Needle bearings

[Drew62]

A mate lent me his ms 441 over the last few days to see if I wanted to buy it.Its by no means new(pre mtronic) and I quite like it and given its history will probably buy it.What really suprised me is when I looked it over this morn,I discovered the bearing cage behind the clutch drum is made of plastic.From an engineering point of view,I cant get my head round why you would do this with a low value but fairly important part?Is it just penny-pinching or is there a valid reason why you would do that?Also I wondered is this common practise through all the pro range?

[sawguy21]

That bearing only turns when the saw is idling so it doesn't see a lot of stress.

[Drew62]

Fair point,but just curious is there a valid engineering reason for the change?

[Mad Professor]

Another reason why 038s will be going ,when 044/440/441 are made into beer cans.

Have a look at an 038 clutch bearing , vs 044/441.

[barbender]

I don't know the specific construction of that bearing, but many plastic bushings are self lubricating. Some of our forwarder grapples use nylon bushings. These are high stress applications, and the manufacturer recommends a 1000 hour grease interval. So Stihl may not be cheaping out, but using a material that is engineered to be superior in the application.

[Air Lad]

During the earlier trawling days( 80's 90's ) we experimented with nylon/teflon products to try to get away from steel in the marine industry
They worked well under medium loads and were self lubricating as stated. Especially when getting wet with sea water and run on stainless pins.Some of these modern plastic's have evolved 
In regards to the plastic roller cage I think the cage only helps to keep the rollers aligned
as the rollers do the real work.. And only when at idle
Hope this helps you Drew