History of the Blower Roots Blower Company, Connersville Indiana

The idea of the rotary positive machine was not a new one. Many earlier examples are known, the most famous being the Pappenheim Engine, perhaps dating to the 17th century. The German engineer Franz Reuleaux described this engine as well as a number of other early examples in his Kinematics of Machinery. These devices all used a similar principle, that of two opposite rotating wheels geared together by teeth or lobes. They were used as pumps and ventilators among other purposes.

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Reuleaux also states that shortly before the Roots invention almost identical blowing devices were constructed in England. He cites one made by George Jones of Birmingham in 1859 and an earlier one of 1853. it is not impossible that the Roots simply copied recent British work and secured an American patent for it. However, as far as it is known, there would have been no way for the Roots to know about the British work, and the examples cited by Reuleaux preceeded their work only by a year or two at any rate. Thus, although the idea was an old one, the Roots should be credited with perfecting the design and first putting it into operation on a large scale.

This is the conclusion of the London-published Engineer of 1867 reporting on the exhibit of the Roots company at the Paris exhibition: "Mr. Roots has the merit of having brought the machine independently to such a state of perfection as to render it superior in many respects to the ordinary fan, and to make it an aspiring competition with the blowing cylinder."

The first major use of the Roots blowers was in cupola furnaces. The first two experimental machines were tested in foundries and large numbers of blowers were manufactured for this purpose. A large blower for the West Cumberland Hematite Iron Works in Workington, England, was described in 1872. At the Philadelphia Centennial, Roots blowers were praised by the Scientific American Supplement as efficient and economical devices for use in foundries:

In a force-blast blower there are two great benefits: economy of power and certainty of result. The blowers exhibited by the Messrs. P.H. and F.M. Roots, of Connersvi1le, Indiana, seem to come up to these requirements.

In reference to economy of power, they, operating by a regular displacement of air, which is forced forward in constant quantity at each revolution use all the power applied either in driving the machine or forcing the air forward. Friction is slight. The internal parts do not come in contact during running, simply approaching each other as close as possible without an actual contact; this renders the blower practically air-tight. The power applied is absorbed but slightly in running, and is therefore almost entirely applied to the work of forcing the air forward. Results are as far as possible certain with these blowers...In securing the best possible results, the proportional amounts of iron to be melted, fuel used, and of air supplied in a given time, should be fixed and unvarying. As these blowers measure and force forward a definite quantity of air at each revolution, constancy of melting conditions are secured."

In 1917 industrial Management magazine reported that rotary blowers were still largely used for cupola work. It also stated that they were most economical for pressures between 1/2 pound per square foot and 8 or 9 pounds per square foot.

Another major use of the blowers was in mine ventilation. This was a relatively new field and Roots blowers constituted some of the largest installations in the 19th century. Already by 1870 several Roots blowers were in use in mines of the Comstock lode. Two of the largest Roots blowers ever made were installed at the Chilton Colliery near Ferryhill, Enqland in 1877. The impellers each had a diameter of 25 feet and were 13 feet wide. The maximum capacity of the two machines was 200,000 cubic feet per minute. The ventilator was housed in an engine house with a perforated roof. The Engineer of London, reporting on the results of tests run on various ventilators, concluded that the Roots machines were the most efficient that had been installed in mines. The other ventilators compared were those of Cooke, Waddles, Rammell, Leeds, and Guibal.

Of the many uses to which the blowers were put, certainly the most spectacular was in the underground subway constructed by Alfred Beach in 1867 under Broadway in New York City. This "aeolar" had an iron shell 21 1/2 feet high and impellers 16 feet long. At 60 revolutions per minute it produced 100,000 cubic feet of air a minute. Costing $20,000, the machine was transported on five large platform cars. The "Western Tornado", as it was called, was pictured in a contemporary pamphlet with the figure of a man inside to show the huge scale. The "aeolar" provided the power for a 22 seat passenger car which ran on tracks from Murray to Warren streets. The car was literally blown to one end and then sucked back by the action of the machine. Other uses were in pneumatic tubes, aeration and agitation, supercharging and scavenging on diesel engines, and in vacuum processes.

Most of the patents which the Roots brothers took out after 1860 were modifications of their first scheme. In almost every case these alterations were intended to allow a closer fit, less friction in operation and cheaper means of construction.

