by MBTA3247
3rdrail wrote:Paul's original statement is somewhat misleading. Trolleys do have a peak horsepower (if they draw too much power the motors will burn out), but for short periods it can be very high, allowing for rapid acceleration. This is made possible by using an external, essentially unlimited source of power, whereas internal combustion vehicles are limited to whatever their engines can provide.BostonUrbEx wrote:Also, the wires give a sense of permanence. A bus route is (or at least feels) less likely to change if it's wired up. It's simply more attractive to ridership...Some either transit or real estate group did a survey years ago and found that trolleys raised real-estate values more so than bus lines which did not. The poles, wires, (and rails in some cases) gave a sense of permanence just as you say.
3rdrail wrote:they have no rated peak horsepowerWhat does this mean?
An electric motor's power depends on the current which it recieves. All trolleys have a relay on their master controller which limits the current, otherwise overloads and unexpected power and speed could occur during surges. In San Francisco, Muni's Marmon-Herrington's had a push-button that the motorman could press for fast acceleration and getting up a steep hill, along with heavy-duty resistors. What it did was merely increase the setting on the relay. They left the cars and diesel buses in their dust. If you ever have occasion to operate Boston's Pullman-Standard trackless trolleys up at Seashore, you'll find out that they crawl and appear under-powered due to the voltage delivered because of conditions (and wisely so !). Put that baby in Cambridge and she'll be a rocket ! (Anybody from Seashore know what you're putting out up there on the TT wire with other activity going on at the same time ?)
Seashore's TTs use the same 600V as the trolleys, but on a separate circuit. Unfortunately the power station's current rating is less than what we really need, hence the poor performance of the TTs (and why the rapid transit and interurban cars almost always overload the power station when they come out).
"The destination of this train is [BEEP BEEP]" -announcement on an Ashmont train.