Bob & Ron's vintage Link Trainer (aka Blue Box) restoration adventures
We built a Meikraft Model of the Link Blue Box Trainer. It is tiny – 1/72 scale. Easily fits in a 3” diameter dome. Lots of hidden detail inside the fuselage like rudder pedals, yoke, an instrument panel, and even wood trim. Ours is #171 of 550. The kits are out of production, but show up on ebay.com from time-to-time.
After all the bellow rebuilding, lubrication, and reassembly; the moment of the first turning motor test arrived. We could not believe it when the motor jumped into action with just a small vacuum from a vacuum cleaner hose held near to the port. Clockwise with one port, counterclockwise with the other. It is great fun to watch the sliding valves sequence the bellows. We decided to skip the timing alignment for the time being – sometimes it’s best to quit while you’re ahead.
As we started to become familiar with our new Blue Box and how it was supposed to work, we needed to decide how faithfully to the original we could restore it. We went through each subsystem, checked to see if it existed in our trainer, and to what level it could be restored. We felt that a total faithful restoration was beyond us because components such as wax capacitors, selenium rectifiers, porcelain switches, etc. were bad due to age or just plain worn out; exact replacements no longer exist. Phenolic is used throughout the trainer. Cloth-covered wire, real rubber, real leather, and no plastic make it hard to faithfully replace parts in today’s world of available materials. This trainer was missing key pieces such as the wind drift mechanism, connectors, and even the spindle. We hope to restore it to at least some level of flyable. For a functional system, we felt that some level of compromise was in order. We settled on using everything original that we could, but were willing to substitute modern materials and components where necessary. Our rule-of-thumb is “if today’s technician needed to get the system ready to train a pilot, what minimum compromises would he make in order to make it functional?” We also want the system to look nice, so modern paint, glues, etc. are in order.
The very first subsystem we tried to restore was the vacuum turbine. And the first irreplaceable component turned out to be its Tobe Deutchmann dual noise-suppression condenser (left side of picture). We measured this big old wax capacitor — zero microfarads. We substituted two small modern caps. More about the turbine is discussed in the “Blue Box restoration hints” pages.
On September 15, 2016 Bob K, my long-time friend and business partner, said “do you want to go look at a Blue Box?” We had both worked in flight simulation engineering at Wright Patterson AFB as civilian employees for many years. From 2000 – 2021 we founded and operated Protobox LLC in Riverside, Ohio providing flight simulation support, visual displays, and specialized electronic circuitry to the simulation industry. The Link Trainer known as the “Blue Box” or “Pilot Maker” was the first real flight simulator Ed Link invented and produced to train instrument flight to pilots. Bob showed me an old ebay.com advertisement for a Blue Box located in Kentucky. Next day we took my 6′ x 10′ enclosed trailer and were off to Isen, KY for a look at a Blue Box. We knew very little about a Blue Box, other than pictures, and one we had seen at the local Air Force Museum.
The Blue Box was among several simulators Dan had for sale. His garage, barn, and carport were like a museum of old flight simulators. He had two T40’s, the first trainer I had ever supported. He even had 2 of only 18 Link Blue Box helicopter simulators ever built. — and an old Willys 1946 Jeep. Bob negotiated the price, then the adventure began. The Blue Box never fit in my trailer; we returned to Ohio empty handed. Next day we rented a 19′ Ryder truck with a lift gate and headed back to Kentucky. This time success, and the following day the Blue Box was in our high-bay building in Riverside, Ohio awaiting much needed attention.