Interesting Stuff

[tok-tokkie]

I have seen some really interesting stuff on this thread.
Here is a video about the McLaren MP4/4. It happens to be a F1 topic but that is incidental.

[johnny comelately]

As "we" move into electrification this subject becomes more important.
Here are the basics, and from what I interpret we still dont know what electricity is or electromagnetism. Humans are clever that way though, they figure out how to use it anyway.
Is that ideal, probably not as shown by the size of vehicle electrical componentry and the heat problems, our children will look back at these times and smile.There has been a parallel situation with IC engines where for a century we just made it work but in the last few years it has been approached scientifically which has unlocked the true behaviours of an IC engine. This has been perfectly shown in the diesel Le Mans cars and now more amazingly in the latest F1 motors.

[Tommy Cookers]

... There has been a parallel situation with IC engines where for a century we just made it work but in the last few years it has been approached scientifically which has unlocked the true behaviours of an IC engine. This has been perfectly shown in the diesel Le Mans cars and now more amazingly in the latest F1 motors....

the true behaviours of an IC engine were for a century .....
locked out by F1 and GP rules (being capacity-based not fuel-based) - so rewarding fuel inefficiency not fuel efficiency
eg F1 has just allowed (80 year old) Miller cycle and (80 year old) power recovery turbines

and it still bans any kind of energy accumulation (for better laptime) - unless done electrically
until 30 years ago power electronics (and batteries) were rubbish - that's what prevented wind power

[johnny comelately]

... There has been a parallel situation with IC engines where for a century we just made it work but in the last few years it has been approached scientifically which has unlocked the true behaviours of an IC engine. This has been perfectly shown in the diesel Le Mans cars and now more amazingly in the latest F1 motors....

the true behaviours of an IC engine were for a century .....
locked out by F1 and GP rules (being capacity-based not fuel-based) - so rewarding fuel inefficiency not fuel efficiency
eg F1 has just allowed (80 year old) Miller cycle and (80 year old) power recovery turbines

and it still bans any kind of energy accumulation (for better laptime) - unless done electrically
until 30 years ago power electronics (and batteries) were rubbish - that's what prevented wind power

Only in a digressing macro sense are you right but you have missed the point which is our current designs and rules about the electrical side (and materials) will be looked on as cumbersome as was our approach to IC engine power because we did not understand the fundamentals just the resultants.
What I was referring to was the combustion efficiency: while chasing performance, as opposed to performance and efficiency, we simply maximised everything and then running as lean as we were game but still so very rich and then played with timing all to avoid detonation (still the case necessarily with nitro engines). And now we run them an "impossible" lean that would have been impossible to fire up without backfire damage and would have destroyed the engine if it did and would not have had any power!
What did you think of the explanation of the electric fundamentals by the way?

[Tommy Cookers]

... our current designs and rules about the electrical side (and materials) will be looked on as cumbersome ...
... combustion efficiency ....
....now we run them an "impossible" lean that would have been impossible to fire up without backfire ....
What did you think of the explanation of the electric fundamentals by the way?

nothing cumbersome - the electric cycle (apart from the battery) is c. 95% efficient (helped by 8-speed transmission)

indicated thermal efficiency ITE (not combustion efficiency) is .....
the work applied to the piston crown relative to the heat content of the fuel

the consensus seems to say F1 is Miller cycle and so leaning isn't beyond precedent - given the fuel is heated etc

the electromagnetic fundamentals haven't changed - the devices eg FETs etc have (and liquid cooling helps)

[johnny comelately]

... our current designs and rules about the electrical side (and materials) will be looked on as cumbersome ...
... combustion efficiency ....
....now we run them an "impossible" lean that would have been impossible to fire up without backfire ....
What did you think of the explanation of the electric fundamentals by the way?

