Freeze-o-Matic Mk.I
Project Story
In the spring of 1999, I was attending Texas State Technical College in Waco, Texas, where I was in the Mechanical Engineering Technology program. I had already caught the design and manufacturing bug, and was proficient enough with Auto Cad to draw good 3-view working drawings. I had been invited by Steve Thomas to join the Denton, Texas chapter of the Christian Service Brigade on their big spring campout at the Lyndon B. Johnson National Grasslands near Decatur, Texas. Naturally, I accepted the offer, and after my classes were over on Friday I drove the Silver Stallion to the Grasslands, about 2-1/2 hours north of Waco. I hadn't been there long when Steve started talking about how he really wanted fresh, homemade ice cream for the camping trips.
Steve Thomas handles all of the cooking and food-related planning for the campouts, of which 80 to 100 men and boys can attend, and Steve has always provided more than enough food, by way of a massive smoker rig and two other trailers of associate cooking equipment. He uses the smoker, two Army surplus field ovens, a portable propane griddle and range, and several propane burners to make what is possibly the best camping food I have ever had. Normally, the best meal is served on Saturday night, where Steve treats us hickory-smoked beef brisket, as well as an occasional chicken or wild boar, sausage, and all the trimmings like beans, potato salad, and bread. For desert, he makes peach cobbler in the field ovens, and he always wanted ice cream to go with it.
So it was that I found myself designing a very large ice cream machine. I started off with some vague ideas from Terry Snell, and engineer who is involved with CSB, and had worked at an ice cream plant in the past. He gave me the idea for the curved-edge scraper, known as the dasher, and suggested the use of a plastic known sold under the trade name Delrin. I drew sketches of many different arrangements for the dasher assembly, and finally decided upon the one seen in the photo, with a cross-drilled 1 inch diameter stainless steel shaft into which five (one is missing in the photo) crossbars were placed. The ends of the crossbars have a shoulder that fits into respective holes on the dashers, and the whole unit is located in the casing by two acrylic bushing plates, which I machined on a Fadal CNC mill at TSTC.
The overall capacity was originally planned to be 5 gallons, but after playing around with some volume and inside surface area comparisons, I decided that the only way to freeze ice cream at a decent speed using brine and ice was to keep the diameter of the cylinder at 7 inches or less. This meant that a 5 gallon unit would be over 50 inches high, once the displacement of the internal parts was taken into account, and with a 7 inch diameter, there would be no way to physically access the bottom of the container once the ice cream was ready, or to remove the bearing plate or clean the apparatus. I suppose I could have made a bottom bushing plate similar to the one on top and installed o-rings inside and out, but that idea seemed a little impractical at the time. So, after talking to Steve, we decided to scale down to 3-1/2 gallons of capacity, and the project was under way. I had the first part, the freezing cylinder, made by Stewart Stainless in Waco. they did a very good job, and rolled it from 16 gauge stainless steel, and welded the seam all along the side and installed a cap at the end. Their work was very good, and they charged Steve $200 for the item. Little did he know this was only the beginning.....
The next set of parts to be made were the internal components, and everything but the bushing plates were made at Halsey Engineering and Manufacturing, Inc. of Denton, Texas. Next, the whole freezer vessel assembly needed to be made, and ended up being the most expensive (but also the most impressive) part of the whole project.
Between school and work in the summer, I think it took me a year to finish the ten-page drawing package that was required to fabricate the freezer vessel. This part of the machine holds the brine and ice, and is built stoutly, since it weighs over 300 pounds when loaded with everything. There is an internal cavity between the inner and outer walls which is filled with foam insulation, and there are stiffening baffles places every 30 degrees on the inside, and a ring at the top and bottom to hold the freezing cylinder, I would have been happy to build it myself, but I just didn't have access to the kind of equipment needed to fabricate such a monster. Steve never actually told me how much it cost, but it was somewhere on the order of $2500 to $3000. Finally, a crank handle was fabricated, and the device was ready for a test freeze.
I made the first run late one night before a small CSB water sports campout. I made one gallon of ice cream base, and finished freezing it at about 2:00 that morning. I must admit, the ice cream was everything I had hoped it would be; I had a certain amount of apprehension, since the design wan unproven, but it ended up working exactly as I had planned. The next day at the lake, we made a full 3-1/2 gallon batch, and it worked fabulously.
Steve and I had talked about motorizing the uit from the beginning, and we may still. Another improvement would be an ice-agitator to keep cold brine in constant contact with the cylinder.
Assembly View of the freezer bucket
