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Joints: Different types & their contribution to the automotive industry

What I want to show is how a simple joint changes everything and what do quality obsessed companies do to a simple hardware to make it timeless.

BHPian aquavivarium recently shared this with other enthusiasts.

I have been reading this portal since 4 years and joined recently. I guess the core thought behind this group is the sharing of original, unbiased and unique ideas. Each of us is special and thinks differently.

We all had experiences and our own learning curves. Being in different parts of the globe, having different backgrounds and social positions adds new dimensions to the conversations. Irrespective of such a vibrant mix we all have one thing in common – love and commitment for our set of wheels, be it cars, bikes etc.

Since humans invented assisted means of mobility the world has changed faster than men could fathom, wheel is the numero uno invention. From experimental to novelty and then mass production. A metal or wooden box with initially 3 then 4 wheels, propulsion and control surpassed every other type of transport. It was for a simple reason STABILITY, this design did not require balancing, was easy to maneuver, could be modified easily to suit utility and gave a comfortable ride.

No wonder this design was chosen to be pulled by domesticated animals, we had two wheel designs but the instability is obvious:

Patent for the first “Benz” car was registered in 1886, as a few bold people thought to replace horses with Horsepower. Still these were restricted to experimental models OR for a very few elite.

“Necessity is the mother of invention” proved true as First world war lead to development of Piston engines on a large scale. Carbon based fuel powered engines entered main stream, massive industries were set up , piston engine proved its might and became the backbone for providing power and transport . Although the driving force was war a few began to imagine and develop the idea of a personal means of transport using similar engines for the masses.

At the end of First world war ,we saw the emergence of “ Car “ , it was a fun machine for the few lucky , was mostly handmade and assembled with focus on just one thing –Quality. Customers now were the bourgeoisie, the rising class and then we had the second war. With the piston engine well established now was the turn of the Jet propulsion. Post 2nd war , car was already a common sight and manufacturers already aimed for mass production. Now Quality was in focus but not top priority, still a few remained committed and to this day give us products which “ feel “ different and “age” differently.

Remove all branding from a 10-15 year old Lexus OR Maybach and compare with a average family car of same type & age , what is it that keeps a good quality machine going on and on, answer lies deep inside in a simple Bolt and Nut “ joint ”. And this is precisely my topic and I intent to explain “Quality” by the most elementary and innate feature of any machine . Starting from the simplest cycle to the Large Hadron Collider, everything we make and assemble has a “Joint “.

Difference between a Rolls and a Maruti is very obvious. In fact, it is stupid to compare, yet both serve the same purpose. Let us assume we take all the major parts of a Rolls eg – chassis, engine, upholstery and everything we see in a Rolls, and assemble it in a Maruti plant, will we get a Rolls?

Please note I don’t intend to downgrade Maruti, I have bought their cars and always appreciate their suitability to Indian ecosystem . What I want to show is how a simple joint changes everything and what do quality obsessed companies do to a simple hardware to make it timeless. I have mostly made the pics myself, they are not technically accurate and still convey the underlying message .

Now lets start by example:

Our joint will consist of two metal pieces joint by a bolt and nut. We shall continue to improve the same and give reasons alongside:

Basic: As shown, we have joint two metal pieces by a bolt and nut, they can take all the tension and shear loads, torque is fully tightened by hand tool, this is a fairly sturdy joint. We see this happening at most repair shops.

Calibrated Torque (use of torque wrench): Anyone with basic mechanical knowledge knows the importance of correct torque, it depends on the bolt/nut size, thread type, material etc. It is a measure of how hard the threads of the two will engage with each other OR amount of friction lock. Less torque will loosen and more will create undue stress on the joint and might lead to a material failure. Torque values for nut and bolt are different and must be kept in mind. In high temp. areas to prevent jamming of the nut a "neverseez“ compound is also used on the bolt threads.

Locking NUT: All joints are subject to vibration and/or thermal cycles, over a period of time the nut is bound to get loose and results can be catastrophic, and various ways are used to lock. As shown, we can use two nuts, lock nut or a cotter pin in the hollow shank of the bolt which prevents the nut from unscrewing itself. Bolt head also can have a provision for wire locking. Lock wiring is a skill, which takes time and will to learn.

I have experienced bloody fingers and much resentment myself, but to complete a complex lock wiring job gives a satisfaction like art work. In aviation, wire locking bolt is a very widespread.

Chamfering/beveled edge: Loads paths in materials tend to accumulate at sharp corners, thus edges are rounded for a larger surface area contact to prevent edge cracks. As shown above notice the edges are now cup shaped thus sharp edges are avoided.

Washers/Bushings: They serve two purposes; Distribute the load on a larger surface thus prevent the damage to sheets and they are made of softer material thus they wear out protecting the main hardware. Washers can also be lock type.

Surface protection: Metal corrodes or oxidizes to slowly weaken and give away, especially in high temp, acidic and abrasive environs . Dissimilar metal corrosion also happens at joints. Thus electroplating, primer, paint , enamel coating is done on the hardware and the sheet to make it long lasting.

Sealing the Joint: to make the joint lifelong Or in places with extreme environs like fuel tank, bridges, under ocean etc . The complete joint is made invisible by completely covering it with sealants like silicon etc.

Thus we see the evolution, might not be technically spot on ,but the message is loud and clear: Quality and character of a machine is more built in then visible, what it gives is feel, handling, running dynamics and graceful ageing than the bling bling we experience . High quality products are so because their creators do different things AND things differently. It is the zero-compromise culture with continuous improvement and an eye for detail that these manufacturers strive fo , be it a engine mount or a upholstery clip, they know that it is just not the quality material but also the way it connects to others which effects the final product.

Perfect execution of a sharp turn on a long winding road is motorists heroin. In those moments no one is looking at a 10 inch screen or hearing a BOSE sound , at that time your vehicle is your song and a good engineered machine will give you that pleasure all its life.

Car buying decision has biases, we see the Koreans pulling customers by increasing touch screen size, putting fancy white lights and adding chrome. Very well engineered products like the Compass are not people's favorite, Fiat Palio was a hot hatch still had a early demise. My suggestion to people before buying is to read long term reviews and If Germans ask for a premium price, its not for what you see but what's inside right up to each nut and bolt.

I am an engineer and work on commercial aircraft like the Boeing 737 and Airbus 320. I have visited factories where they are built and assembled. Will post on commercial aviation soon.

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