Take Out the Slack, Jack

Today was another busy day at the Museum, as usual, so there was a lot going on that I didn't get to photograph.  But in line with IRM's educational purpose, we have another fascinating mechanical subject to talk about: slack adjustment!  I'm sure you're just dying to hear about this.

But first, I spent most of the morning fixing the rest of the windows in the 308 so they can all be raised and lowered easily.  Not very educational, I admit.

Of course, many other people were working on various projects.   Here Tim is sanding down recently installed wood on the 1754.

All of the corners on the car have now had new wood posts installed.

In the Cleveland PCC, Ed Woytula points out the wiring that's being installed.

New wood blocks for the 28 have been made and painted, as seen here.

And John Arroyo was working on the Liner, and so on.

But the main Car Dept. project for this afternoon was replacing a bad axle on North Shore 749.  This is not easy.  First you disconnect everything, then the truck has to be pulled out from under the car, then the motor is lifted off the axle, then the truck is lifted off the axle, and so on.  And we want to do as much of this as we can before the car itself has to be raised, so here project manager Joel is working on releasing the slack adjusters from the truck.

So what's a slack adjuster, you ask?  The brake rigging on a railroad car has to apply an even and predictable force to all the wheels, but over time the brake shoes wear down, and if this goes on long enough, there's too much slack action and the brakes do not function well.   On most older railroad cars, including the CA&E for instance, the slack adjuster is just a large turnbuckle with two locknuts.  Once a year we run the cars over the pit, loosen the locknuts, adjust the turnbuckle as needed, and all is well.  (I'm sure the CA&E did this more often.)  But the North Shore decided to improve this process with automatic slack adjusters on all their passenger cars.  

The automatic slack adjuster is a mysterious device, but the basic idea is this.  There is a large stack of metal shims inside the housing, and as slack develops in the brake rigging, the shims fall down one by one to keep the overall slack the same.  In the picture below, you can see a large number of shims, which are basically squares with a tab on one side. An adjuster waiting to be taken apart is at the top of the picture, and you can see the tabs in the slot, I hope.  Anyway, we spent a lot of time disassembling the adjusters, flattening and cleaning the shims, and so forth.  No matter what Joel thinks, I'm sticking with turnbuckles.

I should mention that we had quite a good crew working on this project.   Cliff and Lucas McKay were helping out, although I didn't get a picture of them.  Also Nick, Brian LaKemper, Richard, Gregg, and who am I forgetting?

The pilot has to come off to get the truck out from under the car, and here Gregg is using a torch to free some frozen bolts.

I had to run over to the Steam Shop to borrow a special socket, and they were very helpful.  Thanks!

Richard is holding the wrench while the impact wrench does its job.

Once the pilot is removed, you can see right to the motor.

Then we start getting ready to jack up the car.   The car stands are more or less in place, as well as the pneumatic jacks.

The locomotive is brought up to pull the car out, but first we need to clean the bearing surfaces on the axle we're going to put under the 749.

This is a spare truck which will provide a replacement axle.  First the bearing surfaces need to be cleaned.

Joel starts out with a scraper, and later the truck was run back and forth several times to smooth out the surfaces.  I had to leave before this process was complete.

But these younger guys, they'll probably be at this all night.  We'll let you know when the 749 is ready for regular service again.