nothing cumbersome - the electric cycle (apart from the battery) is c. 95% efficient (helped by 8-speed transmission)
IT IS CUMBERSOME IN TERMS OF WEIGHT, SIZE AND COOLING REQUIREMENTS (INCLUDING THE BATTERY)

indicated thermal efficiency ITE (not combustion efficiency) is .....
the work applied to the piston crown relative to the heat content of the fuel
THE ABILITY TO HAVE THESE CURRENT ENGINES HAS BEEN ENABLED BY A DEEP DIVE INTO THE FUNDAMENTALS OF COMBUSTION UNDER IC ENGINE CONDITIONS AT AN ATOMIC LEVEL, NEVER BEFORE DONE. ALONG WITH ADVANCES IN MATERIALS TO ENABLE THE EFFICIENCY.

the consensus seems to say F1 is Miller cycle and so leaning isn't beyond precedent - given the fuel is heated etc
FUEL HEATING CAME FROM UNDERSTANDING COMBUSTION AND YES THAT HAS PRECEDENT BUT THE MOLECULAR LEVEL OF KNOWLEDGE REFINED ITS USE.
I WISH THE TERM "MILLER CYCLE" WOULD NEVER HAVE BEEN COINED AND SHOULD BE DISCONTINUED AS IT IS A GO TO FOR THOSE THAT SHORT CIRCUIT EXPLANATIONS (nothing personal there Tommy). TIMING IS TIMING AND WHAT WORKS FOR A GIVEN, JUST WORKS.

the electromagnetic fundamentals haven't changed - the devices eg FETs etc have (and liquid cooling helps)

[johnny comelately]

This slightly eccentric talk broadens the idea of combustion, quite the chemical journey...
"Electric Solid Rockets - Throttleable Solid Propellant"

[Big Tea]

I post it under interesting stuff, but I think (for now) it only affects those in California with solar, but as with these things I assume everyone wil follow on.

If you have solar in U. S., it is worth your time to watch it.

https://www.youtube.com/watch?v=cogaWBFVJWg

It concerns a time limit for existing 'contracts' after which there is a huge drop in value

[Tbrownishere]

I have seen some really interesting stuff on this thread.
Here is a video about the McLaren MP4/4. It happens to be a F1 topic but that is incidental.

Good stuff, thanks!

[Tommy Cookers]

I post it under interesting stuff .....
https://www.youtube.com/watch?v=cogaWBFVJWg
It concerns a time limit for existing 'contracts' after which there is a huge drop in value

wasn't/isn't this expected ? - and general ?

seriously .....
now that government's policies have got many big players into solar power generation etc ....
would anyone now want to put solar panels on their own roof ?

[diffuser]

I post it under interesting stuff .....
https://www.youtube.com/watch?v=cogaWBFVJWg
It concerns a time limit for existing 'contracts' after which there is a huge drop in value

wasn't/isn't this expected ? - and general ?

seriously .....
now that government's policies have got many big players into solar power generation etc ....
would anyone now want to put solar panels on their own roof ?

Also, if everyone is just using the grid as a battery, who pays for the grid?

[Big Tea]

I post it under interesting stuff .....
https://www.youtube.com/watch?v=cogaWBFVJWg
It concerns a time limit for existing 'contracts' after which there is a huge drop in value

wasn't/isn't this expected ? - and general ?

seriously .....
now that government's policies have got many big players into solar power generation etc ....
would anyone now want to put solar panels on their own roof ?

I posted it more as a prompt to anyone with or preparing a system as you have to have finalised the agreement soon to keep the current payments.

[johnny comelately]

Change of pace with this but for good reason, these geniuii are at the forefront of their disciplines: physics, chemistry, physiology or medicine, literature, economics and peace. It is one of the drivers of progress.
What is fascinating (to me) is their clear articulation of complex subjects and how they demonstrate the art of discussion.
There is one for each recent year, all totally different.
For example, the lady who works with laser development invented the use of lasers to act as tweezers that can hold a single cell without damage!

