nitflegal Posted January 11, 2021 Share Posted January 11, 2021 Since we have many people who are doing this work on AFV's I thought it might be amusing to share our fun experiences over the years. To start, did anyone know that a 45 year old M48 driver's periscope "glass" fragments with paint stripper? I didn't until yesterday. . . Link to comment Share on other sites More sharing options...
sunday Posted January 11, 2021 Share Posted January 11, 2021 Roman Alymov has enough experience restoring tank optics, but I think there is a verb missing in your post, between "M48" and the "?". Link to comment Share on other sites More sharing options...
nitflegal Posted January 11, 2021 Author Share Posted January 11, 2021 10 minutes ago, sunday said: Roman Alymov has enough experience restoring tank optics, but I think there is a verb missing in your post, between "M48" and the "?". I tried to use fragments as my verb but fair enough. Never seen that with an optic before and the joy of restoring previous gate guards is that there is 2-4 mm of 20 different kinds of paint layered together. Link to comment Share on other sites More sharing options...
sunday Posted January 11, 2021 Share Posted January 11, 2021 (edited) 14 minutes ago, nitflegal said: I tried to use fragments as my verb but fair enough. Never seen that with an optic before and the joy of restoring previous gate guards is that there is 2-4 mm of 20 different kinds of paint layered together. Sorry, English not first language. Fragmenting as in two- or three-piece prisms coming apart in the individual prisms, or fragmenting as in solid pieces of glass fragmenting in smaller pieces? I guess the former is quite possible, but the later quite difficult with mineral glass, as most paint strippers are organic solvents. Edited to add: I had a vague recollection of the traditional, optically clear adhesive used in optical assemblies, so went searching the intertubes. It is very possible that those optics were held together with Canada Balsam, which has good optical properties, but poor resistance to solvents. Edited January 11, 2021 by sunday Link to comment Share on other sites More sharing options...
RETAC21 Posted January 11, 2021 Share Posted January 11, 2021 1 hour ago, nitflegal said: Since we have many people who are doing this work on AFV's I thought it might be amusing to share our fun experiences over the years. To start, did anyone know that a 45 year old M48 driver's periscope "glass" fragments with paint stripper? I didn't until yesterday. . . I hesitate to ask, but why was the glass painted over... ? Link to comment Share on other sites More sharing options...
Wobbly Head Posted January 11, 2021 Share Posted January 11, 2021 (edited) Lenses and prisms can be glued together, sometimes they are glued to the top of the periscope housing with rubber cement and the front windows are also just glued in . We used isopropyl alcohol to clean lenses and widows using something stronger would dissolve the cement causing what happened. As for actually fixing optics unless you have training and have worked on them before it's best to leave them to experts as some of the tests and adjustments seem counter intuitive and they require a gentle touch sometimes. Sometimes the glass gets painted over when they are painting the vehicles the paint is usually removed with a razor blade the glass is tougher than the steel blade and rarely scratches if done right. Edited January 11, 2021 by Wobbly Head Link to comment Share on other sites More sharing options...
sunday Posted January 11, 2021 Share Posted January 11, 2021 (edited) 4 minutes ago, RETAC21 said: I hesitate to ask, but why was the glass painted over... ? Prisms are painted in the back to reduce light leaks. Edited: The non optical active surfaces of prisms, i.e. those that should not transmit light are painted in order to prevent light leaks, and the rear of the metalized, reflective surfaces is painted to protect the reflective coating. Edited January 11, 2021 by sunday Link to comment Share on other sites More sharing options...
Wobbly Head Posted January 11, 2021 Share Posted January 11, 2021 26 minutes ago, sunday said: Prisms are painted in the back to reduce light leaks. Edited: The non optical active surfaces of prisms, i.e. those that should not transmit light are painted in order to prevent light leaks, and the rear of the metalized, reflective surfaces is painted to protect the reflective coating. Also be very aware that most reflective surfaces (mirrors) in optics are front silvered most mirrors you use in home are rear silvered and the mirrored surface will scratch easily. Link to comment Share on other sites More sharing options...
sunday Posted January 11, 2021 Share Posted January 11, 2021 Indeed optical mirrors are silvered in front. Classic examples are reflector telescopes. Some prisms do not need the silvering, I vaguely recall. Link to comment Share on other sites More sharing options...
