Posts by ChemEng 15 publicly visible posts • joined 14 Jun 2009
Some years ago I was opening a tin of paint to start on the outside of the house. My neighbour, a retired nurse, shouted over the fence "at least put a rag round your hand to do that, you wouldn't believe the number of people I've seen with a screwdriver stuck through their hand".
Since then I never seem to be able to find a rag at the right time, but I am very very careful.
In my experience most manufacturing locations identify production batches by a straightforward numeric series. One manager I knew was very proud of the method he invented personally which was DDMMYY+numeric order for that particular day. He was quite clever in other respects and well regarded in his field, also stubborn. It was an American company with interdependent manufacturing and retail locations throughout the world. He didn't survive the introduction of centralized global planning and stock conrol.
A company I worked fo used to produce thousands of tpa of a commodity product but for internal use only. As part of a major expansion scheme they started to sell the product on the open market against some very big, well established names. The material was identified, in 20 tonne lots, by a consecutive Lot number, with the unimaginative format L ######.
There were several reasons to differentiate between internal and sales material and, after much debate. we production people decided to identify sales lots by a 'P' prefix and a new series of numbers.
After three months the sales people reported back that our material was being called 'that poo stuff' by the production crews using it. We apologised and offered to change the system immediately to whatever they recommended. The answer was 'No way'. It might be a joke but they like it and they're asking for it by name. We couldn't buy advertising like that.
My Grandson's primary school has started to use Google Classrooms to set and collect remote classwork during locdown. I don't know if it costs the school anything but users need to have a Google account or similar to log in. It also needs at least Chromium to function in anything like a useable way. Once in, there is a labyrinth of extra Google services that can be signed up for to make usage more convenient.
I've had a couple of remote hospital consultations recently which will also only function on Chromium.
In a few months my family have changed from dedicated Googlephobes to apparently enthusiastic regular users.
Services provided to the community by Google during lockdown have grown Chromium to the point where it has now become big enough to harvest/cull/shaft, pick your own metaphor.
Can anyone advise me on this please:-
If left in situ, how do the various telemetry systems react to long term isolation from the internet?
Do they only report when they can? Do they cache information for transmission when possible?
Is any cache time/volume limited and where is it?
In other words what is the possibility of the machine eventually becoming mired in MS excrement? After 30 years exposure to (the outer fringes of) MS systems, one thing I have learned that they are not good at tidying up after themselves.
I think I managed to keep the worst of the telemetry stuff off my Win 7 machine but, if I didn't, I have a smug feeling of satisfaction knowing that the last thing it reported home was burning a Mint ISO to a thumb drive. The Windows machine still exists of course, too much dedicated stuff on it, but it will never see the internet again.
So, once more, a new MS OS has lead to another computer sale, but for the last time as far as I'm concerned.
Posted from my Linux machine (and it's really rather good)
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@Chemist enquiry re Thalidomide
Sorry to be late with this but, for the record:-
To my personal knowledge Thalidomide was certainly trialled against multiple myeloma around 2001. I understand that it is still used in this field as such. However, I believe the materials named Lenalidomide and Revlimid are both derivatives of Thalidomide, if not just alternative commercial names for the basic material.
I once asked around for advice on selecting a consultant metallurgist for a potential corrosion problem in our pressurised SS processing vessels.
The main gist of the advice (from a Mech Eng Professor) was "try to find one with only one arm."
That way we might just avoid over use of their favourite phrase -
'but on the other hand ......'
Agreed.
Thanks for the explanation about the early variable speed drives It was some time ago.
Some of the earlier AC postings read rather like the work of a young disciple, hence my attitude. Now I seem to have roused the master himself.
I've deliberately refrained from expressing an opinion either side of the IC / electric debate. I don't know enough. However, to paraphrase an earlier post.
I'm not anti green, I'm anti spin.
I set out to nail the vaguely inferred >90% overall efficiency figure, and I probably got as close as I'm going to get. IMO people are becoming confused and apathetic about the current mixture of science, hype, spin and FUD they are being deluged with from all sides. It doesn't help the cause when apparent men of science lose credibility in their own community by indulging unnecessarily in the more political arts listed.
I'll now happily bow out of this as you suggest.
(Graduated London 1964. First assignments were heat & mass balances on high temperature rotary kilns fired with finely divided coal. I really have been around for a very long time!)
Considered using variable speeds once but had to abandon the idea. Safety regulations - the motor casings got too hot!!! (Somebody explain the implications of that to AC please)
Stop trying to side step the issue. Electric motors can be very efficient. However, the motor is only one part of the total system in an electric car and the overall efficiency is very much lees than 90%. Nearer 60% as stated
I've probably done more energy / mass balances in the real world than AC can possibly conceive of. A good place to start learning is rule one, which AC is either ignoring or has never learned :-
First define your system boundaries.
In this case the boundary is the car, not the electric motor, and the start point is the AC wall outlet as stated earlier in 'Everything's 90%'.
If this thread achieves nothing else this glib statement must be debunked in the context of electric cars.
The usual electric motor is static and runs on stabilised mains power. It runs essentially at constant speed under constant known load and can be designed to be extremely efficient.
The car however must rectify the AC power source then store it. The DC output must then be converted back to a very special form of AC suitable for automotive (speed controlled) use. Only now do we get to the 'electric motor'. This is far from the standard unit described above and must operate under widely varying speed and torque conditions. It might have a 'sweet spot' and, if the design engineers are ever allowed to release the true efficiency of their composite systems, this is what will be quoted. Away from this optimum design region efficiency must fall off rapidly.
To recap:
Standard electric motors - very efficient - better than 90%
Electric cars - complex series of processes running under difficult conditions - probably less than 60% overall.
Everybody seems to try to apply 90% efficiency to all parts of electric cars, and then to the car itself. So far we've seen this magic figure applied to battery charge / discharge and standard electric motors. It could also be applied to the charge rectifier / control system, especially if very fast charge times are needed. Then there's the drive inverter - variable frequency motor speed control systems aren't easy.
Ignoring mechanical transmission losses it should be noted that overall efficiency of the electrics (ex AC wall outlet) is now down to 0.9 power 4, or 66%.
Also many years ago, we had the bearings on a 80kw motor fail so catastrophically that the rotor shorted out the windings. It tripped every overload back to and including the main site incomer (north). The emergency generator started up on auto, ran up to speed and connected into the system. Then cut out on overload. It did this twice more on auto before locking out. Started to check the system before connecting to the alternative incomer (south - what else). Found a dead short caused by the distribution panel in the original fault path having all the terminals (3 phase) fused together as one solidified lump of molten metal.
I can imagine a direct lightning strike being somewhat worse!
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