Trains that 'chug'

Haha, always good to have a few more views! Maybe my eyes are playing tricks on me. Just seems like every time the wheels go round there's a very brief, very subtle moment where it slows down?

I've got a Plarail KF-02 HD300 Hybrid Loco that's been a serious chugger right from BNIB.

I've had it completely stripped down, gearbox and all, twice, without finding anything at all wrong with it.

But it Keeps On Chuggin', as Robert Crumb didn't say.

It could be down to a bit of slack in the gear train, witch when running builds up and then realeses, due to maybe the spring on one of the gears, or it could be down to a bad conection between the motor commutator and brushes, those are the only things I can think of

Well I had the C12 apart this evening. No cracked gears (should hope not, since it's new!) and no noticeable dirt or debris causing an issue. Motion of the gears seems okay when run by hand, although that isn't a particularly scientific test!

The one thing I must say is that there is clearly some stress on the motor when the chugs happen, you can hear it slow down for that moment. Same noise as pressing down on the engine as it's running.

The motor inside is soldered in. I'll order a torque-tuned motor and get my soldering iron out when it arrives, and take it from there.

[Super]

Let us know how it turns out

Small update, I bought a new motor, a Tamiya Hyper-Dash 3.

Installing it wasn't too tricky, the photo shows some dissasembly and the new motor soldered in place with one terminal on a metal plane that goes around the side of the housing and the other to a wire that connects to the far battery terminal.





And... it still chugs. Although it runs faster so the chugging is much less painful to witness.

I'll still buy another C12 soonish and see how that performs.

[Super]

How closely did you inspect the worm gear that slips on the shaft that is on the motor itself. You test with a new motor seems to narrow it down to gearing...right? I have seen a very fine split in the worm gear that is not very noticeable and affects engine performance. Do you have a lighted magnifier glass? Hoe hard was it to remove and replace from the old to the new motor shaft?

Yes, I'd say it ought to be a gearing issue at this point. Unlikely to be the housing.

The worm gear wasn't too keen on coming off, so I held it in hot water to soften the plastic. Then it popped off fairly easily. I didn't notice any cracks but I'll happily inspect under a magnifier when I re-open it (I do have a lighted one)

If I get another C12 that runs nicely I'll swap some parts around to try and narrow the issue... or break the pair of them!

[Super]

If it was tough to get the spur gear off then I would have to assume that its fine especially if it was the same resistance when putting it on. If you have it apart again, check out real closely the other gears with the magnifier as they cracks, if any, can be hard to see even to the trained eye. Also, I think there may be a large, flat, round gear that is being driven by the motors spur gear, its on a metal shaft of it own, make sure its not loose from that shaft and it meets the spur gear in its middle.

Sounds like good advice, thanks! I'll update again when there's news. Even if no fix, it would be nice to prove why it chugs.