Propeller Off Boulevard Engine

[B Hosticka]

Hello All,

This propeller came with a (the) Boulevard Engine of 1910. The engine is about 20 to 25 HP four cylinder inline Overhead Cam with the thrust bearing for Tractor installation. The total weight of the engine is 85 pounds dry.

There are no markings whatsoever on the propeller but the metal hub flange is stamped S.&.F. It appears to be made of Mahogany with four plys. The airfoil is almost symmetric with the maximum thickness at 50% chord. It is nothing at all like any Clark or NACA airfoil. There is no leading edge protection. The rest of the hub is still frozen on the crank of the engine.

I vacillate between thinking that this is original with the engine and thinking that it is a later replacement. Arguments for it being original is the primitive airfoil and constant chord. Arguments against is the small diameter. But then, the engine power is very low and the hole and bolt circle are very small which argues for a small propeller.

Diameter: 72”
Pitch From Measurements and design exercises is About 50”
Engine RPM (1911 Literature) 1200
Engine HP (1910 sizing) 20-25
Chord (constant) 5 ¼”
Thickness at hub 3”
Hole: 1 ¾”
Bolt Circle 3 ½”
Bolts 6, 5/8”
Flange Diameter 4 1/16”



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[B Hosticka]

Similar Airfoil

Hello Again,

In the recent WWI Aero magazine No.192, there is a clear photo of the framework for an Antoinette wing which shows a similar airfoil shape to that of the Boulevard Propeller. It is perfectly symmetrical and is defined by segments of circles. Thus there is no difference as far as the shape goes between leading edge and trailing edge. Only the angle of attack defines the leading edge.

This is evidence that at the time in question (1910), symmetric airfoils were not far out of the accepted practice and lends weight to the possibility of this propeller being original with the engine..

[Bob Gardner]

Many thanks for telling us about your prop. I know how difficult it is to research these early props. Some are hand carved, with no markings whatsoever. Others have minimal markings, sufficient to warrant many hours of research, but insufficient to allow a definitive answer to be found. I have spent hundreds of hours doing it. You have got much nearer to a definitive answer than I have ever achieved. Frustration, your name is early propeller. Hopefully this forum might become a focus in years to come of all our individual knowledge.

[B Hosticka]

Boulevard and Benoist

The continuing story of the Propeller off the Boulevard Engine:

The Boulevard Engine Co. of St. Louis shared quarters with the Aeronautical Supply Co. (ASC) at 3932 Olive St until 1910. When ASC moved to new a new location (6664 Delmar Ave.), there is a mention of an inventory clearance sale where "[...] a six-foot laminated propeller, beautifully finished with a five-and-one-half-foot pitch" was offered (reported price of $27.50). Boulevard Engines continued at the Olive Street location after the ASC (which evolved into the Benoist organization) moved out.

The above propeller is indeed a 72 inch laminated propeller but the estimated pitch from observations seems a bit less than the 66 inches. It is difficult to reconcile either a 72 x 66 or a 72 x 50 propeller with a 1000 to 1200 RPM engine of any power. But the hard evidence is that both the prop and engine exist as a pair with no indication of modification to the Propeller.

I guess that modern design methods were not followed in laying out and matching propellers to engines and airframes in 1910.