Would the starting and continusous trctive efforts increase due to computer control of wheel slip on an SD40-3 over an original SD40-2 and if so what are they?
Hi
Folks , before this leads into controversial ‘believes’ , let’s mind what electronic controls – any electronic controls ! – can do and what their limits are and invariably will be :
As the locomotives are , mechanical imperfections of design to start with and maintenance to further make it’s impact , prevent them from realizing full theoretical potential of actual adhesion limit – in other words : they slip wheels before tractive effort total has reached the level of real physical limits with a theoretical ‘perfect’ design : with practical construction there is a margin left unused between theoretical and practical limit of tractive effort that can be put on rails .
This applies to any concept of locomotive , steam , diesel-hydraulic , diesel-electric , straight electric or what ever .
Since all SD40-3’s are rebuilds after the originals were manufactured and sold by EMD, the precise answer depends on the specific details of each rebuilt unit’s mechanisms and controls, as well as the operating conditions/ parameters noted in the post above - i.e., a NS SD40-3 is not the same as a CSX SD40-3. For a little more info on that, see these somewhat related threads:
http://cs.trains.com/TRCCS/forums/p/147281/1635106.aspx
http://cs.trains.com/TRCCS/forums/p/20546/290640.aspx
http://forums.railpictures.net/showthread.php?p=94113
http://www.railroad.net/forums/viewtopic.php?f=53&t=79386
- Paul North.
Can you find out if the traction motors are still rated at 1050 amps continuous? If they are, continuous TE presumably hasn’t changed?
And then there are differences in weight, both dry and from consumables. Whose control system makes them “-3s” , etc.
One carrier that has both SD40-2 & SD40-3’s rates the Tractive Effort as follow
SD40-2 - 82100 pounds
SD40-3 - 82945 pounds
Off those ratings it would appear the improved wheel slip controls allows for slightly more tractive effort. In comparison GE Dash-8’s & 9’s are rated at 108600; EMD AC’s are 137000 & GE AC’s are 145000.
The SD 40’s are nominal 3000 HP engines and all the others are nominal 4000 HP engines.
CN’s SD 40’s, SD 40-2’s and SD 40-3’s with PTC (positive traction control ) are all rated 85000 lbs. Without PTC there are/were 70000 - 74000. PTC was an in house wheel slip control.