Yaw Damper Modification on M7s

While waiting in Jamaica yesterday afternoon for my connection, I observed 7153-4 and was surprised to see that the third rail shoe beam fuse boxes on all four trucks had been relocated but that the yaw dampers themselves had not been installed. The brackets for the dampers were there, however. Is this common practice, that is, letting the cars out of the shop before completing the job?

Also, at around what number did M7s start to come with the yaw dampers from the factory?

Yes, I know this is a mechanical, not electrical, question Tom.

On the earlier delivered cars, they were delivered without yaw dampers, but were added later as the cars were sent down to Arch Street shop. Perhaps this pair wasn't retrofitted yet?

Jay

The cars were originally supposed to have the yaw dampers on them. The bracket on the car body has always been there, on all M-7 cars.
The manufacturer removed the dampers from the design, for whatever reason. Luckily, they kept manufacturing the cars with the brackets on the car bodies.

Then, there was a problem with the 750 VDC buss between the shoe fuse boxes on either side of the truck. It was a solid buss bar type of thing that was fatiguing and breaking, from what I can recall. They changed the design to move the shoe fuse box off to the side, with more forgiving flexible cabling. But the cars were still not retrofitted back with yaw dampers at that time.
Then, the yaw dampers were added back on, although apparently with a slightly different mounting arrangement than the original yaw damper design. There is some welding on the trucks involved with the latest mod, so the trucks need to be changed out again. AFAIK, it is all covered under warranty.
The lower numbered cars, with the original setup, will of course receive trucks only once, that have all the modifications done on them.

So, technically, there are at least three differnt types of truck configurations running around the LIRR.

That's the best I can do with that for now. If I can find out the exact particulars, I'll explain it better. But, few people here likely know the particulars, to tell you the truth. Up in Equipment Engineering, somebody knows. At our level, it's gonna be tough to find someone that knows the whole story, but I'll try. There's one knowledgeable guy that the LIRR raided and hired from BBD. He may know.

Tom

Hey Tom,

I KNEW you'd know this stuff!

Thanx!

Theory # 1: Maybe a smart design engineer spec'd the yaw dampers, and then the accountants were looking to cut cost of production, and eliminated them, hoping the passengers wouldn't complain too much about the swaying . But they left themselves an "out" by installing the mounting hardware, figuring that if the passengers did complain it wouldn't be too hard to retrofit the cars.

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Theory # 2: Maybe the dampers were being built by a sub-contractor who was delayed in production for some reason. And BBD rather than delay deliveries of the first few hundred cars, built them with just the mounting hardware figuring they'd go back & retrofit all the dampers later in the course of warranty work..

H-E View,

They both sound plausible to me.

The question remains, however, of which was the first pair sent from BBD with the dampers already installed.

Or, better still actually, on or around what date did BBD start outshopping cars with them installed.

Yeah! Yeah! That's it!

I looked around in the online manuals they gave us, and the dampers are noticeably absent in all the drawings.
I can't find a reference to any yaw dampers anywhere.
Obviously, the retrofit would require new drawings to be inserted into the books and online manuals.
I did find this drawing of the original bus bar assembly, though.
M-7 Bus Bar 133k jpg
I don't know what they were thinking with this design, but it didn't work out. It involves one of the modifications mentioned in an earlier post.

Tom