How to make a single-frame motor for a Bolex Camera

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to HOME pageCopyright © ANI-MATO, J-E Nystrom, 1996. This information may not be published, transferred or distributed in any way without permission. However, you may publish the author's internet address:

Here you can see the switch and the axle, and also how to make the holder for the switch. The holder can be either soldered, or attached with screws and nuts to the base plate. The important thing is to adjust it exactly, so that the roller moves freely, the switch clicking once per turn.

Microswitches usually have markings, NC, NO and C. We'll use the NO (normally open) and C (common) terminals of the switch.

Here's the schematic on how to connect everything. (If you are unfamiliar with electric schematics, ask for help from an electronics hobbyist...) Bidirectional syncronous motors usually have 4 leads, but some may have only 3, some have 6. A 4-lead motor must have 2 of the leads connected together, as shown. A 6-lead motor will have leads connected in pairs. Check the motor specification and follow the color coding of the leads. The direction switch and capacitor should be built into the switch box, and also a connector for the pushbutton lead, as well as a suitable receptacle for the power supply's plug.

Here we see the completed motor from the top. On the right, you can see the connector for the trigger pushbutton's lead. Exactly how you attach the box and the components in it is not critical, but when routing the leads, make sure that a lead cannot be cut by a sharp metal edge! This may cause a short-circuit, heating your power supply. (It may even burn out it's internal fuse, making it unusable!)

When you have everything put together, it is time to finally attach the motor to the camera body.

Before you do that, you MUST set the cameras spring motor clutch (to the left of the winding crank) from the "MOT" to the "O" position, and the cameras side release (below the speed regulator) MUST be pressed and locked into the leftmost position, "M". Otherwise the camera will stall when you run the stop-motion motor.

IMPORTANT: When attaching the motor, the "fork" can be in two positions, since it is symmetrical. It MUST be attached so that the motor stops with the shutter closed. This is easy to check: Unscrew the lens, and look into the camera. You should see the film gate for 1/3 second when the motor shoots a frame, and then the shutter should cover it. If you see the gate after the motor stops, you must re-attach the motor after turning its axle 1/2 turn. Then check again. If you ever remove the motor to use the camera spring-wound, be sure to check this when you re-attach the motor!

The EFFECTIVE exposure time is 1/4 of a second: the shutter angle is about 130 degrees when fully open, and you should also consider the 25% absorption of the reflex prism. So, reading the exposure meter at 1/4 second is just about as exact as you can get. All this, of course, assuming that your motor runs at 60 RPM.