Ditmar Duo

 

 

DITMAR DUO

 

There was getting to be rather a lot of literature such as instructions, so it's now on a separate page, see Ditmar Instructions.

 

Be warned if you have a Ditmar Duo; the wiring can be in a highly dangerous state (see below where this warning repeats).

 ditmar1     Ditmar1a     ditmar1b     Ditmar1c     Ditmar1d     ditmar2

Her is a pic of a Ditmar and some leaflet stuff. Ditmar produced a unique version of the dual-gauge machine. It had twin paths for the film, alongside each other, with a lamp and a lens that moved across to serve whichever gauge was in use. Most were black but some had a light-coloured snake-skin-like finish (Bob Andrews had one). I suspect that these were earlier machines, where the projector could be removed as a unit from the base, which held the motor et al. 9.5/16 and 8/16 versions were produced (and, I later discovered, an 8/9.5 version).

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Be warned if you have a Ditmar Duo; the wiring can be in a highly dangerous state.

The Ditmar duo is quite a complex and sophisticated machine. I acquired an 8/9.5 one at Argenteuil last year and have just (Feb 2012) gotten around to looking at it in more detail.

 ditmar3     ditmar4     Ditmar5     ditmar6    ditmar7     ditmar8  

The motor drive belt from the small pulley on the right to the larger one (centre) had almost vanished - just a few dried-up scraps left. Note, however, (Pic 1) that there is a second drive belt. This set-up appears to be because of the still picture mechanism, which is on the lower shaft. There were only a few inches of mains lead left, so I have had to go inside. The Instructions I had originally envisage the entire projector body lifting away from a base carrying the motor. This projector is not like that - you have to go in thru the bottom (pic 2). The great bulk of the wiring is stiff, single-strand copper, covered with what looks like a heat-resistant sleeving and seems to be in good nick. The mains lead and the lead to the lamp were both badly perished, with the inner insulation of a 2-wire fabric-covered cable crumbling to dust, leaving the machine in a highly dangerous state. I later found that there was a 3rd problem wire, running from the main Paxolin board seen in Pic 2 to the motor speed resistance wiper, looping twice round the shaft of the wiper because the point of connection rotated with the control and flexibility was needed, hence the use of the same perishable type of insulation.

The mains cable enters thru the small hole (bottom centre in Pic 1, also visible in Pic 2), and goes to two solder tags on the reverse side of the Paxolin board in Pic 2; I have marked where with black dots. (The other holes are about setting up the mains supply for the pilot lamps and the motor). So one has to remove the securing screws for the Paxolin board and push it around, bending all those single-strand wires, to get at it.

Note there was no earth.

The lamp supply is interesting. In Pic 1, you can see lower left a triangular-shaped Paxolin insert. For use with a lamp matching the mains voltage supply, which can be from 110 to 250, the two top holes are fitted with a shorting plug. Otherwise, a resistance can can be attached. In either case, the switch below the Paxolin insert controls the lamp, altho' there seems to be no interlock with the motor switch, so it is possible to burn films if care is not taken.

(LATER. I lied; there does seem to be an interlock at least on this 9.5/8 model).

It seems to me that this set-up would make it possible to fit the Ditmar with a lamp of any wattage and voltage you choose, so long as have a suitable tranny to plug in. It is the other side of this Paxolin insert that the connections for the lamp are found. In Pic 2, this insert can be seen to right, with the body of the switch visible. One has to remove this switch to be able to get at the contacts and solder new wires in place. Pic 3 is a closer view with this switch disconnected - fortunately it has screw terminals so it's relatively easy. You can see another piece of Paxolin stood out on spacers from the side; it is this that carries the terminals for the lamp wires. Then we have to go into the lamphouse for the other end of the wires. The lamphouse slides across for the different gauges, and Pic 4 shows, with screws partly undone, one side of the slide fittings - note also provision for a locking screw. Pic 5 shows the underside of the lampholder removed from the slides; access to the lampholder seems good but, in fact, thanks to the the precise location of the screws securing the wires, it is impossible to access them without removing the holder completely. Note also the silvery thing underneath the lower pivot for the lampholder. This is a shaped aluminium duct that takes some of the cooling air from the fan towards the gate. The Ditmar Instructions appear to say that it can take a lamp of 500w and maybe more. I'm not convinced - both elements of the condenser were split right across, and the only likely cause is excess lamp heat. Fortunately, I had a spare.

To revert to my point about the complexity and sophistication of the Ditmar. Note first that it is Austrian made, like Eumigs. The Ditmars seem to be well and sturdily constructed. The spool dogs are very neat, being simply turned round to change gauge, and the film retaining roller mech is very satisfying - pulling and turning raises and lowers the assembly very smoothly, a bit like some early B&H machines. There are two pilot lights and provision to operate using a resistance or tranny if desired. We have a still picture mech, too, (useful for lamp cooling without running the mech) and two mini- reservoirs for centralised oil distribution, accessed via a side cover.

