Metro to take 7000 series out of service after defect was discovered in axle

But in the long history of rail, this is a rare problem, except on the Metro 7000's, as I understand it. Maybe a coincidence that Metro uses a non-standard gauge? Add in longstanding governance and openness issues, and the increasing use of opaque subcontractor manufacturing contracts. Like everyone here, I'm hoping the truth comes out eventually, but it's not guaranteed. More likely we'll find out why Tri-rail may not be fit for MiamiCentral Station!

west point
As I understand it the problem is that wheels are sliding on the axel enough to put the wheels wider or narrower than gauge specs. "IF" that is so then the fit between axel and wheel needs to be tighter. that means that the axel will need to be thicker, the wheel opening smaller or a combination of both. Consequently, the machinery that presses the wheels onto the axel will need to be set at higher values or maybe a different machine?

The wheels are pressed to a shoulder on the axel making it imposable for the gauge to become narrower.

The manufactures of wheelsets use presses that press both wheels onto an axel at the same time. They are designed to allow the assembly wheels sets of various wheel axel diameter combinations.

But before that is done a study of interaction between the axel and wheel metals will need study. Also, the possibility of metal creep on either part also has to be considered. Certain aluminum alloys can have this problem.

Formula to calculate the proper interference fit of wheels to axels have been around for many, many years. Those formulas use measurements from the wheel bore to multiple radial points on the hub of the wheel.

The possibility of the above might be occurring due to wheel over heating because of hard braking on the wheels? Anyone know if braking is done on the wheels only or do the axels have additional disks to absorb braking energy? Additional disks are difficult to place IMO due to each axel being part of traction system.

All of WMATA's cars are fitted with ventilated disk brakes. The brake rotors (friction rings) are bolted to the ends of axels.




kitchin
But in the long history of rail, this is a rare problem, except on the Metro 7000's, as I understand it. Maybe a coincidence that Metro uses a non-standard gauge?

The gauge difference (.25 inches, 6.35mm) is in the track not the wheelsets.

WaPo has a detailed story today updating the saga, mostly about a dispute between WMATA and the safety commission over wheelsets that are right at the limit. https://www.washingtonpost.com/transpor ... stigation/

Byline of the article: The latest hang-up: Technicians didn’t know whether to pass or fail a railcar if its wheels moved precisely 1/32 of an inch

My response: USE METRIC LIKE THE REST OF THE WORLD!!!

The question I have now, though is: Are there lock-rings that lock the wheel to the axle? We know it's fit against a shoulder on the inside but how about the outside? Is there anything that prevents the wheel from shifting off the axle?

Metric measurements? That has 0 to do with the problem of having a protocol that doesn't define pass/fail at a single value. >= or <= are needed not just > and <.

drwho9437 wrote: ↑Sat Jan 08, 2022 5:09 pm Metric measurements? That has 0 to do with the problem of having a protocol that doesn't define pass/fail at a single value. >= or <= are needed not just > and <.

...ze joke has flown over ze heads of ze doctor...

STrRedWolf
The question I have now, though is: Are there lock-rings that lock the wheel to the axle? We know it's fit against a shoulder on the inside but how about the outside? Is there anything that prevents the wheel from shifting off the axle?

I have never heard of securing railroad wheels to axles with and kind of retaining rig. I have only seen interference press fits used.

You may have come up with a quick and dirty solution that could save having to replace the bad wheel sets.

Press the wheels on axle to the proper gauge, face the wheel hub and cut a grove in axle with the same lathe tool, install the retaining rig / lock ring / circlip.

The next question is, are the wheels lose enough to spin on the axle? if so this solution will not work.

SBJ (and Everyone): I have been following the 7000 series car problem thanks to this topic...
This problem reminds me of the NYC Transit R46 car fleet truck problems (carbuilder: Pullman-Standard;
truck supplier: Rockwell International) when the cars were new (late 1970s-early 1980s) when cracks developed
in what turned out to be defective trucks causing the entire fleet (745 cars?) to be removed from service until the
defective trucks were either fixed or replaced by the supplier. The 40+ year-old R46 fleet remains in service today.

Can the supplier(s) that manufactured the defective axles and wheels be held responsible and be required to
replace these essential car components under a warranty or a legal court order for the WMATA? MACTRAXX

Sand Box John wrote: ↑Tue Jan 11, 2022 8:18 pm I have never heard of securing railroad wheels to axles with and kind of retaining rig. I have only seen interference press fits used.

You may have come up with a quick and dirty solution that could save having to replace the bad wheel sets.

Press the wheels on axle to the proper gauge, face the wheel hub and cut a grove in axle with the same lathe tool, install the retaining rig / lock ring / circlip.

The next question is, are the wheels lose enough to spin on the axle? if so this solution will not work.

"Quick and Dirty" but it's used in the automotive industry for wheel bearings and such. Looking at Youtube channels Bus Grease Monkey and South Main Auto lends to a lot of "out of the box" thinking in the rail space.

Although if it's loose enough to vibrate out (away from center), it's probably loose enough to spin on the axle, so I'm more inclined to get these trucks swapped out for known good at manufacturer cost.

Nothing quick and dirty is going to be certified to run on public transit. It was a standard fitting or milling done wrong, somewhere in the depths of U.S. assembly or manufacturing, and then covered up by Metro staff for years. (I'm assuming it is unlikely the defect was made in Japan.)

Metro has paused reintroducing the 7000-series for at least another 90 days. https://www.wmata.com/about/news/7000-Series-Update.cfm

https://wtop.com/dc/2022/02/metro-7k-up ... nitor/amp/

The wheel problems with Metro’s 7000-series railcars could be more complex than originally thought, according to the transit system’s CEO.

As Metro investigators continue to work on a “root-cause analysis” of the problems, “I think they’re starting to get to the point where this may be, the root cause may be, a series of root causes,” said Metro General Manager and CEO Paul Wiedefeld...

Meanwhile, he said the agency is investing in technology — typically used by larger railroads — that will help measure wheelsets and more.

“As we start to understand this better, it’ll be a tool to bring back the cars sooner,” Wiedefeld said.

Metro orders measuring devices to speed up inspection of 7000 series
https://www.washingtonpost.com/transpor ... rail-cars/

And the outage of the 7Ks are causing stofrage problems, they are layed over the the Silv er Line N route extension and Im not sure if the Green line Greenbelt Test track is being used for 7K storage

Robert Paniagua wrote: ↑Mon Feb 14, 2022 9:31 am And the outage of the 7Ks are causing stofrage problems, they are layed over the the Silv er Line N route extension and Im not sure if the Green line Greenbelt Test track is being used for 7K storage

I heard that since the got the Dulles Storage Yard connected up, all the 7K's are being stored there for the time being.