From cube-lovers-errors@mc.lcs.mit.edu Sun Jul 27 21:30:37 1997 Return-Path: Received: from sun30.aic.nrl.navy.mil by mc.lcs.mit.edu (8.8.1/mc) with SMTP id VAA29606; Sun, 27 Jul 1997 21:30:36 -0400 (EDT) Precedence: bulk Errors-To: cube-lovers-errors@mc.lcs.mit.edu Mail-from: From nbodley@tiac.net Sun Jul 27 11:09:16 1997 Date: Sun, 27 Jul 1997 11:05:58 -0400 (EDT) From: Nicholas Bodley To: Edwin Saesen Cc: CUBE Subject: Broken 4^3s; advice on repairs to plastic (medium length) In-Reply-To: <199707260506_MC2-1B9B-F7B3@compuserve.com> Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Edwin's mention of broken center pieces reminds me of a period roughly 15 years ago when I was quite active disassembling various cubes and their relatives; I'm fairly sure that it was these center pieces that impressed me as being fragile. Even the wondrous innards of the 5^3 are not as delicate, although fascinating. I'm trying to remember without much success whether I actually broke a piece. I think I did. Some plastics, I'm just about sure, can't be dissolved by any readily-available liquids, and i think the 4^3s were made of such material. (Acrylics can be "solvent-welded" very successfully.) Plastic welding is possible with probably any thermoplastic (i.e., one that can be melted after being molded), but is a skill just as is metal welding, and needs expensive hot-air tools (others also?) designed for the purpose. I would not recommend it for something so precious as a 4^3, unless you can find an expert. Finally, adhesives are worth considering. After all, the colored stickers are retained by adhesive. Not at all sure, but I think I did have success with cyanoacrylate (CA) (famous in the USA for its tradename "Krazy Glue"). This is a strange substance that seems not to be well understood, and it might be a good idea to learn more about it (even if you already think you know) before trying a critical repair. At least, if your repair is unsuccessful it will come apart, with probably little damage (no promises!) to the surfaces. The adhesive can then be scraped off. (Of course, you'll let it cure before reassembly...) As with almost any adhesive, clean surfaces are quite important. 99% isopropyl alcohol (no longer costly; try a good drugstore) is a worthy cleaner; rather few, uncommon contemporary plastics are attacked by it (but the clear printhead drive rack in an Oki printer disintegrated in a very few minutes, maybe 8 years ago). I doubt that any plastics used for these sorts of puzzles would be sensitive to alcohol. Not sure of my information, but I believe that curing of CA is triggered by absence of oxygen combined with an imperceptibly thin film of water on the surfaces (don't try to wet them!). Very low humidity might inhibit curing. For those who are really serious, the model-builders' magazines have ads for different versions of CA adhesives; after all, models have been made of plastics since WW II. Look into (i.e., catalog pages (Web?)) the products of the Loctite Corp., which makes a variety of industrial adhesives. There are other companies like Loctite, but Loctite has the most-successful marketers IMHO. (Note that there's no "k" in "Loctite"!) By the way, the Pocket Cube (2^3) is a bear to disassemble and even worse to reassemble. If it weren't for the really-good-quality polymer chosen for it, it (more than likely) could not be manufactured. The difficulty is in that the cubies have to be distorted ("sprung") to disassemble it. Whether this plastic retains its ability over many years to be bent out of shape but not crack, I don't know! All of this is offered with the best intentions; if I'm wrong about some particular, and you're reasonably sure that I am, by all means please let me know! The brittle plastics used before WW II, in general, are a different matter; alcohol is probably a bad idea in general. The modest amount I do know is really off-topic. I hope that this isn't too lengthy; this List seems to be willing to carry long messages at times. |* Nicholas Bodley *|* Electronic Technician {*} Autodidact & Polymath |* Waltham, Mass. *|* ----------------------------------------------- |* nbodley@tiac.net *|* When the year 2000 begins, we'll celebrate |* Amateur musician *|* the 2000th anniversary of the year 1 B.C.E. --------------------------------------------------------------------------