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Unexpected use of FR2 of the week: Phenolic gears (aussie.zone)

submitted 18 hours ago* (last edited 18 hours ago) by WaterWaiver@aussie.zone to c/electronics@discuss.tchncs.de

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FR2 is the brownish material that many cheap circuit boards are made of. It's a mixture of phenolic resin and paper. Apparently it's quite useful to make gears out of:

Phenolic Gears exhibits superior shear force, help reduce machinery noise, absorbs destructive vibration unlike metal gears, phenolic is non-conductive, protects the mating metal gear train, and are known to outlast metal gears under severe continuous service. (source: https://www.knowbirs.com/phenolic-gears )

(Main pic stolen from here)

(Many more pics here)

Has anyone seen these used anywhere? I've read a hint regarding pool equipment, but I have never seen them there. I assume the fibres allow them to last longer than plastic/resin only gears.

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[–] dgriffith@aussie.zone 4 points 14 hours ago

Older engines had them in their timing gears - they were in 6 cylinder Holdens, for example.

They give an amount of cushioning/vibration dampening that you can't get with steel gear sets.

[–] genuineparts@infosec.pub 1 points 10 hours ago* (last edited 10 hours ago)

Old big EMCO lathes had phenolic gears in their gearbox. I know because I got to rebuild one and that was one surprise I came actross and that day I learned about phenolic gears.
Probably also useful as a safety shear point. Better to grind a phenolic gear to dust that to break something expensive.

Also I will never forget the smell of the gear oil.

[–] Gronk@aussie.zone 2 points 14 hours ago (2 children)

Woah those are some cool properties, I wonder how hard these gears would be to manufacture at home? I'm looking at implementing my own custom gear reductions in servos but I don't think my 3d prints will mesh well enough or withstand long usage

[–] nerb@techhub.social 1 points 10 hours ago

@Gronk @WaterWaiver

I printed 2 gears for my 7x12 lathe out of a filament from Igus.

https://www.igus.com/product/20322?artNr=I190-PF-0175-0750

Been in use for over 5 months and from inspection are in good shape. Quieter and unlike the originals durable. One is sacrificial and will shear if the lathe jams. When I jammed it it loaded the motor pretty heavily then let go so it did work. Some replace that gear with a metal one but I wanted the sacrificial feature so I do not blow the motor and speed control.

You need a heated chamber and they recommend heat treating it before use which I did not do since I was not certain it would not change the dimensions.

They have a few other filaments that are also useful. I went to this after multiple attempts to 3d print delrin. Even made a wood bed and finally gave up.

It's not cheap but I still have over 90% on the reel left after printing 3 gears.

[–] WaterWaiver@aussie.zone 2 points 12 hours ago* (last edited 12 hours ago)

There are some youtube videos of people machining them (sadly my browser does not support smell). Looks like you treat it like any other solid material: hobb or mill the teeth. This is much more expensive than 3d printing.

You might be surprised by your 3d printed gears. If you keep the detail size large they work really well, but backlash is definitely an issue.