Tim the Tank Nut Posted January 11, 2021 Share Posted January 11, 2021 MEK takes the layers of glass apart. I forget which glue puts them back together but it can be done. It's not that complicated a process for restoration but if you are going into combat with it just get a new one... I've really learned some hard lessons over the years restoring stuff. If you are going to drive it the track tension better be right. Turret pumps are dangerous. Linkages must always be free of any obstruction. Cleanliness matters a LOT!. If it is old and rusted and irreplaceable think twice or ten times before beating on it. Yes the gauges are radioactive. No, they won't hurt you unless you eat them. Link to comment Share on other sites More sharing options...
Harold Jones Posted January 11, 2021 Share Posted January 11, 2021 3 hours ago, RETAC21 said: I hesitate to ask, but why was the glass painted over... ? Gate guard or monument tanks are rarely masked up before being being painted. How much paint ends up on exposed glass depends a lot on the person doing the spraying and once it's painted over it's more likely that it will get painted over again and again. Link to comment Share on other sites More sharing options...
sunday Posted January 11, 2021 Share Posted January 11, 2021 3 minutes ago, Harold Jones said: Gate guard or monument tanks are rarely masked up before being being painted. How much paint ends up on exposed glass depends a lot on the person doing the spraying and once it's painted over it's more likely that it will get painted over again and again. I thought main optics would be retired, but then there are a lot of x1 sights that do the useful function of keeping a hole closed. Link to comment Share on other sites More sharing options...
Wobbly Head Posted January 11, 2021 Share Posted January 11, 2021 47 minutes ago, sunday said: I thought main optics would be retired, but then there are a lot of x1 sights that do the useful function of keeping a hole closed. 57 minutes ago, Harold Jones said: Gate guard or monument tanks are rarely masked up before being being painted. How much paint ends up on exposed glass depends a lot on the person doing the spraying and once it's painted over it's more likely that it will get painted over again and again. It's not just gate guards that get painted over and over again even some in-service vehicles suffer from this. Removing periscopes and some sights require the use of the size 9 removal tool (foot and body weight) to get them out. Link to comment Share on other sites More sharing options...
nitflegal Posted January 12, 2021 Author Share Posted January 12, 2021 3 hours ago, Harold Jones said: Gate guard or monument tanks are rarely masked up before being being painted. How much paint ends up on exposed glass depends a lot on the person doing the spraying and once it's painted over it's more likely that it will get painted over again and again. I measured with a ruler, the paint over the glass was 4-5mm thick. From the glass out it was beige, then black, then forest green, then olive drab. Link to comment Share on other sites More sharing options...
Harold Jones Posted January 12, 2021 Share Posted January 12, 2021 I'm not surprised, I imagine it was repainted quite often over the time it has been sitting outside. Link to comment Share on other sites More sharing options...
nitflegal Posted January 13, 2021 Author Share Posted January 13, 2021 I will throw in that especially on aircraft the amount of spackle used to fill damage before painting is amazing. The amount of times I've been sand-blasting paint away and you watch the structure start to dissolve is frightening. . . Link to comment Share on other sites More sharing options...
MiloMorai Posted January 13, 2021 Share Posted January 13, 2021 18 minutes ago, nitflegal said: I will throw in that especially on aircraft the amount of spackle used to fill damage before painting is amazing. The amount of times I've been sand-blasting paint away and you watch the structure start to dissolve is frightening. . . You do know that the wing of the P-51 used "spackle". Link to comment Share on other sites More sharing options...
nitflegal Posted January 14, 2021 Author Share Posted January 14, 2021 On 1/13/2021 at 1:05 PM, MiloMorai said: You do know that the wing of the P-51 used "spackle". Filling the panel lines? Yup. I'm talking where there is a hole of dent and instead of a true repair there is drywall compound. I've even found the fiberglass mesh used in drywall and duct-tape embedded in the putty. Sometimes actual plaster. Or Elmer's plastic wood glue. Link to comment Share on other sites More sharing options...
DB Posted January 21, 2021 Share Posted January 21, 2021 Cosmetics in a nutshell. Link to comment Share on other sites More sharing options...
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