Tag: Vacuum turbine

Vacuum to the ANT-18’s fuselage

We recently added the second wing to our ANT-18. That made it look a lot better. We fixed a few wiring problems in the main control box, and replaced external power wiring. We installed our restored Telegon oscillator, and cleaned, lubricated, and tested the turbine. Like our other turbines, the Toby Deutschmann suppression condenser had to be replaced.

Broken vacuum connection between turbine and spindle.

The vacuum hose that connected our turbine to the spindle was broken in a couple places. The connection was unlike models Esp and C-3 whose hose is short and at the same height. The ANT-18 has an additional separate set of commutators hanging below the standard 28 rings. This assembly causes the vacuum entrance to the spindle to be much lower than the turbine’s vacuum source. Our vacuum connector was obviously not an original part; it consisted of several short pieces of 1-½” PVC pipe poorly glued together. We still don’t know what the original connection looked like. We decided it would be better to have a slightly longer hose with a smooth bend rather than the additional two sharp 90-degree corners introduced by the broken connector pipe. We ordered a hose that was ultra-flexible; however, it only came in bright blue or green. After a bit of sanding, primer, and flat black paint, it now looks like an old rubber hose.

New vacuum connection hose.
New vacuum connection between turbine and spindle.

We had to try it out, by turning on the turbine. We had just completed restoration of the turning motor, so that was in good shape. The pitch and roll bellows looked and felt pretty good, but as soon as vacuum was applied to the fuselage, the pneumatic cloth on the pitch bellows ripped. That’s the next task – rebuild the pitch and roll bellows.

 

They don’t make em like that anymore —

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.

Original Tobe Deutschmann motor condenser VS replacement

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.