BNSF is having problems providing DPU units to trains. The specially equipped locomotives are not being provided efficiently, leaving trains stalled in yards awaiting power.
Surge in business, plus a lot of the SD40's are LUGO. Still surprising when half the fleet is DPU equipped.
Maybe we will see a surge of those SD40-2's headding out of LUGO. I love to see them back out pulling again. Steve
Maybe there might be a few fuel tenders out, ah that would be nice to see a set of -2's with a fuel tender.
Hard to believe these machines are still working tonnage with nearly 40 years of age on them! I'll take 'em anyday over the omnipresent GEez... Here's a neat consist I bagged east of Cut Bank, MT; matched power!
Nice shot Hemi. Pushin or pullin I would not care how they got back on the rails again. However we are seeing a whole lot of CEFX units here in Denver. Interestinly there are a lot of SD70MAC's that I have seen lately not in coal service but just pulling what ever is needed. Also a new helper set at the big lift has been a pair of brand new ES44AC units so I would wonder why DPU has been an issue. Even if it is a surge in business I would think these units would be best used else where but hey who am I? Steve
Shoot, only one truck of the ES44AC equals a whole SD40-2.... Amazing! What percent adhesion are they both good for?
I shoulda known... I haven't done that sort of math in years!!!! Guessing 420,000# for the GEVO, and 390,000# for the SD40-2, I come up with about 39.5% (!?!?!!!) for the GE, and about 21% for the veteran EMD product. Wow! How on God's green earth do they rack up adhesion numbers like that????
It's an AC unit... the DC is ~26% (@ 415,000lbs) As for the AC unit and it's high adhesion factor, it all boils down to physics... I'll try to explain as simply as I can (please don't take that the wrong way): When we talk about an adhesion factor for a locomotive, in reality we're talking about friction (more accurately, the force of friction). To find the force of friction, you do the exact same thing that you do to find TE, take the weight and multiply by a factor... in the case of friction, that factor is the coefficient of friction. There are two types of coefficients, static and kinetic... or put simply, not moving and sliding. The static coefficient of friction of various steels on steels is ~.4-.75, the kinetic (i.e sliding) is ~ .2-.5. Let's say I took a 10lb piece of steel and set in on another piece of steel, then started pushing on it. I can apply as much as 4 lbs of force to that block before it starts moving (static), but the moment I apply any more than 4lbs, it starts sliding (kinetic), and the amount of force I need to apply drops VERY quickly to around 2 lbs of force. Note that I must apply at least 2lbs of force to keep this block moving at a constant speed. This is very important becuase it shows that even at a constant speed, becuase of friction (ANY type of friction... air drag for example) I still have to apply a force. Understanding that, let's make it more complex... this time it's a wheel. When a wheel rolls along a surface, the point of contact with that surface is stationary, and the force of friction is at a right angle to the wheel (from a line from the center of the wheel to the point of contact)... therefore the coefficient of friction is going to be static. This may take a while to grasp... basically if you take a wheel and spin it in the air, it's rotating on the center axis. If you take that same wheel and place it on a surface, it's no longer rotating about the center axis, it's rotational axis is now the point where it touches the surface, and this point is continually changing along the diameter of the wheel. If a wheel is not rotating and it's still moving... it's sliding, and therefore you'd use the kinetic coefficient... You can apply the same in reverse... if an object with wheels (say, a locomotive) is moving and the wheels arent rotating, they're sliding. Knowing this, a locomotive that can keep it's wheels from sliding will generate much more TE than one that can't... and that's where AC comes into play... Even if a wheel seems to be rotating just fine, you can still have an imperceptable (unless you're the engineer ) amount of sliding, and even though it's imperceptable, it still has a net effect on that coefiicient of friction, and thus TE. AC traction motors (and the software) have the ability to apply full torque with much greater precision than DC traction motors... not that DC hasn't come a long way, it has in both the software that controls them and the actual motor capabilities... it's just that AC motors have a distinct design advantage. Note that ACs finer control comes at a cost, and not just financial... less than optimal rail conditions can cause an AC unit to perform erractically.
