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Member postings for Martin Kyte

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

Thread: What sort of things DO NOT inspire you
25/02/2020 13:56:27

Tattoos

Thread: Coal being phased out
25/02/2020 13:50:45
Posted by Derek Lane on 25/02/2020 09:36:14:

Someone with more knowledge than myself may know the answer to this question.

If the weather is down to us humans how long does it take for the "pollution" to take effect in changing the weather, if this weather that we are having now was caused by all the smoke and smog of the victorian era then with all that has been done so far must contribute to reducing the weather?

I'll have a go at a partial answer at least with the caviat that this is my understanding only and I am not a climate scientist. Broadly speaking :-

Prior to large scale 'biology' on the planet global temperatures were determined by solar irradience, albedo (ration of radiation absorbed to reflected) and the insulating properties of the atmosphere which varies according to composition. This was a dynamic system which oscillated wildly with positive and negative feedback loops.

With the advent of large scale biology additional feedback loops arose that had the effect of stabilising the climate.

Vulcanism (generating dust in the atmosphere), geological subduction (recycling of carbonates again through vulcanism) and variations on solar output and mean orbital radius shifted the equilibrium from time to time.

As with any regulating system biology (mostly plants) can only cope with a certain degree of disturbance. The human emissions of CO2 for much of the last 200 years was within the level that the biosphere along with oceanic absorption could cope with. In recent decades atmospheric CO2 has pushed the regulating mechanisms beyond capacity and the result has been a rapid rise (in geological terms) of global temperatures.

To go back to the original question (with all that has been done so far must contribute to reducing the weather?):-

What has been done so far is to reduce the rate at which CO2 is increasing in the atmosphere with the ambition of halting net additional CO2 by 2050 or before. This has already 'baked in a probable rise in temperature of 3 to 4 degees by 2100 at which point, hopefully we get to a new equilibrium. We are already at around +1.5 degree's. In order to reverse the rises our only lever is to draw down CO2 and there are currently no large scale methodologies of doing that although people are trying. So with what has been done so far we hopefully will succeed in slowing the rate at which things are getting worse and with luck end up in a situation which is survivable

Global temperatures with time

regards Martin

25/02/2020 11:02:58

Getting rid of the bit coin miners would be a start.

Current estimates are that Bitcoin is using around seven gigawatts of electricity, equal to 0.21% of the world's supply. That is as much power as would be generated by seven Dungeness nuclear power plants at once.(3 Jul 2019)

regards Martin

25/02/2020 08:58:51

Well whatever anyone 'chooses' to believe they had better hope that climate change is man made, because if it's not we have no way of doing anything about it and it's goodnight nurse.

regards Martin

24/02/2020 13:09:20
Posted by JA on 24/02/2020 13:02:43:

Forgive me but have I missed something hear? I thought that the phasing out of coal and wet wood is an attempt to reduce the emissions of toxic and carcinogenic particles.

https://www.theguardian.com/environment/2020/feb/21/house-coal-and-wet-wood-to-be-phased-out-by-2023-to-cut-pollution

JA

Edited By JA on 24/02/2020 13:06:13

It is. I just thought it was interesting how one goal can pull in the opposite direction to another.

regards Martin

Edited By Martin Kyte on 24/02/2020 13:33:17

24/02/2020 12:30:57

The phasing out of soft house coal is interesting as an example of conflicting aims. Coal is a hydrocarbon and the various grades of coal are largely defined by the carbon/hydrogen ratio. When burnt part of the heat out put comes from Carbon and part from Hydrogen and other volatiles. Heating coal in the absence of oxygen produces coke and town gas (hydrogen(50%),methane(35%),carbon monoxide(10) and ethylene(5%)) of which the hydrogen at around 50% merely produces heat and water so is quite environmentally freindly.

It is clear to see that the more volatiles in the coal the less CO2 will be produced for the same heat output as more heat will come from hydrogen, methane and ethylene and less from pure carbon. So as far as CO2 is concerned banning soft coals and burning anthocite coals will increase the CO2 output assuming the number of coal fires stays the same.

