Without a method of converting the power produced by the engine into useful thrust an aircraft would just be sitting still and creating a lot of noise and not get anywhere. In the past, all kinds of different propeller designs were tried: sometimes flat wooden blades, from one bladed counter weighted to multiple blade models rotating at various speeds.
Variable pitch propellers have a distinct advantage compared to fixed pitch models. This translates into a more fuel efficient, higher performing aircraft with much improved rate of climb and shorter takeoffs for those tight places!
Hoffmann Propeller GmbH was established in 1955 by Ludwig Hoffmann and Richard Wurm. Together with six employees they started production for motor glider propellers. Overhaul and manufacture of U.S. aircraft propellers formed a second leg to stand on for the company soon afterwards. In the course of time, both scopes expanded strongly and design and manufacture in two other sectors had become important: propellers for hovercraft and blades for wind tunnels. At the moment Mr. Dipl. Kfm Richard Wurm jr. is the owner of the company.
The company designs and is manufacturing propellers for the general aviation, airships, vintage aircraft, air cushing vehicles (hovercraft) as well as blades for wind tunnel and for other special applications. Contact them for your exact requirements.
The propeller is – together with the engine – one the major components of an aircraft. Its characteristics considerably affect performance and perceived noise level. Only, if the propeller is individually adapted to the aircraft, optimum efficiency is achieved. Hoffmann guarantees such a customer work taking into consideration all requirements.
The big advantage of the wooden composite construction is that blades - even single makings - are manufactured individually so that no moulds or castings are required for this. The low weight of the base material is an additional advantage of this way of construction. The design criteria are safety, performance, affordability, service and these have the utmost priority at Hoffmann.
A typical Hoffmann propeller consists of three major sub assemblies: the hub, blade and spinner:
The hub is made of forged aluminum alloy which guarantee high strength. Axial movement of the piston is transferred to the pitch change knob by a fork and pitch change blocks, whereby the blade angle is changed. The pitch change is limited by mechanical stops. The corresponding blade angle can be adjusted when the propeller is installed on the craft.
The composite blades are made from hardwood in the root section and light Spruce for the blade part itself. It is then covered with fiber reinforced epoxy (FRP). Blade vibrations are dampened by the wood ensuring a long life. Several layers of polyurethane paint is used for finishing, which is UV resistant. The tips are painted in a different color for visibility when the propeller is rotating.
The spinner is one piece of aluminum alloy and is screwed to the spinner bulkhead which is also made of an aluminum alloy sheet.
For the general aviation market they manufacture 2 - 5 bladed propellers in wooden composite construction which are either fixed pitch, ground adjustable but most are variable pitch, hydraulically or mechanically controlled with optional provisions for reverse thrust and feathering up to an input power of 400 kW and a maximum diameter of 4 m. Considerable importance is given to low noise operation. The product range also includes propellers for unmanned vehicles (UAV).
Hoffmann Propeller can be contacted at the following addresses:
|Hoffmann Propeller GmbH & Co.KG|
|83022 Rosenheim Germany|
Text and images used with permission (pending) of Hoffman Propeller.
The next link shows a video tour of the factory and how these blades are made. For more detailed blade and pricing information we refer you to the website of Hoffmann Propeller.Written by EAI.