Brakes : From Drums To Discs

Brakes : From Drums To Discs

Since the dawn of automobiles to now, they have come a long long way ahead. In terms of technology, aesthetics and performance. So much ahead that now the automobile manufacturers have to limit the true potential of their vehicle’s performance, just to keep it under control because the way accidents are happening anyone and everyone could turn out to be a damp squib.

The automobiles these days are capable of going well over 300 km/h with ease, fascinating. The scenery around you turns hazy, close your eyes for 5 seconds and you would have passed half a kilometer. Scary! Isn’t it? But imagine yourself with having no brakes at that speed, and that is something which is really scary. As the top speeds go higher and engines become more powerful, we need stronger, smarter and effective brakes. Not to forget the first automobile accident happened when a steam-propelled vehicle lost control and hit a wall, at a staggering 3 km/h. Well, that is how far automobiles have truly come ahead.

Today our emphasis is on brakes, the principle of braking is quite simple : to slow down an object by removing its kinetic energy. The braking systems these days are the pinnacle of current day technology with pneumatics and electronics; but one of the early component which started it all is, Drum Brake. While Drum Brakes have been here since more than a century, they are turning evanescent gradually as everyone is shifting to Disc Brakes. Braking systems have seen themselves evolve from:

– Wooden Block Brakes

– Mechanical Drum Brakes

– Internally Expanding Drum Brakes (Shoe-Brakes)

– Hydraulic Brakes

– Disc Brakes

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But out of these, Drum Brakes and Disc Brakes have impacted braking systems the most. With Drum Brakes laying out the base to advance in terms of new braking systems, Disc Brakes have taken over from them with grace. Today, we will simply compare Disc Brakes and Drum Brakes.

Working :

Drum Brakes :
They work by pushing outwards, two semi-circular shoes housed within the Drum.
The Drum spins with the wheel and the shoes push against the inside wall to apply brakes.
All major system components are within the Drum.
It is an internally operating system, as the Drum is mounted inside the wheel hub.
 
 Disc Brakes :
They work by contracting the brake pads mounted inside the calipers.
The calipers are mounted on the disc shaped rotor which spins along the wheel.
Calipers are on the outside making it an externally operating system.

 

Construction :

Drum Brakes :
 

It consists of a cylindrical drum made of cast iron.

It also has a pair of shoe-brakes, return springs and actuating mechanism.

It can also be called internally expanding type shoe-brakes because of its function.

 
Disc Brakes :

It consists of a disc shaped metal rotor, with a mounted caliper.

The caliper consists of brake pads and piston for activation.

On application the caliper contracts the brake pads to apply pressure.

 

 

Major Differences :

Drum Brakes Disc Brakes
 
Maintenance is cheaper. Higher maintenance cost.
Comparatively weaker performance. Superior performance.
Evanescent technology. Fresher and stronger system.
Simpler Operations. Complex working.
Performance suffers under rains. Better performance under rains.
Heat dissipation is lesser. High heat dissipation.
Faces a lot of brake fade. Works well against brake fade.
 

 

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It is clear that Disc Brakes have a superiority, but we still find vehicles using Drum Brakes at the rear. You might be wondering why? But the manufacturers know that under braking, the weight of the vehicle shifts forward and it is majorly the front brakes which undergo the braking stresses. Almost 3/4th of the braking is done by the front brakes, so the rear brakes are there for the assistance only and that is why the manufacturers use Drum Brakes or smaller Discs (in two-wheelers). This also saves them manufacturing cost and helps them provide as much safety as possible. Also if you consider in terms of cars, Drum Brakes can also double up as parking brakes (hand brakes) as Disc Brake requires separate mechanism for the same purpose.

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With continuous advancements we now see, different high-end materials like carbon fiber being used for Disc Brakes. Also electronics have taken up the charge in making braking systems better, safer and more efficient. Electronics such as :

ESP – Electronic Stability Control

TCS – Traction Control System

EBD – Electronic Brake Distribution

ABS – Anti-lock Braking System

EBC – Engine Braking Control

But we will talking about this in our future post as we dedicate this one to Drums and Discs.

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