On the Class 37, 40, 45 and 47 holding the semicolon key moves the train brake lever from the "Running" position to the "Release / Overcharge" position. "Release" is pretty self-explanatory, but what about "Overcharge"? More importantly, what does overcharging the brakes do and in what scenario would you overcharge them?
Release is a bit counter intuitively named position while running with air brakes... while it does technically release the brakes it should NEVER be used for doing that, to release the brakes the handle should only be placed in the running position. The release position is used to overcharge the brakes which is to say increases the brake pipe pressure above the standard 72.5psi (up to between 76-78psi). The purpose of this is to cause any distributors and hence brakes which may have gotten stuck on to release (hopefully this never happens). On returning the handle to the running position the overcharge is bled off very slow taking about 2-3 minutes to do so, this has to be done slowly otherwise the distributors will apply the brake. Misuse of the release position can result in the brakes dragging. If an application is made while an overcharge is in effect the control reservoirs will seal at the pressure they were applied at, meaning that distributor will not release the brake until the brake pipe pressure is above the control reservoir pressure (so if you apply the brake at an overcharge of 75psi, you will have to create above 75psi to release the brake fully again). Since the running position will only create up to 72.5psi you would need to use the release position to release the brakes. If you suspect dragging brakes the correct procedure is to hold the brake handle in the release position for around 30-60 seconds, before letting the handle back to the running position. Once there the brake handle must be left there for 2-3 minutes, if you do apply the brake you will need to do the whole procedure all over again. On Vacuum brakes the position will still technically overcharge the air brake on the loco, but it doesn't matter as the distributor isn't working on the air system so the above does not apply. In vacuum operation the position will speed up the vacuum exhauster's allowing you to release the trains vacuum brakes quicker.
I did wise guy. Of the 25 results, none really answered my question. The only one that did come close was in the topic "Long Train Problem [main-spessart Bahn Br 185.2 Db 88109 Service]" where a user by the name of breblimator asked how to get very heavy/long trains moving. TrainSim-Matt replied. "If you ever have trouble getting started, put your brakes in release and press-hold the "brake overcharge" for 15 seconds. then wait about 2 minutes and the brakes should come off." He then went on to say in the same post. "Sometimes wagon brakes get an overcharged reservoir and the normal release pressure won't trip them to release." While this answered some of my question it didn't answer it completely.
So, is this charging and release behaviour actually modelled in TSW or is just applicable in the real world?
