Dunbar Celebrated Rotary Popper
By Bruce Wm. Anderson
Motive Power - The Sound of a Dunbar Popper Popping Corn
|
Picture 1
THEORY OF OPERATION: The Dunbar & Co celebrated Rotary Air Poppers were very revolutionary. The popper consisted of a cylinder made with two layers of screen. The outer layer of screen wrapped around the cylinder and overlapped itself leaving a space of approximately 3/4 of an inch (see Picture 1). The outer screen was extremely heavy to handle the heat of the open flame or electrical resistance element. It had a dense weave to keep the raw popcorn within it. When the popping cylinder was going in the clockwise direction the raw popcorn and/or old maids would be contained by the outer screen. By disengaging the popping cylinder with the clutch from the drive mechanism the cylinder could be hand rotated counterclockwise one revolution which would then discharge the raw popcorn (old maids) where the screen overlaps itself into the old maid container. After discharging the old maids the popper was then ready for a new batch of raw corn to be scooped into the front of the popper. The inner screen consisted of a lighter wire with a larger weave (3/8 inch or 1/2 inch square). In the early years the inner screen was made of hexagonal shaped screen as in the catalog picture above. The inner screen was formed in the shape of an auger. This screen was attached to a piece of stamped sheet metal with large openings, which Dunbar calls a (stamped steel) separator. The separator is also attached to the outer screen. The raw corn would slide through the separator as it was rotating. Once the now larger popped popcorn approached the inner screen it was scooped up by the separator and inner screen and augured out the front of the popping cylinder onto the steam table. An ingenious new design for popcorn poppers!
Picture 2
The earlier Rotary Air Poppers had a bicycle chain gear reduction and drive as outlined in the 1907 through 1912 catalogs. We are aware of only one surviving Bicycle Chain Drive Popper. It can be seen in picture 2 and is owned by Docs’ Popcorn Company, Bruce and Darlene Anderson.
Picture 3
Picture 4
After 1911 a new Popper drive was introduced that made use of beveled gears for the gear reduction and drive. Variations of this can be seen in pictures 3 and 4. This greatly simplified the drive, was more robust, and made it very reliable. This drive was used from 1912 to the present.
The inner screen could be purchased in two different sizes. The smaller size (3/8 inch) was generally used for white popcorn and the larger size (1/2 inch) was used for yellow popcorn. Yellow popcorn usually has a larger popped kernel than white popcorn. Because of this larger kernel size more bags of yellow popped popcorn are produced per ounce of raw popcorn. This results in a lower overhead, thus more profits. However, many prefer the taste of the white popcorn. Dunbar’s build orders show that some double popper machines were ordered with a different size screen weave in each popper. Today’s popcorn varieties have been selected to have larger kernels. The Dunbar 12 by 15 inch and 8 by 15 Poppers were the most used poppers in the steam powered era. The 12 by 15 inch Rotary Air Poppers use the faster speed of 26 revolutions per minute (RPM) and the larger Rotary Air Poppers use the 21 1/2 RPM. If the Rotary Air Popper revolutions per minute (RPM) is too slow there is an increased chance of fire within the popper. If the revolutions per minute (RPM) of the popper is too fast you will see an increase in raw corn throw-out from the front of the popper. If the burner flame is too hot the popcorn will pop to a larger mushroom shape but the popcorn will be tougher.
The inner screen could be purchased in two different sizes. The smaller size (3/8 inch) was generally used for white popcorn and the larger size (1/2 inch) was used for yellow popcorn. Yellow popcorn usually has a larger popped kernel than white popcorn. Because of this larger kernel size more bags of yellow popped popcorn are produced per ounce of raw popcorn. This results in a lower overhead, thus more profits. However, many prefer the taste of the white popcorn. Dunbar’s build orders show that some double popper machines were ordered with a different size screen weave in each popper. Today’s popcorn varieties have been selected to have larger kernels. The Dunbar 12 by 15 inch and 8 by 15 Poppers were the most used poppers in the steam powered era. The 12 by 15 inch Rotary Air Poppers use the faster speed of 26 revolutions per minute (RPM) and the larger Rotary Air Poppers use the 21 1/2 RPM. If the Rotary Air Popper revolutions per minute (RPM) is too slow there is an increased chance of fire within the popper. If the revolutions per minute (RPM) of the popper is too fast you will see an increase in raw corn throw-out from the front of the popper. If the burner flame is too hot the popcorn will pop to a larger mushroom shape but the popcorn will be tougher.
Picture 5
The popper burner consists of a cast-iron center section with multiple pipe burners tapped into the cast iron center. It is supported by screws on the ends of 4 of the pipe burners (Picture 5)
Pictures 6, 7, & 8
We know of two styles of maple wood handles that Dunbar used on its Celebrated Rotary Poppers (Pictures 6, 7, & 8).
Article by Dunbar & Co 1955 on How to Wire Cylinder