Help with tractive effort/horsepower

Lutherb, I'm afraid that I don't follow your clarification of the high-adhesion concept. Are you saying that a locomotive is considered to be a "high-adhesion" locomotive simply because it is configured with GE's so-called "HiAd" truck and that if it is not configured with that "high adhesion" truck, it is not considered to be a high-adhesion locomotive?

Lutherb, I checked CSXT's "Locomotive Consist Make-Up Guidelines" to see what models it classifies as "high adhesion" units. The following were included: SD60 series, SD70MAC, SD80MAC, Dash 8-40 series, Dash 9-44CW, AC4400CW, and AC6000CW. Some of those units are configured with the so-called "high adhesion" trucks and some are not; however they are all configured with microprocessor traction control systems.

The "wheel-slip control" systems that you mentioned were in use before the microprocessor control systems were introduced. The former systems merely corrected wheel slippage; but the latter systems included "creep control" which improves adhesion by allowing the rotational speed of the wheels to exceed ground speed by certain percentages. In other words, on CSXT at least a unit's classification as a "high adhesion" unit does not depend on the design of its trucks; it depends on the design of its traction-control system.

UPRR, that grade is a seven mile long pull, in a hill that is actually 13 miles long. There are 30 curves, in the seven mile, 1.8 percent portion, with the ruling grade being just over a mile in length. The grade is 49mph, until you reach the first curve, where it becomes 30 mph, for those 7 miles. The final mile, before reaching the apex, is also 49 mph. hitting the base, in 8th notch, at 52 mph results in a speed of 24 mph, when reaching the restricted portion of the grade, and an average speed of 12-14 mph up and over, those 8 miles from the board, to the top. 2 greasers, located in the 2 straight sections of track, between the 2 "horseshoe" type curves, crawling up the canyon. We occasionally will pull to a stall, with those damned GE "toaster motors" giving up, once they drop below 9 mph. after several minutes of 9 mph running, at 1500 amps, the loco automatically de-rates itself, to prevent overheating the motors, and therefore grinding the train to a stop. We wait for a following train to assist, before we would cut off, and have to secure every single brake on the remaining portion, of the train. BNSF is "great" for adding 4 axle motors to the train, while only looking at the HP ratings. NOT the way to move potash, or grain, over the mountains......

UPRR engineer wrote:Cant replace three 4300 HP units on a local that just barely makes the hill on the branch with two 6000 horse GE's. We had a GE rep. with us that day.

I was on the brakemans extra board back then.

Stauffer is the name of the branch we use to run to the soda ash mine. We leave the plant with the loads on about a 3% grade up and over the hill/mountain. With three AC motors the most cars you can pull is about 60 loads. That day with the GE guy with us, i think we had about that. Another thing about the hill, there was some burn outs in the rail right about where you get the whole train on the hill. ----> Jacob's Ladder, im guessing a SD 40-2 left those. I was in the 2nd motor as we left the plant, the combination of running over Jacob's Ladder and having them all on the hill brought us almost to the point of stalling out, i jumped off to see just what those new GE trucks do to cause all the bucking and jumping. Those axles can and do move about 5 to 6 inches eather way on those springs. We stalled out a couple seconds later, the engineer left it in the 8th run, im sure the GE guy thought that it would start again. We had a talk before we left, the hog asked the conductor if it was ok if he ripped the train in half, so maybe thats why he also left it in the 8th run after we stalled. After about a minute or so we stopped trying and i walked back and cut the train and they took half up to the pass at the top of the hill.

That hill is so steep if there is a week knuckle or drawbar you'll find it on the hill. Theres a limit on how many cars you can pull, no matter how much horse power/tractive effort you have, you'll over come the strength of the knuckles. The most ive pulled out of there is 75, with four motors, AC, GE and EMD..... two knuckles that day. So a conductor has to decide how he wants to spend his time, double the hill, or find the weakest link.

