# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DcTcsULRUbt
- **Gondola URL:** https://gondola.cc/posts/69422657-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/ebf46139b9.jpg
- **Posted:** 2026-08-21T13:30:32.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Forged carbon is not forged, and it is not woven. It is chopped fibre compression moulding, and it has taken over the boutique end of bicycle componentry.

Conventional carbon parts are laminated. Continuous fibre prepreg is cut, oriented ply by ply, then cured under vacuum or in a bladder mould. That works beautifully for tubes and beams, where load paths run in straight lines. It works badly for small parts with teeth, ribs, bosses and bearing seats.

Forged carbon solves that geometry problem. The charge is a moulding compound of chopped tow, typically 25 to 50 millimetres long, pre-impregnated with epoxy and dropped into a matched steel die.

- Die heated to roughly 140 to 160 degrees Celsius
- Pressure in the region of 70 to 140 bar
- Cure cycle measured in minutes, not hours
- Fibre flows into every feature under pressure, net shape

The result is quasi-isotropic. There is no weak transverse direction because there is no dominant direction at all. The marbled surface is random tow orientation frozen in resin.

Pulley wheels are the ideal test case. A jockey wheel is small, toothed, and spins far faster than most riders realise. An eleven tooth pulley on half inch chain has a pitch diameter near 45 millimetres. At ninety revolutions per minute on a fifty tooth chainring, chain speed is roughly 0.95 metres per second, spinning that pulley beyond 400 revolutions per minute.

Low rotating inertia therefore matters, as does dimensional stability under chain tension. Moulded carbon delivers both, with tooth profiles formed in the die rather than machined afterwards.

The compromise is honest. Discontinuous fibre gives up much of the tensile strength of a well laid laminate, and property scatter is real because local orientation is random. Most designs answer this by pressing in an alloy bearing carrier, keeping metal against metal where the fits must hold.

Randomness, controlled properly, becomes a material property.

#stemantics #forgedcarbon #compositesengineering #bikeengineering #materialsscience

## Stats

- **Views:** 5,966
- **Likes:** 37
- **Shares:** 0
- **Comments:** 1

## Tags

materialsscience, compositesengineering, bikeengineering, forgedcarbon, stemantics

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