The range of variation that is beginning to emerge is somewhat of a problem. The earlier models seem to be those where the body lifts off the base (this is the type in the Instructions shown); the change to the later more conventional access via the base is quite substantial. Having found the problem with the wiring, I checked into my original 9/16 Ditmar. This seems to have undergone the same sort of repair to the wiring before it reached my hands. Other differences can be seen - plastic rather than chrome for the inching knob and framing, for example, suggesting a late model - and, irritatingly, there are now only two holes in that external triangular Paxolin insert. And the lamp only seems to work if the two holes are shorted, and the switch seems to do nothing at all. I don't have any later Instructions to cover this and tell me what is deliberate and what might have been altered when it was re-wired.

The biggest defect with the Ditmar, of course, is that it only has 300' - 400' spool capacity, and the shape and style of the arms (top and bottom are identical) means extension pieces are likely to look pretty ugly.

Ditmar13     Ditmar14     Ditmar11     Ditmar12

A front view of the 8/9.5 gates and a rear view of a set of 9/16 gates. The back view in particular shows the cleverness of the design and its simplicity in use. At the top of the front, fixed gate it should just be possible to see the holes which fit over pins on the mech. The bottom of the gate is then secured by the pin shown passing thru the two "brackets" and into the body of the machine - the pin just has a a split end like many plug/connectors and is a push fit. The rear gate fits into smaller versions of the slides used for the lamphouse and is a very neat, satisfying push fit. Note there is a thing that looks like a cam on the left end of the cranked rod that moves the gate in and out of position. This seems to act to prevent one fitting the gate in place without setting it in the open position. Note also that we have leaf springs in the form of metal strips, with a single point of contact.

Moving on to the claw. The first pic is of my 8/9.5 machine, the second of a junk 8/16. This latter seems to be a lot older. In the first pic, the slots at the rear of the claws should be engaged with the rod just above them - this was taken while I was fiddling about. I could swear, too, that this rod is bent to the left towards the end nearest the viewer, but I have no idea if this is deliberate or not. It don't seem to affect the 9.5 side, which runs fine. Note that, in line with the general quality of the machine, we have optical framing working by moving said rod.

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I seem not to have shown you the Ditmar extension arms I made.

ditmar9       Ditmar10

The first pic shows where I cut the existing arms. There are several different types of fitting screws for the arms, including ones where the screw thread that goes into the projector is fixed into the knob by a splined section, which is presumably push-fitted. In order to remove this to make all the work and painting easier, I had to drill thru from the outside end of the knob and knock the splined section out. This hole will now need re-covering but, fortunately, there is also a pattern of knob with a shiny bit in the centre, which I can easily copy and still look original. Pic 2 shows how I did the arms. Given the taper of the arms, I was reluctant to just add a straight piece, which I think would look ugly. Instead, I tapered the extra section as a continuation of the original taper. This brought the wide end nearer in size to the diameter of the round section, where it is not really noticeable. Because of the shape of the projector, the lower arm needs to be significantly longer than the upper.

The proof of the pudding will be in the eating, but I have reservations about the type of construction I used, but only in the context of using glue - some form of brazing would be fine. But I have never been a great fan of the Araldite school; I just don't think it's strong enough to hold joints together if it comes under any strain. What I used here was something called J&B Weld, which claims it is really tuff, but I still have my doubts. If the arms don't hold up in practice, I shall have to find a way to do a bit of aluminium brazing.

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I have a Ditmar which I was thinking of selling on. As usual, I checked it out first and found that the motor was being very lethargic, barely reaching projection speed even at max volume. Now, the Ditmar is a multi-voltage machine; the base has a pair of screw terminals of the usual type for this.

 Ditmar15     Ditmar16

Now, as I understand it, these two screws adjust the voltage for the motor and the pilot lights only; the lamp has to be the right voltage for the supply. So the motor should work fine on either 110v or 230v, so long as these screws are in the correct position. I tried first with 110v, and got the weak motor; then I tried 230v and got a better motor but also, after a minute or two, some smoke and you can see in pic 2 that those two coil things seem a bit cooked on the left of the pic. I assumed these were suppressor things (there is a second resistance like the motor speed control that I assume does the voltage) and, being cooked, could be discarded. But then the motor didn't work at all, and I have been waiting to be fit enough to clamber up into my garage loft to see if there is anything helpful among my Ditmar spares.

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I have been re-familiarising myself with the Ditmar Duo. I had given up (at least a year ago) at a point where the motor on an 8/9.5 model had been running very slow and there had been some burning/smoke. I suspected a coil fitted as part of suppression and had identified a spare coil when the complexity of fitting the damn thing overcame me. Without it, the machine wouldn't run and there it rested. 