Theres knuckles all over that hill, and a drawbar or two pitched off the side.

Back a couple years or so when SD 40's were the norm on this local we tripled the hill on some days. Eather we had 2 locomotives or 90+ cars released. Try thinking how we did that with a pass track that only holds about 43 cars.

At RS Mess (Rail Switching Services) when we got upgraded from SW1500's to GP 9's. The mechanic they sent in to prep the units said we could handle the same amount of cars with one GP 9. So my bosses eyes lit up thinking he was gonna save some money on his fuel bill. So we latched on to 40 loads at the start of our shift with him onboard, pulled them out.... and couldnt shove them back. Threw alot of sparks from the wheels tho.

FMC, the mine i used to switch cars for, gets its coal from a local called the 2nd Kemmer. I think they haul around about 45 cars with two SD 40-2's. One night we saw them with two of those GE 40-8 with the standard cabs try to shove up the coal tracks to the tipple. (Third try) Shot sparks off of every wheel higher then the locomotives lighting up the night sky. One of the coolest things ive saw with the railroad.

lutherkb wrote:I just wanted to clarify that High Adhesion is a physical design element applied to the engine's trucks where as wheel-slip control is the micro-processor controlled aspect of efficiently getting the most moving power out of an engine.

Exactly!

Wheel slip control is exactly as it sounds – microprocessors or whatever monitor wheel RPM and acceleration (rate of change of RPM). When sudden acceleration is detected (indicating wheelslip is happening) power is reduced to the traction motor until slipping stops. Power is then is gradually reapplied.

High adhesion truck - also called a zero weight transfer (or ZWT) truck - utilizes mechanical linkage to pass the torque reaction from the traction motors directly the locomotive underframe instead of to the truck frame. This eliminates the weight transfers and unequal axle loading that otherwise occurs when power is applied to the traction motors. (On a conventional truck the leading axle will have less adhesion than the trailing axle rail as power supplied to the truck is increased. This makes the lead axle want to slip under high power loading.)

Want an automotive analogy? Think of a non-ZWT loco truck like a drag race car. The application of power to the dragster's rear wheels causes a weight shift to the rear of the car. In the extreme case the drag car’s front wheels become completely unloaded and are lifted clear of the road surface - ie. a "wheelstand". A similar weight transfer occurs with non-ZWT locomotive trucks under high power levels - though obviously never enough to lift the wheels from the rail.

FarmallBob wrote: When sudden acceleration is detected (indicating wheelslip is happening) power is reduced to the traction motor until slipping stops. Power is then is gradually reapplied.

under high power levels - though obviously never enough to lift the wheels from the rail.

All this adhesion talk isnt what its cracked up to be, "power is reduced to ALL the traction motors" when you get real close to the point of stalling out. "Power is then gradually reapplied" No.... no its not when you get real close to the point of stalling out. While all that is going on it about throws you out of the seat.

"under high power levels - though obviously never enough to lift the wheels from the rail", but in curves you can feel the wheel flange riding up on the ball of the rail. I've never saw it 1st hand, but i have heard of power derailing like that.

Kinda off topic here but here is a picture of an OCI RR car that we pull up Stauffer hill. OCI use to be Stauffer Chemical, STAX's.

Jay Potter wrote:Lutherb, I checked CSXT's "Locomotive Consist Make-Up Guidelines" to see what models it classifies as "high adhesion" units.

Where is this document?

UPRR engineer wrote:
All this adhesion talk isnt what its cracked up to be, "power is reduced to ALL the traction motors" when you get real close to the point of stalling out. "Power is then gradually reapplied" No.... no its not when you get real close to the point of stalling out.

I've been told by an engineer that on the GE WideCabs the onboard computers actually have the capability to shut out individual traction motors that it detects to be slipping.

I don't mean to argue with you here UPRR Engineer. You seem to know your stuff and I trust by your name that you are actually an engineer so you may know better/different. I only offer this opinion from what I have been told by other engineers.

