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tomjkear

Repair a cracked plastic gear

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Hi guys. 

This is actually a part from a vintage cassette recorder but I'm sure there will be people in the rc community that know how to deal with things like this. 

This tiny gear has cracked right the way through and it creates enough space between those two teeth for it to not mesh properly with the other gear. 

I highly doubt I'm going to be able to replace this part so I'm looking for ideas on how to repair it. The gear slides right off the shaft and the gap does close when squeezed hard together. 

The only ideas I have are trying to glue or trying to melt the two pieces back together. I'm not feeling optimistic because the part is so small and because its such a tight fit on the shaft, which might reopen the crack after attempting to fix it. 

What so you recon? Is it a goner?

Cheers :)

IMG_20200710_193258.jpg

IMG_20200710_193300.jpg

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My go-to place for such information is tapeheads.net. There are people there who have repaired all kinds of cracked gears and there are even replacements moulded by members for the more popular models.

If I recall correctly, a typical problem with these tiny pinions is that they shrink over time and crack. Drilling the hole out slightly before gluing might help keep it together afterwards. 

But check with the experts. Perhaps by starting here;

http://www.tapeheads.net/showthread.php?t=68327

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19 minutes ago, Yonez said:

My go-to place for such information is tapeheads.net. There are people there who have repaired all kinds of cracked gears and there are even replacements moulded by members for the more popular models.

If I recall correctly, a typical problem with these tiny pinions is that they shrink over time and crack. Drilling the hole out slightly before gluing might help keep it together afterwards. 

But check with the experts. Perhaps by starting here;

http://www.tapeheads.net/showthread.php?t=68327

Excellent info, thanks, I'll check it out!

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I used to send my gear to ProDigital in PA, but they recently closed as the owner died of cancer...  Sucks, I wanted to get my PCM-r500 tuned up this year...

Terry

 

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In case anyone is interested... 

I removed the gear from the shaft and gently pushed cocktail sticks into the hole to open out the crack. 

I then smeared a tiny amount of super glue along the crack, pulled the cocktail sticks out and used a clothes peg to hold the gap closed over night. 

Following evening I checked the glue had held and used a dremel tool to bore out the hole very slightly. It now slides easily but securely onto the shaft. 

I think it's fixed because very little load will be put through this gear... the drive belt would slip, or even snap, before that happened. I'm guessing the crack is the result of shrinking with age as mentioned by Yonez. 

Happy days. Cheers :)

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