Overview

Belts are one of the standard ways we move objects or power from point A to B. In the context of the robot, it means that they are very often used to deposit the gravel into the collection bin, dig using a bucket elevator, or as a part of a powertrain. As such, it's important to choose the correct belt for the application, which heavily depends on the length required, the power transmitted, and the stability needed.

This article will mainly cover the different types of belts and common issues the team has had. For calculating the amount of power a belt will transmit look at https://www.tec-science.com/mechanical-power-transmission/belt-drive/power-transmission-of-a-belt-drive/ . For shopping or just checking some belts out, try https://www.mcmaster.com/drive-belts.

Types

Flat

Flat belts are... flat. They are not as commonly used anymore due to the other types having greater upside, but they can still be used for power transmission. These belts can go off center easily, but a crowned pulley or edge guards can fix this. They have the greatest variety in lengths, widths, and sizes due to their simplicity, and can also be used for transferring material easiest.

V-Belt

V belts have a trapezoidal cross section to fit within a groove in the pulley. It is one of the best types of belts for power transmission as they practically cannot go off center due to the V-shape. Due to the large cross sectional area, they require a larger pulley and are very strong.

Ribbed

Also called a multi or poly v-belt, these are equivalent to v-belts attached side by side and are typically stronger then a typical v-belt.

Chain and Sprocket

While technically not a belt, they're used similarly to transfer power. These can't slip, however are not ideal for a dusty environment as the particulate can easily jam the chain links.

Timing

Also called a serpentine belt, these belts have ridges going across the belt, making it act similar to a chain and sprocket. These belts will also not slip, but will also break instead if the belt gets jammed. This makes them useful for synchronized motion. A disadvantage is that these belts tend to be more expensive and require specialized pulleys matching the tooth density.

Common Issues

Slippage

Belt slippage happens when the force placed on the belt is larger than the friction between the belt and the drive pulley. This is usually caused by a low amount of tension on the belt, which is discussed in more detail at https://dreisilker.com/blog/how-improper-belt-tension-can-affect-your-belt-drive-system/. If a belt is being used to power an excavator, slippage is not necessarily bad, as it is much better for the belt to slip when it jams itself on a large rock than to snap the belt from overtensioning.

Creep

Belt creep is the elongation of the belt due to the constant stress being put on it. This will happen faster the more stress that is put on it (load, tension).

Misalignment

Belt misalignment occurs most often with flat or conveyor belts, where the belt tries to go off the side of a pulley. Likely causes are a slight discrepancy in the tension between the two sides of the belt or misalignment between the pulleys either translationally or rotationally. Hence, it is important to assemble the pulleys fully aligned and be able increase the tension on either side of a wider belt.