02 Feb 99, Derek Harling <derek.lola@sympatico.ca> wrote:
>
> Low melting point? - Oh! - we used it for buttons
> on the ends of piston pins in my Mini Cooper S -
> seemed to work OK - were we just lucky? -- Derek
>
>Chris Kantarjiev wrote:
>>
>> Teflon is pretty good stuff. Not as hard as delrin,
>> but harder/firmer than rubber. The thing to beware
>> is that it has a relatively low melting point (I'm
>> remembering about 250 degF) and emits toxic
>> fumes as it melts.
We're kinda getting off the bushing theme, but:
Speaking of toxic fumes, Delrin gives of formaldehyde when burned and
urethane gives off cyanide. Vinyl (not a bushing material) gives off
chlorine and hydrogen chloride. Your street-car's interior is full of
vinyl and urethane foam padding. Choose your poison.
Teflon is a family of resins and specifications vary drastically.
Some Teflons would be excellent bushing material. Even temperature
characteristics vary and some Teflons resist high temperatures very
well. How hot does a frying pan get? The main draw back to it's use
in bushings is it's cost. There are many other resins that are also
good bushing materials at a fraction of the cost.
Teflon is commonly used for wrist pin wear-buttons, but there are now
other resins that would be better. Polyimide (Vespel) has far
superior high temp, wear and friction characteristics. Vespel
bushings replace ball bearings in some severe duty applications in jet
engines.
Regards,
Tim Engel
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