[Vwdiesel] Roger the Glowplug

[Lee Hillsgrove]

>> Thanks Roger...Ah yes I looked at the Bosche site; as I suspected the
plug
>is
>>  said to be regulated ..ie a built in cut out probably a mechanical
device,
>>  rather than a thyristor.
>>
>  That wasn't how I read it.  It seemed to me it was more like they
regulate
>the coils so that the tip gets hot first.  My interpretation of that is
that
>they
>use different coil spacing, resistance  or size for the tip of the element
>and
>less rapid heating stuff back toward the threads.  <shrug>




 Most of the electric heaters we use at work to heat the platens in the
presses are made this way, with increased watt density towards the ends to
make up for heat loss. Picture a screen door spring that has been stretched
out in the middle and that's about the size of it. Each unit of length of
resistance wire outputs a given number of watts - pack more wire length in a
linear inch of heater element, and you have higher watt density and thus
more heat when compared to a similar length of heater with less length of
heater wire inside.

 I don't think you'd be able to vary the resistance wire diameter over the
length of the heating coil and get good results because the thinner sections
would dissipate nearly all of the heat while the thicker wire would just
conduct the current to the area of highest resistance. I think it's Ohm's
law.........   :-))

 As far as I know, the glow plugs are just dumb resistance heaters, and that
Chilton is full of hooey!  :-))

  Lee
  Oo-v-oO
  PP-ASEL
  KB1GNI