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How Far Can You Throw That Bucket?

I’m presenting more detail on turbosuperchargers and bucket wheels to follow-up my previous posts, Gremlins, and Lazy Daisy’s Gremlin’s, Part 1 of 3, Part 2 of 3, and Part 3 of 3

During my research into gremlins, and particularly the gremlins infesting the 384th Bomb Group’s B-17 known as Lazy Daisy, I had to delve into a subject with which I am very unfamiliar, the mechanics of the B-17.

I am not at all mechanically-inclined, and in reading about Lazy Daisy’s gremlins (i.e., mechanical issues) some terms were more familiar ( like “broken piston heads,” “dropping oil pressure,” and “runaway props”) than others (like “lagging superchargers” and “throwing a bucket”).

So, to learn more, I asked a lot of questions and did a lot of reading. Here’s what I’ve learned.

Turbosuperchargers

In Lazy Daisy’s Gremlins, Part 2 of 3, the 384th Bomb Group’s Fred Preller and John Edwards helped me explain these terms, and since then, John and the 384th’s Keith Ellefson provided me with new information that I think deserves further review.

Remember the comment by pilot David Rucker after he used Lazy Daisy on the 29 May 1944 mission (in Lazy Daisy’s Gremlins, Part 3 of 3)? Rucker suggested,

A/C (Aircraft) 222 (Lazy Daisy) be taken out of combat because of oil regulator supercharger.  You cannot stay in formation with the electronic type.

John Edwards shed some more light on superchargers with,

When we say supercharger, that was a common name for the component as a whole. The actual name is turbosupercharger. There were two types of superchargers used, frequently called stages. You have a first stage which is used at lower altitudes and the one commonly referenced for higher (combat) altitude… The supercharger intake is a scoop on the bottom of the engine nacelle [the outer casing/housing of an aircraft engine]. This scoop feeds air into the charger which is the conventional way a supercharger worked back then.

The comment from the pilot is important because the GE [electronic type like Rucker mentioned] charger is a very widely used supercharger. It’s function operated in two stages as Fred indicated… [see Part 2 of 3].  I can’t determine other known vendors for the superchargers so for now I can only say that the tech data … clearly states the supercharger must be connected to an oil pump. These instructions apply to the B-17F and G model aircraft and Lazy Daisy is a G so this tech info applies. Therefore I can’t explain why the pilot mentioned the ‘oil one’.

Note: John is referencing a section named Removal of Turbosupercharger from B-17 Airplane of the book World War II – General Electric Turbosuperchargers.

With John’s new information, I’m not sure why Rucker phrased the reference to both the “oil regulator” and “electronic type” superchargers as he did either.

Apparently, the different models of B-17’s used different supercharger types and the transition from the (older) oil regulator to the (newer) electronic type came between the F and G models. I had determined that on all of David Rucker’s missions, up to the point of piloting Lazy Daisy on 29 May 1944, he had been assigned only G model B-17’s.

Combat Data Specialist Keith Ellefson told me that it was still possible that some of the G models Rucker had flown might still be of the older oil regulator type. Keith said,

I don’t know if all the G models were equipped with electronically controlled superchargers. I suspect that some of the early Gs were built with the oil control system until the inventory of oil control systems was used up and then the electronic system was phased in to replace the oil control system.

And even if Rucker had only flown the electronic type, Keith added,

Pilots would have to be briefed/trained on the difference between oil regulated and electronic regulated superchargers as the new ships came into the inventory. The controls for each system are different and it would be immediately apparent to the pilot when he got into the ship for a mission. In reality, I am sure that each pilot in the squadron knew which ships still had the oil regulator system and which ships had the electronic regulated system. From what I have read, the electronic system was a big improvement over the old, oil regulated system.

Keith also shared some information written by Wellwood E. Beall, who was Vice-President in charge of Engineering at Boeing Aircraft Company, that indicates that the electronic system was a “significant improvement” over the oil regulated system. The link to Beall’s document is below in the Further Reading section, and Beall’s more comprehensive text with illustrations in PDF format follows in the list.

Wellwood Edmetson Beall, who died in 1978, was an aerospace pioneer – an airplane designer and engineer – who had major roles in developing the B‐17 Flying Fortress, the B‐29 Superfortress, and the Boeing 707. In particular, for the B-17, Beall ordered continuous modification in the B‐17 Flying Fortress to meet changing battle conditions over Europe in World War II.

The History of

Turbosuperchargers

The information from Fred, John, and Keith led me to search the internet to learn more and I found a most interesting article in Google Books about the history of turbosuperchargers in B-17’s. Since it looks to be from a publication that is now in the public domain (a compilation of the 1945 issues of Air Force – The Official Service Journal of the U.S. Army Forces), I want to share part of it here.

