From the Washington Post - the problem appears to be pretty definitely determined to be that the wheels are shifting out of gauge on the axles, the questions are why and how good was management’s response to the problem
Federal investigation into suspended rail cars puts focus on inspections, maintenance (msn.com)
I’ve lived in DC since 1965 and have observed WMATA since it’s inception. The culture there has been plagued with responsibility/accountability problems. “We’ve all got good jobs, so let’s not make each other uncomfortable.” This attitude may also extend to relationships with their contractors and suppliers.
Rick
The bigger question is how were these cars accepted from their supplier with ‘shiftable’ wheels? Or has the wheels being movable on the axle been a result of maintenance wheelset replacement by WMATA?
Suspect that this investigation will take a long time. The primary cause appears to be the wheel set going out of guage specification. However the why may be very difficult to pin down. Also the Hawaii incident may be examined although that wheel set reduced guage. Some possible investigation subjects.
Are there wheel brakes or just disk brakes ? Wheel brakes might heat up the wheel causig it to expand around the axel.
How are the wheel sets constructed ?
a. Are the wheels just pressed onto the axel ?
b. Are wheels heated before being pressed on to axel ?
c. Have there been instances of old wheels removed and new wheels installed on same axel ?
d. Assembly errors ?
e. Any kind of key way to prevent guage changes installed or maybe needed ?
Is there some kind of types of metal interaction between axel metal and wheel metal ?
Is return current causing some kind of electrolysis axel to wheel ?
When wheels go onto axel what quality control is builder ( installer ) using ?
Is it possible that this problem might be wider effecting any of towed passenger cars, or locomotives, or freight cars ?
Any enviromental factors ?
Any other possible causes ?
It isn’t new technology to press wheels onto axles.
And it’s my impression that keeping the wheels placed on the axles has been pretty successful over the last century. Or two.
This would include shoe brakes and disc brakes and all sorts of alloys.
It might be interesting to look at the drawings and specs for this item.
It might be interesting to see if they were followed.
It might be interesting to see who chose the specs.
It might be interesting to show all of the above to a few experts in the field.
Ed
“It’s not a bug, it’s a feature!”
My grandfather - a railroad machinist - was doing it a century ago
Forging wheels and axles and pressing wheels onto axles
https://www.youtube.com/watch?v=8hBeeZ1Pvsg
Replacing wheel/axle assembly on freight car trucks
It seems they have found the problem…
On Friday, news site Greater Greater Washington reported that Kawasaki Rail Car had initially been pressing the wheels onto axles of 7000 series cars at lower pressures than was typical for other Metro cars. The pressure was increased in 2017, but it was not clear whether cars that already had been manufactured were altered.
Lower pressure pressing on the wheel implies less "interference’ in the fit and a less secure location of the wheel on the axle. The fact that they changed the design suggests they were aware that the earlier wheelsets were inadequate. Metro should have insisted on the earlier cars being fitted with new wheelsets.
Peter
Sounds like Kawasaki is open for a big law suit.
What exactly is meant by pressing wheels on with lower pressure ? Does it mean that either axel diameter was less or wheel inside diameter was more ? Does it meant that wheels were pressed on at a higher temperature so the inside diameter of the wheel was greater ? Were the diameters actually tapered for fit with a change in taper ? Or something else ?
Normally the wheel inside diameter is slightly less than the axle outside diameter at the wheel seat. A lower pressure means that the difference in diameters is less and the wheel is less securely located.
While separate wheel tyres were usually heated for installation on the wheel, wheels were usually pressed on cold.
Peter
I think there is supposed to be more to the ‘lower installation pressure’ business than “less of an interference fit”. There was discussion somewhere – if I recall correctly it had something to do with Siemens – that used a thin layer of anaerobic locking that had the effect of a lubricant preventing asperity-to-asperity tearing when the wheels were pressed to spec. There were papers about using a combination of cryo on the axle and profiled heat on the wheel, with ‘robotic’ control to press the wheel rapidly the whole way onto the fit to preserve the differential expansion right up to fine position alignment… with monitoring of the moment-to-moment pressure vs. location. I had thought that interference fitting with temperature control was reasonably settled technology… but I am seldom surprised at what ‘the competition’ in consulting does when there is an assumption to be made or a corner that can be shaved [D)]
When it comes to 21st Century business - there are very few if an corners that business won’t cut to generate a lower cost factor of their products! Safety be damned. Witness PSR in the rail industry - Lord only knows how other industries cut their corners.
And the beat goes on.
Half of WASH METRO rail operators have expired recurrent training and operating line checks. Metro reducing services again. If an airline had done this without FAA approval that airline would have been grounded.
This bunching will requiring 2023 some operators early. No way this bunching this year will be the best. Congress should clean house of management.