Loose Wheel Nut Indicators

Today's trivia is all about loose wheel nut indicators.

These seemingly simple devices are placed over the nuts used to secure a wheel to its wheel plate. Clearly they are designed to give a visual indicator to the driver when the nut slips. However the question I wanted to answer was: why do wheel nuts slip?

Wheel Failures

The problem of a loose wheel is clearly significant. Both in terms of control of the vehicle involved and anything else in the path of the wheel.

It was estimated in 1992 by the National Transportation Safety Board (US) that there were between 750 and 1050 incidents per year relating to heavy trucks. The actual figure is expected to be higher, as these are the reported incidents.

Typically when a heavy truck loses a wheel it will continue to travel at the speed of the truck, and might fly high into the air because it is suddenly no longer under load.

Certainly we can from video examples that the wheels have a lot of energy.

Driver was ok in this video

Causes of failure

There are numerous reasons why wheels fail to remain attached to the vehicle. Of these the most common are failures of the wheel fastening. Simply put the wheel nuts that hold the wheel to the wheel plate shake loose.

Another possibility is shearing of the wheel plate lug

Nuts and Bolts

In normal use, a nut-and-bolt joint holds together because the bolt is under a constant tensile stress called the preload. The preload pulls the nut threads against the bolt threads and holds it in place. The nut cannot rotate without overcoming the friction between these surfaces.

If the joint is subjected to vibration, however, the preload increases and decreases with each cycle of movement. If the minimum preload during the vibration cycle is not enough to hold the nut firmly in contact with the bolt and the bearing surface, then the nut is likely to become loose.

The amount of tension we can apply to a nut is based on the hardness of the steel. Harder steels are able to withstand greater tension before they fail. There are various standards which govern the hardness of steel fastenings like nuts and bolts.

Graph showing the behaviour of a bolt under tension including the elastic and plastic regions

Steel

Commercial grade steel for use in joint assembly fastenings are hardened by two different methods depending on the type of steel used:

• Low (less than 0.25%) carbon mild steel which is 'case hardened'
• Medium (0.25%-0.5%) carbon and alloy steel is 'through hardened'

The carbon content of the steel is significant in how its hardness can be improved. Mild steel with a low carbon content when heated and quenched will not increase in hardness. Only medium and higher carbon steels can improve in this way. This is known as 'through hardened'.

Instead low carbon steels are heated and sprayed with a chemically reactive carbon compound. When the steel is quenched this reactive coating forms a hardened case around the softer steel.

Oil, water and high pressure gas can all be used to rapidly quench hot steel

Conclusion

The problem of a loose nut on a wheel is surprisingly complex.

In order to secure a wheel assembly correctly you need appropriate fastners. Nuts secured against the bolts hold the wheel in place, because they can generate enough friction to prevent the nut from loosening.

They can only generate that preload friction because the steel the nuts are made of is sufficiently hardened to ensure the thread does not deform under load. Too little tension and the nut will easily come loose from vibration. Too much tension and the bolt threads might strip or the entire bolt shear off.

Maintenance schedules are there to check that wheels are fastened correctly on regular intervals. However, loose wheel nut indicators are there to provide a visual inspection method by drivers prior to driving the vehicle.

References

Metallurgical engineer from MEA Forensic

Compilation of wheel failure video

Research by the Ministry of Transport Ontario

Bolt Science FAQ

Drones

Today's trivia is all about drones, and some of the interesting developments in the field of drones.

One of the key characteristics of a drone or UAV (Unmanned Aerial Vehicle) is that it unpiloted. Control for the aircraft might be remote control or it might have a varying degree of autonomous control built into it.

A drone configured for racing, as we'll see more of later.

We will only be focusing on the civilian usage of drones for this article. Military usage is ever expanding in a variety of roles. The US military is now training more UAV pilots than conventional aircraft pilots.

Technology

There have been a number of key contributing technologies which have all recently been developed to bring drones to the wider consumer market. Remote controlled aircraft have always been present in the market for hobbyists. Drones however are marketed at a much wider audience and a price which makes that feasible. It is now even easier to build your own drone.

The following are the key components which make up a quad-copter.

Battery - The battery of choice is LiPo - Lithium Polymer or more accurately a hybrid which uses a liquid electrolye instead of a completely dry cell LiPo. Functionally we are dealing a light, compact and high energy density battery technology which gives out more power than conventional rechargeable battery technologies. Because it is made of folded layers of coated material it also does not need to be packaged in a metal container thus saving weight. A trade off in these batteries is that they have less potential charges than earlier batteries.

Motors - The motors of drones are another key area of development. Small and compact with high power outputs. Either brushed or brushless motors are used, with brushless motors becoming increasingly popular. Brushless motors flip the existing motor design on it head by having the rotating part of the motor hold the permanent magnet, and the electro magnets are fixed inside the casing. This allows brushless motors increased efficiency over brushed motors.

Example of the sensor board which could be combined with Arduino to build your own drone

Flight Controller - The flight controller of a drone is made up of three main parts. Electronic Speed Control drives the motors, Inertial Measurement Unit provides position inputs and the Flight Controller which is typically an 8-bit processor. These three elements combined together allow the drone to not only hover but perform a whole range of operations.

