PGR derailleurs use a distinctive operating mechanism:
- The nipple of the cable is held by a fixed ferrule that is at the inside end of the tube along which the pulley cage slides. The cable is clamped at the lever.
- The end of the cable outer pushes the pulley cage along the tube.
- Unlike pull-chain mechanisms, this allows the derailleur to be top-normal.
- A single, tightly wound, helical, spring both tensions the chain and powers the sliding tube mechanism.
- Helical springs are often used in compression, but this one is used in tension. The mechanism uses washers with wings on them to engage with the first and last coils of the spring.
Other than this PGR derailleurs are decently constructed alternatives to the, say, Simplex derailleurs of the time.
This is a pleasantly clean example of a PGR 2 with the following features:
- The main arm is steel.
- It has only one pulley wheel, which, oddly, is in the position that is usually reserved for a tension pulley.
- The sliding tube is 46mm long, possibly indicating that this is a 3-speed system.
- The main arm is labelled 'MARCA DEP.', indicating that PGR has a registered trade mark. One day I will work out how to find this.
The example is missing three small parts:
- The dropout bolt.
- A rivetted-on outer cable guide (see my other PGR derailleurs).
- The small ferrule that fits in the end of the tube to catch the cable nipple.
- Derailleur brands: PGR
- Country: Italy
- Date of introduction: 1946?
- Date of this example: unknown
- Model no.: unknown
- Weight: 196g excluding 3 small parts (see commentary above)
- Maximum cog: unknown - but not too large!
- Total capacity: unknown - but not too large!
- Pulley centre to centre: it only has one pulley wheel, mounted on a 68mm sprung arm
- Index compatibility: friction
- Chain width: unknown - but the pulleys are narrow
- Logic: top normal
- B pivot: none
- P pivot: sprung
- Materials: steel
