Truckin` right

The Scream is up for sale. As a painting it`s anything but remarkable - well, to me anyway - despite those swirly lines and its creepy, abstract horror.  But obviously my opinion is not shared by all and a price tag of something like 50 million has been placed on it – dollars or pounds I can`t remember, when anything goes above the price of a house the cost is irrelevant to anyone in the real world.  So, if I were to paint an exact copy, would it sell for a similarly extortionate amount?  No, of course not.  The reason is that there`s something obscure about art: something has to be in the observer as much as in the work itself.  Or rather, something lurks in us the observer that we must then put into our observation.  The Scream is a great painting because we have accepted it as such.  Our minds tell us something like this:  famous works are worth a fortune; famous art is great art; The Scream is a great work of art; The Scream is worth a fortune. Placed in context - great works are in galleries or a private collection - the painting is positioned in our mind.  The Scream is something special that exists out of common view.  To `see` it we need to be in a particular, characteristic place – stick The Scream on the kitchen wall next to your kid`s finest works and nobody will give it a second look.

In what was described as a social experiment, the Washington Post recently put a concert violinist on the platform of a Boston metro station, playing an instrument worth, apparently, several millions of dollars.  In the previous week the same man had played to audiences paying $100 a seat for the privilege of hearing him.  The metro experience was a little different – no one really took the time to listen.  Travellers came and went more intent on catching a train or hurrying off to whatever it was they were supposed to be doing rather than listening to one of the world`s top musicians.  When small children stopped, supposedly to enjoy the music, they were soon whisked away by an impatient guardian.

The questions asked as a result were about perception, taste and the priorities of people.  Were people too busy to appreciate art, or was it that most just didn`t like that particular brand?  Or was it simply in the wrong place? We certainly like things where we expect them to be, and as we expect them to be.  A violinist in the underground is a busker, not a world class performer.  A violinist performs in evening dress; a violinist performing in jeans is a busker.  Everything is neatly ordered in our minds for recognition purposes, helping us through the day: we know what a petrol station looks like, what a main road should be and what the entrance to a track that will lead us into trouble is like.  Can you imagine not having an idea of what to  expect every time you enter a cafe or restaurant?  We need to know about a number of different situations to be able function, even if we are in a totally new place, one we`ve not been to before.  We need to recognize the familiar so that we can categorize it and act accordingly.  We are assured by the familiar; a world where everything is as it should be.

This is why the Ford Motor Company has always had my admiration: they certainly haven`t always stuck with the familiar. In terms of styling, Ford seem to have no fear in going their own way, often presenting new models that are very different from predecessors or contemporaries. The Cortina Mk3, Probe, Sierra, Ka, all these cars were pretty radical in their day.  Curvy when others were boxy seemed to be the trade mark. In many cases, it was only the distinctive badge that identified them as Fords.  But innovation is always a calculated risk - with the emphasis on calculated - and daring has its limits:  with such a wide range of products, throwing in a few wildly different models now and again had little effect on the overall perception and identification of the brand.

Truck manufacturers, in contrast, have far fewer models and even fewer platforms to build on.  Similarly, cabs retain generic styling across most of the range.  Things are tweaked until no more can be done but build a completely new vehicle.  So when a new range is introduced - say, once every decade - a completely different truck is presented to the market.  It`s here that identification, recognisability, familiarity and possibly, customer loyalty, can become a bit blurred.  Is it a Volvo? A Scania?  How does a Volvo truck present itself as a masterpiece, a famous concert violinist and not an unknown busker?  It retains a distinctive feature from range to range, model to model. 



Volvo`s F89 had the distinctive, pronounced grill ...



... which continued as a feature of the F10 ...

... and then in the FH range

We like everything to be as we expect, things to be where we expect them to be and our trucks to look as they should.  Any indication will do, no matter how small, as long as everything seems right: The Scream is in a gallery; the violinist is in tails and up on the stage; the Scania has a Scania grill. 

It`s a Scania - horizontal, grill width lines ..

... all the way down to the bumper and carried on through the years

Building a Scania V8 R500 - Part 2. Suspension, drive axle

I`m building a Scania R500 - from a 1:24 scale kit produced by ITALERI.

I`ll be discussing aspects of truck construction as I go along, hopefully highlighting some basic truck technology.  It`s easy to think that modern vehicles bear no resemblance to those of the past, but that`s not true.  Suspension and steering; engine, transmission and final drive; and tyres are all there to maximise the laws of physics, and have retained the same configuration since diesel replaced steam.  Cost and natural performance limits have meant that the chassis abandoned long ago in car design is still used in truck manufacture.   Yes, your truck is computer controlled and a modern marvel;  but so is the modern cruise liner - which is still a Titanic underneath.   




