DCC and Coreless Motor Problem

Model Railroader Electronics and DCC
1

I have a Precision Scale loco with a coreless motor. It ran very smoothly a very low speeds on DC. After installing a Titan decoder the buttery smooth low speed operation went away and the loco would surge at the lower 25 or so speed steps.

I tried bypassing the decoder and running again on straight DC and the smooth running returned. Hmmm. A call to QSI customer support revealed that they are very frustrated with coreless motors and recommend installing a can motor. I’m not adverse to doing this, but somehow the idea of ripping out a very expensive Swiss motor and replacing it with a Chinese can motor as a cure just doesn’t feel right.

Basically QSI recommends futzing about with the BMEF PWM CVs (of which there are a LOT) to see if I can improve things. So far no joy.

My guess is that because cordless motors don’t cog they somehow are not suitable for PWM.

Any ideas?

2

They just have vastly different characteristics. Try turning BEMF off entirely - the paremeters will need to be much different for a coreless motor vs a normal iron armature motor. PWM is fine, just do not for any reason disable the high frequency drive, low frequency PWM WILL kill a coreless motor. They work best an pure smooth DC, but you can still get decent operation with DCC decoders.

That said, the nice Canon motors in my Stewart switchers are normal iron core motors and are about as good as it gets, and would be a suitable replacement if it fits. Very smooth and quiet, good power at low speeds, and absolutely no issues running with DCC. Also, instead of QSI, consider ESU Loksound, they have perhaps the finiest motor drive of the common sound decoders - the Europeans seem to do a lot better on the BEMF and motor drive, mainly because there seems to be more automated operation where it is criticial that the locos move exactly as expected.

–Randy

3

Yup, turn off BEMF. I also found the same issue with kato locos…but setting it to standard throttle solves the issue. David B

4

I do not have experience with Titan sound decoders, but I do have some experience with coreless motors and non-QSI sound decoders. I installed Tsunami sound decoder in Trix Mikado, and have Trix GG-1 with factory installed sound decoder (I assume it is ESU Loksound V3.5 or earlier). Both locomotives have coreless motor (Maxon).

GG-1 performed perfectly out of the box. This locomotive really creeps on track, with BEMF switched on, even at speed one. I just had to adjust CV 3 and 4 according to taste, and top speed.

Mikado on the other hand was more difficult to adjust. CV values for motor control and slow speed (CV 2, 10, 209, 210, 212, 213 and 214) had to be adjusted specifically for that kind of motor. I have Tsunami in other locomotives with iron core motors, and CV’s in that locomotives are set on other values than in Mikado (especially CV 210). Moreover, in these other locos, CV’s are not the same in all locomotives – each loco requires separate set of these CV’s, to get most out of Tsunami. But with Mikado, all those values were not helpful. Just a note: I hardwired Tsunami in Mikado – original wiring was completely discarded.

Having in mind that Titan is one of the latest sound decoder that was put on the market, I can not believe that it can not control coreless motor perfectly. What you need to do is to try to find combination of CV values for motor control with BEMF switched on. This procedure can be very exhausting and frustrating.

To get Mikado run as I wanted, it took hours and hours (on several days!) until locomotive was running satisfactory: slow, smooth nice start, the same from movement to stop, chuffing sound sensitive to locomotive load and speed. Of course, it is Tsunami, so it can not beat ESU in motor control, but still, very nice and smooth running was achieved, without jerking or similar.

I would never replace Maxon coreless motor with iron core motor if Maxon coreless motor is working well and its size is appropriate for

5

They should all work, the amount of adjusting to make it work though, will vary. Note the common thing - ESU + Coreless = works great right out of the box.

Haven’t seen anything yet that makes me rethink my decision to start using nothing but Loksound when I want sound decoders.

–Randy