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Blog Entry# 1662429
Posted: Nov 26 2015 (18:54)
71 Responses
Last Response: Nov 30 2015 (17:06)
71 Responses
Last Response: Nov 30 2015 (17:06)
WAG9-LGD-31191 --- Sam picked this one up at Dankuni sidings on 15th June 2012.
Link: click here
Courtesy: Sam
Link: click here
Courtesy: Sam
68 Posts
The same issue that caused the acceleration problem can also be partially responsible for wheel slips. During acceleration and normal running, when the reaction torque sets in and the front wheels rise up slightly, they become more prone to slipping and in such cases, the un-powered axle ( which in case of WDP4 is the one closest to the loco centre I guess) does not really contribute anything to mitigate the loss of tractive effort. And since the original WDP4 did not come with independent traction control for each TM, this could have potentially lead to wheel slip problems in slightly adverse conditions such as wet tracks or mild gradients. Most probably it was not a regular problem, but could potentially have caused a few issues. Addition of independent traction control could have mitigated this problem as would adding an extra TM ( will increase weight and also lower the effect...
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The WDP4 has an erratic adhesive weight distribution due to Bo-1-1-Bo wheel configuration. Although it has 6 axles, only 4 are powered by motors. So, its adhesive weight is only 2/3 times its overall weight (119t). And besides, only the axles 1, 2, 5 and 6 are driven by motors, which means the adhesive weight is concentrated at the ends unlike a Bo-Bo type loco whose weight is distributed throughout and is more compact with a shorter wheel base which actually improves the loco's ability to negotiate curves. A gradient is a vertical curve basically. WDP4 is quite long (in terms of length) and has a longer wheel base (which practically suits a Co-Co type loco) for a loco with just 4 motors.
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Agreed. Another thing to note is that the WDP4 tackles this issue by having the 2 TMs as far as possible from the Centre of gravity of the loco, so that the Torque due to the TM's weight can offset the reaction torque, thereby improving the weight transfer characteristics of the locomotive. This approach however creates a minor problem as the trailing wheel in the front bogie, the one which has the maximum weight transfer, is now un-powered and cannot be controlled effectively to mitigate the slip. However, this will only be a minor nuisance and not a serious problem because of the EMD's creep control system, but it does show that such a wheel arrangement is a tricky thing to manage.
The acceleration problems used to occur while starting and at low speeds, not while cruising at decent speeds.