Soft coal however produces more pollutants in the average domestic hearth. Open fires are not brilliant at complete combustion and a lot of the soot and ash particulates are sent up the chimney with no filtering or any other clean up so in order to improve air quality smokeless coal is better.

So you pay's your money and takes your pick, either less CO2 and more air pollution or more CO2 and cleaner air.

Personally I think that the CO2 output trumps everthing at this point in time.

As an additional comment, we may be better to return to town gas with it's nice clean 50% hydrogen rather than the high methane Natural gas we use today.

regards Martin

Thread: Four Jaw chuck
24/02/2020 11:32:30

One of my most used 'tools' is a sprung (spring?) centre which makes setting up to a centre pop/centre hole very straight forward in the 4 Jaw. Easy to make too. I also have a dial guage that lives in a QC tool holder which also saves faffing around. Never bothered with a second chuck key.

regards Martin.

Thread: Effect of Tensioning a Boring Bar
24/02/2020 10:08:45

Hi Michael

My point was that the prestressing of concrete was not an attempt to increase stiffness or stop vibration but to ensure that the beam remained in compressive load. As you correctly say the force vectors are the same albeit with the sign change.

regards Martin

24/02/2020 09:47:41
Posted by Kiwi Bloke on 23/02/2020 09:51:48:This makes initial deflection (lateral and torsional) minimal, until the preload is overcome. My understanding is that preloading a sprung system moves the stress/strain curve sideways, but doesn't alter its slope. So, with appropriate preloading, stress, up to the preload, can be applied without producing strain. The stress/strain curve of the preloaded system is thus initially vertical i.e. infinite stiffness (where 'stiffness' means Young's modulus). Or perhaps not. Have I gone wrong somewhere?

ummm, I think so. If you have a linear strees strain curve and preload puts you somewhere on the curve additional loads will still cause the same magnetude of extension or compression as without preload. Concrete beams are a bit of a red herring as the object is to ensure that all loads are compressive as far as possible.

I don't think the answer will be found in static deflection analysis but only by considering the dynamic system.

Boring bar chatter as far as I can make out, (and I do not set myself up as an expert in this field) appears to be be primarily modal rather than regenerative in nature. By this I mean that the bar bends into and out of the cut and also twists one way and t'other, with the tool tip oscillating in an elipse. I do not have the ability to do the maths but intuitively I can buy into the tensioning of the bar having an appreaciable effect on the energy transfer between the two modes of oscillation by causing the natural frequency of the two modes or oscillators to be non harmonic and thus making the dynamic stiffness or maybe resillience would be a better word? increase.

I do however note Graham's results on static tests which have not really been explained. Maybe the tesioned bar is twisting as well as bending as the load is applied. I don't know.

regards Martin

Thread: Adjusting an M&W level
19/02/2020 15:24:08

Is this any help.

https://www.bowersgroup.co.uk/media/wysiwyg/MW550-03_Cropped.pdf

I would have thought that the level adjuster(s) should be at 90 deg to the hold down screws and should act by inserting or withdrawing a tapered seating. You don't need a perfectly level surface to test it so long as it reads somewhere withing the scale. Just mark the initial position and rotate by 180 degrees for a second reading. They should be identical when perfectly adjusted.

regards Martin

Thread: Linked belt for Myford 7
18/02/2020 16:28:35

There is a right way round you know with these belts. Maybe that's why some find they slip.

regards Martin

Thread: Switches
17/02/2020 12:13:45

1no/1nc is

1 pair of contacts normally open and 1 pair normally closed.

Wire the pair you want.

regards Martin

Thread: marine steam engines
17/02/2020 12:10:33

There you are look, worse things do happen at sea !

)

Martin

Thread: Bulbs
17/02/2020 11:17:42

Used to be a single size gas mantle, before that it was just a flare. Even oil lamps had different sized wicks.

You could always go back to candles or even just go to bed when it gets dark.

regards Martin

Thread: Encryption software
17/02/2020 09:19:09

It's interesting to find out how fast a computer can crack your passwords these days.

