Zenit-E parts

As an Industrial Design student, one of the things I have to do is analyse products on design, function, and use of materials. What the people of the Applied Techology class usually want us to analyse are garden tools and small power appliances, but there's no reason why I couldn't extend the concept further to, say, an entire Zenit-E. After all, wasn't I the guy that took one apart till the Point of No Return, and is now stuck with a pile of metalwork that was once a camera? Sure, I could just take my loss, but I'm too much of a curious student and a camera enthusiast to not take the opportunity to see how the Russians constructed cameras. And I'm enough of an enduring altruist to let the world look over my shoulder.

From an engineering point of view, the most remarkable component of the Zenit-E is its robust, one-piece, die-cast body. The reason it's so remarkable (and why you don't see them that often, not even in Leicas or Nikons) is that it's really hard to uphold the small tolerances required for a precision optical instrument. For instance, you have to avoid mechanical effects like shrinking and cavity forming when the liquid metal is cooling, which means avoiding large wall thickness differences, which means a very conscious design stage. Also, the interlocking dies you use to form such complicated geometry would be extremely expensive, hard to manufacture, and only lasting a few ten thousand cycles. These reasons combined make it a very uneconomic process. However, there are a number of distinct advantages to a one-piece body. One is that you drastically cut down on parts, because most of the geometry is pre-formed. The second is that the end product will be extremely solid and homogeneous, so more durable. The third is that it might even be a cheaper process for mass-produced products than making a number of loose parts and joining them together, because that implies extra dies, extra manpower, extra machinery, extra unforseen difficulties, et cetera. The overhead on those things becomes massive when you manufacture over 300.000 units a year.

In a free-market economy, most manufacturers wouldn't have chosen for a fully die-cast body like this, because it implies a couple of things. Your design cannot be altered halfway through production, because that would mean having to throw away your old dies and create new ones, which is prohibitively expensive. Also, your product would need to be mass-produced in massive amounts to make the investments worthwhile. The overhead costs would be enormous. Plus, the end product may be heavier than possible (as, indeed, the Zenit-E is). However, in a communist economy, most of these drawbacks are unimportant. Because there is basically no competition, factories can get away with manufacturing the same model for (tens of) years. Thus the numbers of manufacture are larger than in a free market situation, which can make this seemingly uneconomic process viable. Factories can work economically despite the efforts, because labour is cheap and the products don't necessarily have to generate profits. All of this was undoubtedly taken into account in the Soviet Union at the time, and the probably sensible decision taken to create a one-piece body.

A close-up of the body. The amount of detail captured by the casting process is huge, and eliminates a lot of postprocessing and extra parts. The one-piece body also acts as a solid base for the rest of the components. The screw holes were drilled in later.

The top plate is stamped from sheet metal. Stamping is a simple process that involves a press and a plunger shaped like the end product. The press drives the plunger through the blank (the unprocessed sheet metal slab), which takes on its shape. The plunger is then retrieved, the residual material removed from the edges, and the product is finished.

The holes were punched out later. Punching is a very cheap and simple process where you punch out holes in steel plate with a press. The Zenit-E uses standard diameter holes (24, 12 and 7mm), which makes the process even cheaper. The composite hole for the calculator dial might have been punched with a custom knife, or in two parts: first the circular part, then the irregular pieces.

As is visible on the inside, the plunger had a knurled face. This is done to apvoid slippage of the material and make sharper edges.

The little rubber ball that prevents the wind lever from damaging the top plate (only present on later models) is fixed on the inside with a small ring bearing.

The X synchro contact is screwed onto the top plate with a nut.

The mirror cage is a fairly simple element that is constructed on a cast metal base. It has lots of small metal parts that are all screwed on. The working is simple and easy to understand: as the L-bar on the bottom is tilted by a wheel in the bottom of the camera (not shown), it flips up the mirror. When the wheel recedes, a spring moves the mirror back down again.

The L-bar translates its movement onto the mirror by a small wheel. The wheel moves along a curved trajectory, which means the mirror is not raised with uniform speed. (This is evident when you operate the L-bar by hand: the end of the swing is much faster.)

The spring that moves the mirror back into viewing position.

The back of the mirror is furbished with fake leather that acts as a hinge. Probably mechanical hinges were deemed too prone to corrosion and degeneration.

The lens mount is a simple milled component. The screw holes were drilled.

The latch that locks the back door is cut out of strip metal by punching, and is bent on one side to create the tab. The entire element is also slightly bent to create a spring-like tension. (Effectively the only force that keeps the back door shut.)

The light meter itself is an OEM component, as the label indicates. I have no idea where they were made.

The light meter is encased in a cast metal part with room for the needle and the contacts. The whole assembly is screwed in the top plate, with the wires hidden under the prism. Through the photo-electric effect, the selenium cell creates a current that is translated to a movement of the needle. The light meter is a standalone component and gives no information in itself; the user has to read meaning into the movement through the calculator dial.

This mask on the inside of the camera behind the mirror is a nice piece of formed sheet metal. This is a delicate and finely crafted part. It's very difficult to create refined pieces like this, and bending them exactly to spec. It's painted (a somewhat reflective) black to absorb scattered light.

The dial under the wind lever. This part was first milled, then drilled.

The calculator dial. Looks like the dial above, but isn't identical. Is also first milled, then drilled. Then engraved and numbers painted in a paint-engraving process that I haven't figured out yet.

Miscellaneous rings. These are all milled. perhaps apart from the black one, that looks (with its homogeneous thickness) like it could have been stamped out and then calibrated.

Miscellaneous rods. These were all milled; perhaps the long, small rods were drawn first, then milled. The sprocket teeth were probably made by moving a chisel with the tooth shape in negative along the bar's axis, to ensure parallellity. All of the rods have little inserts that were fitted in and "squashed" into position at the ends.

The self-timer mechanism is a standalone component that is triggered by a push at the top, and outputs a movement to the shutter at the end of its trajectory. This is basically a clockwork motor with an inertial flywheel as a delay mechanism. A very nice piece of fine-mechanical engineering, this was installed pre-assembled behind the sprocket.

The cogs in this part are very delicate and resemble those in small clocks. This part was probably manufactured in a fine-mechanical workshop, then relayed to the main production belt.

The wind lever is first stamped from a metal plate, then bent, then polished (perhaps), and then used as an insert for the plastic injection-moulding process that forms the finger grip at the end. An insert is a metal part you place in an injection-moulding die before you inject the plastic; the liquid plastic then encapsulates it and the two are joined for life. The part of the lever inside the finger grip is probably punctured for a better grip.

These aren't all the parts in the Zenit-E, but they're a representable minority. I think that what shows is how the Russians worked with fairly basic techniques that were available even to small workshops (like bending and punching), with the notable exception of the rare use of injection-moulded plastic and, of course, the die cast body. The Zenit-E is not the most sophisticated camera in the world, and some of the mechanisms are fairly dodgy (like the leather hinge for the mirror), but you have to give it credit for being one of the last hand-built, authentic workshop cameras.