DIY belay glasses
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So, I embarked on a project to create some cheap belay glasses. For the uninitiated, belay glasses are a type of spectacles that allow you to look forward but use a prism to reflect vision upwards, thus allowing a rock-climbing belayer to watch their climber without having to crane your neck backwards (which really starts to ache quickly, especially if you're wearing a helmet). These glasses typically sell for > $100.
So I found a Chinese gadget store that sells cheap ($8) "reading glasses" which work exactly like belay glasses, except that they reflect vision downwards, thus allowing you to lay down on your back staring at the ceiling but hold a book upright on your chest/belly and be able to read it. Thereby saving your neck from having to crane forward - the exact opposite direction of the belay problem.
Now of course what I need to do is to find a way to modify these glasses to flip the prisms so that the reading glasses become belay glasses. The glasses themselves seem to be completely solid moulded from some sort of tough plastic (aside from the arms on hinges). The glass prisms are easily removable. So it looks like I need to find a way to shear off the prism-holding bits and flip them and reattach them. But they need to be reattached quite strongly because the prisms are a bit weighty. So shearing off the plastic prism "cups" and re-glueing them along the sheared edge probably won't be tough enough to do the job.
My three problems are:
1.) Is my approach the best approach?
2.) Assuming (1), what is the best way to shear off the plastic cups without wasteage of any plastic (eg. "sawdust" effect), because these cups are only just big enough to hold the prisms?
3.) How to reattach the cups with a lot of structural strength?
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I haven't seen any kind of screen printing on 4chan. I'm looking to get into screen printing to save some money on my band's merch. Might eventually start up a small business when I get everything figured out. If anyone has any resources, tips, links, deals on cheap supplies, etc., post it.