Wheel spin damage by E1331 OFS ???

[PietConradie]

I have received these pictures as a "FORWARD" via email - no details about the incident or the unknown photographer - the pictures appear to be authentic.

The photos are likely to have been taken by the repair team.

The 1st picture was taken at 10h04 on 4 May 2009 and the last one at 12h53 the same day.

Has anybody more details on this incident, and how (un)common is this?

[Kevin Wilson-Smith]

My first reaction was these are fake! But I have looked at the pictures very carefully and they appear to be genuine - or really superb fakes - but I really do not think the latter as there seems little point in going to all the effort this would have taken.

Which leaves me gobsmacked.........! And still a bit unconvinced!

How does something likke this happen? Is it really that feasible? Is the melting point of the wheels higher then the track by such a large degree?

[Derek Walker]

I have to admit I am also puzzled, of interest is that both tracks are affected, so whatever went wobbly was on that axle. I dont know anything about how these things are powered but that wheel was either going really fast and everything else was going nowhere, or that axle was the only part doing anything and the loco couldnt get going. What puzzles me though is how much damage was done, surely at one point the axle wasnt touching the rails any longer? how hot must steel get before that sort of damage happens? It will be interesting to find out what happened, this cant just be some cowboy popping wheelies.

[PietConradie]

Kevin,

Your first reaction was my exact same thoughts and I immediately started looking for clues of a fake, but could not spot any yet. Yes, it would take many many hours in photoshop to fake this ... not impossible.

So I am also guessing and maybe the experts could help answering questions like:

(1) Would the steel used on the tyres of the driving wheels of the loco have a higher melt point - after all these "tyres" have to grip the rails all the time to move the train, so one would expect the "tyres" to be of a higher grade steel than the rails below.

(2) If one set of driver wheels on the loco was doing a wheel spin, the rail below the set of wheels would endure continuous friction at the contact point, while the driver wheel itself has the friction & heat spread around the wheel's circumference - might help explain the one-way results a bit. I also imagine that the driver motor and wheels as a group lower themselves automatically as the rails melted away, causing further damage ... again the experts have to give their views.

(3) I would dearly like to know how long it actually took to cause all this damage? A matter of seconds or much longer? And why could the loco driver not remove power to the wheels earlier? Did something got stuck?

(4) I have picked up that some locomotives are fitted with wheel spin control making them more economical top run - would the locomotive in question be fitted with such controls?

(5) Maybe someone can still prove or report that it's all a nasty fake. Then I shall apologise right away for wasting the time of the good Friends on the forum!!!

regards
piet

[John Ashworth]

Then I shall apologise right away for wasting the time of the good Friends on the forum

Don't apologise - even if it turns out to be a hoax, it's a very interesting one!

[Tom Macrery]

I vote for fake for several reasons:
1 - I would guess that it would be impossible for only one axle to spin for long enough to cause this extensive damage happen without the driver intervening.
2 - The rail in picture 4, while the damage looks similar, is not in the same setting - compare grass and ballast.
3 - The locomotive numbers are not the same in the two pictures.

[Tom Macrery]

Revision to my point 2 above - Yes, I see that the section of rail could have been removed. But could it have been removed in the short time between the two pictures - just over an hour. And would the two sections of rail have been removed and a new rail temporarily welded in place in order to move the train?

Added Point 4 - The odd circumstances surrounding the receipt of these photos by Piet - no details, a "forwarded" email (often hoaxes), no dates, no place.

Question - When the wheels stopped spinning and were then sitting in the depressions of the rails, how would the train have been moved? Jacking? Towing? Pinching?

[PietConradie]

Question - When the wheels stopped spinning and were then sitting in the depressions of the rails, how would the train have been moved? Jacking? Towing? Pinching?

I have the same question as the one Tom ended with. I am currently trying to work backwards in the chain to trace the source of the email. Don't hold your breath yet!

How much can one gather from these pictures? I still notice more details when taking another look.

