Intermatic Timer Pinon Gear

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?

Reply to
John Keiser
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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.
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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

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.

Reply to
Cydrome Leader

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?

Reply to
John Keiser

Lowest bid supplier?

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):

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

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. :)

Reply to
John Keiser

I stand correctified.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

Yeah, the $6 timer only lasts about 15 years. ;-)

But I agree it's annoying. All the other gears are brass and don't wear.

Does anyone know of a replacement source other than to cannibalize other timers?

--- sam

Reply to
Samuel M. Goldwasser

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.

Matt Roberds

Reply to
mroberds

I don't think so because installing a replacement from another motor will get you another 15 years. :)

--- sam

Reply to
Samuel M. Goldwasser

Intermatics response: "The TN711 has been discontinued and replaced with the TN311 which is known for it's durability."

Reply to
John Keiser

I think the wife bought a 4 pack at Costco since I seem to have 4 of these and they are all bad!

Reply to
John Keiser

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