The case was modified In a series of patents. Originally sheet metal bent to the proper shape was used. In 1864 the Roots patented a shell made of two pieces of cast iron joined together by metal plates. In 1868 they further modified the design by placing packing strips in the case which formed the contact surface for the impellers. This was done to cut down on friction and to allow the cast iron case to be made rough since the impellers were no longer in contact with it. This reduced the costs of boring and polishing. Later in the same year a patent was obtained specifying soft metal or plaster of Paris for this purpose.

The shape of the impellers was also modified several times. In 1886, the Roots patented a design for impellers which were constructed of a metal core adjusted to the desired shape by wood strips. This was more economically constructed than solid iron impellers and allowed them to be renewed without entirely reconstructing the entire impeller. In the same year, the Roots also modified slightly the shape of the impellers creating the Figure-8 shape which became very common thereafter. The design of the impellers was subsequently modified in 1868, 1881, and 1882.

This week’s column is by Jay Boggess. Next week we will return to the Delta Municipal Power Plant for Part II.

Pretty quickly, early on – when it comes to diesel engines, you hear the word “Roots Blower”.  But who IS Roots?   Today in the era of Wikipedia, this is an easy question to answer, but not when I was a kid.

I’d first heard of the “GMC Roots Blower” associated with supercharged dragsters & hot rods.  Later, while reading my father’s 1944 textbook “Internal Combustion Engines – Analysis & Practice”, I discovered a cutaway section of the General Motors 2-stoke CI (compression ignition or diesel) engine, below:

Click for larger – GM photo, from Internal Combustion Engines ©1944

Later, I learned that Cleveland Diesel, Fairbanks-Morse and Electro Motive Division diesel engines all had Roots Blowers, but no one ever explained why it was called the Roots Blower.

In 2003, a random visit to the History Colorado Museum in Denver came across this artifact:

Click for larger – History Colorado Museum – Jay Boggess photo – 2003

A mine ventilation blower for ventilating underground hard-rock mines, built by the P.H. & F.M. Roots Company, Connersville, Indiana.  The placard listed a date, but the low-res digital pics of the era do not allow me to zoom in – other sources point to the mid 1880’s or so.

Another datapoint came from another random visit, this time to the nearly preserved Bethlehem Steel blast furnaces in Bethlehem, PA (thanks to my former EMD colleague Mark Duve, who insisted we stop).

Click for larger – Bethlehem Steel blast furnaces – Bethlehem, PA 2004 – Jay Boggess photo

The building in the foreground of the photo was unlocked, we ventured inside and discovered these:

Bethlehem Steel blast furnace blower rotors – Bethlehem, PA 2004 – Jay Boggess photo

Very distinctive, two-lobed Roots Blower rotors – look carefully and you will see counter-weighted steam engine eccentrics on the end of the rotors.  Inside the same building were the matching horizontal steam engine cylinders for driving these rotors (I took photos but the passage of 16 years has lost those).  I later learned that blast furnace blast supply was one of the first uses of Roots Blowers.

So who were P.H. & F.M. Roots?  Wikipedia points to a 1931 book, “Indiana One Hundred And Fifty Years of American Development” which provides most of the answers.  Philander Higley and Francis Marion Roots were brothers.  Francis was the youngest brother, born in 1824, went searching for gold in California in 1849, came home in 1850 and started working with his brother Philander in manufacturing.  They patented the “Roots Positive Blast Blower” in 1866.  Francis passed away in 1889, Philander passed in 1879.  Their company was purchased by Dresser Industries in 1931, and renamed the Roots-Connersville Blower Company.  In WWII, they produced low-pressure blowers for blowing ballast tanks in U.S. Submarines, as well as centrifugal blowers for various low-pressure/ high-volume uses, eventually submerged in the vast Dresser product line.

Roots Blower Applications:

Submarine Ballast Tank Blower:

Click for larger – collection of the Bowfin Museum, Pearl Harbor, HI – Jay Boggess photo Roots blower on USS Bowfin, Pearl Harbor, HI – Jay Boggess photo

This is listed on the drawing as a 1600 CFM blower, designed and built by the Roots-Connersville Blower Corporation, Connersville, Indiana.  The driving motor is a 1750 RPM, 90 horsepower, intermittent-duty DC motor.

To digress extensively – WWII submarines had two systems to blow their ballast tanks – 3000-PSI stored compressed air reduced down to 600 PSI to start the surfacing process and 10-PSI low pressure air supplied by blowers to finish the job once a submarine surfaced.  It was this low-pressure job that either Roots Blowers or centrifugal blowers were utilized.  Another interesting use was that when a sub is submerged, various tanks are vented inboard the sub, raising the internal pressure of the boat several PSI above atmospheric pressure.  If the hatch were immediately opened, the rush of air was known to launch sailors overboard.  Instead, the hatch between the conning tower and control room would be shut, the boat surfaced and the bridge hatch opened.  While the captain checked to see if the coast was clear, the low-pressure blower is started finishing the blow of the ballast tanks and reducing the excess air pressure inside the rest of the boat.