(1) I think the problem was caused by the 2nd loco in the consist. That one was probably E1331. If one looks from the front of the consist (5th pic "23.jpg") and compare with the next (6th pic "22.jpg") I would say that the visible features best match that of the 2nd loco.

(2) The 2nd picture ("58.jpg") shows fresh oil leaks from the motor casing of the unit behind the driving wheels -- note evidence of leaking oil on the damaged rail section in the last and 3rd last photos. Would that be reason enough to believe the driver wheel with the oil tears had once been over the damaged pit before the photo sequence were taken?

(3) Has anyone noticed the little wedges (each on the end of a wooden handle) placed behind the wheels - visible in the 6th photo ("22.jpg").

(4) On the aside, diamond (dust) wheels are used to cut diamonds, so I guess in the same way steel could cut steel.

[Derek Walker]

I think the little wedges may be for the sand spreading system. The pipe goes upwards to the sandbox. My gut instinct says these arent faked, I have fiddled with images myself and tried a stack of things, and these dont have the faked feel about them. Bigger pics examined at pixel level would reveal tampering at any rate. Where are all our electric loco drivers when we need them???

[PietConradie]

Apparently loco no E1331 is a member of the Class 6E1. Paxton & Bourne's 1985 Locomotive Guide states that each axle-mounted motor in these units has a continuous power output of 550kW, giving a total continuous power output of 2200kW per loco. The publication notes: "The successful application of this new generation motors required careful mechanical design to ensure maximum transfer of power to the rails without causing the wheels to slip" The Class 6E1 has a sophisticated series of traction links, clearly visible (also seen in one of the photos DSC00022.jpg above) on the outside of the bogie to optimize this function.

The class 6E1 has electronic wheel-slip detection, but in 1982 two Class 6E1's were equipped with microprocessors to test modern computerized methods of propulsion control. In 1985 the Class 6E1's was the most numerous single class of locomotive which then consisted of 859 loco's.

FICTIONAL SCENARIO: As a total layman I propose a possible scenario for the happenings - a total guess - and it would still be nice to get the real facts: The consist of 4? 6E1's, with train in tow, creeped up very slight incline (fact supported by wedges placed later on the "backsides" only of driver wheels - seen in one of the pics DSC00022.jpg above). The train was approaching a red signal, and the driver was hoping that the signal would turn green - finally the train was held at a standstill by applying just enough power to prevent the train from moving backwards again. At this point, wheel slip occurred on an axle under one of the units further back in the consist, but the driver failed to recognize the seriousness of the noise, or the noise was masked by other working noises, such as the cooler fans and other equipment. Although these units are fitted with wheel slip detection, this function clearly failed on this occasion.

[Tom Macrery]

Excellent fictional scenario, Piet. You can qualify as our Sherlock Holmes. Why might only one axle slip? Would all the other wheels be just 'holding' with a little bit of power and static friction?

But I have the solution! I will show these pictures to John Dadford tomorrow at Capital Park. He is our most knowledgeable technical expert. He will most certainly have an opinion, and I will report back to the forum on Sunday. Perhaps he even heard of the incident?

[John Ashworth]

Tom, print them off and give them to Nathan to show Uncle Cliff A (or send them to Cliff by e-mail as attachments). He's up to date on modern traction, and also tapped into TFR's insider knowledge of incidents.

[PietConradie]

Good morning all Friends!

I take the liberty to post some technical information from sources elsewhere on the web, as I think this may aid in our understanding of this unusual incident ... optional reading !!!
piet

WIKIPEDIA: CAUSES OF WHEEL SLIP

The causes of locomotive wheelslip are various, but the predominant factor lies in power to weight ratios. Ideally, locomotive designs will have roughly equal power to weight ratios that enable smooth acceleration from a 'cold start', or stopping position. However, if the power of a locomotive vastly exceeds its weight, then an imbalance ensues which causes the violent turning of the wheels through loss of traction.

