The Sonoma Rotary kiln appears to be supported by poured concrete. In the front of the picture, rails are supported by a poured concrete wall at floor level. The walls form pits where hot calcined ore drops and cools after being calcined in the kiln. In some cases, the pits were lined with steel.
The first band, positioned approximately 10′ down the length of the tube is supported on what appears to be a brick floor, one course higher than the poured concrete floor. The additional brick course plus fact the rollers are larger in diameter than the wheels that run on the rails would allow the kiln to be modeled at a slight angle from a horizontal position.
The second band approximately 40′ down the length of the tube is supported on a poured concrete pier that looks to be about 3′ off the floor. Taking away the effect of the brick course, the rise would appear to be roughly 1 inch for each foot of run.
The support on the far end includes the chimney and hopper. See the hopper and chimney page for more details. It is made up of brick and is high enough to fully surround the rotary kiln tube.
The floor itself appears to be a double layer of brick on top of the wood floor, supported by wood beams. Presumably, the purpose of the brick is to provide fire protection on the floor in the area of the kiln.
This image shows the kiln tube at the kiln hood end. The hood will be fabricated from the right piece 1 1/4″ code 40 PVC joiner. The two tires will be made up of narrow pieces like the piece in the middle. The rollers that will support the tires are just below the tire in this photo.
The side of the rotary kiln accepting ore crushed to fit through a 2″ screen serves the following functions.
- It supports the end of the kiln.
- It provides an exhaust for the chimney.
- It includes a hopper that allows incoming ore to be loaded into the kiln.
This only photo of the prototype of the hopper and chimney area is not very revealing.
This is from a 1917 rotary kiln drawing and shows a hopper and support mechanism from the side.
This shot of an early English rotary kiln shows a masonry firebox support with the chimney coming out the top.
A close look at the first photo reveals the fire box feeding the chimney to be also made from masonry. The end would have been deeper on the Sonoma kiln to allow the hopper to be placed near the top front and the chimney to come out the top rear. Note that the chimney diameter in this photo appears to be around two feet, but the chimney on the Sonoma kiln is of a smaller diameter, slightly smaller than the hopper tube.
Time to make some executive decisions.
- The fire box supporting the hopper and chimney will be modeled based on the English kiln in the above photo, except it will be wider to support both the chimney and the hopper.
- It will be all brick up to the point the chimney and hopper exit the fire box. Construction will use .060 styrene sheet with Plastruct rough brick applied to the surface.
- 1:1 dimensions will be 14′ high by 10′ wide by 8′ deep. That scales to 3 1/2″ x 2 1/2″ x 2″.
- Both the chimney and the cylindrical portion of the hopper will be 2′ in 1:1 scale or 1/2″ scaled.
- The kiln will be supported with a PVC ring similar in size to the tires.
- The fire box will have a fire door similar to that in the above photo except the top will be squared rather than rounded.
- The rectangular portion of the hopper will be built to accept material from the conveyor on order which scales to 4 1/2″ high.
This is a shot of the styrene piece that will be the wall of the fire box that receives the kiln cylinder. I used the PVC joiner to scribe a circle that would allow the cylinder to pass through the wall. Then I drilled 1/8″ holes inside the circumference (mostly) and used an Exacto knife to connect the holes.
The next step is to glue a PVC joiner to the back of this sheet, then use a rat tail file to size and smooth the final opening. While the epoxy was setting up I moved on to the fire box roof. Two openings were required, one for the smoke stack and the second for the cylindrical portion of the hopper. I drilled 1/4″ holes in the roof, used the stack to draw two circles, then used a rat tail file to file the opening so it would accept 1/2″ tube. As you can see I used a couple of pieces of Plastruct square tube to convince the chimney not to lean.
This shot shows progress in the fire box, hopper and chimney area. In addition to the top of the firebox supporting the chimney and tube portion of the hopper, the firebox wall facing the tube is also shown. As you can see it is designed to support the cylinder at a downward slant from where it enters the fire box. You can also see the three other sides and the bottom of the fire box. The firebox will be surfaced with Plastruck brick which is on order. The brick will come most of the way up the fire box. The last portion will be modeled as a steel hood.
I’m estimating the end hood to be 3 feet deep in 1:1 scale or 0.75″ in 1:48. This will be modeled using a slice of the joiners for 1 1/4″ code 40 PVC. A scction will be cut from a portion of the bottom of the PVC piece to allow the brick to extend below the outer diameter of the joiner to model the dumping of calcined ore into the steel lined concrete bunker below the kiln. A close look at the band surrounding the brick on the left side reveals that the brisk is recessed somewhat from the end using an L girder formed to the curve of the end hood. The best approach may be to wrap the PVC joiner slice in brass or styrene to form the overlap then place a brass or styrene ring vertically against the brick and horizontally from the inside against the wrapping.
