Arnold S2 cracked gears interesting phenomenon

[mecgp7]

Probably like many, I have a few Arnold S2s and all have suffered from cracked gears on the axles. They still operate well as long as you can accept the "clicking" they make when running. Recently I bought the collection of Arnold S2 parts that was posted here.
Combined with my own spare parts and the complete S2s there were some 27 axles with gears. All (mine and the purchased ones combined) except 7 had cracked gears. What was really interesting was that all 7 uncracked gears were heavily greased. The others were not. Pure speculation, but perhaps the grease prevented the cracking??

The best solution is to find the the wheelsets from NWSL, but maybe a little grease can preserve existing gears until they are found.

[JMaurer1]

Apparently this was a VERY common problem. I have two or three myself and while I haven't checked them for some time, I wouldn't be surprised that they now have cracked gears. At one point I planned to get the NWSL replacement gears but I can't find it on their website any longer...the one that I thought it was says its for the Walthers/Rapido S2 (?). I have too many locomotives anyway and who knows how I will get a decoder in it (I know its possible, I've seen it done, but not by me...).


Spur Gear, 0.3mod x 15 Teeth x 5.15mm OD x 0.039" Face x 1.0mm Bore, Delrin
Compatible with: Walthers/Rapido S2;  (axle)
Part Number:  2152-6

[C855B]

... Pure speculation, but perhaps the grease prevented the cracking??

Interesting observation. I wouldn't be surprised if that was the case. If it was a petroleum-base grease, it could have ever-so-slightly softened the plastic enough for it to yield to the pressure of the press fit rather than splitting.

[brokemoto]

It has been a good five years since I sold off the last of my Arnold S-2s, so my memory is imperfect on the precise construction of the things, but I do remember the basics.  There was some kind of wiper that extended from each truck that made contact with a metal plate on the underside of the chassis.  The wiper and the plate frequently got dirty from grease and the dirt that grease attracts.  This was from normal greasing, mind you.  Once they got dirty, of course, it compromised the electrical contact thus compromising performance.

It was relatively easy to address the problem.  As I recall, you popped off the fuel tank with your fingernail.  You then took a jeweller's screwdriver and slid two panels toward the middle of the locomotive.  The trucks popped out.  You then took your Q-tip soaked in LL track cleaner, swabbed the wipers on the truck and the metal plate.  Finally, you replaced the trucks, slid back the panels, replaced the fuel tank and it was alright again.  The problem was that this happened so frequently that it was a pain in the [donkey].  I would guess that while over greasing could preserve the gears, you will be disassembling the thing daily to clean the grease from contact points.

All of mine had cracked gears when I sold them.  I did, of course, advise potential buyers of this as well as its being characteristic of the breed.  All of them ran poorly with the cracked gears.  Of course, I did advise potential buyers of that.

[peteski]

Yes, the few which I own have cracked gears. Some of them were flooded with grease, so I don't think grease prevents cracking.

Those cracked gears are the reason I'm worried about the longevity of the more recent Hornby/Arnold locos (like the SW-1 or U-boats, and other European prototype locos) since they utilize the same wheelset design (plastic gears press fit onto metal axles).

I ordered replacement (brass) gears from a company in Poland, but those have another issue I need to address before retrofitting them onto the wheelsets.

[nkalanaga]

I suspect that the "Walthers/Rapido S2" is the same Arnold loco.  "Rapido" used to be an Arnold brand, long before the current Canadian company was founded, and Walthers imported a lot of early, and some not-so-early, Arnold models.

[Sokramiketes]

Late life problems aside, the Arnold S2 was really a genius piece of design.  The tooling on the body was really well done, and crisp.  The mechanical advantage behind the small diameter worm shaft was great (when the spring was straight).  And serviceability was easy.

It was even one of the first NA locomotives to be offered with DCC. 

[Jim Starbuck]

I agree with Mike. This model no doubt advanced N Scale considerably and was the first NA model factory decoder equipped.
If you cut the tube portions off of an Atlas geared axle tube it gives a cheap direct replacement for the cracked stock gear. It doesn’t address the tall wheel flanges though.
I have one that I reworked with a coreless motor with small diameter brass worms, lights and a modern decoder. I turned down the flanges and used the stock wheelsets.
It’s one of my favorite switchers.
Someone on the forum developed 3D printed pilots as well.
These have good bones for modifying albeit not the easiest but the results are worth it in my opinion.

[peteski]

I agree that (especially for diecast body) they have excellent details, the truck side frames look really good too.  Because they are all metal, they have decent pulling ability.  The mechanism with spring "worms" is something Arnold rapido has used in other models too.  The motor is of an older design, but it works ok, and is reliable.  The wire-free design using a PC board is also quite impressive.  These were still designed and produced in Germany.

The only shortcomings to me are the cracking gears (which only showed up after several years of use), and installing a light in the front headlight is a major pain in the butt (neither headlight is illuminated in that model).

[u18b]

The reason the gears crack is because there is a casting dimple.   The crack happens at this dimple.
it is very thin there.

[JMaurer1]

Thanks for the reminder Peteski...I never could understand the lack of a headlight.

[Jim Starbuck]

Thanks for the reminder Peteski...I never could understand the lack of a headlight.

It’s been quite a while since I did mine but I seem to recall drilling straight back from the headlight through 7/8” of metal to get the magnet wires into the shell.

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[peteski]

Yes, headlight can be installed, but it is not the easiest job.  You have to drill through quite a thick metal casting, then run very thin wires (no room for anything heavier).

[pmpexpress]

Apparently this was a VERY common problem. I have two or three myself and while I haven't checked them for some time, I wouldn't be surprised that they now have cracked gears. At one point I planned to get the NWSL replacement gears but I can't find it on their website any longer...the one that I thought it was says its for the Walthers/Rapido S2 (?). I have too many locomotives anyway and who knows how I will get a decoder in it (I know its possible, I've seen it done, but not by me...).


Spur Gear, 0.3mod x 15 Teeth x 5.15mm OD x 0.039" Face x 1.0mm Bore, Delrin
Compatible with: Walthers/Rapido S2;  (axle)
Part Number:  2152-6

The Northwest Short Line 2152-6 gears can be found on the following web page:

https://nwsl.com/products/spur-gear-0-3mod-x-15-teeth-x-5-15mm-od-x-0-039-face-x-1-0mm-bore-delrin

In addition, currently made to order with a lead time minimum of 2-4 weeks, definitely not cheap, the Arnold/Walthers S2 Diesel Upgrade Geared Wheelsets are also available.

https://nwsl.com/collections/geared-wheelsets/products/n-scale-wheelset-40-64-1-0mm-x-0-445-flush-axle-with-15t-spur-gear-4-pkg

https://nwsl.com/collections/geared-wheelsets/products/n-scale-wheelset-40-72-1-0mm-x-0-445-flush-axle-with-15t-spur-gear-4-pkg

Given the pricing of the individual gears, one would be better off purchasing the replacement NWSL wheelsets.

Installed in the cab and a very snug fitting, factory delivered DCC equipped Arnold/Walthers S2 locomotives were fitted with Lenz decoders.

[ogre427]

I have 2 with the NWSL wheel sets in them. Yes, they are expensive, but they run beautifully and something else not mentioned here is the much better-looking wheel profile. The non "cabbage cutter" flanges improve the looks of the model tremendously. (I would post a photo, but for some reason, it says I'm not allowed to.)