Back in January, I posted about the Cembre connectors Metro has been using for the past few years.
A member of Metro management (who I knew casually the entire 27 years I was at Metro) recently discovered that post and commented on it. He said:
“You neglect to mention the rail clamp also has a small surface area. You also fail to mention that the frequent cause of Cembre failure is, like a rail clamp, faulty installation practices.”
In that post I wrote (in part):
“Rail clamps do break, but typically it is because the person who installed the clamp over-tightened it. There is a torque spec (maybe 50 lb-ft) but management has never issued techs torque wrenches so they are left guessing at what is the proper torque. Most people over-tighten just about everything – it seems to be human nature. If snug is good, then 200 lb-ft is better, right?”
So, we agree that “faulty installation” is a factor but I would suggest that a large portion of the blame for that rests with management. Over the years my coworkers and I repeatedly asked for torque wrenches so that we could properly tighten rail clamp bolts and other hardware. Our requests were ignored — for _decades_. I imagine things haven’t changed, and techs are still expected to ‘guesstimate’ when torquing hardware. In addition, we did not receive, nor am I aware of, any official training on the proper installation of rail clamps. Any training was ‘OJT’ (on the job training) — often left up to technicians (not supervisors or instructors) which meant it was hit-and-miss. I wrote about the lack of training here.
The Cembre lugs, particularly the ones that are mfrd with a 45 degree bend, tend to break:
This may be due to the copper being brittle and prone to stress cracks, it may be due to the cable being installed with tension on it (or both) but they appear to be more likely to fail than the rail clamps.
The statement, “…the rail clamp also has a small surface area” is disingenuous. The rail clamp ‘basket’ (the part that makes contact with the rail) clearly has a much larger surface area than the two small flat washer sized areas on the Cembre connector. See the photos in my initial post. It’s not even close. What that means is that when carrying high amperage, the Cembre connectors are more likely to become burnt and pitted — and fail, causing train delays and unnecessarily risking ATC techs’ lives (because anytime employees go wayside they risk injury or death) when they could be performing other duties.
Here is a close-up photo of two rail clamps that I took after one of the back-to-back derailments just north of the Shady Grove platform. Hopefully there is enough detail visible to show how they are constructed. The one on the right was damaged by the train:
Here’s another that shows the ‘basket’ around the cable better. It is another derailment photo, the clamp was broken and the cable and basket were moved:
I’ll close the same way I did back in January:
For the safety of my former coworkers and the convenience of the passengers, I hope ATC management will do the right thing and admit that using the Cembre connectors – however well-intentioned – was and is a bad mistake.
ATC should go back to using the rail clamps (or something better).