[C44-9W]

This is about North American intermodal (container) cars that are articulated, ie. have a single truck and fixed couplings between "cars". They come in groups of 3 and 5. Some NA railroads call these groups a single car. The articulated platforms have the same number, with A, C and B added (or A, C, D, E, B for five car sets). A and B are always the ends.

The 3 car sets generally have two brake vales, the 5 car sets generally have 3 brake vales. There also are articulated auto racks.

Unfortunately this seems not to be entirely consistent across railroads. I am most familiar with BNSF.

I have looked at a small sample of MSTS/OR intermodal cars, and each of the cars in a set has a MaxBrakeForce defined. Thus there is the risk that the simulation uses more brakeforce than the prototype has.

• Should the model (.wag) only specify brake parameters on the A and B cars (for sets of 3), or the A, D and B cars (for 5-packs)?
• Are the models (.wag) correcting this by averaging the real brake force across the 3 cars (ie. the values are 2/3 of the real values, repectively 3/5)?
• How does the simulation handle this?

I am specifically asking because I want to calculate the tons-per-operative brake, an important train characteristic.

Quote

Tons per Operative Brake
The gross trailing tonnage of the train divided by the
total number of cars having operative brakes. For
example, a 100-car train with all brakes operating,
having a total train weight of 6,000 tons, has 60 tons per
operative brake (6,000 tons divided by 100 cars).
Train lists showing average tons per car or platform will
equal tons per operative brake when:
• The train list is current (no additional pickups or
setouts have been made).
• No brakes have been cut out.
• There is one brake per car or platform (Note: This
is not the condition for some equipment, such as
articulated intermodal cars)

BNSF Air Brake & Train Handling Rukes

Quote

The car comes equipped with two complete air brake systems. The handbrake is located at the B end and operates the brakes on the end truck and the adjacent intermediate truck. Each unit is designed to carry one 40-foot ISO container or a 48-foot to 53-foot domestic container.

National Steel Car

Quote

If a five platform intermodal car is equivalent to three operative brakes and a three plaform intermodal car is equivalent to two operative brakes, how many operative bakes does a two platform articulated auto carrier equate to?

Tons per Operative Brake (Trainz Magzin Forum)

[pschlik]

The way I've elected to do this is simply have the C and E vehicles (of course, 3-packs only have C) set as an "Air_piped" brake system. Air piped removes the control valve from those vehicles, so you get the correct number of control valves in the train. Of course, don't forget to recalculate any brake forces under the assumption that the braking force is split between 2 or 3 units and not all 3 or 5; the units with brakes need to compensate for the ones without brakes to maintain the required braking performance. If you want to get particularly pedantic, the outer trucks usually use 7-ish inch truck mounted brake cylinders, while the inner trucks use 9-ish inch truck mounted brake cylinders so you actually get more brake force (theoretically, about 25% more) on the D unit than on the A or B simply because that E unit has more of the big brake cylinders (the E unit also has more weight on its bogies).

Two-pack units are odd, I don't know the exact setup of the air system on those, but I figure it's close enough to accurate to use the same brake force on both of the vehicles.

This will be mostly accurate except in the way adhesion works-in real life a single unit might have a weight of 80 tons but because it shares bogies with two other units also weighing 80 tons the actual weight on the two bogies will be more like 160 tons (hence the use of heavy-duty 125-ton trucks instead of 100-ton). OR doesn't have a concept of the bogies sharing weight, so it will act as if there's only 80 tons on the bogies, which gives you much less grip than reality. Theoretically that could lead to wheel slide when it wouldn't happen in reality, but if brake forces are set to reasonable levels, this probably won't happen anyway.

Should look into adjusting what OR thinks the adhesive weight is to include a portion of the weight of connected articulated units-it already can detect when something is articulated. I think that could help resolve some other adhesion issues people have seen with, eg, articulated steam locomotives.

[C44-9W]

Thanks for the detailed explanation, Phillip. I guess I have a nother project to do. None of the articulated intermodal cars I am using have an air_piped brake system.