13 people indicate they have made this mini quadcopter design

Frame - There are numerous frames to choose from, each with a different intended purpose. It is also possible to 3D print the frame for a drone. This allows even more customisation around the design and functionality of the drone. The sharing and refinement of designs might further simplify the ability of individuals to build their own drones.

Uses

The usage of drones has grown rather dramatically. The following are a subset of the uses for Unmanned Aerial Vehicles:

Delivery: Both Google, Amazon and others are actively exploring the idea of drone based delivery systems. I would hazard a guess that if they succeed in participating with the regulatory authorities in each country, drone deliveries will be actual reality.

The latest version of the proposed Amazon Prime Air drone, video

Photography: From amateur photography to journalism to wildlife research and more. The fact that a camera can be mounted on a drone and the image recorded or transmitted back makes for very compelling options. Footage often appears in the media which was recorded by a drone.

Getting unique views of something which might not be possible otherwise video

Another example of gaining a unique perspective

Racing: Perhaps the most exciting possibility of drones is the ability to race them. Typically done using FPV (First Person View) allowing the pilot to see the view from the camera on the drone. Because drones fly in a three dimensional space it also makes sense to lay out courses in locations which lend themselves well to this. Drone racing is only just beginning, but it is clear that there is interest in this novel and exciting sport.

Racing drones in an empty stadium with Drone Racing League

Another example of drones and their maneuverability Drone Racing

Safety

The aviation authorities of the US and UK and many others are rapidly issuing guidelines explaining how people should fly their drones. This is a pivotal time for drones and legislation and the next few years will see developments particularly in the commercial area of drone usage.

Flying safely should be an obvious requirement, I would imagine because people are physically disconnected from their drone they make different decisions. There doesn't seem to be much people cannot crash their drone into:

• Planes
• Trains
• Buildings
• Lakes
• Power lines
• Athletes
• The White House

etc.

Wildlife may not be impressed with your drone

LEGO

Today's trivia is all about LEGO and some of the interesting things people have done with it.

History

Lego History

The LEGO company was not called LEGO to start with. It was founded in the early 1930's as a carpentry business, and later moves into wooden toys, they take on the name LEGO from Leg Godt "Play well" in Danish and establish a motto of "Only the best is good enough".

In 1942 their factory producing wooden toys burned down. However they seemed to bounce back from this setback quickly. The first patent for a LEGO brick we recognize today was issued in 1958, but the company had been building a brick system before that and finally settling on a plastic style brick.

Automatic Binding Brick design around 1950

Scale of Production

LEGO Facts

There is a lot of LEGO in the world. In 2012, 45.7 billion LEGO bricks were produced in a single year at a rate of 5.2 million per hour.

The modern manufacturing process for LEGO operates on huge and almost completely automated scale.

A video detailing the entire manufacturing process

• Large silos store coloured plastic granules in huge quantities.
• The plastic is melted at 232 degrees C and injected into a mold before cooling and storing in a tub.
• Robotic vehicles travel the factory collecting the filled boxes for storage.
• LEGO kits are made up from the stored blocks (by hand? uncertain.)

There are currently around 4,200 different parts or elements in the current LEGO range.

Minifigures

Boba Fett from the Star Wars Cloud City LEGO set is one of rarest and most collectable minifigures ever created.

Minifigures are the little characters in LEGO.

• First developed in 1978 and exactly four blocks high (without a hat) they are made in a similar automatic fashion.
• LEGO designers chose the color yellow to best represent all races and ethnicities.
• An estimated 4 billion have been made – making it the world’s largest population group!

Life Hacks

Google

People understandably find LEGO rather useful, here are some of the things they've created using it:

Repairing walls

Lots of different things

Model Building

People are also rather enthusiastic about building almost anything LEGO:

The world’s tallest LEGO tower at 34.76 meters

A 1:1 Scale model of the LEGO X-Wing model Article

Creating models from science fiction games like Mechwarrior - Full Size

Castles

I don't know what this is, but its quite impressive Link Full Size

Going Further

Even more facts about LEGO

Re-Brick

Marine Cables

The Submarine Map of the World produced by TeleGeography, complete with the inclusion of depictions of sea monsters in the spirit of medieval/renaissance cartography - Full Size

Today's trivia is all about the cabling system that makes up 99% of all international data transmitted, an essential part of the Internet, the marine cable network.

The first successful cable attempted was between England, Dover and France, Calais in 1851 and by 1858 there was another successful laying of cable across the Atlantic, from Ireland to Newfoundland. (The 1857 attempt failed in cable break)

From there it became quickly clear that the ability to communicate both securely (as opposed to radio where anyone could receive the message) and quickly was apparent. At the time the company operating the cable was charged at $5 a word, and could transmit at a rate of 6-8 words a minute.

This lead to a boom in the marine cable industry and by 1901 the Eastern Telegraph Company had established a large network around the world.

Map of the Eastern Telegraphy Company - Full Size

Technology

The early cables where a combination of a number of advancements of the time to produce a viable marine cable.

