5/14/20 The last several days have evolved around motor testing to see what the spec are for the motors on hand.
The objective is to discriminate between the motors. As has been seen in the various motor variation tests, the draw bar force can vary significantly as show below:
If this can be related to a particular motor, it will take some guess work out of deciding which motors to run in the next phase of the Grade & Train length experiments. The ultimate goal is to understand what the trade offs are to be able to have excellent train pullers.
The initial process is to consistently calculate the motor torque at twelve volts power supply. For simplicity, the motor efficiency is assumed to be the same for all motors at this condition. This is not true, but the variation is likely no more than twenty percent. This is a selection process. The actual running will identify the winner. The purpose here is to select four or five motors out of 50 motors. The preliminary data indicates this 12 volt torque varies by 100 to 200 percent. These comparisons will be made looking at shaft speed and input power as well. The exact selection criteria will be discussed in a later post.
7/10/20. The testing thus far has produced some interesting results:
- one of the five initially selected motors is a dog. The Sagami #4 follows the predicted speed ratio from the motor only tests, but does not produce the anticipated torque. It’s train length is near the bottom of the engines tested.
- One of the motors, Atlas China #3, that was ruled out because of a low predicted torque blew the socks off the tests. Established the current record for number of cars pulled (41) on a 2.5% grade. For this reason, this motor is replacing the Sagami #4 in the base series.
- The engines in the whole test series have different wheel architectures. Some are stock Athearn 42 in, some are stock P2k 40 in & others are Athearn NiAl replacement wheels. These later come in both diameters. Because of the diameter and friction coefficient impacts, this is likely presenting some variation in the tests. That will be examined in the three engine series.
check back often, it should be informative.
