Fortunately the superglue will be mostly on the inside of the case and the lens peeks out to the outside. Only a very small amount of glue is required (e.g. 3 small specks).
Its probably still a good idea to protect the lightpipe surfaces: try putting cling-film over them: apart from anything else, cyanoacrylate[*] doesn't stick to it.
[*] The generic name for so-called 'superglues' is cyanoacrylate, aka cyano or cya. "Superglue" is just the tradmark used on the first, severely weakened, cyanoacrylate glues to be generally available to the public. If you want a much better glue, visit your local model shop of buy the stuff online. Go for Zap, Hot Stuff or Grip: I prefer ZAP. Its stockists also sell accelerator for use with Zap CA (see below) and debonder, which dissolves the cyano and is a near essential for releasing stuck fingers.
The standard Zap is very runny, sets very much faster than the rather anaemic Superglue and is a lot stronger, but be careful because its extremely good at gluing fingers together. It cannot and will not act as a gap filler: surfaces to be glued must fit well.
Zap CA is thicker, can be used as a gap filler and takes more like 10-15 seconds to set, so you get a bit of repositioning time.
BTW: the reason cyano sticks fingers so well is that it was originally developed as a medical glue. Moisture on the surfaces being joined catalyses its setting. This is also why the stuff will let go sooner or later if used outside or where the finished glue joint can get wet: a good medical glue should quietly dissolve and vanish once the would it closed has healed and cyano is a very good medical glue. It your work is likely to get wet, a lick of paint, model dope or nail varnish will keep water away from the cyano. I've been using cyano for building and repairing model aircraft since it first came on the market and 5 minute epoxy, which is often preferable because it has several minutes working time compared with the seconds you get from cyano, before that. 5 minute epoxy is often my first choice unless I'm in a real hurry because its generally rather easier to work with than cyano.
Apologies if this has got too close to TL:DR size, but I hope its useful info for at least some of you.
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martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
I used the term superglue because most people probably know what I am referring to, and indeed it is cyanoacrylate. The specific brands under which it is sold probably vary a lot by country. The one I used is branded "Bison".
I would not worry about the lightpipes. They are just there to show the LED status and they will work whether they are opaque or not.
The camera lens is covered by a small sticker upon delivery, it would be wise to keep that on until the glue has settled.
As far as the history goes, I was quoting from the Hunter brothers, whose Hotstuff brand was, I think, the first retail brand that sold cyano in small (5-10ml) quantities. I certainly knew about it before the so-called "Superglue" appeared on non-hobby retail stores in smaller packs and similar or higher prices per pack than Hotstuff.
BTW, don't use nitromethane as a debonder unless you really can't get anything else. Like all organic nitro compounds, nitromethane is readily absorbed through the skin and is moderately harmful to your liver.
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martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
It still works on same principle, and the first light pipe aka poor performance fibre optic was demonstrated I believe and patented in Ireland around 1860's using candle, bucket with glass panel and hole for water to escape out the other side.
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Sure, but the key phrase here is "internal reflection" and I bet the moulded sides are nice and shiny. If you do something that makes the sides of the lightpipe non-reflective such as 'smoothing' them with sandpaper or using some reagent that attacks the surface, then to a first approximation the only light to come out the end will be photons that have gone the full length of the pipe without being reflected off the walls.
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martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
Acetone is far easier to obtain and 100% effective IF you can keep the CA soaked in it long enough.
the main problem is that it evaporates too fast.
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Acetone should be OK to unstick fingers or get cya off a finger, but make very sure there's none left on your bench or fingers before you touch the Pi case because acetone and/or its vapour may attack the lightpipe or the case.
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martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
Talking of cases - I would like one that was larger than the pi with short cables that would bring all the pi connectors out to a common backpanel. Having them at all points of the compass is a bit of a pain.
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