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That makes me want to go inside my older machine and mark the current positions, say with a sharpy or dye. Mine had the main plastic timing pulley break in half
by awful 9y ago
That makes me want to go inside my older machine and mark the current positions, say with a sharpy or dye. Mine had the main plastic timing pulley break in half and is un-obtainium. So I epoxied the pieces together, while drilling holes and embedding steel wire reinforcement. Works like a champ, though I go the feeling it was built with planned obsolescence, as the rest of it was built like a tank.
- jacquesm 9y agoSometimes such a plastic parts sole function is to break to avoid major damage to the rest of the machine. If you make it stronger and the same conditions occur something else might break or bend that is a lot harder to replace or repair. You'll see the same in farming equipment, there are usually one or two sacrificial bolts in there that will be happy to snap if the tool gets wedged, rather than that the tool snaps.
- awful 9y agoI get the sacrificial analogy, but in fact, the larger problem is IF the cam does fail, will it allow interference that will lock up at speed and potentially destroy the highly powered but delicate mechanisms, as you find destroys engine valvetrains, mainframe printers, among others. And this is what it did; when it failed everything locked, but luckily nothing was destroyed because otherwise built like a tank. The alternate explanation is that it is simply a very complicated cam device with many extreme contours, expensive to fabricate from anything but plastic injection, with high force followers that cause it to fail over time, leading to a trip to the sewing machine repairman. edit: I called it a pulley, but it in fact was a complicated cam.