Monthly Archives: September 2016

9-28-16 thoughts on the motor testing

In thinking about the various reports on the motor testing, it struck me that a different slant would be meaningful. So far, the focus has been on holding the test bed constant. Where possible the only change is the motor. However, several motors have been tested in a number of test beds. In those cases, the only constant is the motor. Trucks vary from inside farm to outside. Wheels vary from stock to NS RTR. The number of axles vary from 4 to 6. There may be some interesting results that show up when looking at the data this different way.

The last day or so, several of the motors have been examined with that in mind. It is worth the effort. Of course, the focus has been on completing engines, so there are still tests to be run on most of the engines. The interim results will be worth discussing so interim reports will be written where it is meaningful.

An issue that keeps finding it way to the top. This is that not all motor possibilities will go in every engine. The primary issue is the length of the of the motor assembly that includes the flywheels and any inflexible couplings. With the position of the motor relative to the truck tower an unacceptable shaft angle is created that will adversely impact the performance. In some cases, the length is just to long.

The other aspect that impacts the situation has ro do with the type coupling at the flywheel. Basically there are at least three variations. First you have the old Athearn BB style keyed shaft with female couplings. These tend to vibrate making noise and losing power. The beauty of this is the extend over a fairly long length. The second and clearly an improved type is the dog bone. These are smaller in diameter and will have less vibration and thus less noise. The problem is the dog bone has to be a specific length. If slightly long, it will cause friction and rob power and speed and make noise. If too short, it will come out of the couplings. Some couplings hold the bone in place, some do not. The NWSL couplings used here did not. The Athearn couplings have restraint. This requires a tailored dog bone for almost every motor and position. Tends to be time-consuming. The third drive variation comes from Athearn. As indicated earlier, the tower coupling has a restraint and accepts a dog bone end. The flywheel has a hex opening to act like the coupling on other flywheels. This eliminates that part, combining it with the fly-wheel. This is likely a better solution, but again has the same kind of length issues as the regular dog bone. The problem here is a limited source, at least I haven’t found a NWSL type replacement. It may exist, I only recently need to find one. Athearn makes several lengths. Again it requires knowing what you need, which varies again with motor and position.

I have gone through this for information and to remind myself that 3 of the last four motor installs failed because the available dog bone was the wrong length.

There is a fourth wrinkle that also impacts the success of these installations. The dog bone coupling diameter. Atlas Roco motors have coupling diameters that are at least twice the norm. This also requires larger dog bone ends. These are readily available, but tend to have the same length issues as the normal dog bones. This makes some installations take longer than expected. Time goes by. It will be worth it in the end.