Pre a gauges

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Jules Dielen
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Pre a gauges

#1 Post by Jules Dielen » Thu Jan 18, 2018 1:21 am

Is the glass on pre A gauges supposed to be convex or concave?
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Tony Proasi
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Re: Pre a gauges

#2 Post by Tony Proasi » Thu Jan 18, 2018 8:55 am

Pretty sure only the green faced viegles are convex. At least they are the only ones I have noticed to be that way.

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Jules Dielen
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Re: Pre a gauges

#3 Post by Jules Dielen » Thu Jan 18, 2018 9:35 am

Thank you Tony, yes i meant the early Veigel gauges, for a 52.
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Norm Miller
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Re: Pre a gauges

#4 Post by Norm Miller » Thu Jan 18, 2018 10:39 am

Jules,

Food for thought;
Were they concave to prevent reflections into the side glass, hmm.
Did the 51-52 have the hoods over the speedo also.

Norm
 

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Jules Dielen
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Re: Pre a gauges

#5 Post by Jules Dielen » Thu Jan 18, 2018 10:59 am

Hey Norm,

yes a hood over the 2 large gauges, none over the temp gauge.

I'm sure it was to prevent glare, but both convex and concave glass have the same effect. I have a pre A VDO speedo that is convex and a pre A Veigel gauge that is concave but both have been opened at one point, hence the confusion.
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James Davies
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Re: Pre a gauges

#6 Post by James Davies » Thu Jan 18, 2018 6:02 pm

"Dished" Is that concave?

=)

Yeah, the Veigel gauges with the green lettering had dished faces to prevent glare. Worked pretty well! The VDO gauges starting in May 1954 also had dished glass, but eventually by 1955 flat glass on these was used.

What's the date on the back of your VDO gauge with the dished glass?

Meanwhile, the Störk temp gauge has "bubble" glass, i.e. convex, to make space for the pointer. Go figure.

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Jules Dielen
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Re: Pre a gauges

#7 Post by Jules Dielen » Thu Jan 18, 2018 6:19 pm

Hey james! How's the little one??

I'll check the date on the VDO, but it is convex (domed, not dished). Again, it's been opened up so very likely the glass was just installed inside-out.

If you want to see a convex lens, look at an early 924... wheeeeew. it's mad max style
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Erik Thomas
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Re: Pre a gauges

#8 Post by Erik Thomas » Thu Jan 18, 2018 10:31 pm

Early post war Mercedes 170-220 Etc. VDO gauges, which are very similar to those used on 356's were the source for convex glass - back when the Mercedes gauges were "easy" to come by, out of old rusty junkyard cars. I had a 356 Tachometer fitted into my 1950 Mercedes 170-S, as they are the same diameter, and it was a good match to the speedometer. convex glass and all. The speedometer shops used to have the chrome rings, but only flat glass. We had to supply the convex glass to them. I am not sure if this is still the same today. The convex glass really helps prevent glare.

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Jules Dielen
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Re: Pre a gauges

#9 Post by Jules Dielen » Fri Jan 19, 2018 12:51 am

My domed glass vdo pre a gauge is dated 7.55.
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Albert Haefner
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Re: Pre a gauges

#10 Post by Albert Haefner » Fri Jan 19, 2018 7:59 am

Never saw a green Veigel with a flat glass.

Many préA VDO instruments had concave lenses but I think they became flat by the end of 1954, perhaps first on Speedsters..

Concave ones were invented by some intelligent Porsche designers to provide reflexions .
Not very effective indeed, not much better than flat glasses.

The dials in Veigel and VDO préA instruments are further moved backwards to let enough space for the concave glasses.

I will continue my research among my 100.000 préA pic collection to find out a confirmation
 

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