something wrong!
I have two Riverossi 3 truck heislers and have experiance with a two truck @ my buddy Dr Tom's (the infamous Dr.G) C & S. We have been running these critters on exterme RRs for 20 years, and they are , out of the box, unmodified, the best pullers out there.
granted mine are ancient, but Tom has a new release and it is a hoss too. Mine are capable of pushing a seven car train up an 8.5% grade( the locomotive is allways downhill to prevent runaways) the weight of the cars on the 18 in radius cause the cars to derailt before the drivers slip.
The Bachman shay is weak- to light, no place to load with wood. the trucks are not equalized, and the whole animal doesn't have enough float, so it can't stand vertical curves. I had one and it was useless on my mountain. On my valley, it could work one Job, but I have a PFM 3 trucker that could do only that job, and it could pull twicew as much as the Bachman,; which can do curves it can do grades, it can't do both at the same time.
I got one of our DCC guys (thanks Blair) to pop a decoder in mine . and took it to the club. on the 4.5% it can do 3-4 cars pathetic, I have a weastside class a climax that can do better. That shay looks gorgious, but it needs 21 inch radius flat track that is flawless.
If you can work the kinks out of a MDC 2 truck Shay, put a walker model conversion boiler, which back dates the locomotive, and is much heavier, and remotor it with a gear reduction motor you can make a Hill Monster.
My Brass geared power is all stuffed with lead ! can't do DCC on this layout until they make lead decoders.
Make a jumper wire and run that hesler upside down. drag a thum lightly across the tires of each axle and see if you can stall the weel with the motor still running, my guess is you have a gear spinning on a shaft, but thier are other possibilies, but something is wrong in there, and it need to go to the shops!
Bill Nelson - (East tn. Logging on the DG CC & W RR)- close assosiate of Dr. G ( Logging on the C & S in east Tn.)