12-21-2013, 05:11 PM
I'm a little disappointed that the GP7s Bachmann has announced in sound versions for ACL and RI are overdue. On the other hand, I did get one of their D&RGW GP7s:
Unlike the various discrepancies Matt has found for the CN GP9, which Bachmann numbered and lettered (twice) for GP7s, and unlike the L&N GP9, also numbered for a GP7, the D&RGW version is pretty good. Among other things, it's numbered for the first few D&RGW units, which had the plain side sills, unlike the slotted side sills on the GP9s. Also, the shade of yellow is good for the earlier bumblebee scheme.
As a next step in DCC conversion, I installed a TCS decoder in an Atlas yellowbox D&RGW GP7 in the later paint. I wanted to see how well consisting worked.
Based on what I've read, I agree with anyone who says adjusting the motor control CV values is no picnic, and you can only come so close in getting the locos to run together. It turns out that the Atlas loco, at least with a TCS decoder, starts at a much lower voltage, so I had to tweak that. Then I found the Atlas loco had more momentum than the Bachmann, so I had to increase the Bachmann momentum values. Then I found the Atlas decelerates more slowly than it accelerates, so I had to work around that. The two locos will in fact run together now, but it was a fair amount of work!
Unlike the various discrepancies Matt has found for the CN GP9, which Bachmann numbered and lettered (twice) for GP7s, and unlike the L&N GP9, also numbered for a GP7, the D&RGW version is pretty good. Among other things, it's numbered for the first few D&RGW units, which had the plain side sills, unlike the slotted side sills on the GP9s. Also, the shade of yellow is good for the earlier bumblebee scheme.
As a next step in DCC conversion, I installed a TCS decoder in an Atlas yellowbox D&RGW GP7 in the later paint. I wanted to see how well consisting worked.
Based on what I've read, I agree with anyone who says adjusting the motor control CV values is no picnic, and you can only come so close in getting the locos to run together. It turns out that the Atlas loco, at least with a TCS decoder, starts at a much lower voltage, so I had to tweak that. Then I found the Atlas loco had more momentum than the Bachmann, so I had to increase the Bachmann momentum values. Then I found the Atlas decelerates more slowly than it accelerates, so I had to work around that. The two locos will in fact run together now, but it was a fair amount of work!