Cut-away of an 1851 cable used in the Dover-Calis cable

Copper was of course the conductor of choice, however uncertain in quality.

Insulator: Gutta Percha, the rubber-like sap of a tree found only in the British Empire provided a resilient and flexible insulator.

Armour: A method of armouring cables with iron wire ropes was developed to work the hoisting machinery in Germany’s deep mines was used.

Hydrography: In 1849, American naval vessels began systematic deep-sea soundings in the Atlantic which allowed the plotting of an ideal route over the sea bed.

Cross section comparison of marine cables

Cables where initially electrical in nature, until around the late 1980s there was a switch to fiber optics as a reliable and faster technology. Modern cables are are typically measured in the hundreds of gigabits per second, or terabits per second.

Fiber optic cables don't have the signal range of electrical cables, so instead they use solid-state optical amplifiers placed at regular intervals and powered by a power line that runs down the code of the cable to amplify the signal and relay it onto the next part of the cable.

Causes of faults

• Fishing with trawl nets is one possible cause for damage to marine cables, apparently a common practice during the Cold War.
• Earthquake and associated tsunami or mudslide is an natural cause for damage of marine cabling. Whether it is movement on the seabed or movement of the water which causes the cable to scrape against rocks, damage can be done to the cable.
• Thieves in 2007 stole 11km of cable in the Vietnamese sea which connects Thailand, Vietnam and Hong Kong. The repair vessel was perplexed when it was sent out to investigate only to find a large section missing. The thieves were later caught trying to sell 100 tons of scrap cable. Cable theft is on the rise.
• Sabotage suspected in 2013 images and a news article were released indicating that three men with diving equipment where responsible for a large scale outage of the SEA-ME-WE 4 marine cable.

Repair

In order to repair a broken cable, it has to be located on the sea bed. Accurate recordings of where the cable was laid are crucial.

A ship like the Pierre de Fermat is custom built for the task. At 100 meters in length and a beam of 21 meters, GPS positioning and thrusters for positioning, it is purpose built for the task of repairing and laying cables.

The Hector 7 ROV being unloaded - Full Size

In the case of cable repairs, a vehicle like this Hector 7 ROV are ideal for the task. The size of a van, it can drive along the sea bed, locate the cable and then attach to the cable before being brought back up to the surface. Then it can find the other end of the cable and an appropriate splice can be performed to join the two ends together.

References

• History
• Submarine Cable Map

Freeze Dried

Today's trivia covers two subjects in one thus making it rather exciting.

What is freeze drying, and what does it do to coffee?

First developed as a method of preserving medical treatment and pharmaceuticals during WWII. Freeze drying is now often applied to food-stuffs as an effective method of preservation that increases the shelf life of food.

In the case of a jar of instant coffee this will extend its life well beyond that of the original bean based product.

The process of freeze drying food removes almost all the water from the food. In doing so the food is preserved by preventing the usual spoiling agents of bacteria and mold from affecting the food stuff.

However as you might expect this also has an effect on flavor in some cases as water is not the only component dried out of the food stuff. Volatile compounds like acetic acid (vinegar) and alcohols are also prone to loss in the drying process.

Another side effect of freeze drying is that it makes the resultant material quite water soluble afterwards as the process leaves microscopic pores in the material. In the case of pharmaceuticals this is quite the benefit as it allows quick re-hydration. We have Clarence Frank Birdseye II to thank for that, yes the same Birdseye as the fish fingers.

Wet books can be recovered using freeze drying as well.

Sublimation

The principle behind the freeze dried process is sublimation, which brings us nicely to the triple point of water. This is the temperature and pressure where three phases (gas, liquid and solid) of that substance coexist in thermodynamic equilibrium.

Graph showing the relationship between the three states of water against pressure and temperature full sized

When water is cooled below its triple point, we can then use pressure changes to force the water to transition from a solid to a gas by a process known as sublimation. In this case the water literally transforms from frozen solid to gaseous form without passing into a liquid in-between.

Industrial Process

So with this useful knowledge we can understand how it might work in an industrial process like the manufacture of instant coffee.

The coffee beans are roasted, ground and brewed as you might expect. However before the freezing process takes place the coffee is reduced to a syrup to ensure it retains the most of its flavour once dried.

Coffee syrup is moved onto a flat conveyor to ensure it is a consistent depth

Then the coffee is moved to freezer room kept at -50C. At this temperature the coffee will freeze very quickly. The speed of the freezing is important to reduce water crystal size and thus damage to the food stuff being freeze dried.

Factory staff dressed in thermal insulation when entering the industrial freezer

Once completely frozen the coffee is then broken up into granules, before being moved to a pressure chambre.

Sheet coffee is broken up into smaller pieces whilst at -50C

From here we move onto the pressure chamber which will reduce the pressure whilst warming the coffee to speed up the process of sublimation. In the image below the coffee takes 5 hours at 60C to sublimate almost all of its water.

The coffee granules are placed on trays and moved into a vacuum chamber

Then as you would expect bottling and packaging commence afterwards.

The factory in this video produces 420 tons of coffee each week.

References

For those that want to see the process in action, this video is informative.

Wikipedia:

• Triple Point
• Freeze Drying