Repair vcr crack gear???

There is a couple of tips relating to repairing broken plastic gears somewhere on my 2 tips files on URL below

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Don't use crazy glue or you'll have to remove it to make a quality repair. Glue simiply doesn't work well enough on nylon, which is best repaired by melting it back together with a soldering iron and some scrap nylon of the same type (another nylon gear, not a nylon wire tie). As with metal welding, melt the material almost all the way through. If the center hub of the gear is cracked, melt it back together and place a metal sleeve (thinwall tubing - brass, steel, or aluminum from a hobby or hardware store) over it, using epoxy to hold it if the fit isn't snug.

I'll assume this gear is nylon. In 25+ years experience, I have yet to discover an effective and lasting method for bonding nylon to itself.

Solvents/adhesives supposedly made for the task don't perform well, either, nor does heat welding. It's very difficult to keep a cracked/slipping gear together when it's under that kind of torsion/shearing stress.

That said, there are always alternatives. If this unit is worth the trouble and expense to ya, you could make a mold of the original and have a machine shop cut a new one from metal stock, or cast one yourself. Better still, find for sale a used -- possibly malfunctioning for a different reason -- vcr of the same model series as yours with a good gear and cannibalize it.

There is no way. Nylon is molded 100% bone dry and absorbs moisture after that. Once absorbed, no weld is possible. Unless you can mechanically repair it you are screwed.

I've had to make many gears and misc. parts. Go to your nearest hobby shop and buy some Alumalite plastic. It's a two part liquid plastic that you mix together and it is completely set and hard in 3 minutes. They also make a rubber casting compound to copy the original gear with. I've been using it for years to make gears and other parts for older copiers and such.

Ray L. Volts wrote:

I used to weld nylon gears in hotel TVs all the time when I didn't have spares, and not one cracked again. I even still have a 30 YO Sanyo Sears with a small gear that had lost some teeth. The new teeth I welded on have held up for at least 10 years now, and I was rough on that tuner, wearing holes all the way through some of its contact fingers.