Filament Winding

In a transformer that powers devices with valves or tubes (radio - amps). there is an apart winding to power the filaments of these tubes. Typical, 5, 6.3, 12.6 volts and a higher amp. rating than the high voltage. (mostly the thicker wires)

In old televisions this winding was not always necessary, while filaments of the same amperage were put in series to attain the same voltage as the higher voltage of the transformer.

Most of the tubes, diodes, triodes, etc.. needed a hot cathode to perform.

The filament heats the cathode, and in some tubes, is even part of the cathode.

Here is another context for the term "filament winding." Pressure vessels such as propane tanks are now made by wrapping a filament of fiberglass or polypropylene or something in a pattern that crisscrosses itself a lot and is impregnated with resin. This gives a lightweight (and maybe translucent) tank, with good tensile strength in all directions.

Trans,

Yes indeed, and with the disappearance of valve or bulb technology, possibly the processing new standard. Prove again, that elaboration of the OT can guide to a right answer.GA.

Filament winding is a fabrication technique for creating composite material structures like tubes, pipes, gas bottles, and now lately pressure vessels for sub sea and risers for offshore oil drilling. The process involves winding filaments under varying amounts of tension over a male mould or mandrel, ore on to an aluminium/plastic gas bottle liner. The mandrel rotates while a carriage moves horizontally, laying down fibers in the desired pattern. (CNC controlled winding machine)

The most common filaments are carbon or glass fiber that runs thru a resin bath of synthetic resin like polyester, winylester, epoxy etc. to wet the fibers before they are wound on to the mandrel. Ore use fibers that is pre impregnated with ex epoxy resin, called tow-preg. Once the mandrel is completely covered to the desired thickness, the mandrel is placed in an oven to cure the resin. Once the resin has cured, if it is a pipe/tube, the mandrel is removed, leaving the hollow final product.

The angle at which the fiber is laid down will determine the properties of the final product. A high angle "hoop" (circumferential winding) will provide crush strength, while a lower angle pattern will provide greater tensile strength in the longitudinal direction. Normally a mix of different angels are used to get the right properties.

Ex a drive shaft contains a lot of 45 deg. fibers to take the torque/twist force, but also some low angels 5-10 deg. to give it stiffens and some "hoop" to give it circumferential strength.