Saw blade and diesel engine: what they have in common

1. Step 1. Saw blade — is part of — Saw. A toothed steel blade.
2. Step 2. Saw — evolved into — Chainsaw. A mechanized saw.
3. Step 3. Chainsaw — has part — Sprocket. A sprocket drives the chain.
4. Step 4. Sprocket — is part of — Continuous track. The drive sprocket engages the track and pulls it round — just as a bicycle sprocket pulls the chain.
5. Step 5. Continuous track — is part of — Excavator. Most excavators run on tracks.
6. Step 6. Excavator — has part — Diesel engine. The drive is a diesel.

Open Evothings