Fix for Slipping Gear

Earl,

Have you tried a drop of CA followed w/accelerator? It looks to be a nylon type gear...it might work.

"Pappy"

Can you remove the gear and make some grooves(knurl) with a side cutter then replace gear with a drop of CA.

franktrain

Instead of grooves, I take the shaft and use a punch to put a couple of divots in it.  This raises some metal that will "bite" into the gear when you press it back on.  No need for glue, and CA won't stick to that gear all that well anyway.

I have also distressed the shaft on prior repairs, but I use the teeth on vise grips to do it.  I don't think I could keep a punch centered on that small shaft well enough.  I thought someone might have come up with a better method of securing the gear.

Earl

Yep, if it's too small to keep the punch on it, the vice grips are a good choice.  I don't think there's many better ways, that's how most gears and wheels are secured from the factory, that must know something.

Earl,

I was thinking about this and maybe this gear is supposed act like a clutch and save the motor from excess torque? Make sure the mechanism is not binding causing the gear to spin? 

franktrain

The only other option is to remove the gear and grind a slot in the shaft and glue in a metal "key way", or small bar stock (use epoxy or JBweld). Then machine with a dremel tool the gear so the"tooth" for the "bar stock key-way" slides into the gear.

I have yet to find an adhesive that will stick to nylon. Distorting the shaft is a good idea if you can do without bending it. I have also used music wire as a key. You would have to cut a small groove in the shaft. Something like .030" wire should do it. Put the gear on the shaft and heat the wire with a soldering pencil while pushing it into the gear. That should lock in place. The most difficult part is finding a fine enough cutter or disk so that the keyway is not too wide.

I see J Daddy beat me to this.

Pete

Yep, gluing the nylon gear is pretty much a non-starter, I've never been successful doing that either.

Get some very thin brass stock and make a sleeve shim.  That sleeve can be glued to shaft and nylon gear slipped over it.  You do need to be careful and are you sure the gear has not cracked?  G

Metal sleeve is a good idea, but it, too, needs to be knurled.  I spoke to a Loctite rep many years ago, bought some very expensive stulff, tried it on Celcon acetyl gears.  It failed.  I have a special knurling tool, and did most of the steam axles for the Babbitt locomotives when they were being produced in Kentucky.  A knurl is the only way.

Loctite works great metal-to-metal.

A downside of the metal sleeve is it will stress the nylon and then crack. Nylon shrinks over time and will crack on its own. They might be OK for spur gears running loose on a shaft but not for driver gears. If Lionel insists on using them they should come up with a better mounting system like a square hole on a square shaft or some other key. Relying on friction only leads to failure.

Pete

Because they shrink and get tighter?  I thought his problem is a loose gear that is slipping.  Knurling also stresses it; it is a press fit.  The issue is getting the proper fit.

That is why I asked if it was cracked.

You can always bore open the gear more, and sleeve with the correct size.  Since the sleeve can be made longer than the gear width, it gives you plenty of extra area to get the sleeve bonded to the shaft.  An epoxy fillet while not a perfect bond to nylon will give more grip to help the internal press fit.

I don't think this is a high torque accessory with a nylon gear and inexpensive can motor.

Otherwise buy the new gear, looks like some brass ones Lionel has might even be a match.  G