7-8-20 The Mashima 1833 on the Pennsylvania PA-1 broke all records for draw bar force & # of cars on a 2.5% grade. The screening tests did not imply that it would be any good let alone fantastic. While this is the most dramatic surprise, several other engine/motor combinations have lead to surprising results.
This is likely caused by an number of factors:
- The motor performance characteristics(map) are not simply scales of each other with otherwise the same shape. Thus the no load test is not representative of the performance under load. This is not a surprise by itself, but the apparent large magnitude has negated the earlier screening trends.
- From engine to engine the wheels are made of different materials and are different diameters. This is impacting the force in the rail at a give total weight. While this was expected to cause some variation, it was not thought to be large.
- The drive shafts and tower gears are different. Some have dog bones and some have the Athearn BB plastic splines. Some of the tower gears are metal & some are plastic. Again, a know difference that was thought to be small.
This result will require additional tests, first to identify the “best” pulling motors. Secondly the impact of the wheel size and material will need to be examined. The shaft & gear impact are more difficult to examine so that will be left for later depending on the results of the first two items.
7/10/20- the examination of wheel material & size was initiated on the BN U30B engine.
So far The tests have been done on 42 in NS, 40in SS & 2 different sets of stock Ath BB 42in wheels.
The results are surprising!
The previous best result was with stock BB outside frame wheels with six axles.
There the DB force correlated with the number of cars pulled in a 2.5% grade.
Here the wheels are inside frame. The two tests with the stock BB wheels had the poorest DB force.
The NS & SS showed the best DB force. However the number of cars pulled was considerably short of the correlation. Most tests have been very close to the correlation, this is a puzzle?
The SS pulled one car more. While the stock BB pulled about 1/2 the cars.
7-10-20 the tests have been repeated with additional wheel options. The examination was performed on stock P2K 40 in. & NWSL 42 in SS. In this case, as had been done in earlier tests, running the train on at least the 2.5% grade with max train length before measuring the draw bar force on the level surface. Doing it that way seems to yield results that are consistent with each other. In these two tests, the maximum number of cars correlated with the measured draw bar force.
7-11-20 Ran a third set of Ath BB 42 in. & repeated the 42 in NS & the 40 in SS tests following the process described above. With the latest tests it appears that the 42 in stainless steel(SS) wheel sets yield the longest train on a 2.5% grade with the stock BB 42 in wheels pulling the shortest train. The latest tests did not change the assessment. Will post data in a stand alone post.
Decided to bring the Penn PA-1 into the base series. May repeat the wheel material & diameter variation examination with the best motor/ engine combination. In the mean time, on with the motor & base engine tests.