The Crowe River order includes some brick sheet that should cover what I need on the lower end of the tube as well as the base for the chimney at the upper end.
I’ll need to locate suitable boiler doors for the hood and fabricate the piping for the oil line feeding the burner. The support trucks on the two sides and the rail construction are being logged in the Rails, Wheels and Rollers Log.
This log will document modeling of the electrical motor and gears driving rotation of the cylinder of the rotary kiln.
The drive gear in all likelyhood was electrically driven. I’m hoping this Crow River motor is appropriately sized.
In at least one rotary kiln installation I observed the use of bevel gears. So I ordered these from Crow River.
The most vexing problem related to the kiln tube was locating a scaled version of the large gear surrounding the rotary kiln cylinder. Then I stumbled on a Spirograph set containing a wide variety of gear sizes. I purchased the kit hoping one is of the ideal size for this application. I’m going to keep my fingers crossed on this one. Additional work on the tube will need to wait until the Spirograph gears arrive. One of these should be large enough to go around the rotary kiln tube. Another should be small enough to serve as the final output gear from the electrical motor. Gear tooth density is appripriate for this model and the gears will mesh – that’s what Spirographs do.
The Spirograph arrived. It turned out that the 84 tooth gear accepts Code 40 PCV Joints perfectly. So I cut two very thin pieces and epoxied them to the Spirograph gear, sandwiching it between. When the sandwich dried, I used my drill press to drill holes around the inside edge of the PVC joint slices. After connecting the dots. I used the Exacto to trim the gear flush with the inside of the joiner, allowing my gear mechanism to slide on the tube as shown on this photo.
Immediately below the gear on the tube is the electric motor I ordered from Crow River Products to power the rotation of the tube. The motor is sufficiently beefy that it is credible in this application. The light colored plastic gear is the 24 tooth gear from the Spirograph set. which will be used to transmit power from the motor to the large gear surrounding the kiln. I also show a pair of beveled gears I ordered from Crow. I need to work on the arrangement of the gear box.
This log will document modeling of the rotary kiln rails, wheels, and rollers pictured further down this post.
If you look at the earlier photo of the rotary kiln, you will see the front shroud is supported by freight car wheels on rails. I intend to model the support brackets with styrene, the rails with scrap rails, and the wheels with sourced freight wheels. A rough estimate of 1:1 diameter would be 18″.
I also plan to model the support brackets for the rollers supporting the tyres from styrene. The wheels will probably be modeled using appropriately sized pulleys. A rough estimate of 1:1 diameter would be 24″.
This drawing of tire assembly design shows common British practice in the early 1900s.
With these two applications in mind, I picked up these 33″ HO wheels off eBay. At 1:1, they should be about 1/3 inch in diameter. Any left will be used as clutter, probably in the Sausalito Shops scene.
I also ordered Crow River Products 24″ pulleys to be used as rollers for the tires.
The 24″ pulleys arrived. They are a very close match to the rollers that supported the prototype tires as shown in this photo.
This log will document modeling the rotary kiln 50′ long tube and tires pictured in the above photo.
1 1/4 inch code 40 PVC has an outside diameter of 1.66 inches, just a hair short of the diameter in the above takeoffs. The connectors that join two lengths are 1.97 inches, also a hair short of the diameter of the tires in the above takeoffs. I picked up a 2′ length of 1 1/4 inch code 40 at Home Depot along with three connectors.
I cut the 1 1/4″ PVC to 12.5″ (50′ in 1:1 scale) with my chop saw and cut the remaining piece in half, fitting the connectors on each end. Then I sliced off a number of sections of the connectors. From the bands on the tube I will select:
- One will hold the tube on the kiln hood end. I’m estimating the with of this piece to be 3′ at 1:1 scale, or 3/4″ in 1:48. That is the size of the longest slice on the tube. It is slanted slightly to counterbalance the fact the tube will be mounted at a slight angle to horizontal.
- Another will be hidden behind the hopper on the far end and serve as a bearing for that end. Width may be somewhat immaterial as it will be hidden inside the hopper. Of the four medium length slices shown I’ll pick one and sand to a slight angle to allow the end to stand vertically even though the tube will be slanted.
- I’ll pick the best two of the three narrow bands and sand appropriately so they can serve as tires.
I plan to make use of a trick I learned from David Fletcher for putting rivets on boilers. If I wrap the tube with thin brass sheet or thin styrene, I can press rivets in the sheet with my drill press from behind the sheet. Final alignment of these parts will be somewhat dependent on the solution used to handle the large gear surrounding the tube. So much of the work on this part of the kiln will need to be suspended until my gear source, the Spirograph, arrives.