I see replacement pinon gears in common Intermatic lamp timers was discussed in 2005. A more current model [TN711] and drive motor [WG2030] uses a pinon gear that has readily crumbled [in the heat and humidity of Hawaii, anyway]. The remnants are a golden, waxy color. Poor quality nylon? The gear train is hard plastic. The gear train works fine. My question, for curiosity's sake, is why would the pinon gear be made of such soft/poor/fragile material?
Let me guess... you're using it to run a swimming pool chlorination system? Of course, I discovered this that hard way. Nylon is destroyed by strong aqueous chlorine compounds. See chemical compatibility charts at:
Another possibility is LOW humidity, as in a refrigerator. When Nylon
6/6 is molded, it is stiff, hard, and brittle. In order to give it some flexibility and resiliance, it is given a water bath. Nylon is hydroscopic and typically absorbes about 3% moisture by weight. If you dry nylon out with a combination of cold and low humidity, it reverts back to its native stiff and brittle state and crumbles.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Might just be cheap trash plastic. The smallest spinning gear is also going to get the most wear. The oddest problem I ran into with intermatic timing motor modules was demagnetized magnets, making them too weak to start up most of the time. I still haven't figured out how to cross reference those things into something you can still buy even though it looks like they still make them. The circa 1980s ones had molded pinion/magnet assemblies made of some type of hard black plastic.
Good guess Jeff, but no, used to time lamps in the house while on vacation. Not near the swimming pool and not in a refrigerator. I have several timers and I noticed that at least 2 have stopped turning. Disassembly of one revealed the rotted pinon gear in an otherwise virginal looking timer. Your explanation seems to rule out Hawaii's high humidity as a cause. Perhaps "just" age. Any clever idea as to what design criteria dictated use of this grade nylon?
Supposedly, Nylon tends to yellow with age but not lose any of its strength. Indoor use and being inside a box eliminates UV exposure and dehydration as possible culprits. Another bad guess(tm) might be that the Nylon was attacked by solvents in the lubricating grease, but it's difficult to imagine that the little grease inside the timer would do much damage. Nylon can be depolymerized with steam in the presence of assorted catalysts (used in recycling plastics), but that's also unlikely. Yellowing in Nylon can be caused by UV exposure, which is also unlikely.
Lacking any additional forms of attack, I think we can safely default to the Nylon having been improperly prepared or molded, and having destroyed itself. In other words, I have no idea exactly what happened.
No recall notices on the TN711: You might be able to get a replacement timer by contacting Intermatic, but methinks a digital timer might be a better replacement.
Useless, but interesting items found while Googling:
Method for restoring whiteness to yellowed nylon fabrics
Retr0bright (which doesn't work on nylon but works well with ABS):
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Thank you Jeff. Oh, I have ample replacements from garage sales. I did contact Intermatic only to complain. The nylon was mush - way beyond restoring. :)
I wonder if the switch contacts generate enough ozone to do anything to the nylon?
Maybe that one crummy gear is a "fuse" for the drive train? I have a '64 VW that has one fiber gear in the wiper motor gearbox, while the rest are metal; I suspect it might be there in case the wipers are frozen in place by ice.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.