Maybe I misunderstood what he said. But this is how I recall it. No harm intended.

Lutherb, with regard to the "Guidelines" that I referenced, that is a Mechanical Department instruction issued for use by personnel at the railroad's locomotive service centers. It provides the machinists who service locomotives with information about locomotive characteristics and discusses which locomotive models should be operated together and the order in which various models should be positioned in a consist.

With regard to the information that you received from the engineer, he or she was discussing what GE refers to as "single-axle control". It doesn't apply to all GE widecabs, just to the AC-traction ones. When wheel slippage occurs on a DC-traction unit and traction-motor current is reduced in an effort to correct the slippage, the current is reduced to all the motors. On an EMD AC-traction unit, the current is reduced only to the motors on the truck which has the slipping wheel. On a GE AC-traction unit, the current is reduced only to the single motor with the slipping wheel. The theory behind "single-axle control" is that overall tractive effort will be maximized, at any given time, if there is no reduction of motor current to axles with wheels that are not slipping.

You work for a railroad there Jay dude? Your quote below, deals with something else im thinking. Like putting a SD 40 behind two big AC's, smoking the traction motors on a long steep pull. They try to remind hogheads that the DC motor back there cant take as much abuse as the one their running. The guys at the diesel pit care less about the characteristics of a motor unless it is a fault. In the real world of railroading they dont care one bit about the consist position on a set of power.

Jay Potter wrote:Lutherb, with regard to the "Guidelines" that I referenced, that is a Mechanical Department instruction issued for use by personnel at the railroad's locomotive service centers. It provides the machinists who service locomotives with information about locomotive characteristics and discusses which locomotive models should be operated together and the order in which various models should be positioned in a consist.

As far as the power reduced to one traction motor if that wheel slips, im gonna have to see for myself next time im making a hard pull. From what ive seen so far id have to say that statement is false. Theres a screen an engineer can bring up that shows whats going on with every traction motor, ill tell you for sure if it really happens that way. I believe it doesnt work that why because when the motors are really fighting to get to the top of the hill, and a wheel does slip, you can see, and feel the tractive effort drop signifigantly as does the speed, it doesnt feel like a reduction to one axle, the motor speed slows.

The last time i made a big pull up Stauffer (couple weeks ago) with a SD 90 on the point, the conductor said he has only saw one of these motors exceed the 150,000 pounds ( and it didnt stay there long for any long period of time before slipping, then it dropped way down, on the whole motor, didnt feel like just one truck, then surged back to and above the 150,000 mark ) of tractive effort once, that day was the second time he saw one try that hard. Im not much of an amp watching kinda hoghead, (unless its DC on a hard pull. That the way you do it Golden-Arm? ) but next time im out testing a GE's tractive effort control system ill let you know if whats printed on paper is really true.

UPRR Engineer, no, I've never worked a single day for a railroad; but I think you'll find that what I said about traction control on the GE AC units is accurate. And you're right about the consist Guidelines. The Guidelines are supposed to prevent things like AC-traction units leading DC-traction units; and no one reads the Guidelines.

lutherkb wrote: I don't mean to argue with you here UPRR Engineer. You seem to know your stuff and I trust by your name that you are actually an engineer so you may know better/different. I only offer this opinion from what I have been told by other engineers.

Maybe I misunderstood what he said. But this is how I recall it. No harm intended.

Ok buddy.

So your positive, from what you've read or heard..... full power remains to all the other traction motors? No reduction of tractive effort except to the one that slipped? You might be right, ill bring that screen up next time and let you know. But it sure doesnt feel like it, and the tractive effort bar/meter on the main menu screen says other wise to what you claim. Ill find out in the real world and let you know.

Golden Arm? A little help here buddy. Whats your take on this computer controlled tractive effort crap. You ever pay close attention to the traction motor screen when all that slipping, bucking and kicking goes on when your pushing the limit on those GE's?