When I got it out again, I looked again at how the coil was connected, using my 9.5/16 machine as a guide. The coil wires are incredibly thin and there are four of them, all to be connected in the tangle of wires on the rear of the paxolin board in the base, which was a bit daunting. (I shall add this to the end of the Ditmar page, which I have repaired, so you can see the pix.) The only suppression arrangement I have previously encountered involved a capacitor across the motor brushes, and now that modern electronics are not really worrried by spark interference, you can remove this sort of suppression without problems and the motor still runs fine. So I could not understand why this was not true of this coil. So I consulted my guru, who mentioned that coils like this could actually be part of the circuit, so naturally the machine would not run without it. I took a flyer and inserted wires to shot-circuit the two sets of coil wires (it's a double coil), This did the trick and I was back in business. This was where I found out that I had probably mis-diagnosed the problem in the first place, at least in part. The real problem was with the motor, which continued to get slower and slower and finally stalled. Unsurprising if this had in turn led to the issue with the coil in the first place. 
Luckily, I had a spare motor among my bits and pieces, tho' it was a real pain to remove the old one and fit the new one and finding all the right connections to make (being reversible, the motor has four leads).  Once I had the motor out, the problem was easy to find: lack of lubrication. I have not kicked myself too hard for this, since it is pretty much impossible to lubricate without removing the motor. It has ball race bearings at each end, and the only access is via holes where you would expect to find oil holes on a conventional motor with a simple brass contact bearing. However, the bearing race itself covers most of the hole, and lubricant would therefore need to travel along the side of the bearing, then turn a 180 degree corner to actually get into the bearing cage and do any good. You might think you have squirted stuff in, but it would have great difficulty reaching the right place. A piece of truly crap design. Once lubricated, a quick bench test with jump leads connecting to the projector showed it was working fine.

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I have been doing some finishing-off work with my 9.5/16 Ditmar Duo. You may recall that a long time ago I showed pix of some extension arms I had made to allow the use of 900' spools, but I have never actually gotten round to mounting them. I was a bit concerned at the time about how sturdy the joins were; certainly for the bottom arm, these concerns have been borne out. This arm needs to be quite long, to keep a big spool out of the way of the base of the projector and below the path of the light from the lens. It also gets a strong pull from the take-up belt, and the way the arms are mounted leaves only a very smalll area to bear all the load of holding the thing in place. The last pic below shows just how far off true the arm can get. However, moving the washer seen between the knob and the arm to between the arm and the lug of the machine makes quite a big difference; this is because it is a tapered washer I made to help offset the various influences taking it out of line (not least that I think I made the extended arm bent in the first place!). As I suspected, at least one of the joints is weak and I think I shall have to fix something rigid along the length of the arm to stiffen it up, for which the Ditmar has fortunately plenty of room. However, despite being a tad flimsy in some ways, the arms certainly look fine when the reeels are on - I was afraid they would be out of scale and make the machine look unbalanced.

Ditmar17     Ditmar18     Ditmar19     Ditmar20
   My other project has been to fit a separate lamp switch at the front of the machine. At the back, there is a triangular paxolin thing (see the first pic of the second row at the top of the page) with 2 (in some cases three) connections and a switch below. Shorting the two connections, or the top two of the three, allows the lamp to work. My 8/9.5 machine has 3 connections and the switch serves also to turn the lamp on and off. This seems a pretty useless facility as it duplicates the effect of simply removing the shorting plug and is, being at the back, in completely the wrong place and very difficult to operate. The 9.5/16 one has had the switch set up to give dim/bright switching for the lamp, but one is still left without any sensible way of turning the lamp on and off. I have sorted this by mounting a switch in a box under the base - pix 1 and 3 above should make this clear. I used a spare Ditmar motor switch and a very small plastic box. There is room for this because the Ditmar already has the fan housing and the voltage change connectors protruding below the base of the machine. Note also the length of the adjustable legs - I have left them at pretty much maximum extension for these pix. Since one only needs a bit for tilt or level, this length seems excessive. And you cannot get the paxolin cover of the base off without removing the legs completely, as they go thru enclosed holes in the paxolin and, to boot, it is very difficult to remove the screws holding the paxolin until the legs are off anyway! One ends up repeatedly doing large amounts of screwing and unscrewing of these mile-long threads when working on the machien, re-assembling for test and etc, etc, etc. Tiresome.
Anyway, back to the plot. Even with those legs, there is a limit to the size of box that can realistically be used and we are talking 110v or 240v here so we have to take care. I had to remove the screws from the connections on the side of the switch and do a bit of filing down just to fit the switch into the depth available. I then filed a small slot for the wire in the socket where the screw had been, to make space for the wires to fit and be soldered in place without exceeding available thickness. (This is part of the reason why there is a mini-junction box on the other side of the base, as I didn't want to have to unsolder those wires or have excess length flopping about. The other part of the reason is that I cut the darn wires too short.) The box is mounted onto some copper-clad paxolin board I had to hand, using countersunk screws. This board is cut away as necessary and held in place by the same screws that hold the main baseboard in place (and has the same holes for those legs).