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Railroad Trucks with Batteries

Discussion in 'Technical' started by Joel Weber, May 20, 2018.

  1. Joel Weber

    Joel Weber Member

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    I've been trying to figure out whether there would be any obstacles to building railroad trucks that have batteries built into the trucks. Much of the rationale for trying to do this is that if the batteries were installed in the rail car body instead, an existing rail car body might not have enough structural strength. Using existing car bodies would reduce the costs of converting to electric, especially if commuter rail agencies want to keep using their bilevel cars which often have unique dimensions for each agency, although Don’t Run Bilevels argues that moving to single level cars for faster loading and unloading would be better in the long run.

    At least in the US, commuter rail cars are typically lighter than freight cars, and so a railroad that can handle both would likely be able to accommodate some added battery weight in a passenger car. For example, kawasakirc.com Massachusetts Bay Transportation Authority Bi-level Coaches reports 131,000 pounds for the heavier of the MBTA's Kawasaki bilevel coaches, which is a bit less than double the 80,000 pounds reported for a Tesla Semi doing 0-60 in 20s, which is 3 MPH/s

    RAILROAD.NET • View topic - OpenBVE Kawasaki M8 EMU V1.0 Released (1/8/15) seems to think 2 MPH/s is good enough for Metro North with overhead power, and https://waterfrontseattle.org/Media/Default/Library/Other/06012013_Final_Seattle_Waterfront_Historic_Streetcar_Technical_Evaluation.pdf mentions some streetcars being capable of 3 mph/s acceleration.

    If the set of batteries and motors that would be installed in one Tesla Semi get installed in one railroad truck, with every truck in the train powered, this would provide about the right amount of acceleration for the train. If the Semi ends up having 800kWh and there ends up being roughly 1,000 pounds of battery per 100kWh, 2 x 800kWh per train car would be around 16,000 pounds per train car, which in the 131,000 pound example would result in 147,000 pounds, which is still under the 2 x 80,000 pounds that the two Tesla Semi powertrains would be able to accelerate from 0-60 in 20s.

    Assuming building complete new railroad trucks to be able to use space efficiently, there's then the question of whether the batteries will fit in the space in the trucks. http://www.skf.com/binary/82-62732/RTB-1-02-Bogie-designs.pdf has some information on typical truck designs.

    If we assume the goal is basically to install four Model S battery packs per axle, one issue is that narrower, taller packs may be desirable in the railroad application, since the wheels on a train are about 4' 8" apart, and apparently the Model S pack is about 70" wide. But perhaps centering the roughly 112" pack length on the train axle might work with a compact secondary suspension. A 5" thick pack, 70" wide, times four, would have a cross section of 1400 square inches; if a 1400 square inch cross section were resized to be 4' wide, it would need to be about 29" tall. Depending on ground clearance requirements, if the pack were designed to have space for the axle it might be possible to have the top of the pack even with the top of the wheel and have 7"+ between the bottom of the battery pack and the top of the rail. (Additionally, the wheel flange is probably a bit higher than the top of the wheel at the point where the nominal diameter is measured, so raising the pack to the top of the flange might provide a bit more clearance.) And the Model 3 cells may lead to a more compact battery pack, and perhaps it would turn out to be possible to downsize the pack to something smaller than 800kWh per truck while still getting adequate range and performance.

    Does 235/40R19 mean the Model 3 tire diameter is 19" + 2 * 3.7" = ~26.4"? If so, it appears that whatever number of revolutions per minute gets a Model 3 155 MPH ought to provide about a 113 MPH top speed with 36" railroad wheels or about 128 MPH with 32" railroad wheels.

    Batteries in railroad trucks also ought to work for North American intermodal freight; the trailer on flatcar train cars are likely light enough that adding batteries is likely no problem, and Well car - Wikipedia describes articulated units where I suspect putting batteries only on the end trucks and not the middle trucks would end up meeting the per truck weight requirements.
     
  2. Joel Weber

    Joel Weber Member

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    The challenge with a 9' long pack per axle is that if 3' of that length is even with the 3' horizontal wheel diameter, and 3' goes toward the center of the truck, 3' would need to hang off the end of the truck, and Bi-Level Kawasaki Coach on MBTA Commuter Rail makes it look like that might not necessarily work.
     
  3. Joel Weber

    Joel Weber Member

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    6' long x 4' wide x 29" tall inside the wheels, plus 6' long x 1' wide x 29" tall on the outside on each side might work, though.
     
  4. ewoodrick

    ewoodrick Active Member

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    I think the point that you may not be familiar with, is that essentially all train engines are already electric hybrids. Trains have been electric for many years.
     

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