Comparing belt drive dynamics to chains, slippage is the first differentiator that comes to mind. Of the two power transmission systems, chains have the advantage, with physical sprockets engaging against chain links. Belt drives, on the other hand, rely on supplementary components, such as tensioning arms, to maintain positive contact with featureless spinning drive pulleys.

In applications that are characterized by intense startup energies, chain drives are simply the logical choice because of this fact. High-torque, heavy-load scenarios are typical chain-driven systems, promoting zero-slip and creep-less rotational energy coupling. Although creep and slip sound like interchangeable terms, they are different from one another. Slip is slippage between the belt and pulley, whereas creep is an elongation effect caused by material deformation. Chains, although metal can deform slightly, don’t typically suffer from creep.

Belt drives have evolved teeth and are not to be outdone. Expect to find these timing or synchronous belt drives in engines and other intricate mechanical systems that rely on nth-degree power transmission control. These non-slip belts provide synced-up contact, eliminating startup slip and transient power transmission losses.

Source: navintar/Adobe StockSource: navintar/Adobe Stock

Belt versus chain key differences

Belt drives are cheaper to install, as they're made of soft, flexible materials. Industrial fabrics and plastics, combined with reinforcement metal threading and rubberized layers, ensure a long life while minimizing drive creep and slip. Chain systems are obviously that much more expensive to install and maintain. They’re made of durable alloys and must be lubricated to keep frictional losses at bay.

Ideal for lower load applications, belts require less general maintenance — although they do age faster — and their flexible construction allows for greater shock energy absorption. Chains can produce more noise, and they’re only ever as strong as the weakest link in a bush roller chain. It’s not a clear-cut matter of one being superior to the other. Rather, it’s the application that decides which system should be installed.

Generally speaking, belt drives are the quieter, vibration-dampening solution, one that’s used in low to moderate-loading applications. Chains are the capable choice for higher torques, but their lubrication needs make maintenance a more complicated issue to deal with. A loss in system lubrication introduces friction, thermal losses, and audible noise.

Belt drives are a less practical solution in hot or caustic environments, and they wear faster, slipping and sliding as they age.

Engineering mathematics

With engineering mathematics, considering applications becomes simpler. The unbiased truth is clearly seen in formulas, with their constants and variables. For example, the torque formula (T = (F2 - F1) ra) can apply to both belt and chain drives, but it’s more used when expressing chain dynamics because there are fewer losses of note to attribute to chain systems. Where

T = Torque, F1 = Slack side tension, F2 = Tight side tension, ra = Radius of the pulley.

There’s a direct correlation between pulley size and the force, in Newtons, applied by the drive system. In belt drives, things get more complicated, as seen in these formulas: T = (F2 - F1) ra µ or T = (F2 - F1) ra (1 +C).

The formulas are similar, but now there’s a coefficient of µ and C to account for when calculating overall torque. The latter coefficient expresses creep, whereas the former one is used to offset the effects of friction, as imposed by a belt drive that is experiencing slippage.

Examples of belt and chain systems

A record-breaking power transmission system, using belt drives, transports Bauxite across a 50 km distance. It’s located in Boddington, Australia, and is known as the South 32 Overland Conveyor Belt. In Germany, the gigantic Bagger 293 bucket excavator uses chains to drive its buzzsaw-like wheel, while belt-driven conveyors carry coal to be crushed and delivered to power stations. If there’s an incline on one of these lines, chains take the place of slippage-prone belts and pulleys.

These are extreme examples but highlight certain scalability-related efficiency challenges. As equipment grows larger, losses multiply, too. Keeping these losses low then becomes a major problem. To do so in belt-driven systems, idler pulleys and spring-loaded tensioners keep belts tight and slippage low.

Special carbon-fiber belts are also entering service. They can be seen in use as timing belts and in other applications that don’t require substantial form factors. As for chains, the Bagger 293 has a small team of workers operating around the clock on walkways to maintain its drive systems, ensuring lubricants reach their destination, among other important duties.

Future research

The trapezoidal v-ribbed belt design has been around for a long time now. It uses the laws of physics to slot high-tensile flexible belts into pulley grooves, thereby increasing grip as the system gains speed. The belt seats tightly, slippage drops, and system efficiency rises. Cogged belts are currently being explored as material improvements develop as well.

Meanwhile, chain drives are seeing an uptick in developing nations as heavy-duty distribution systems flourish. More marine propulsion cargo equipment, vehicle engines and aerospace applications demand exacting chain-driven technological solutions. Variable pitch architectures, friction-reducing alloy coatings and new space-age lubricants are likely to rise in the coming years, too.

Trends indicate a shift toward the internet of things market, with a whole new branch of technology called condition monitoring on the rise. These little sensors create network meshes, transmitting signals to a central server. Technicians can then see, in real-time, whether lubricants and coolants are reaching a chain or pulley system. Idler tension can also be picked up by one of these sensors, as can the vibrational events that cause wear and tear.