[Minneapolis 109-509 Partial Motor]

This motor is currently in store as an exhibit in one of the corridors of the Department of Mechnical Engineering in the University of Minneapolis in Minnesota, USA.

A Komet/Walter fan from North America, Mark Ganzer, has kindly supplied a collection of pictures which he took on a trip to the University.

In the background of the picture below, you can see that the motor is displayed alongside an information plaque which labels this as an HWK 509-A2 "Rocketjet".


Known History.

Currently, the provenance of this motor is unknown. One can imagine that it its history is similar to all other US 109-509s, in that it was brought back to the USA for evaluation after the war. The interesting feature of this motor is that it has been sectioned at various places, to show the construction details. It could have been done for the captured aircraft fair at Wright Field, or as part of the training programme at the University of Minneapolis - to date, each suggestion is completely speculative.

Correspondence with the Department of Mechanical Engineering has so far failed to bring forward anyone who knows anything of the motor's history.

The following photographs were taken in July 2001.

Photographs © Mark Ganzer - used with kind permission -


Mark's photographs show that this is a substantially complete motor, but has a number of parts missing or disassembled. The most obvious piece missing is the fuel pump / turbo-pump unit. Also gone is the electric starter and the tachometer for the turbo-pump.

[Minneapolis 109-509 Partial Motor]

The C-Stoff control plate has been cut away in several places, irritatingly, one of those places seems to be the manufacturer's data plate which cannot be seen.

The motor has not been regularly attended to, as it has a generous coating of dust, but it has been fitted to a suitable stand making it moveable (although the bolts holding the motor to the frame are reversed, the frame being on the trailing side, rather than the forward face, but that's not important). Interestingly, the curved pipe hanging over the side member of the thrust plate is the steam outflow pipe from the steam generator, which should have been attached to the turbo pump. This might mean that the other pieces of the motor are still within the Mechanical Engineering Department - they may be displayed, or used in demonstrations elsewhere.

Although not shown in this view, the combustion chamber has been sectioned, giving an excellent view of the internal structure.

The data plate is missing, but the pictures clearly show the accessories unit and gearbox, and even though the pump unit is not fitted, there are bolts for the electric starter motor and tachometer. There is no evidence of fuel line air ejectors. These factors make this model of motor most likely an "A-1" series, despite the label.

[Minneapolis 109-509 Partial Motor]

The close-up of this section of the frame, minus the missing turbo pump, shows some interesting details. The two gear wheels shown would connect to a toothed spline on the end of the turbo pump shaft. The furthest wheel drives the tachmoter, telling the pilot the rotational speed of the turbo pump. The nearest wheel (on the right) is the drive from the electric starter motor, which spins up the turbo pump to operating speed during starting. The connector on the top right of the picture is one of the connections for the starter motor.

Just visible between the gear wheels is a narrow strip which is the internal end of the dip-stick, for checking the oil level in the accessories gearbox.

[Minneapolis 109-509 Combustion Chamber]

One of the most interesting aspects of this motor is that the combustion chamber has been sectioned to afford an excellent view of the interior.

The red area in the picture is the interior of the combustion chamber, where the combustion of the fuels occurs. The burner plate with the twelve fuel injectors is shown very nicely, as is the arrangement, designed to produce full combustion and an even thrust over the range of power settings.

The yellow area is the cut surface of the combustion chamber, and shows the space where the cooling C-Stoff flows to reduce the temperature of the chamber during power running. The shape of the combustion chamber and the narrowing of the exhaust venturi is quite clear.


The second picture shows a very interesting detail through the cut section of the combustion chamber. The narrowing and shape of the throat of the venturi is illustrated well.

[Minneapolis 109-509 Combustion Chamber]

The large space below the venturi narrowing is the space into which cooling C-Stoff is first introduced into the combuster chamber lining space. As you can see, an inner sleeve directs the flow towards rear of the chamber and then back through a narrow gap between the combustion chamber inner shell and the liner.

The flow then curves around between the two parts of the combustion chamber towards the burner plate. In this picture you can make out the nine (one group of five and a second group of four) swirl vanes, which appear as dots on the inside of the liner. These are square section wires, welded to the liner, which spiral around the surface of the combustion chamber, directing the flow of cooling C-Stoff around the outside of the combustion chamber to the rear, where it is collected in a ringed area (shown in the illustration above) and fed back towards the body of the motor via the fuel filter.


Photographs © Mark Ganzer - used with kind permission -
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