Tenshodo 71010 C62 Gear Replacement

[EMUHunter]

I recently bought a "junk" condition Tenshodo diecast C62 at auction, and am working on restoring it.

 

It was listed with parts broken off, NC/NR, and all the usual "junk" item considerations, but intriguingly the QSI sound, motor and lights were listed as working even though the locomotive didn't move, so I bought it. The exterior was in surprisingly good shape, but the engine wouldn't budge at all.

 

 

After opening it up and inspecting it, it's the classic old modeler's favorite — cracked gears!!  I was surprised to see the gear cracked all the way through, but it explains why the loco wouldn't budge an inch 😅

 

 

 

After doing a bit of research, it turns out this is a somewhat common with this run of Tenshodo models (which makes for a pretty terrifying thumbnail):

 

I measured the gear with a set of calipers and bought this replacement from NorthWest Short Line:

 

Spur Gear, 0.5mod x 22 Teeth x 11.9mm OD x 0.098” Face x 5.0mm Bore, Delrin (part 2241-6)

 

NWSL is great if you're in the states, though it's not too hard to find a gear with the same dimensions elsewhere if you aren't.

 

Gear Replacement

Replacing the gears isn't too bad overall, but pretty terrifying due to the detailed nature of the model — I accidentally broke off some parts when taking off the shell. The video linked above is a great guide for anyone else trying to do this repair, and helped me out a lot. Thank you to the person who made it!

 

The basekeeper plate is screwed on with three screws, which includes the front joint for the rear truck.

 

The front and rear trucks need to be unscrewed to access the other sets of screws holding the mechanism in place. One note of caution: the front and rear truck screws are **not** equal lengths. Keep track of which one is which!

 

Next up is removing the driving rods and drivers. The rods are screwed in place with a hexagonal, flat-faced screw on each side. I used a set of pliers to carefully unscrew them.

 

Remember the order in which you removed the rods, and take care not to bend them! Another warning: there's a small washer separating some of the rods which is easy to forget. Make sure you don't lose it.

 

Afterwards, you can remove the driving wheels.

 

The next step is the scariest by far — separating the axle from the driver. See that big set of pliers above? I used it as a makeshift holder for the wheel while I "carefully" smacked the axle out of the driver. (as careful as you can be with a hammer and a wood spike, that is!)

 

Next up is sliding the gear onto the brass holder. Unfortunately, doing this puts some pressure on the gear, which is likely intentional to make things snug, but it might be why the gear snapped in half in the first place. A more permanent fix would be to swap the whole assembly out for a brass gear like in the video.

 

 

Fortunately, you can press the axle and driver back together with your hands. Another "gotcha" with reassembling: make sure you have the driving wheels properly offset, and the rods in the right positions (refer to photos, as well as where the counterweights/cranks are located).

 

Reassembling the mechanism and testing:

 

It works!! After giving it a little more time to run in on the rolling road, I'll reassemble the rest of it.

 

Overall, not a bad repair — the mechanism is well designed overall, with most parts screwed together rather than clipped like on cheaper models. Strange design choice with the gear though — it might save a bit of production cost, but it introduces the good ol' Proto 2K flaw to the model as it ages. Repairing models isn't for everyone, but I find it pretty rewarding, as well as a way to save a bit of money.

 

Thanks for reading this far, hope you found this helpful!

[RS18U]

Nice write up, and well done.  I see these split gears on other brass models, and with Bachmann ones like their Shay.  My understanding is they use a 'plastic' style not only for cost, but noise.  Brass on brass can be noisy which is more noticeable on newer engines with quiet motors.