Other causes include the contact of oil with the flanges and rims of wheels, which reduces adhesion with the surface of the rails, and a general loss of traction on steep gradients when pulling heavy loads.

WIKIPEDIA: ALLEVIATION OF WHEEL SLIP

Most locomotives are fitted with sandboxes so that sand or Sandite can be dropped on the rails to improve adhesion. Modern diesel locomotives and electric locomotives are fitted with electronic wheelspin detectors which automatically reduce the power supplied to the wheels if wheelspin is detected.


STANDARD LOCOMOTIVE versus PROCESS LOCOMOTIVE ADHESION

COPIED FROM THIS SOURCE http://www.railspur.com/Process Locomotives/Adhesion.htm

ADHESION

Adhesion is a measure of the resistance of friction to slippage between two parallel planes. In the case of a locomotive railwheel the parallel plane is the point on the steel railwheel where the railwheel contacts the steel rail. The maximum force or pull that a locomotive can generate in order to pull a train is limited by the weight of the locomotive and the amount of adhesion that it can maintain without wheel slippage. Once the wheel starts to slip the pulling force is lost. According to the Physics books the maximum adhesion for smooth steel on smooth steel is 42%.

If you add sand to make a sandwich between the wheel and the rail the sand can increase the maximum adhesion because it provides a rough surface that can dig into the small pores of the steel and provide a higher adhesion coefficient. This is especially important if the rail is wet. For wet rail without sand the maximum adhesion for a smooth steel wheel on smooth steel rail is about 10%. With sand on wet track the adhesion can be as high as 30%. Sand on dry track can increase the adhesion to about 40%. This is why locomotives have large sand boxes in order to apply sand on steep grades, wet track, and other slippery spots.

Adhesion is not the same as the friction coefficient because the friction coefficient is a static number. The amount of adhesion that can be maintained is also affected by the acceleration of the railwheel with respect to the steel rail. As soon as the railwheel begins to turn the amount of friction that can be maintained begins to drop.

STANDARD LOCOMOTIVES
(with conventional wheel slip systems)

For locomotives with standard DC traction motors and conventional wheel slip systems the average adhesion is about 25%. The force required to move the train is defined by the old physics equation Force = mass x acceleration. The force derived from the acceleration can not exceed the force of derived from friction otherwise wheel slip will occur and the locomotive will lose traction. The acceleration must be controlled to prevent railwheel slippage.

Acceleration on a standard locomotive is controlled by controlling the electrical power to each traction motor on a locomotive. That is normally done by controlling the throttle position on the diesel engine and letting the generator put out as much power as it can at that throttle position. It the throttle is opened too much then the power of the traction motors will over power the friction forces under a given load and cause spinning of the railwheels. When an axle begins to slip the wheel slip system will see a voltage spike and cut power to all of the traction motors for a second or two and then reapply the power.

If the operator maintains a throttle position that is too high the traction motor will again over power the friction and the wheel will slip. This in turn causes the wheel slip system to cut power and the process is repeated.

Unless the operator drops to a lower throttle position or lightens the load the locomotive will chatter loudly as the power to the traction motors is turned off-on-off-on-off-on, etc. This will cause damage to the locomotive and to the railroad track. The locomotive is not "smart enough" to turn down the throttle position itself, to control the rate at which throttle changes occur, or to simply stop and display an overload alarm.

The success or failure of the operation is strictly in the hands of the operator or engineer controlling the locomotive. A poorly trained operator can do significant damage to the locomotive and the track system in a very short period of time. Sometimes in less than one shift.

PROCESS LOCOMOTIVES
(with microprocessor controlled wheel slip systems)

Process locomotives put the throttle control and the control of the voltage and current to each traction motor into program that is installed on the master Programmable Logic Controller (PLC) microprocessor which in turn controls the locomotive.

The PLC can make adjustments in 1/20th of a second that the operator would take at least 2 to 3 seconds to respond to. By making corrections 40 to 60 times faster than a human operator can the process locomotive can control wheel slip much more precisely.

