SKETCHBOOK
A primer on blocks
Getting your bearings...
A Plain bearings are simple and usually cheap. They can withstand large loads and are fine for things that don’t move much—like mast halyard sheaves.
B Roller bearings come in all shapes and sizes, and move easily while withstanding high loads.
C Ball bearings aren’t quite as strong, but can cope with loads from different angles.
D Some older blocks had Tufnol, or plastic, sheaves running on a plain stainless steel axle pin.
E Modern blocks can be made of hi-tech plastics and stainless steel, and have selflubricating bearings. These can be rollers or balls of different colors that indicate the sort of loads they can bear.
F Traditional bearings and sliders need some lubrication, such as oil, grease or a silicone spray. Too much, however, might attract dirt and cause them to jam.
G Hi-tech cars and travellers occasionally need a touch of their special lubricant. But too much can cause the rollers or balls to skid, rather than roll as they should.
H Modern bearings often just need a fresh water rinse. A garden pressure spray makes a handy shower for the crew and can be used on the deck gear as well. Adding washing-up liquid can help, but should be avoided in ports with very strict pollution controls.
I Old corroded tracks can benefit from scrubbing with a mild abrasive, like toothpaste, or a plastic scouring pad with a bit of oil. Lemon juice will often dissolve the white corrosion deposits on aluminium—but do rinse well afterward.
J Neglected old masthead sheaves can corrode and jam. In bad cases, the halyard might wear through or saw into the stuck sheave. Try pouring on some hot water to wash off the salt: at the same time the “thermal shock” might break everything free again. If not, soak it in penetrating oil, pick at the crud, then knock out the pin and replace the sheave.
K Some recirculating balls will fall out when cars are removed from their tracks. Slide them into special “ball holders” to stop this. These can also be used to refill the cars with new balls. Captive ball bearings are available, but they might not fit onto the older-styled tracks.