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| Re: Wheel Axels (343675) | |||
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Re: Wheel Axels |
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Posted by WillD on Sun Nov 26 18:34:41 2006, in response to Re: Wheel Axels, posted by Subterranean Railway on Sun Nov 26 11:24:28 2006. You just described the propulsion layout on a PCC II LRV :)I apologize for the quality of the photo, it was taken with a crappy P&S digital camera from the inspection bay at Elmwood Depot, but it should show things well enough. The large, roughly hex or octagonal housing in the upper left corner is the differential. From that one the upper right you can see the axle to the rear wheel. Going down the picture from the differential you see the brake disc, needed only for the last few MPH since the asynchronous motor, located immediately behind the disc, handles most braking through regenerative or dynamic braking. On the right, behind the rear axle is the motor for the front axle, the brake disc, and the differential, arranged in mirror to the rear axle's powertrain.  I should say that I don't know whether the differentials are fixed or not. I know engine braking is possible through a differential, so the fact that all braking outside the electric track brakes (visible as the black bar with silver dots on it in the photo) goes through the differential should not be a major problem. It is entirely possible that Kiepe outdid themselves and installed a limited slip differential or something similar in the PCC IIs, or they simply have a gearbox in there which converts the longitudinal axis torque from the motor into a transverse axis torque for a fixed axle. At the time I was underbody I never thought to ask anyone what the case was. However, it isn't absolutely neccesary to have one motor supply both wheels through an LSD. The GG1 used one motor for each of its twelve driven wheels. If a modern locomotive, DMU or EMU were to borrow the GG1's approach and use between eight and twelve AC asynchronous motors of lower power than the current four to six motors on most locomotives yet retain the traction control and other features you could have each wheel powered exactly as needed, responding to the conditions immediately at the railhead/wheel interface, and probably always at zero speed relative to the rail. This could have tremendous benefits for things like wheelslip and resulting wheelflats, as well as reliability. Admittedly it could increase the workload on the motor shop, but it would also probably make that work somewhat easier since it'd be smaller motors. |
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