WaLLyworld SW1200 worm mesh problem?

[sizemore]

I have a SW1200 that when running the long hood truck skips randomly. The truck rolls freely on track when pulled from the chassis. The issue only occurs when engaged by the worm.

Because I've added the decoder I cant pull the board to see the action. Just wondering if anyone else has ran into this issue and find a possible solution, before tearing it down on the operating table.

Thanks,
The S.

[wazzou]

I've switched one to KATO worms and find it to be a much smoother operator. 
I haven't done the others I own yet but have heard of similar successes by others.

[ryan_wilkerson]

Which worms did you use? A part number or locomotive it comes from would be very helpful!

[wazzou]

I'll check but aren't all KATO worms essentially the same?

[peteski]

I'll check but aren't all KATO worms essentially the same?

Many are, but if you want to get technical, not all are the same.  Plus some of the new trucks with the integrated worm use much finer worms.

[JanesCustomTrain]

That's the one you need from Kato.

926580
Worm Gear and Joint Set (includes worm, bearings, shaft, and universal), 2 ea
N-Scale / Fits: P42

Jane

[sizemore]

I've switched one to KATO worms and find it to be a much smoother operator. 
I haven't done the others I own yet but have heard of similar successes by others.

I assume these are nylon/delrin and a press fit on the LL motor shaft?

The S.

[u18b]

Sizemore has hit the heart of the matter.

If you have an older LL loco, then it will have PLASTIC worms.  They are crap.

Once in a while, you get a LL SW that runs quiet, but not often.  The plastic worms are not perfectly round and wobble.

Walthers saw the light and placed brass worms on the later release.   I doubt you need to replace the brass walthers gear.

So pull the shell and tell us what you see.

[sizemore]

So pull the shell and tell us what you see.

Plastic. That's why I was asking about the nylon/delrin replacements if they were a direct press fit replacement. I really think its play in the motor shaft, and the first "tooth" of the worm tapping out on a tooth in the crown gear. I may try to file down the first tooth on the worm, see if that stops the skipping.

The S.

[u18b]

I have never heard of the plastic worms skipping (even though they are crap and should be replaced).

So a cracked or damaged truck gear is possible.

Also check the nubs on the top of the truck tower.  They can wear or be damaged.  If the truck is not snug in the frame, then looseness could also alow a tooth to skip on the worm.

[sizemore]

I have never heard of the plastic worms skipping (even though they are crap and should be replaced).

So a cracked or damaged truck gear is possible.

Also check the nubs on the top of the truck tower.  They can wear or be damaged.  If the truck is not snug in the frame, then looseness could also alow a tooth to skip on the worm.

I tested with a truck from another 1200 and it does the same thing. Which in my mind eliminates the truck as the issue, and potentially the frame.

The S.

[wazzou]

Yeah, sorry, mine are all Life-Like.  I hadn't realized that Walthers switched to Brass.

[sizemore]

I took a look at it last night and tore it all down and I think I found the problem. The motor is angled down hill towards the long hood ever so slightly, like in the thousandths of an inch range. I think the angle is just enough, to change the mesh depth between the crown gear and the worm when the truck bolster rides on the frame behind the folded pick-ups. The motor shaft has enough lateral play, that the worm tooth rides on the next tooth in the crown. Anyway I think that's the issue, I'll grab the Kato gears and see how they turn out.

Thanks,
The S.