[johnny comelately]

THE ROMAN PANTHEON.
Built BC or about 100 AD

ROTUNDA.
The 4,535-tonne (4,463-long-ton; 4,999-short-ton) weight of the Roman concrete dome is concentrated on a ring of voussoirs 9.1 metres (30 ft) in diameter that form the oculus, while the downward thrust of the dome is carried by eight barrel vaults in the 6.4-metre-thick (21 ft) drum wall into eight piers. The thickness of the dome varies from 6.4 metres (21 ft) at the base of the dome to 1.2 metres (3.9 ft) around the oculus.[51] The materials used in the concrete of the dome also vary. At its thickest point, the aggregate is travertine, then terracotta tiles, then at the very top, tufa and pumice, both porous light stones. At the very top, where the dome would be at its weakest and vulnerable to collapse, the oculus lightens the load.
No tensile test results are available on the concrete used in the Pantheon; however, Cowan discussed tests on ancient concrete from Roman ruins in Libya, which gave a compressive strength of 20 MPa (2,900 psi). An empirical relationship gives a tensile strength of 1.47 MPa (213 psi) for this specimen.[51] Finite element analysis of the structure by Mark and Hutchison[53] found a maximum tensile stress of only 0.128 MPa (18.5 psi) at the point where the dome joins the raised outer wall.
The stresses in the dome were found to be substantially reduced by the use of successively less dense aggregate stones, such as small pots or pieces of pumice, in higher layers of the dome. Mark and Hutchison estimated that, if normal weight concrete had been used throughout, the stresses in the arch would have been some 80% greater. Hidden chambers engineered within the rotunda form a sophisticated structural system.[54] This reduced the weight of the roof, as did the oculus eliminating the apex.[55]

The top of the rotunda wall features a series of brick relieving arches, visible on the outside and built into the mass of the brickwork. The Pantheon is full of such devices – for example, there are relieving arches over the recesses inside – but all these arches were hidden by marble facing on the interior and possibly by stone revetment or stucco on the exterior.

The height to the oculus and the diameter of the interior circle are the same, 43.3 metres (142 ft), so the whole interior would fit exactly within a cube (or, a 43.3-m sphere could fit within the interior).[56] These dimensions make more sense when expressed in ancient Roman units of measurement: The dome spans 150 Roman feet; the oculus is 30 Roman feet in diameter; the doorway is 40 Roman feet high.[57] The Pantheon still holds the record for the world's largest unreinforced concrete dome. It is also substantially larger than earlier domes.[58] It is the only masonry dome to not require reinforcement. All other extant ancient domes were either designed with tie-rods, chains and banding or have been retrofitted with such devices to prevent collapse.[59]

Though often drawn as a free-standing building, there was a building at its rear which abutted it. While this building helped buttress the rotunda, there was no interior passage from one to the other.

The grey granite columns that were used in the Pantheon's pronaos were quarried in Egypt at Mons Claudianus in the eastern mountains. Each was 11.9 metres (39 ft) tall, 1.5 metres (4 ft 11 in) in diameter, and 60 tonnes (59 long tons; 66 short tons) in weight.[46] These were dragged more than 100 km (62 miles) from the quarry to the river on wooden sledges. They were floated by barge down the Nile when the water level was high during the spring floods, and then transferred to vessels to cross the Mediterranean Sea to the Roman port of Ostia. There, they were transferred back onto barges and pulled up the Tiber River to Rome.[47] After being unloaded near the Mausoleum of Augustus, the site of the Pantheon was still about 700 metres away.[48] Thus, it was necessary to either drag them or to move them on rollers to the construction site.

INTERIOR.
Upon entry, visitors are greeted by an enormous rounded room covered by the dome. The oculus at the top of the dome was never covered,
The oculus at the dome's apex and the entry door are the only natural sources of light in the interior. Throughout the day, light from the oculus moves around this space in a reverse sundial effect: marking time with light rather than shadow.

https://en.wikipedia.org/wiki/Pantheon,_Rome




ROMAN CONCRETE
Roman concrete, like any concrete, consists of an aggregate and hydraulic mortar – a binder mixed with water that hardens over time. The aggregate varied, and included pieces of rock, ceramic tile, and brick rubble from the remains of previously demolished buildings.

