LGB Mikado Derailments

[pmindigo]

After installing new traction tires on my two Mikados, they now run smoothly over the switches! Problem solved…. at least for the next 20+ years!!

 

[pmindigo]

After installing new traction tires on my two Mikados, they now run smoothly over the switches! Problem solved…. at least for the next 20+ years!!

 

[pmindigo]

New traction bands filled the gap in the drive wheels and solved the switch derailment problem!

 

[AlanL]

Thanks for the feedback and great news that your Mikado's are now running reliably with traction tyres fitted.

It was a curious problem that had us fooled and there was a concensus that the point control mechanism was to blame.

I dare say that the problem of no traction tyre is unique to the LGB Mikado. More than 60% of it's weight (4.5 pounds) is on the 4 th driver and this weight (and imbalance) resists the traction tyre groove climbing off the moving blade. Also the trailing truck on this loco is so far behind the 4 th driver that it will not resist the blades opening.

A suggestion of the cause of the problem -
The full outer diameter of the driver digs in to the tiny gap between the curved stock rail and the tapered moving blade. As the loco moves forwards it pulls the blades inwards as the moving blade thickens. Eventually the groove will climb up the rail but the trailing truck is a long way behind the 4 th driver and there is nothing to stop the blade from moving, not even a point motor. If the trailing truck was closer to the last driver, it would stop the blade from moving. The trailing truck approaches the open blade and therefore de-rails as does the tender (from post#1).

Alan

 

[pmindigo]

You say that you're thinking about adding a spring to the trucks. Are there not springs on them already? I don't have a LGB Mikado but all the LGB locos I have with leading or trailing trucks have springs to help keep the wheels on the rails.

Yes they do have springs. The front spring is levered behind the mounting screw.

 

[pmindigo]

For information the LGB Mikado has a srung lead truck and gravity trailing truck.
I have regularly ran trains through facing points without any motor or spring switch to hold the point blades in position. The wheel profiles and flanges are very course and tolerant to errors. If you wanted to deliberately move the point blades with a model locomotive you would find it impossible. Even if the blades started to open, the big flanges and course wheels would try to push the blades back to the stock rail.

Could I suggest that the point blades are closing in on the locomotive wheels either due to flexing of the point as possible in full size but unlikely with our models, or the pile of the carpet below the point is pushing the throw bar.

The LGB Mikados are a fairly weighty beast and are pushing the track into the carpet causing the throw bar to move slightly. Try it with a piece of card below the point to isolate the carpet.

The leading truck jumping on the frog may be lack of spring, incorrect gauge or track flexing?

Alan

You are correct, the Mikado does have a sprung lead truck and a weighted trailing truck.