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#1
12-21-2008, 02:18 PM
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Yamaha HX90 from Kozin
Another to add to the collection. This time a Yamaha HX90, free from Kozin - ?????. This motorcycle was produced in 1972 and sold apparently only in Japan, though a very similar 100cc version, the LS 2, was available in the United States. The kit also has alternative parts for the AX125 (AS 3 in the US).
Quite tricky, as the parts are in a sort of beta state, and the only build assistance comes from 17 not very high-resolution photographs of the prototype build, and labelling of many of the parts with their function on the motorcycle. The labelling is, of course, in Japanese and the PDF file is locked against data extraction, so it took some labour to transcribe the text and get it translated. It was worth it though, to unravel several mysteries. The original model is fairly close to 1:8 scale, so I have scaled it to 57% to match most of the rest of my motorcycle models at approximately 1:14. The result is about 130mm (5 inches) long. Alan 
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#2
12-22-2008, 09:55 AM
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That looks great, Alan. I plan on building some motorcycle models eventually- are the spokes actually paper? They are so thin!
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#4
12-24-2008, 04:24 AM
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Thanks, guys. No, the spokes are not paper but sewing thread - even I am not crazy enough to try cutting out things that thin.
With Christmas upon us, I only have time to give you one more photo for now, but will get back to you next week. [Please forgive the glitch on the tyre tread - it is something I hadn't noticed in real life, but which shouts at you in the photograph.] Happy Christmas, or whatever you celebrate at this time of year, to you all. Alan
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#5
12-24-2008, 06:12 AM
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A glitch? I don't think I could build one that good:o Are you talking about that spot in the 8:00 position? If so, I would like to know what you do to fix it.
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#6
12-28-2008, 11:43 AM
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Right, the family invasion over Christmas is over, so I can get back to the finer things in life.
Matthew, happily the problem with the tyre tread was not serious. One of the tabs on the sloping shoulder was not securely glued to the tread, and had spread slightly. It was easy enough to slip a scalpel blade in and break the small amount of adhesion, then ease the tab back into place and slip in some more glue. This new photo shows the result; there is a slight wrinkle where the paper stretched as the tab moved but otherwise things are OK. Alan
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#7
12-28-2008, 11:49 AM
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Wire wheels part 1
Right, this is how the wheels go. I didn't take any photos while building the wheels for the HX90, so I shall have to use older ones as illustration. Also the technique has changed a little with experience, so I shall have to mix them up a bit. Don't be alarmed when bits change size and colour - the principle is right.
The first thing is to make the hub. This consists of two flanges and a spacer drum, and each flange has three layers (photo 1). I coat the back of the flange pieces with cyano for strength, then drill them using a 0.55mm drill in a pin chuck. The size is somewhat arbitrary, but is just big enough to pass a No.10 sewing needle, which is the smallest I have. The outer parts of the flange have alternate spots drilled out, while the slots in the centre piece are drilled at each end, then opened up with a scalpel. I also drill out a 1mm central hole, to fit over a pin for alignment (photo 2). One side piece and the centre one are threaded on the pin, and glued together with the holes lined up with one end of the slots. The second side then goes on the pin, but is not glued yet (photo 3). Lengths of sewing thread are then passed through the holes. [Silver monofilament line would probably look better, but I am concerned that (a) it may be too stiff to take the sharp bends required, and (b) it may be hard to glue securely to the rim.] Finally the loose side is fixed to the rest, giving it a twist so that each hole lines up with an undrilled spot on the other side, and the thread sits in the slot in the central layer. The result is a horrible tangle (photo 4). More to come... Alan
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#8
12-29-2008, 08:53 AM
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Wire wheels part 2
...
Now we do the same again for the opposite flange, and join them together using the central spacer. The flanges need to be rotated slightly so that each spoke comes out half way between two spokes on the opposite side. This makes the tangle even worse. The rim needs to be prepared. For the HX90 this is a simple cylinder, with equally-spaced holes drilled down the middle. On other models it is made up of two shallow conical half-rims. The last piece of equipment is a lacing jig. This is a piece of thick cardboard or foamcore with the spoke runs printed on it with a large hole for the wheel to sit in. The edge of this hole is built up with extra rings of cardboard as necessary to make it about the same thickness as the wheel hub. All around the outside are knifecuts into which the spokes can be pulled, to hold a light tension (photo 5). The spokes are threaded through the appropriate holes in the rim, starting with those emerging from the inside of one flange, which fill every fourth hole. Then the spokes from the outside of the same flange go through the central hole of each set of three remaining, but offset round the circumference so that each spoke crosses two of the inside ones. Then the whole thing is turned over and the spokes from the opposite flange led through the rim. This takes a good deal of thought to ensure that the spoke pattern will be right. The result is still a bit of a mess (photo 6). ...
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#9
12-29-2008, 08:55 AM
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Looks good, Alan:D
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