Folks, I noticed some years ago (when I owned both a 71 and a 74 TR6) that
the later gauges are more easily read at night due to, I think, more light
from the illumination source (bulb) actually reaching the gauge face and
indicating needle.
The recent thread on same prompted me to have a look at a couple of
oilpressure gauges I have on the bench. One of each vintage. Here are a
couple of observations:
1) The later style gauge has a green lens that tints the light. This is a
ring of translucent plastic that fits between the gauge face and the facia
that hides the needle movement.
2) On the earlier style gauge the light from the bulb only has access to
the gauge face via the opening for the needle movement (which is hidden by
the facia) and the white paint on the inside of the case is intended to
improve the amount of light that actually makes it that far.
3) On the later style gauges, there is a gap of about 1 mm (.04 in) all the
way around the gauge face. This allows light from the bulb to illuminate
the gauge face from the full 360 degrees. With more light from all angles,
the gauges are easier to read.
The next task is to evaluate is the older style gauges can be modified (by
adding slots perhaps) to improve night time visibility.
More trivia to follow.
Dave Massey
71 TR6
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