There are a number of 'online password testers' available, don't use live one obviously.

Here are 4 examples.

6%#863 - 6millisecs

blooge3 - 2 secs

railSTEELtell - 16 thousand years

railSTEELtell1@ 16 billion years

The third example is good and interestingly the easiest to remember. Often sites will insist on some numbers and other characters also so I added 1@ which doesn't really make it that much harder to remember.

The construction is from Floyd's lyric on wish you were here. Pick a phrase/verse or lyric. Extract 3 words capitalise one of them and add some numbers/other characters.

Weak passwords are worse than useless, tough passwords do not have to be hard to remember.

regards Martin

Thread: Effect of Tensioning a Boring Bar
12/02/2020 09:49:34
Posted by DrDave on 11/02/2020 19:45:59:

This purports to be a 10 mm tube with a 6 mm hole with a 5.8 mm pin down the centre, both 70 mm long. Material is "steel". A nominal 200 N shear load is applied at the RH end and the LH end is built in. I also found a solid 10 mm bar lurking in another corner.

Varying the frequency of the 200 N load from 0 Hz to 5 kHz gave the three curves below. They are not all quite what I expected...

The solid bar gave the silver curve: a typical single degree of freedom forced response curve. Good. The "Loose" curve is for the model shown above: only the outer tube has responded to the load. The static deflection is slightly greater, because it is hollow. To my surprise, the natural frequency and the size of the peak have increased (not that the axis has a log scale). The frequency has gone up because the mass has decreased more than the tube's moment of inertia, one of the useful properties of a tube. I am not sure why the magnitude of the peak has gone up.

I then tied the two free ends together. I have called this "preloaded", to signify that it is modelling a boring bar when it has been pre-loaded. This has produced some interesting results. It has two resonance peaks: one for the tube and one for the bar. I am surprised that the first peak, and its magnitude, are nearly identical to those for the solid bar. Make from that what you will, because I certainly don't know!

Evidently the two-piece boring bar does work to reduce/eliminate chatter, but the mechanism but which it does this is still obscure. I would suggest friction between the two parts acting to damp the vibration, but the elephants had all left the office by then & were nowhere to be found...

fem response.jpg

Dave

Very interesting. Effectively the rod down the middle of the bar has added another degree of freedom allowing resonant motion at two different frequencies.

So maybe the best way of thinking about the tensioned bar is as two coupled oscillators something along the line of 2 pendulums of dissimilar length both hanging on a line which couples them togather. Energy will be transferred back and forth from the one to the other at at the beat frequency in a similar way to the employment of tuned mass dampers for tall buildings etc (google it).

This company actually produces a tuned mass damper boring bar.

**LINK**

I don't think for a minute that the simple tensioned bar we have been discussing approaches a tuned system however the addition of the tensioned rod certainly seems to have the effect of disrupting the single frequency simple oscillation.

I did try and find a video of coupled pendulums of different lengths but so far have failed.

regards Martin

Thread: cylinder boring
11/02/2020 13:42:01
Posted by JasonB on 11/02/2020 13:07:06:

I always do the cylinder first and then the piston but do the opposite when it comes to the crankshaft and all that fit around it as the crankshaft is the harder to make so bearings, flywheel and pulley are all done after.

That fits with the philosophy of protecting the investment you have already made either in money or time. Retain as many second chances on high value components as you can.

regards Martin

Thread: I just had to buy this
11/02/2020 12:51:32

Were the three wise monkeys the personification of design, production and quality depts?

Hear nowt

See nowt

Say nowt

;0)

Martin

Thread: New from the edge of the Fens
11/02/2020 11:21:30

Aha, perfect timing Ian. I have just the project for you, Marham are offering their Victor gate gardian free to a good home to anyone who promises to restore it.

**LINK**

Could be an ideal starter project and as has already been said you have the ideal skills.

Welcome to the madhouse anyway.

regards Martin

Thread: cylinder boring
11/02/2020 08:53:10

. . . . or which do prefer to scrap the piston or the cylinder. Not that any of us get it wrong :O)

regards Martin

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