Friday, October 30, 2009

More Disassembly

When I started this project, I never realised how many components made up this Pathé Marignon projector.

above As an example, look at the lens holder in this photo. A very intricate assembly built around a precision aluminium casting. The lens itself is threaded and can be push into and out of the holder against a sprung pin which mates into the thread on the lens.

The pressure plate is visible in the foreground and in use is held against the gate by pressure from two small springs, just visible in this photo.

Some of these screws and components are very small and require a jewellers screwdriver to move.

Unfortunately the paintwork on this piece, although in better condition than that on the main chassis, had also been affected by 50 years of oil and grime. It will need repainting, and to do that means completely disassembling it back to the plain aluminium casting, then removing the old paint and re-spraying it with new paint.

A collection of small used yoghurt containers proved invaluable for this project. As each subassembly is taken apart, all the pieces are placed into one or more carefully labelled yoghurt containers.

above Here is a view underneath the projector base, after it has been removed from the metal box which my father had fitted and which housed the controls and electronics for sound-on-film. You can see the large brass flywheel poking through a hold cut into the metal base. The flat brass plate is about 6mm thick and is used as reinforcement for the comparatively thin steel chassis. Onto this brass plate the flywheel bearings were mounted.

None of this will be needed in the refurbished machine, because my plan is to remove the sound capability and restore the projector to its original silent condition.

above Here is the flywheel and its shaft and bearings viewed from above. This entire assembly was added by my father in the 1950s. It’s certainly very solid. Together with the metal box mounted underneath the machine and containing a heavy transformer for the exciter lamp, these additions would have added considerably to the weight of the projector. This entire assembly will be done away with. The flywheel is not needed for a silent projector and the metal base has been drilled and filed so many times that it would be impossible to repair. It will be replaced by a new base.

above You can see the shutter assembly here (on the right). It fits onto the end of the main drive shaft (on the left). The shutter does one full turn for every frame of film that advances. As you can see, the light is interrupted three times in each cycle. During one of those interruptions, the film is quickly pulled down by the claw mechanism

You can see a rounded-triangular cam on the end of the drive shaft. This moves the claw mechanism up and down while at the same time, a ramped ring on the shutter assembly (you can’t see the ramping easily in this photo) pushes the claw forwards when it needs to grip the film. It’s a simple yet ingenious mechanism which works quite reliably.

above Taking things one step further, here is the old metal base with the flywheel assembly removed. This is one for the dump.

above A few steps later, we can see the inside of the aluminium chassis with all but the motor and claw mechanism removed. I am impressed with the quality of engineering and the finish in this machine designed and made in the early 1950s. The chassis however, like almost every part of this machine, is covered in a thin layer of oil. The outside grey crackle-finish paint has changed colour from its original neutral grey (visible in parts newly exposed) to a dirty green-grey. It needs to be completely stripped and repainted.

above A view from the rear gives a clearer look at the claw mechanism visible above the motor. You can see the layers of grease, oil and dust on the unpainted metal surfaces.

above A closeup of the motor and claw mechanism with the rear of the film gate visible at right. The motor is a subassembly which mounts onto the main cast aluminium chassis with four screws and a set of eight rubber washers to isolate the motor vibration from the main chassis. Unfortunately, as can be seen here, these rubber washers have long ago perished, not helped I’m sure by the presence of oil. They will need to be replaced also.

above The lamphouse subassembly is made from folded sheet steel, painted black. At the left you can see the condenser lens which focusses the light onto the film gate. The lamp is 110 volt 250 watts. I’m not sure whether such lamps are still manufactured, but luckily the lamp in the machine still works and my father had the foresight to purchase a stock of spares which may come in useful. Note the brass and porcelain lampholder visible through an opening to which the fan cowl connects, ensuring an updraft of cooling air to prevent the lamp from overheating.

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