml

Theres many others. These are all you need.
These two both work without activator. But a hell of a lot better with it. Esp the red one. Use the red one on clean threads and its like its welded on!

[martin007]

The most famous Loctite if cyanocrylate.

[Burgerman]

I think you are talking about spermarket superglue. Thats just loctite branded cynoacrolate. Which in itself is a recent development.

Thread-locking fluid or threadlocker is a single-component adhesive, applied to the threads of fasteners such as screws and bolts to prevent loosening, leakage, and corrosion.

Most thread-locking formulas are methacrylate-based and rely on the electrochemical activity of a metal substrate to cause polymerization of the fluid. Thread-locking fluid is thixotropic, which allows it to flow well over time, yet still resist shocks and vibrations. It can be permanent or removable; in the latter case, it may be removable merely by force or may also require heating, for example. Typically, brands are color-coded to indicate strength and whether they can be removed easily or require heat for removal.

If you spent any time working in industry or on vehicle engines then the surprize was that superglue now exists at all, long after threadlock was common. And then only recently was the brand called loctite superglue used. Maybe in the last 20 years. I was using loctite threadlockers on truck engines when an aprentice at 17 in 1976 and it was far from new then! At this time the word superglue or cynoacralate was unknown to the domestic or hobby world. Never mind loctite branded superglue. So it may be the most recognised by you. But its a "new" thing to the loctite brand compared to the many threadlockers they were famous for.

They added the loctite name to the superglue to help its sales, marketing. Hoping that the brand recognition they were actually famous for, the threadlocker used by many professionals in industry would rub off...

[martin007]

The most famous Loctite if cyanocrylate.

Famous = Widely known.

Which is more famous, a supermarket glue (Loctite) or a glue only used by professionals?
The answer is obvious.