In early March, 1939, Lt. P. H. Robey took a YB-17A up to 25,000 feet in a test run and clocked its speed at 311 mph. This was 100 mph faster than a B-17 had ever flown, even faster than any of our fighter aircraft had flown at that altitude. The test flight was an astounding performance for those days, but no one thought of it as milestone in the development of jet propulsion in this country. Yet, indirectly, that’s just what it was.

If that test flight had been unsuccessful, all orders for turbo-superchargers on B-17s would have been cancelled, for it was the turbo that produced the 100 mph margin in speed – and in early 1939 the turbo-supercharger definitely was on the spot. At the time of the flight, orders for turbos on B-17s had already been technically cancelled. The paper work had been initiated and forwarded to Washington. Boeing Aircraft and the AAF [US Army Air Forces] had lost faith in the turbo. For 20 years, the AAF had struggled with the gadget only to have one disappointing flight test after another. The Robey test used a turbo that was equipped with a new regulator, the final hope for assuring reliable performance.

As soon as the B-17 rolled to a stop after the record-breaking flight, the telegraph wires to Washington began to sizzle. Headquarters read the test results, threw the cancellation papers in the waste basket and issued a directive that all AAF high altitude bombers should be equipped with turbo-superchargers from that date on.

~ “Growing Pains of Jets” by Major Robert V. Guelich, Air Force Staff, June 1945 issue of Air Force (The Official Service Journal of the U.S. Army Forces)

For more information about turbosuperchargers, including the entire article “Growing Pains of Jets,” refer to the Further Reading list below.

Bucket Wheels

(And what it means to “throw a bucket”)

The 384th Bomb Group’s Historian, John Edwards, shed a little light on the bucket wheel that the pilots’ referred to “throwing,”

The wheel on the bottom of the [super]charger, which looks like the carousel of an old slide projector, is called ‘the bucket wheel’ as I found in [Roger] Freeman’s “The B-17 Flying Fortress Story on page 55.

The article, “Growing Pains of Jets” also explained the pilots’ phrasing of “throwing a bucket.”

The search for high temperature alloys [which could withstand the stresses of hot turbine wheels] was stimulated primarily by the AAF development program to the turbo-supercharger. This program was kept alive by a handful of men who refused to lose faith when time after time the turbo-supercharger would overheat and throw its buckets out of the turbo wheel.

~ “Growing Pains of Jets” by Major Robert V. Guelich, Air Force Staff, June 1945 issue of Air Force (The Official Service Journal of the U.S. Army Forces)

But the Pilot Training Manual for the Flying Fortress B-17 presented by the Aviation in World War II website explains turbosuperchargers and bucket wheels in short order in a section on Turbo-superchargers (links in Further Reading below).

Each engine on the B-17 has a turbo-supercharger which boosts manifold pressure for takeoff and provides sea-level air pressure at high altitudes.

To operate the turbo-superchargers, engine exhaust gas passes through the collector ring and tailstack to the nozzle box, expands to atmosphere through the turbine nozzle, and drives the bucket wheel at high speed…

…The amount of turbo boost is determined by the speed of the turbo bucket wheel.

As for the gremlins who liked to antagonize the pilots of Lazy Daisy and other AAF aircraft in WWII, I think disrupting turbosuperchargers and bucket wheels were probably a favorite pastime, and seeing which gremlin could throw a bucket the furthest must have been a competition for bragging rights. How far can you throw a bucket?

Please browse through the Further Reading links below for further (and quite interesting) reading about turbosuperchargers and bucket wheels and some excellent illustrations of the B-17’s mechanical parts.

* * * * *

Further Reading

Design Analysis of the Boeing B-17 Flying Fortress by Wellwood E. Beall (webpage)

Design Analysis of the Boeing B-17 Flying Fortress by Wellwood E. Beall (PDF document)

Aviation of World War II: Turbo-superchargers

Pilot Training Manual for the Flying Fortress B-17, Published for Headquarters AAF, Office of Assistant Chief of Air Staff, Training

Supercharge Me: How Boeing Helped GE Reinvent Jet Travel (GE Reports)

The Turbosupercharger and the Airplane Power Plant – General Electric, January 1943

Turbosupercharger Field Service Manual – General Electric

“Growing Pains of Jets” which begins on page 24 of the June 1945 issue of Air Force (The Official Service Journal of the U.S. Army Forces), and starting on page 441 of the 1433-page downloadable PDF document. To download the entire 1433-page PDF document, click the sprocket in the upper right corner of the page, then select “Download PDF.” Note: Air Force is a book in the public domain that Google has made available in digital format. Terms of Service available through a link on the landing page.

Sources

Wellwood Beall’s Obituary from the New York Times

© Cindy Farrar Bryan and The Arrowhead Club, 2020


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