I am in the infancy stages of designing a large layout based on the powder river basin, and I have some questions regarding a helix. I would like to design it with 2 levels, that would require a helix(too flat, and no tunnels in the PRB to utilize a nolix). I would run typically 2 units on the point with 1 DPU on my coal trains like the prototype, and probably 24 coal cars. I am concerned that running a live DPU in a helix would cause possible derailments. Does anyone have experience running DPU's or helpers on the rear of a train through a helix with success? I will use DC to power the trains.
Not on a helix, but I have had success on flat or graded layouts with DC, ........so long as the engines speeds are matched, and you have the same voltage output throughout your layout.
I've had limited success with trying this and have had some pretty catastrophic derailments (I have a helix with a 2.7% grade). The problem comes in when a helper loco farther back in the train hiccups slightly (because of a small dirty spot in the track, let's say) and stringlines the train. Or, a lead loco hiccups and causes a derailment if the helper keeps on pushing through evenly. I've pondered with the idea of removing some of the truck gears in a dedicated helper unit so that it will add some tractive effort but not be as cabable of causing derailments. Russ
For what it's worth,I have a SD40-2 with a bad motor,so I removed the motor and just pull it around the layout as a dummy.I use it and a powered unit on the rear of trains as helpers.The extra weight seems to keep the powerd helper from pushing to hard.I still have helper related disasters,but I think they are less frequent.
I have operated through 2 helixes with both DC and later DCC. Using DPU through a helix is a definitive "go DCC". I was never able to operate a 30 car coal train with a rear-end pusher w/o derailments in DC mode. Slight irregularities or even the change in elevation put so much stress on the couplers that I got every sort of disaster one can imagine. With DCC it's a snap. I speed-match the locos and I assign an operator to the DPU and have had no derailments since. YMMV, Michael
