I have heard the above mentioned in regards to steam locomotives over the years and thought it was time I fixed my ignorance and asked what they are and any other details. Along this same line is there a written resource that I could learn what else I don't know :^).

These are the liners that go between the frame of a steam locomotive and the driving box which holds the crown brass on which the driver axle bears. The shoe is theoretically vertical, the wedge slanted relative to the frame, such that the amount of tolerance between the box and the frame can be adjusted for wear and to allow just the right amount of moveability. The openings in the frame are vertical for the shoe, and slanted for the wedge. The boxes need to be able to move up and down as the wheels traverse rough track, controlled by the spring rigging. Part (most) of the process of tramming a locomotive is assuring the correct distance between the center of the stroke of the cylinders and the centers of the axles when installed - shimming and remachining the shoes, wedges and boxes is how we assure all is where it should be along those axes.

dave

Good answer. As they wear, they reach the point of no returm. At IRM I am involved in creating new patterns for the shoes and wedges for our Russian Decapod, Frisco 1630.

Bob Kutella

Dave, I think I got all that, anyone got any pictures?

I was going to hunt down the photos taken a few years ago at Mid Continent RR museum in Wi. They were of the frame being welded and ground down to repair the wear that had happened over many years of use. Not sure of how educational the pics will be, but if I remember right there are a few shots of the welding close up so one could view the repair. They are buried in the steam repair news and were accessable the last time I looked. But the MC website is down and I can't access it right now.

The description Dave has given is pretty good, with pictures it would make better sense yet. I am sure some other folks will find some pictures that they have. If nobody comes up with the pics by tomorrow I will try again. I think they must upload the website on Sunday nites.

Untill I worked on the frame of the Montreal #1 {50 ton 4-6-0} and later on the Polson #2 {70 ton, 2-8-2 logging engine} I know I didn't have a very good understanding of just how important of a role shoes and wedges play. In the case of the Montreal #1 they were beyond the point of no return. Many of the shoes were broken and worn {shimmed too}, two broken driving boxes, and crown brass that were in multiple pieces. Montreal #1 was in such mechanical distress and was before MC ever got the engine. Hard to believe she was the most trouble free locomotve they ever ran. She was the main road engine for many years. Slow speeds and 4-5 trips a day at 9 miles a trip I guess you could get away with that. Good question to ask. Cheers, John.

.

Good helpful photos. Do you have any photos of the crown brass installed?
thanx,
dan

.

So the driving boxes can move up and down within the frame? If so, as the box moves, what keeps the wedge from sticking the box in the up position?

Thanks in advance.

Bob

The height of the wedge is controlled by a bolt that shoves it up and pulls it down - when set correctly, a locknut retains it in position (most of the time).

dave

It's worth mentioning that some "modern" steam locomotives had self-adjusting wedges, developed by Franklin Railway Supply. They used a spring to maintain the wedge in position. One of the big benefits is they can compensate not just for wear, but also for thermal expansion of the driving box and frame. Standard "manual" wedges had to be adjusted to a compromise based on the operating temp of the driving boxes. You had to make sure they weren't too loose when cold and didn't bind when hot.

Here's a link to the patent for Franklin's self-adjusting wedges. Look at the drawings for details:

http://tinyurl.com/yr7yhe

So if I got this right you have the frame, inside of it you have the shoes. Then inside of that you have wedges then boxes and axles?

If you look over Kelly's drawing, you will see the side of the openings in the frame are slanted top to bottom on the left (rear) and straight up and down to the right (front). The shoe fits on the right, the wedge on the left. Sliding the slanted back side of the wedge up the slanted face of the frame opening makes the intersticial space between show and wedge (where the box rides) smaller. Pulling it down opens the space wider.

Go lay hands on some rusty iron and it will be obvious.

dave

That was the part I was missing, Thanks Dave and everyone. I feel good I learnt something new today.