Grade & Train length experiments weight impact

It is well understood that increasing the weight of the engine will increasing its pulling capacity.  The question is how much and at what penalty, if any.  This activity was performed at the same time as the earlier discussed CAT activities.  Here the velocity and current draw are documented as well as the impact on train length at different grades.  

Definition of Weight changes:

I have examined this process before.  Previously it was summarized here:

Specifically, the weight increments are:

Initially as was done on the previous link three weight increments were planned.  The first two are approximately 5.4 ounces each.  The third increment is 5.3 ounces.  The total added weight was 1 pound.  After running the first engine, the third increment was eliminated.  Adding that much weight is unlikely, so the results would be ac ademic.  That increment was adding a significant time in the testing for little benefit.

The experience from the above link showed that the benefit magnitude varied for different engines.  Need to verify that and get an indication of why.  

This activity was performed simultaneously with the previous CAT testing on the same engines.

Which are as follows:

1- ScaleTrains “Operator” BNSF SD40-2 in factory new condition

2- Atlas Kato NP RS-11 in well used condition

3- Rapido RS-18, basically factory new subject to my tests over the last five months

4- Atlas China SP&S RS-3 old release with limited use

5- P2K NP SW1200 in well used condition 

Why five?  While not statistically significant, the average of five will indicate what the benefit of adding weight to the engines.

Standard DC test impact:

Minimum Velocity vs weight:

Minimum current vs weight:

Draw bar force vs weight:

Performance characteristics vs weight:

12 volt velocity vs weight:

12 volt current vs weight:

Summary

1. CAT favorably reduce current draw (power). Increasing weight does not adversely impact this benefit.
2. Cat improves the measured draw bar force. Adding weight also improves the measured force.
   
3. The performance characteristics was improved on four out of the five of the tested engines

G&TL tests impact

Cars vs grade:

Weight ratio vs grade:

delta cars vs grade:

Percent change vs grade:

Power vs grade:

Cars vs weight:

Summary

1. CAT shows a train length improvement at all grades
2. Adding weight also increases the train length
3. At 2.5% CAT shows to be equivalent to adding eight ounces of weight.
   
4. The percent increase in car weight is nearly equal for all grades. CAT yields more benefit at grades below 3%.
   
5. The actual car weight to engine weight is decreasing with added engine weights

Conclusions:

1. CAT his very important
2. Weight is also very beneficial.
3. For any additional tests, CAT will be part of the activity.
   
4. As much weight as practical should be added to the configurations. In the process of any upgrades, weight reductions should be minimized.

What’s next?

There are still a number of unanswered questions about the implied draw bar force effects for a given engine weight. Two items that on the plate are motor characteristics and DCC module.

The next several tests will be focused on the former.