Fairbanks-Morse Opposed Piston 38D Engine:

Click for larger – From the Fairbanks-Morse LSM 38D 8 1/8 Manual – collection of Paul Strubeck

The WWII era FM 38D manual does not use the word “Roots Blower” but instead refers to it as a “Scavenging Air Blower”.  The FM 38D blower spins at 1450 rpm and provides 6000 CFM at about 2 to 4 PSI. The Direct Reversing version of this engine used a set of linkage and air valves on the blower in order to direct the air in the proper direction when the engine is running astern, thus the blower is running backwards.

General Motors Cleveland Diesel Engine Division (CDED) 278A Marine Diesel:

Link to Benyuan

Additional reading:
Buying guide for industrial blowers Cleveland Diesel Engine Division Diagrams – Click for larger Click for larger – Cleveland Diesel Engine Division Photo – Collection of Jay Boggess

Cleveland Diesel mounted their single Roots Blower on the front of their engine, essentially shortening or lengthening the blower to fit the air flow of the 6, 8, 12- or 16-cylinder models of the 278A, as the photos and following table illustrates.

16-278A – 1700 HP Destroyer Escort Engine: 1650 RPM, 6.5” Hg, 5630 CFM
12-278A – 875 BHP Army Tug Engine: 1650 RPM, 5.5” Hg, 4380 CFM
8-278A(NM) – 800 HP Non-Magnetic Minesweeper Engine: 1833 RPM, 6.5” Hg, 2950 CFM
6-278A – 480 HP 720 RPM Tug Engine: 1358 RPM, 4.5” Hg, 2180 CFM   

Cleveland Diesel Engine Division Photo – Collection of Scott D. Zelinka Cleveland Diesel Engine Division Photo – Collection of Scott D. Zelinka

Thanks to Scott Zelinka for the above Cleveland photos showing a pair of the Spiral rotors used by CDED. The clearances between the rotors is set at .024″ (on the 12 and 16 Cyl) and .018″ on the smaller engines. I find it downright amazing that something with this complex of a shape – and interlocking none the less, could be machined so exacting by hand, and mass produced at that, long before computers and CNC.

With the new Cleveland Diesel 498 engine, a small Roots blower was used in conjunction with the exhaust driven turbocharger to provide for lower RPM scavenging. EMD would solve this issue with their own turbocharger on the 567. A centrifugal clutch drives the blower off of the timing gears that would disengage at a certain RPM and allow the turbocharger to freewheel.

Cleveland 498 diagram Click for larger – The blower is in the same location as the 278A series, behind the intercooler here.

EMD 567/645 Roots Blown Engines

Electro-Motive answered the Roots Blower question in a totally different way than its GM sister division CDED.  EMD also had four different engines to support: 6 – 8 – 12 – 16 cylinders.  EMD picked one design of blower, then used that one blower for the 6 and 8 cylinders model and a pair of blowers for the 12 and 16 cylinders, changing the blower gear ratio (and blower RPM) between 6 and 8, and 12 and 16 engines, gaining economics of scale and fewer replacement parts to support.

Below is the 8-cylinder 567 model:

Click for larger – Cleveland Diesel engine manual photo – WWII Army ST tug – collection of Jay Boggess

And here is the mid-1950’s 16-567C model. Note the directional air intake, a sign that this engine was likely built for stationary power generation.

Click for larger – Cleveland Diesel Engine Division Photo – Jay Boggess Collection

The 16-567C pic illustrates another clever design feature that EMD incorporated.  By placing the Roots Blowers high above the crankshaft (driven by the engine’s camshaft drives), EMD designers provided a niche for a generator underneath the blowers, saving overall length of the engine/generator and thus overall length of the locomotive.

These are just a few short uses of the Roots Blower – several other manufacturers have used them, and coming in one of the next parts on the Delta Municipal Power Plant, we will see a giant Roots-Connersville centrifugal blower used to feed the big 31A18 engine. Roots Blowers are common on many different industrial uses outside of engines.

While many thousands of Roots Blowers have been built, I believe their day in the sun has passed.  From my days at the Alaska Railroad, EPA emissions regulations were starting to close in on the Roots Blown engine.  I do not know the specifics, but the GP38-2s AkRR owned