Large Scale Central

USA Cracked Gear Hub Fix

Problem Solving
#1

I recently acquired a USA NW-2 for a project for my dad’s railroad. One part of that project required replacing the stock wheels with Northwest Short Line replacement wheels. Wouldn’t you know–once I opened up the motor blocks, I discovered that 7 of the 8 axle hubs on the gears had cracked, and the axles could spin very easily. This is a known issue with USA gears, though for whatever reason doesn’t seem to get the publicity as gear issues from other manufacturers. Be that as it may, the fix for this is pretty simple. All you have to do is put some sort of clamp around the hub, and voila!

Question is, what to use? A while back, I read about wrapping fishing line tightly around the hub and gluing that in place. Later, I read of using 10mm OD brass tubing. Well, I had neither on hand, and being a rather impatient sort, I went looking for alternatives.

Then it hit me.

Literally.

I was swinging my desk lamp around and one of the springs popped off. I looked at the spring, and I looked at the gear. I measured the spring. I measured the gear. The inside diameter of the spring was just slightly smaller than the outside diameter of the hub on the gear. I could twist the spring on the hub, and the spring tension would compress and hold the hub together.

I put the spring in place, then cut it off with a cut-off bit. I can’t say for certain, but I think the heat generated from cutting the spring off while on the gear may have melted the plastic on the gear just a bit to help hold the spring in place. Dunno, but it’s sure not going anywhere.

The new axles pressed into the gears without any issue, and are very, very snug!

I put everything back together, and it’s very sturdy.

Later,

K

#2

How does the lamp feel about it? (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)

#3

The lamp did shed some light on the problem.

#4

Any port in a storm, right? (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)

#5

Kevin-

Many thanks for your insight, inspiration, and photos.

Any chance you have a portion of the spring left so the internal size can be measured?

The question has merit otherwise those of us with USA locos wait until the problem occurs and then make a measurement from taking the system apart and measuring the axle. There is a local ACE hardware store with possibly an assortment of springs. Your project offers a head start to solving the problem.

Many thanks,

Wendell

#6

Very interesting fix, K… Good on ya’…

OK… Where do we get the springs???

Or are you going to be sole distributor of the lamps??? (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)

I’ve drilled and pinned the gears/axles with a 1/16 inch roll pin but this is much easier…

#7

Stan, most “swing arm” style desk lamps use these springs.

I’ve picked all mine up at garage sales. When they die (usually broken plastic “elbow” brackets or the switch stops working), I save the springs and go looking for a new one to replace it. You might try Goodwill or similar 2nd-hand store as well.

Also, as Wendell noted, most hardware stores have an assortment of springs. The one I used has an inside diameter of 0.325".

Later,

K

#8

Thanks so much, K… (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)

#9

Stan

Not sure if you have a True Value Hardware or Ace (as mentioned) store out your way but they stock lots of springs. I believe Lowes and HD have them too in the hardware section.

#10

I’m using the brass tubing, found at every Ace hardware, some of the USAT locos have very little clearance in the gearbox. I thought that it was the NW-2 that had this issue, but Kevin seems to have no problem.

Hmm…

Greg

#11

Greg, it’s very close on one end of the motor block, but there’s no contact between the hub and the motor block. (I believe it’s the end shown in the photo.) The other end has plenty of room. If the closeness were to be of concern, it’s very easy to take an x-acto knife to the corner to give a little more clearance to the axle. A miss is as good as a mile in this case.

Nothing wrong with the brass tubing if it’s available. As I said, I was impatient, and looked for something on hand to solve the problem. Figured I’d just pass the info along.

Later,

K

#12

yes thank you K

#13

That is a good fix Kevin.

I have a USAT 20 tonner Mighty Moe and it had cracked gears so the last time I was at Charlie Ro I bought gears for it and was surprised that for $20 I got 2 axles, gears and nice shiny wheels. The mighty mow axles also fit the NW2 according to the package so if the plating is worn off your wheels why not get brand new assemblies when your gears crack.

#14

You can also 3D print axle gears.

#15

Dick, how well to they last/work?

#16

Hard to say, David. Depends I guess on what they are made from and how much use they get. I printed new gears for my Bachmann trolleys – you know, the ones that always break their axle gears. I’ve got four of them in two trolleys and have run one of them in excess of ten hours. The other one has no motor (it seized up immediately after I put the new gears in). It’s a Santa trolley, so won’t get much use for a few months. These gears look a little more complicated, but I bet with some measurements, I could cage up one. Besides, they are dirt cheap if you have a library nearby which has 3D printers.

Mine are made in PLA, and I have one in ABS. I’ve got one of each in one trolley to see which fails first. This red one is PLA. No verdict yet.