Bolex DA




DA Page 2              Bolex G & P


Bolex made a number of machines for more than one gauge; the DA/PA type, which could also show 9.5 notched films, and the "G" series in numerous guises (for which follow the link above).


bolex early_c_002c      Bolex early_C_003     bolex early_c_004a     


Here, courtesy the PPT, is a very early Bolex of the PA/DA shape. This is a Model C; when I saw it, there were no 9.5mm parts and I assumed it was 16mm only. Note the ornate logos, the pushmi-pullyu still frame device (altho' I suspect now it is incomplete), the switch (far more use than the direction change lever we got later), the one-piece lamphouse with simple pin fixing and ornate top. I think that, with the front adjuster leg out of the way, the lamphouse will swing open, maybe to keep light from the film until you were ready As you will see later, there could be a "skirt" missing from the bottom of the lamphouse. Less obviously, there are no moveable sprocket retainers. The rollers are held in place with nuts, hidden behind a large gearwheel inside the mech. Which means that to clean them, I had to remove the pin on the sprocket shaft, unscrew the grub-screw in the sprocket, remove the lamphouse and the back of the projector and slide out the large gear wheel on the other end of the sprocket shaft. It now runs bootiful, tho'. I also noted that it has a mesh filter much like the heat filter on later machines, which operates centrifugally.

The shutter (2 blades only) is much thicker metal than the later paper-thin jobbies. The rewind handle is removable but, remarkably, has survived. I will deal with this early type of machine at greater length below.


This Bolex PA (9.5 only) has been adapted to halogen lighting, 900ft spool capacity and separate switching for lamp and motor. These machines, and the dual-gauge DA, give about as good as you can get from notched films, but you do have to manually re-start after each notch, whereas the Baby and Lux do this automatically.

Bolex DA_stackCan a boy have too many Bolex DA's? The problem is, only one of them has the 9.5 parts, so if anyone has some spare......

I recently found that I had a spare 9.5 gate, sprocket and one spool spindle for a Bolex DA. I managed to machine a spindle from a spare G3 one, which is very similar but longer. The gate was more problematic. I had not previously realised that the 9.5 gate differs as between the PA and the DA. The PA slots to clear the 16mm claw are quite a bit lower down than those for the DA. The gate I had found was a PA so I had to lengthen the slots. For some reason, it didn't have the cut-out in the side of the gate to allow the notching mechanism to engage, so I had to machine this, too. Why is nothing ever simple?

Here are a couple of sets of instructions for this range of machines. One is a pdf to avoid me (and you) having to toggle thru a number of separate pages.

daInstra1     daInstra2      thumb daInstra3     daInstra4



There was even a sound version......

DAsdad1     DAsdad2     DAsdad3


Discovering interesting facts about the Bolex DA. I can now see there were (at least) two models, one like the PA but the other with a large rounded protrusion on top. This appears to cater for a much larger shutter. The only one I've seen is in this pic Dino sent me.


Ken Finch has referred me to Gerald McKee's projector book for the story on the Bolex DA and its shutter. I think I have now got the story straight in my head. The original PA and DA did not have the rounded top and used an ordinary 2-blade shutter. The problem with this seems to have been flicker, tho' I must say it is not something I have noticed. Bolex, however, introduced the 1937 Model, which had a larger diameter shutter, rotating much faster, giving three obscurations per frame, so eliminating flicker. However, the faster shutter made more noise and, because it had a big shutter with a single "hole" of about one quarter of the total, tended to stop with titles obscured, requiring manual intervention. At the same time, a more powerful cooling fan was fitted, enabling a 400w lamp to replace the earlier 250w. Naturally, people tended to use the 400w lamp in earlier models which didn't have the improved cooling, hence the usual scorched lamphouse sported by most machines. Better than scorched titles, I suppose.


Have now moved on to a Bolex DA, 1937 Model wiv the bigger, faster shutter, bigger cooling fan ect. In accordance with the best principles of projector storage and the relevant British Standards, this machine has been kept in conditions of unregulated cold and damp and had in consequence seized up solid. Aluminium castings show that white "bloom" in places and some steel parts, especially the more delicate, have rusted. There appears also to be distortion of the rear plate/mech cover which, as it journals a number of shafts, is rather serious and probably accounts for most of the seizing up.

 bolexshutter2     DA 007     DA 008     DA 009

First is a general shot of the mech, showing not just one but two fibre gears. The sprung arm just left of the upper fibre gear has swung down to cover a bearing for the shutter (see pic 2. There is another, adjustable, bearing point in the rear cover). The felt pad on this arm rides clear of the rim that surrounds the gear until a notch triggers a stop; the pad then falls (spring-assisted) to brake the shutter. The gear on the shutter engages with the upper fibre gear as part of the train that delivers the step-up in speed. A significant difference which is not perhaps immediately obvious is the pivot for the arm that runs from below the big gear to the cam shaft. In the earlier DAs, this pivot was mounted directly onto the chassis. Here it is instead mounted onto another, shorter arm, which is then itself pivoted on the chassis. This shorter arm has a spring from its LH end across behind the scissor thing, but the arm is not connected to this in any way. I am at a loss to explain either the additional arm or the scissor thing. The felt pads do not appear to be linked to anything else which might, as I had half expected, apply them as brakes when the mech stops; they seem to be in contact all the time. I do not understand the function of the shorter arm; what it does (in run mode, not notch stop as in the pic) is to shift the position of the longer arm in such a way that the stud on the gauze screen, which sits in the shaped hole in the head of the arm, moves across from one side to the other. The lower end of the arm, which contacts the stirrup, also moves, but I do not see what either action achieves. Anybody know?

I am fairly confident the main problem is with distortion of the back plate. I have tried leaving the machine going in project mode as I insert the various screws; if I tighten them the mech slows or even stops. I can't really see a way of fixing this, tho' I think it will work well enough with the screws only gently tightened. 

Timing the shutter is a pain - each of the many times I have removed the back plate to try yet another approach, the shutter falls out and timing is lost. I need to make a final adjustment so that I can make an empirical test of whether the shutter stops without blocking the gate, or the frequency with which one needs to adjust the inching knob to see a title. I had to take the rear gate out because the notching mech was stuck, due presumably to the rust you can see, so I thought I would show you the complex system of arms that links the various bits of the notching mech. Complicated and fiddly (and that assumes you can even figure out how to remove the gate in the first place).


DA Page 2             Bolex G & P