Belts, chains, and gears
What you'll learn
Pick the right drive for the job — and know which ones slip, which reverse, and which need guarding most.
Same ratio math, three ways to build it — and the differences decide what breaks, what slips, and what saves the machine when something jams.
The three drives
| Belts | Chains | Gears | |
|---|---|---|---|
| Grip | friction | positive (sprocket teeth) | positive (mesh) |
| Slip | yes — by design | no | no |
| Direction | same | same | reverses each mesh |
| Ratio precision | approximate (creep) | exact | exact |
| Lubrication | none (keep it dry!) | required | required |
| Noise / speed | quiet, high speed | mid | precise, compact |
Slip is a feature (until it isn't)
A belt's friction grip is its safety valve: jam the load and the belt squeals and slips instead of snapping a shaft. That same slip makes belts imprecise — they creep a fraction of a percent, so anything needing exact timing (an engine's camshaft, an indexing table) uses chain or gears, where teeth make slipping impossible.
The flip side: a belt only works dry and tensioned. Oil on a belt or a loose belt = slip you didn't ask for, heat, glazing, and a dead drive. Chains are the opposite — they die without lubrication.
Direction: the gear surprise
Belts and chains keep both shafts turning the same way. A meshed gear pair reverses — every mesh flips the direction, which is why a lone "idler" gear often sits between two others doing nothing but flipping it back. (Flip between belt and gears in the ratio tool and watch the arrows.)
Why this matters
When you find slip marks, glazing, a dry chain, or a drive turning the wrong way, the diagnosis starts with knowing which of these three you're looking at and what it needs. Next module: the fasteners holding all of it together.
Check your understanding
Question 1 of 2
A jam locks the driven shaft. Which drive is most likely to protect the machine by slipping?