I've seen a lot of posts on here about useless components ranging from brake pedal clips to timing belt/crankshaft pulleys (The rubber damped ones)
Thinking about it, it wouldn't be too hard to remake them out of metal I imagine. I'd have to ask the experts but would it have an impact mechanically?
One half of me thinks "They make them like this just so they break." The other half thinks "Would they have made them like this unless necessary?"
Thoughts? This is more out of boredom than anything else, but I know a few people who work with CAD/CAM and could probably make these bits...
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It is easier, faster and cheaper to "mould" plastic or composite components in bulk than to machine, cast or extrude metal or alloy components.
The plastic or composite components are also cheaper in raw materials and lighter.
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TourVanMan TM < Ex RF >
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In the case of some timing belt tensioners, sometimes the bearing wears and overheats first, then the plastic gets affected and shatters. So just making a new pulley might not gain you much.
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I had the job of programming making jigs and setting a machining centre to make 1000s of drilled pedals for the Renault Clio/Megane a couple of years ago. The firm went through 3 lads who were running the machine it was such a tedious job. Struck me at the time maybe pressing the things out would have been better but the customer gets what he wants eh.
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The rate of wear of the belt and/or pulley may influence the choice of material for the pulley.
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L\'escargot.
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Dangerous, IMO.
You would need to know why any material/component has been used in the first place. A fuse or relay is a classic example.
Maybe it is better to sacrifice a plastic pulley rather than have the bearing or the spindle go!
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It's a good idea mss1tw, but be careful, as Red Baron says. If you're not careful you could be re-inforcing a deliberately weak component which is designed to break in extreme circumstances and not wreak the rest of the mechanism, e.g. rockers.
Too many machines have been broken by people replacing say a sheared split pin with a bigger one!
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Mike Farrow
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I quite agree with the above two posts suggesting caution.
For example, the rubber two part crankshaft pulleys are made like that for a very good purpose. The outer mass of the pulley is sprung from the inner mass by the rubber. This acts as a rotary mass/spring system, which absorbs crankshaft torsional vibrations over a narrow range of frequencies - this is done to protect the crankshaft. If you made a solid pulley, the crankshaft would be run under a more onerous torsional stress regime, and could fail in fatigue some time later.
Oddly the rubber is employed more as a springing medium in the two part crankshaft pulley, although most would call it a damper. The damping properties inherent in the rubber actually hinder vibration reduction at the design frequency (which may be tuned to a torsional mode of the crankshaft), but as compensation, the vibration is reduced over a broader range of frequencies.
If engineering were as straight forward as coding up some CNC part programs and putting a nice billet of raw material in the machine vise, then a) I'd be out of a job!, and b) engineering would be a really dull job, with no hidden surprises and I wouldn't be interested in it then!
Number_Cruncher
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