SNUB PULLEY

A snub pulley is a small non-driven drum positioned tangentially near a drive pulley to bend the incoming or outgoing belt against the drive surface, increasing the contact arc. A single-drive configuration with no snub has a wrap angle of 180°; adding one snub pulley typically raises wrap to 210–230°, and a dual-snub (one each side of the drive) can reach 240°. Because maximum transmissible tension grows exponentially with wrap angle per the [Capstan/Eytelwein equation](/glossary/capstan-equation-eytelwein), even a modest snub upgrade can lift drive capacity by 25–60 %.

Snub pulleys are smaller than the drive — typically one or two size steps down — and run on the dirty (carrying) side of the belt. Because they make contact with the freshly discharged cover that may be carrying fines and water, they are usually fitted with rubber lagging or a polyurethane wear strip so material build-up on the drum face does not push the belt sideways. They also need a high-quality scraper between the drive and snub to keep carry-back material from contaminating the snub contact patch.

Snubs are the cheapest way to increase drive capacity on an existing conveyor without buying a second drive package — a common retrofit when an upgrade in throughput pushes Te beyond the original drive's slip margin. The [belt tension calculator](/tools/conveyor-belt-tension-calculator) lets engineers test whether a proposed snub upgrade gives adequate Te headroom for a new operating case.