Insulator and Heat Exchanger for Ultra High Vacuum,
High Voltage Discharge Chamber,
W. J. Wheeler
Glass Technician
University of Wisconsin
Madison, Wisconsin
whee112923@aol

Fabrication of 18" Diameter Glass Tube

A supplier of 18" tubing was located *, however, four foot lengths were maximum lengths available. Not having a lathe of 18" capacity, it was decided to build a machine to join two four-foot lengths to one two-foot length. The design of the machine is as follows. The 18" tube was supported internally with a specially designed chucking assembly on a central 6 inch, 14 foot long steel pipe, set on two "A" frames, with roller bearings at each end, and rotated by our Litton HSA lathe through a belt drive. [Figure 1]A supplier of 18" tubing was located *, however, four foot lengths were maximum lengths available. Not having a lathe of 18" capacity, it was decided to build a machine to join two four-foot lengths to one two-foot length. The design of the machine is as follows. The 18" tube was supported internally with a specially designed chucking assembly on a central 6 inch, 14 foot long steel pipe, set on two "A" frames, with roller bearings at each end, and rotated by our Litton HSA lathe through a belt drive. [Figure 1]

It was decided to seal the 4 foot length to the 2 foot section, then to remove this assembly from the lathe, to anneal it, then re-chuck it prior to sealing to the remaining four-foot section. As the 6 foot length of tubing was quite light, two men could handle it easily in the chucking operations. Prior to the sealing operations, a preheat cycle of two to three hours was used, gradually increasing air flow to the two Litton hand annealing burners until a good strong bushy flame burned off the carbon layer deposited in the early stages of heating. A reversal of the preheating cycle was used to cool the tube down to room temperature after the sealing operations.

Sealing the 18 inch tubes was accomplished with two Litton 10 fire 7 jet Lathe burners, set vertically on a movable cart, surrounding the 18 inch tube except at top and bottom. Each burner was fed with its own oxygen and hydrogen cylinder. A spare cylinder of hydrogen and oxygen was T'd in to each burner, In the event the original supply ran out. With this method supply, we were assured 20 minutes of maximum heat per burner. (See Figure 2).

While induction heating would have been the optimum sealing method, the requirement for only two seals and the
financial constraints, dictated the choice of oxygen and hydrogen heating. This method of heating proved satisfactory
on tubing of this size.

Page 1 | Page 2 | Page 3 | Page 4 | Page 5