American Z Line has discovered a misprint on the packing of the SD70M and SD75i run of locomotives. The packaging states that the motors are rated at 10 volts. The 8mm Falhaubers used in the run are actually rated at 8 volts. Operating the locomotives above 8 volts could result in damage to the motor. Rob Kluz
Rob, with any other Z scale loco 10V is way too fast anyway. With the SD70M, it's not going at lightspeed when at 10V. Has anyone tested what typical scale speed for the SD70M is at 8V? Thanks, Randy
Here is a pic with the voltage limited to 8 volts of two SD70's screaming around my test track: They do a scale 120MPH or so now that I did my low friction mod, but before they did close to a scale 50 at 8 volts. This is showing 2 locos that drew 90 milliamps each before drawing 65 milliapms for the pair!
I was recently asked what would happen if the SD70s were run faster than they were meant to. Check it out... we have an aswer thanks to a UP SD70M http://www.railpictures.net/viewphoto.php?id=158771 Ouch... Rob
Only a few people have really seen mine screaming at 8 volts, but Jeff Merrill is one of them and he can attest to their high speed once you get the friction out. The biggest killer is the flex tubing that couples the motor shafts to the worm shafts. If this is not perfectly aligned, then the tube will flex while rotating, and create drag on the motor. I found the fastest way to tweek them was to sand down all 4 sides of the black plastic bearing capture blocks so they rattle around in their frame cradles, and test by measuring current draw. A good value to shoot for is 60-70 milliamps per loco. Sacrifice a bit of noise for less current draw. Who knows, mayby by just running them for several hours they will speed up on their own? As you can see at 8 volts, I am drawing 65 milliamps for 2 locomotives, and they do run very fast now, and can run with speeds like the GP35's do. -Robert
