Armstrong Whitworth Overhauls

With the requirement to focus on manufacture of arms for the First World War, Armstrong Whitworth looked to diversify their engineering output once the Armistice took effect.  In 1920 they introduced a single-cylinder four-stroke petrol engine in 4, 8 and 13 h.p sizes, and a paraffin model in 3, 6 and 10 h.p. sizes.  A high tension magneto provided the spark and cooling was by convection using a water tank.  The numbers constructed were low – possibly no greater than 900 units in total.  The majority were thought to have been used in lighting generator sets.

As readers may recall, this engine featured in a post before Christmas.  It has now been overhauled and is in running condition, with a trolley even manufactured to make it mobile.

There were numerous repairs to be carried out once the engine was in part-form.  Including this flange on the oil pump.

Marking out a new cap for the carburettor.

Cutting out the profile of the carburettor cap.

Machining the various profiles for the carburettor cap.

The finished cap, installed on the carburettor.

Shims for the big ends.

The crankshaft after removal – this required cleaning up and preparing for the new main bearings as well as turning the journal for the flywheel to the correct diameter.

Manufacture of the new main bearings to carry the crankshaft in the engine block casting.  Made as one piece and then split for each end required.

The engine, which is understood to have been used to drive a water pump (or lighting set?) in North Yorkshire in its latter years, did not have a flywheel with it, so a suitable Lister example was adapted to fit.  Here the slot for the keyway is being cut.

The main engine casting, which includes internal shelves and passages to distribute lubricating oil around the moving parts.

The governor for the engine can be seen here, as can some of the oil shelves.  The engine has been made to a high quality, and is positive reflection on the capabilities and reputation of its manufacturer.

Fitting the crankshaft – the new bearing can be seen in the second photo – it’s the clean bronze coloured item around the crankshaft.

With some suitable wheels and axle recovered from the Colliery, a trolley was manufactured to enable the engine to be more readily moved around.

The engine-mounted plate describing the process for starting on petrol and transferring to paraffin operation once the engine is hot.

Priming cup (for petrol) and spark plug hole.

Drilling the mounting holes for the spare magneto found in the stores for this project.

Drilling the mounting holes for the spare magneto found in the stores for this project.

Progress as of mid-January – the engineer is complete and in running condition, the trolley awaits a pair of handles and foot and a suitable water tank is being made (using a redundant air tank from Gateshead 10) for the engine cooling arrangement.  A pulley is also needed, to take the belt drive that the engine will now use to impart its energy into whatever it is being asked to drive.  The engine was always something of an ornament in the garage, so it is nice to see a locally-built and fairly rare industrial item returned to working order and in such a way as to allow it to be better understood and used for engagement purposes at the museum.  The engine will be partially re-painted, but it will be kept in it’s working guise, as whilst the black paintwork may be relatively recent, it already has a patina that is quite authentic for the garage setting where it will reside.

The winter programme of work on the AW Car has been making good progress, with its volunteer team usually carrying out one day per week on it, and the workshop staff filling in when they have time available.  As has been reported previously, the cylinders have been removed and it was planned to leave the main block in place, along with the gearbox.  However, as work progressed it made more sense to remove the gearbox at this stage as well (as a machine shop overhaul) and then the whole engine.  This necessitated more dismantling, but also released the wooden bulkhead, which one of the volunteers will be restoring to remove fading and water damage.

The gearbox, after removal.  There were a few issues that had manifest themselves in use, and a problem with the way in which reverse gear was engaged but would make a commotion when reversing when there was no load upon it.

One of the bearing housings on the gearbox casing had insulation tape, a plastic cap and jubilee clip fitted, to prevent oil egress – a more professional and enduring solution has been made by boring holes circular and the purchase of new bearings (available off the shelf!).

One feature of the car that is missing is the mechanical drive to the distributor.  There was evidence of it, but the drive itself was absent.  Chris has drawn the arrangement up, to enable 3D prints to be made.  This is all quite Escher-like in appearance, especially when rotated 90 degrees – but as will be seen further on, it workers rather elegantly!  The gears are a paired helical spur gear with parallel teeth.  They were drawn as a pair like this, with the 45 degree helix enabling (it was hoped – rightly as it turned out) that they could be rotated 90 degrees and still mesh correctly.

The 3D printed gears were trial fitted to the engine…