Building a Scania  R500    Part 2. Suspension (drive axle)



The live beam (non-independent suspension) drive axle is fitted with trailing arm 1/4 leaf springs and air springs.  The leaf springs are clamped to the axle with substantial fixings to prevent movement (the system has to absorb all drive and braking torques, and deal with uneven bump and body roll).  



The 1/4 leaf springs work with the axle to deal with uneven bump and body roll - they replace an anti-roll bar (stabilizer bar) in this set up.  Some drive axle systems use four air springs an anti-roll bars (e.g. 6x2 DAF 85).

How the 1/4 leaf spring system works - see both the above diagrams 

Dampers dampen the oscillations of the road spring.  Dampers provide ride comfort and have an effect on handling.  Springs store energy and are displacement dependent for the force they provide.  Dampers convert kinetic energy, the energy of motion, to heat.  They are speed dependent for the force they give.  In the simplified diagram above, the damper shows how it provides a greater force on rebound than it does on bump (bounce) by using different sized ports through which oil has to pass.  In reality, the innards are far more complex but the theory of area, force and pressure still apply. 

Next -  Part 3.  Suspension (front axle) 

Building a Scania V8 R500 - Part 1. Chassis

I`m building a Scania R500 - from a 1:24 scale kit produced by ITALERI.

I`ll be discussing aspects of truck construction as I go along, hopefully highlighting some basic truck technology.  It`s easy to think that modern vehicles bear no resemblance to those of the past, but that`s not true.  Suspension and steering; engine, transmission and final drive; and tyres are all there to maximise the laws of physics, and have retained the same configeration since diesel replaced steam.  Cost and natural performance limits have meant that the chassis abandoned long ago in car design is still used in truck manufacture.   Yes, your truck is computer controlled and a modern marvel;  but so is the modern cruise liner - which is still a Titanic underneath.   

Building a Scania  R500    Part 1. Chassis



Channel `C`  section chassis offers good resistance to bending stresses.  All chassis are subject to bending and twisting as  load and road inputs produce opposing and irregular stresses.  Section depth resists bending and flanges counter bending and torque.  The top of the rail will be under compression, the bottom under tension.  The horizontal centre is neutral.  When holes are drilled or cut into a chassis rail (sometimes to lighten the structure), the centre line is the best location due to this minimal stress.   





Ladder rail chassis construction has been around since the year dot - if it works, why change it?  Simplicity, ease of manufacture and, therefore, cost make it the most efficient platform for truck bodies. (The components in this chassis will appear across the Scania LGV range of vehicles.)  For non-independent suspension systems, the twisting that will inevitably occur in the chassis is not too critical and can be catered for by the dynamics engineer




Components are either riveted or bolted to the chassis.  Welding forms a solid piece and causes stress in the join as the chassis twists and bends.  Used as a stress barrier,  riveted and bolted joins allow for movement.  All chassis flex - even though not necessarily visible to the naked eye. A few years ago, I saw a Scania beaver tail, six-wheeler plant rigid that had been converted from a tractor unit.  The chassis had been lengthened with the support of strengthening flitch plates but every annual test necessitated the replacement of some of its body fixing bolts.  The chassis was twisting enough to sheer them.  The vehicle had been re-plated correctly and always passed its test.   

 

Chassis widens at the front, where the engine is positioned.  A narrow chassis at the rear, aligned with the 5th wheel mounting,  fully supports the 5th wheel load (at least 20% of the trailer`s weight).  As the trailer rolls when cornering, a torque is applied to the tractor`s chassis.  This torque is resisted in part by the greater force moment capability of the spread chassis at the front - being wider, the front of the chassis provides greater stability. 

Next - Part 2.  Suspension (drive axle)

Driven Mad

I get quite excited when the police publish examples of the trivial, `waste of our valuable time` 999 calls they`ve received.  For entertainment they are a great distraction, even if for just a few minutes. (“There`s a spider in my bath”, is my favourite so far.)  But, with this in mind, wouldn`t it be great if people like well-driven.net and safelydriven.com published similar examples of the idiots that must surely phone them. 

There could be several categories: 1. Near Miss, where the sound of skidding can be heard in the background in the aftermath of the caller having dialled the number while driving; 2. Swerve, signal, mirror, where the caller had attempted to change lanes on a motorway but there was a truck in the way;  3. “It`s only doing forty”.

If these companies do decide to go along with this small request, action needs to be taken quickly.  The proliferation of telematics will soon render this type of diversion redundant, and another source of comic relief will be lost. And that would drive me mad – we need all the fun we can get at the moment.

P.S.  I saw one on the back of a tanker trailer on the M42 the other day that said, “Driven Wisely?”  Now that`s got potential, I nearly dialed the number myself.