A typical stamp mill was a gravity-run operation, relying on gravity to do all the heavy lifting. To harness the power of gravity, stamp mills were normally built along the side of a steep hill in a step-stair fashion. Each “step” was another part in the process, with gravity transporting copper from one to the next. At the start of this process – and at the top most step – the copper rock would await processing in large storage bins. These bins were fed from above – via an overhead trestle. A typical rock car would be brought up atop that trestle and dump its cargo into the rock bins below by means of a discharge chute in the cars bottom.

Thanks to some consultation with ever knowledgeable Gordy Schmitt (who also provided the photo at the start of this post – thank you Gordy!) I have pieced together the details of how these discharge chutes probably worked. The chute consisted of a wooden funnel at the bottom of the car – which you can see above. Inside the funnel are two chute doors, which serve to hold the copper rock inside the car during transportation. The doors open inward, dropping down to the center of the funnel. Each of these doors is held shut by a pair of chains, which are connected to the doors on one end and to a metal crank on the other. The crank is connected to a wheel on the side of the car which is used to open and close the doors.

The wheel was held in place by a ratchet that when opened would allow the wheel to spin freely. To open the doors these ratchets were tripped, allowing the weight of the copper rock inside the cars to push open the doors. The doors were then closed by cranking the chains around the steel crank – pulling the doors back shut. The whole process is somewhat ingenious in its simplicity.

Heres that same funnel as it looks today. The difference between these chutes and those on more modern hoppers is the continuous wooden side wall which spans both of the chute doors. Modern hoppers consist of only the two sloped chutes without the connecting wall seen here.

Heres an inside look at what the whole discharge shoot looks like today – after half a century of abandonment. This shot is looking down into the car from above (the opposite angle from the diagram). In the middle of the photo you can make out the remains of one of the chute doors sitting in its open position. The sloped floor of the funnel has long since rotted away, leaving just the door and the side-walls. The steel plate seen just in front of the door’s bottom edge would be the doors position when closed.

Here are a few close looks at the door. The door itself consists of a series of wood planks attached to a pair of iron hinges. Atop the hinges is a piece of angle iron, which serves as a divider between the two sides of the chute. It also most likely protected the hinges from damage during the loading of rock.

Heres a closer look at the crank rod, which are still intact for each door. The chains however have either been removed or have fallen off over the years. You can still make out the two connections along the rod in the photo where those chains once were attached.

While the sloped floor of the funnel is long gone, the iron frame still exists as seen here. The large bolts sticking out of the side of the frame held the side-wall in this photo – which is also gone.

Finishing off the rock car is the wheels themselves – known as trucks or bogies. The design of these haven’t changed much of the years, with the exception of the increased use of steel instead of wood. The wheels are marked with their birthplace – Chicago. For the rail fans out there, I included a detailed PANORAMIC IMAGE of the cars undercarriage including the trucks. Most likely this undercarriage will be the only thing left of these rock cars after another 50 years of abandonment.