Shel Belinkoff wrote:
>
> Bad analogy ... Timing belts are used because they are cheaper and
> lighter, but are a replaceable item. They stretch and sometimes jump
> the sprockets, and when they break can cause problems that can destroy
> an engine. Timing chains, which are even stronger, will sometimes
> stretch and need replacement if used in a powerful engine, although
> their replacement interval is usually longer than the belts. They,
> too, have been known to jump a sprocket. Older engines, with gear
> driven camshafts, last indefinitely and are more precise. You'll note
> that racing engines generally use gear drives because they must have
> absolute reliability and absolute timing accuracy.
>
> Since we're talking about a "rubber" belt, my concern is that it will
> stretch or break after a while, causing misaligned frames or failed
> film transport. Gears do not have this problem, but they are more
> costly to manufacture and implement, which is most likely the real
> reason Pentax uses a belt drive.
It wouldn't surprise me at all if they were using some sort of teflon
or nylon belt, and at the low torques we're talking about it may outlast
several other parts of the camera...
Isaac
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