Gravity assisted trolley This concept for light rail is intended to save energy by making use of gravity and taking advantage of the high rolling efficiency of steel or ductile iron wheels on steel rail. Depending on topography of the site, the system would consist of only a gravity accelerated (linear motor assisted) cars following near constant elevation or a mix of constant elevation routes crossed by a modern counterbalanced cable car routes running the steepest possible routes. To avoid complication and accidents, cars would travel in only on direction on each rail. Braking is not regenerative and intermediate stops would not be part of the design. The size and weight of individual cars would be small and maximum speeds under 70 kilometers per hour. All cars would travel in the same direction. They would not share track or have intersections with other modes of transport. Tunneling or use of elevated track would be necessary. View of constant elevation routes crossed of cable car routes. Why use gravity to accelerate and slow cars ? Designing cars to coast most of the route will avoid the need to electrify the whole route. The typical 3 phase 460 Volt commercial power is a serious safety issue and would add considerable maintenance cost to the route. After product development, use of passive permanent magnets would lower the center of gravity of the cars, add mass to help them coast and require no on board control system. Inductor elements would be concentrated at stops or booster sections along the route. Simple cars would mean more cars. The idea would be to have a constant stream of cars with not more than a 15 person capacity; designed for all seating and none standing to reduce height and frontal area. Bicycles and wheelchairs sections could be by folding up benches. The floor would be level at stops but avoid a deep pit as seen on many metro rails. How much elevation drop is needed to gain speed ? ● Ten meters would translate roughly to 50 km / hour , neglecting losses and rotational kinetic energy of wheels. ● Twenty meters would give an initial velocity of 70 km / hour. ● Friction losses of bearings and wheels on rail should be < .2% assuming a 500 mm wheel diameter. ● Traction motors would aid in acceleration and stopping. Gravity is more conservative and would be the primary mover and stopper. ● Look to :http://atg.ga.com/EMS/transportation/limrail/index.php and others. ● What I propose is to keep the coils in very limited areas involving only a small portion of the route length. ● Urban transport is fast if the stops are brief and waiting time is short. In Miami, the 45 mph (73 km/h) Dixie Highway turns into an intermittent 15 km / h parking lot at certain times of the day. Actual trip length depends on gridlock, finding parking and waiting for transport. Those are more frustrating than a leisurely trip speed. How can trolley be economically justified ? The argument against public transport is that it wastes money without conserving energy. Having watched 40 passenger buses roaming around with 3 passengers and the driver, I can understand that sentiment. Real energy savings can only be achieved if the system is widely used. Most people own cars. People would drive and park before paying a dollar a stop and waiting 20 to 40 minutes (often in blinding sun or poring rain) each time they catch the bus. Use of magnetic cards would let people add credit as needed. Parking would be kept out of prime downtown real estate allowing a better pedestrian experience. Parking garages on the periphery of the downtown would generate some of the money. A well utilized system would help the underclass more than fare subsidies. A differential rate structure has kept the mainstream off of metro-rails. The indigent that remain don't pay enough to support the system. Because trolley cars tend to be big and use considerable electricity, the frequency is cut down to save money. Cheap, small cars running often would benefit the whole community; creating support from those who pay property tax and own downtown businesses. What form would the cars take ? Wheels would be on individual casters to provide better tracking and less wasted space. Entry would be from either side with no center walkway. Each small compartment would have direct entrance. Capacity would be seated capacity. Standing headroom would add frontal area. The roof design should shade passengers and protect them from normal rain storms. Drip lines should be away from the entrance areas. Cars might be single or articulated but would not be formed into long trains. The nature of the terminal should allow a single security guard to see the whole area. High traffic periods would be handled by more, not larger, trolleys. The structure might use a central truss with transverse hoops. Torsion flexibility might be used in place of a suspension in allowing wheels to stay in contact when rail twist to bank into turns. Conclusions: ●The most cost effective urban transport will be one that is convenient and well used. ●Topography will be a determining factor on whether linear motor assisted free rolling cars or a counter balanced cable car system is best. ●Entry needs to be fast and convenient. ●Well integrated design is more important than scientific advances. The street cars of the 1920s worked well enough. ●Urban planning needs to be an integral part of mass transit. ●Local, personal and long distance modes of travel need to be connected seamlessly. ●An air conditioned trolley car does little good if the stop is exposed to the weather.
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