Gypsum and quicklime were used as binders. Volcanic dusts, called pozzolana or "pit sand", were favored where they could be obtained. Pozzolana makes the concrete more resistant to salt water than modern-day concrete.[10] The pozzolanic mortar used had a high content of alumina and silica. Tuff was often used as an aggregate.[11]

Concrete, and in particular, the hydraulic mortar responsible for its cohesion, was a type of structural ceramic whose utility derived largely from its rheological plasticity in the paste state. The setting and hardening of hydraulic cements derived from hydration of materials and the subsequent chemical and physical interaction of these hydration products. This differed from the setting of slaked lime mortars, the most common cements of the pre-Roman world. Once set, Roman concrete exhibited little plasticity, although it retained some resistance to tensile stresses.

The setting of pozzolanic cements has much in common with setting of their modern counterpart, Portland cement. The high silica composition of Roman pozzolana cements is very close to that of modern cement to which blast furnace slag, fly ash, or silica fume have been added.

The strength and longevity of Roman 'marine' concrete is understood to benefit from a reaction of seawater with a mixture of volcanic ash and quicklime to create a rare crystal called tobermorite, which may resist fracturing. As seawater percolated within the tiny cracks in the Roman concrete, it reacted with phillipsite naturally found in the volcanic rock and created aluminous tobermorite crystals. The result is a candidate for "the most durable building material in human history". In contrast, modern concrete exposed to saltwater deteriorates within decades.
The Roman concrete at the Tomb of Caecilia Metella is another variation higher in potassium that triggered changes that "reinforce interfacial zones and potentially contribute to improved mechanical performance".

For an environment as prone to earthquakes as the Italian peninsula, interruptions and internal constructions within walls and domes created discontinuities in the concrete mass. Portions of the building could then shift slightly when there was movement of the earth to accommodate such stresses, enhancing the overall strength of the structure. It was in this sense that bricks and concrete were flexible. It may have been precisely for this reason that, although many buildings sustained serious cracking from a variety of causes, they continue to stand to this day.[19][8]

Another technology used to improve the strength and stability of concrete was its gradation in domes. One example is the Pantheon, where the aggregate of the upper dome region consists of alternating layers of light tuff and pumice, giving the concrete a density of 1,350 kilograms per cubic metre (84 lb/cu ft). The foundation of the structure used travertine as an aggregate, having a much higher density of 2,200 kilograms per cubic metre (140 lb/cu ft).

Recent scientific breakthroughs examining Roman concrete have been gathering media and industry attention.[21] Because of its unusual durability, longevity and lessened environmental footprint, corporations and municipalities are starting to explore the use of Roman-style concrete in North America, replacing the volcanic ash with coal fly ash that has similar properties. Proponents say that concrete made with fly ash can cost up to 60% less because it requires less cement, and that it has a smaller environmental footprint due to its lower cooking temperature and much longer lifespan.[22] Usable examples of Roman concrete exposed to harsh marine environments have been found to be 2000 years old with little or no wear.[23]

In 2013, the University of California Berkeley published an article that described for the first time the mechanism by which the suprastable calcium-aluminium-silicate-hydrate compound binds the material together.[24] During its production, less carbon dioxide is released into the atmosphere than any modern concrete production process.[25] Its disadvantages include the longer drying time and somewhat lower strength than modern concrete, despite its greater durability. It is no coincidence that the walls of Roman buildings are thicker than those of modern buildings. However, Roman concrete was still gaining its strength for several decades after construction had been completed, which is not the case with modern concretes.

https://en.wikipedia.org/wiki/Roman_con ... properties

[johnny comelately]

"The entire History and Development of motorcycle Valvetrains" (not quite)
https://www.youtube.com/watch?v=repvvBo_U3M
An extraordinary collection of unique operating mechanisms

EDIT: note the tension springs across the rockers on this Douglas

which evoked: