This is a very interesting Walter motor. It fits the pattern of an "A-2" motor, but has been considerably modified to allow for cooling of the combustion chamber by T-Stoff, instead of the more usual C-Stoff. Walters had experienced difficulties with C-Stoff cooling of the combustion chamber. Under heat, the C-Stoff was prone to deposit copper into the jacket space, fouling it and causing inconsistent cooling.

C-Stoff was also a comparatively costly fuel, and Walters were running a constant search for alternatives to use with the peroxide. However, the cooling (heat transfer) properties of some of these were insufficient for optimal operating of the combustion chamber, and T-Stoff cooling was seen as a viable alternative.

This motor was almost certainly a motor for use on the test stand, rather than flight, as several sections of the pipework are routed outside the main motor frame by significant amounts. This arrangement would not have fitted into an Me.163 fuselage, and there is no record of these motors being test flown in other airframes.

Known History.

There are no concrete details at present. The motor has been on display at the Museum in East Fortune for a number of years. The exhibit description notice has the following footnote,

    Presented by the MOD 1972 . 236

The note is an accession number, the first part of which may be the accession date. This is as yet, unconfirmed. In the time the motor has been with East Fortune, it has not undergone any major restoration work, and has not been overpainted. That makes it a good example for studying materials, castings, part numbers, quality assurance stamps etc.

Following some additional research, the history of this motor configuration has slowly been coming to light, and is discussed in a separate page, which closely links this motor with some post-war peroxide chemistry research at the Ministry of Supply Establishment at Trauen.

Description.

The motor is well preserved. Apparantly in near original condition, it bears little corrosion. The manufacturer's plate is present, as is a "C-Stoff" stencil, on the starboard side.

Leaving aside the extra modifications, the nature of an "A-2" motor can easily be seen. It retains the basic pattern of the "A" Series motor; the box frame, large thrust plate, and vertically positioned main control unit, all recognisable as derived from an "A-1".

However, the differences to look out for are, the repositioned steam generator, dropped down on the thrust plate to a position near the bottom. This is fed by a T-Stoff header tank. Because of this, there is no electric starter motor and the whole port side of the motor frame is open, due to the lack of requirement for the accessories unit, with gearing off the starter motor. These are all quite typical of an "A-2" motor.

All photographs © Shamus Reddin
  - With thanks to the Museum of Flight and the National Museums of Scotland -

The starboard side of the motor. The main fuel flow and equalisation unit and fuel control valve, and the C-Stoff fuel pump inlet are clearly visible.

The blue pipe in the left foreground is the output from the steam generator - this passes around the outside of the motor case and onto the centre of the motor, connecting to the fuel pump turbine.

Ignoring the large diameter, silver return pipe from the combustion chamber, clearly shown passing over the top of the motor back to the main control unit, this view shows some of the distinguishing features of the "A-2" Series motor.

There is a silver T-Stoff header tank for motor starting, (on the right of the picture). The steam generator is (just visible) repositioned, inverted on the lower rear face of the motor thrust plate. There is no port gearbox casing, leaving the end of the main pump unit visible, and there is no electrical starter motor.

The empty space on the port side of the motor shows the electric starter motor is not included in this design.

My feeling is that the entire fuel pump has been repositioned more outboard than would be usual with a standard "A-2". The amount that the C-Stoff fuel inlet protrudes beyond the motor casing seems more than expected. But I'm not certain; it requires careful measurement.

This view shows the output from the T-Stoff pump being diverted under the motor casing, rearwards to the cooling jacket of the combustion chamber. The T-Stoff return appears over the top of the motor to the underside of the main control unit and back into the fuel combustion system.

The extraordinary combustion chamber arrangement of this motor is very different from a standard "A-2". The combustion chamber outer casing is of very heavy guage steel with strong weld lines and a heavily bolted flange. Compare this, with the more elegant "A-1" combustion chamber of the N.A.S.M. 109-509.

The T-Stoff outflow from the fuel pump arrives at the trailing end of the combustion chamber jacket in a single pipe. But a double outlet, merging to a single pipe takes the heated T-Stoff back towards the motor fuel flow control system.

The number of plugs and tappings visible in this system may be for inserting measuring equipment, draining fluids or priming prior to running.

This motor's arrangement is almost certainly just for testing purposes, as the dimensions, together with the added depth of the large diameter return pipes, would not physically fit into an Me.163 airframe. Should the experiments have proved successful, then a redesign to fit an airframe would have been required.

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