My understanding is that because Cambridge St. was roughly doubled in width in the 60s, all the utilities are on one side and the other side is relatively clear underneath.
Moderators: CRail, sery2831
CRail wrote: ↑Wed Apr 28, 2021 6:59 amThis is a little off topic, but what is meant by straight air as opposed to train air?
MattW wrote: ↑Thu Apr 29, 2021 9:27 pmThis is a little off topic, but what is meant by straight air as opposed to train air?Straight air is as Alan described it above. Charge the system and the brakes apply, drain the system and they release. The "brake pipe" in subway cars solely serves to hold closed an emergency valve (so that a train parting will drain the pipe and cause an emergency application) as each car (or pair of cars) supply their own source of air. With train air, the brake pipe pressure, fed from the engineer's brake valve, operates a triple valve in each car. Air via the brake pipe charges each car's reservoir until the reservoir pressure meets the pressure of the brake pipe, centering the triple valve. A reduction in brake pipe pressure causes the triple valve to allow air from the reservoir into the brake cylinders applying the brakes, the more the reduction, the more air is allowed into the cylinders. Returning air into the brake pipe sends the triple valve back into release kicking off the brakes and recharging the reservoirs. Train air can be difficult to wrap your head around, but once you do it all makes sense, it's pretty ingenious.