Process locomotives with automatic individual traction motor control (AITMC or AITMC-PT - the deluxe version) systems can control each traction motor independently of the others on the locomotive.

If an axle begins to slip the AITMC system will pick up the voltage and current changes in about 1/200th of a second. If they reach the set point then the AITMC will cut or trim power to the traction motor on the axle that is trying to slip. By reducing power it reduces railwheel surface torque below the torque necessary to exceed the friction forces necessary to maintain traction. It also starts the automatic sand time to apply sand to the rail for a preset period of time to help the locomotive regain traction.

Because all of this occurs in a fraction of a second it is very unlikely that the operator will ever see a wheel slip. About the only way he would know if there were a wheel slip would be when the automatic sander applies sand or when he checks the alarm log on the HMI computer in the cab. It the operator has connected to too large of a load for the locomotive to pull the PLC program will recognize the amount of activity in the AITMC subroutine and the heating of the rectifier assembly banks and cause the locomotive to stop and display the overload alarm. The operator must then reduce the load and try to move the railcars again.

Because only the axle that is slipping has the power cut or reduced the average adhesion coefficient is much higher than it would be if power were cut to all of the traction motors. Testing has shown that the average adhesion coefficient, or factor, can be increased by 20% and more depending on the type of AITMC or AIMTC-PT system employed.

TRACTIVE EFFORT

Tractive effort is defined as machine weight multiplied by the average adhesion coefficient. This is true for all locomotives and mobile railcar movers. In the subject of ballast the writer explained that on process locomotives the machine is normally ballasted to the maximum allowable weight.

The second part of producing tractive effort is to maximize the average adhesion. The new AC line locomotives have what they call high adhesion control systems that use invertors to control the power to each traction motor in order to produce adhesion levels of 35% and higher. 42% is the theoretical limit according to physics for smooth steel on steel. However, by allowing the rail wheel surface speed to exceed the rail speed by up to 1.5 mph ( in other words controlled wheel slippage ) the apparent adhesion can be increased up to about 50% according to some reports. This controlled wheel slippage is not good for the locomotive or the track; but, it can be an asset for main line locomotive pulling steep grades like those found in the Western Mountain States.

[Kevin Wilson-Smith]

Interesting so far.I am more suspicious this bright Monday morning!

Something that has been worrying me is why is only the one wheel area scooped out?

The bogie has more then one powered wheel - both axles are powered, so there should be a similar scoop in front. So why not more "scoops"?

And in any event even if only the one axle was powered for some reason, how would only one axle sink? The axle is on a bogie and the bogies will not flex laterally to that degree - aside from the fact that the other parts of the bogie would prevent the sink by contacting the rail if the bogie was tilted at an angle - I am talking here about the frame etc that projects at either end of the bogie.etc. See picture one below.

And if for some reason the bogie did tilt and the wheel sink, surely given that the degree of tilt would be be within a reasonable degree, the depth that the wheel had sunk to would not be feasible. The second picture shows this and the tilt here is exaggerated too - in reality at this degree the bogie would be contacting the underframe and there would be visibler damage to the latter.

[PietConradie]

Kevin, I like the angle (no pun!!!) you are taking. I think it is a very valid point and certainly not easy to answer. One would like to see a picture of a complete bogie in the workshop.

From my understanding there is a 550kW motor on each axle (Paxton) and they (4 motors) work independently, so I imagine one axle could slip while the others are still maintaining grip.

I have searched for a side-on picture of these complex bogies - I get the impression that they are indeed flexible to a certain extent - designed to maximize traction of all 4 wheels under the bogie.

I have cropped a photo of a 6E1 loco taken by Andre Kritzinger and which he has posted here:

http://grela.rrpicturearchives.net/show ... id=1512497

This gives some idea of the bogie construction.

However, for me, this picture does not answer Kevin's question - it still looks like some part of the underframe should be damaged. Unfortunately we do not have all the photos of the incident. :(