A VACUUM TUBE LEGO^® SET

Making vacuum tubes from scratch is almost a lost art. It involves plenty of practice in technical glassblowing, as well as an understanding of materials and vacuum techniques. However, vacuum tubes that operate at relatively high pressures and require continuous pumping are easy to build by cobbling together glass tubes, copper piping, and rubber corks. We prefer to use a more upscale version of this technique and follow the lead of vacuum expert Steve Hansen, who uses a neat LEGO set of interlocking glass pipettes and bulbs made by Ace Glass to construct experimental vacuum tubes.^8,9 The glass components and connectors made by Ace are not designed for vacuum applications. Ace makes them for chemistry, air sampling, and chromatography analysis. However, they work really well in the relatively modest vacuum ranges needed to reproduce these early electron-tube experiments.

The set of Ace Glass components that you’ll need to conduct the experiments:

• Ace-Thred #25 “T” connecting adapter (Ace catalog number 5829-12)
• 2 Ace-Thred #25 connectors (Ace catalog number 7644-20)
• Ace-Thred #11 connector (Ace catalog number 7644-10)
• 2 Ace-Thred #25 couplings (Ace catalog number 5841-16)
• 2 Ace-Thred #25 bushings (Ace catalog number 7506-10)
• 7 Ace-Thred #7 bushings (Ace catalog number 5029-10)
• 3 Ace-Thred #7 plugs (Ace catalog number 5846-44)
• 2 Ace-Thred #11 bushings (Ace catalog number 7506-02)
• Ace 1,000 mL Gledhill flask with Ace-Thred #25 connector (Ace catalog number 14205-09)
• Ace-Thred #25 12-in. column (Ace catalog #7488-24 air-sampling manifold) custom-ordered to have 6 Ace-Thred #7 ports as shown in Figure 47b
• Ace-Thred #11 300-mm chromatographic column (Ace catalog number 5820-04)

In addition to the couplings that you will use as part of your vacuum system, you will need some specifically for the CRTs themselves. We purchased ours from Kurt J. Lesker.

• Brass QuickConnec coupling for ³/₄-in. tube (Kurt J. Lesker catalog number B-075-KM)
• KF to QuickConnec coupling for 1-in. tube and a KF connector to match your vacuum manifold (we use a Kurt J. Lesker catalog number QF40XVC100)
• KF to ³/₈-in.-OD tube half nipple to match your vacuum manifold (we use a Kurt J. Lesker catalog number HN-SPL219)

The rods, tubes, and assorted parts that you will need are:

• ³/₈-in. aluminum rod
• ⁷/₁₆-in. brass tube with ¹/₄-in. FIP threaded end
• Two ³/₈-in. FIP caps
• Two 1-in.-OD × 2-in.-long stainless steel tubes (made from Kurt J. Lesker catalog number SST-0100I tube, which is sold by the inch)
• Two ³/₈-in. ID shaft collars with setscrew (McMaster-Carr catalog number 6166K23)
• Seven ¹/₄-in. ID shaft collars with setscrew (McMaster-Carr catalog number 9414T6)
• ¹/₄-in. × 2-in.-long stainless steel, internally-threaded spacers for 4–40 screws (McMaster-Carr catalog number 91125A473)
• Brass screws (McMaster-Carr catalog number 92480A106)
• Brass sheet (0.015-in. thick, K&S Engineering)
• 1-in. ID vacuum rubber hose (Kurt J. Lesker catalog number T100)