Rural Sonore

Details: Category: 17.5 Index

Rural Sonore

RURAL SONORE

A bad habit I fell into in the past was to post stuff to a What's New page but fail to copy it to the relevant main page. This meant stuff dotted about in the What's New Archive and in reverse order because of my habit of putting new stuff on top of old on the page. This is even harder to correct after the Great Software Disaster, so please excuse me if this section is a bit staccato and sometimes out of chronological order. There is a page with Instructions for the machine (inFrench, of course, but with a disagram or two) here.

I had a serious rush of blood to the head (Sep 06) and bought on French ebay 2 Pathé Rural Sonore projectors, that had been converted to 16mm, as most of them were. You may recall this was the first of the 17.5 sound projectors, basically an adaptation of the silent machine known over here as the Rex. This Rural never made it here at all; we got the Home Talkie, an adaptation of the French Natan 175 and, very briefly, the Super Rural, known here as the Super Talkie. Clear so far?

The Rural Sonore is very obviously a converted Rex, especially from the back, with the flywheel looking very much an afterthought. The main lamp seems to feed the sound optic as well. The arm arrangement at the front seems identical to that in the Super Rural/Super Talkie. I have only just noticed that the machine in the Kermabon illustration is different -no rear flywheel. There seems to be instead a large drum, presumably with a flywheel at the back of the projector, in a much more conventional arrangement with a separate exciter lamp. The Kermabon one must be a Mk 2. Or Mk. 1. The pix with blue backgrounds are from ebay.

I seem to have forgotten to take any pictures with the spool arms in place. As you can imagine, I have grandiose visions of re-converting one or both to 17.5. Note that the sprockets are housed in "turrets" attached above and below the mech. These are made of Mazac, which as you know can distort with time. In this case, it can cause the bearing for the sprocket shaft to seize up, which in turn leads to stripped gears.

Actually, I do have a pic with arms after all, as above. This is a working 16mm one.

If you blow up the gear pix, you can see one of the stripped gears from one of my machines (the other machine is fine); the long shaft is driven by the motor and in turn drives both sprockets. The second sprocket shaft is identical to the one shown, but is handed the opposite way. These would have to be re-made by a specialist firm. The 4th pic shows the claw mechanism. Lots of other problems too - one motor has the ends crumbling - Mazac again - which has caused the motor to become jammed. This is not a problem unique to the Rural - the Vox and Lux are also affected. I am pondering how to make new ones, and of course there is the problem of the cam. Problem is, getting work done by any of the handful of skilled engineers left in this country costs so much. Anyone know someone who does it just for love?

I did have a go both for a Super Vox (see under Vox) and for the Rural Sonore. It is not something I undertook lightly, as I simply am not very good at this sort of thing. I have never had any training in metalworking, what little I know is gleaned from books. Either because of astigmatism or some other personal defect, my eye is not at all true and I have great difficulty lining things up precisely etc. I also seem to have no spatial awareness whatever, and those things in IQ tests where you had to rotate a shape always had me foxed. As a result of all this, I tend to work very slowly; I have to figure out what and how to do and go over things repeatedly to avoid (most) of the sillier mistakes. To illustrate my difficulties, I carefully bought a 7mm x 0.75 tap and die to match the thread on the oilers for the Rural motor, then carefully used a 7mm by 1.0 tap, which means I shall now have to make replacements rather than simply re-using old bits.

Here are the original end caps, both sides, in 1 and 2, together with the putative replacement at an early stage. I decided straight away not to copy the round-ended appearance. A close examination should show you the Mazac cracks and distortion. Pix 3 & 4 show the new end at an advanced stage. It now fits, and I just have to finish off on the oiler holes (see above). Not very pretty inside, tho' this do not matter. You can see I've slightly mislocated the opening out slot on top (only done the one so far) and have broken thru at one point, tho' I don't think it matters except cosmetically.

In order to be able ever to do this again and record all the measurements I've used, I've drawn sketches for my records.

Once I've finished it, there is then the matter of testing to see if it will work. All sorts of reasons why it might not. A problem I have met before is that there is a point where the wires join the main windings inside where the wires get crimped and can fray or fracture - we're talking a respectable age here - and short circuit or just lose contact. Then the original jamming of the motor might have overheated it and burnt it out. Or the main rotor may catch the windings - space is very tight inside and it would not be that surprising if things had warped out of true over time. This would be a problem as, although motor rewinding is common, it's also costly.

The actual motor bearings are an interesting pattern. Instead of the ball race one might expect, the motor shaft passes thru a brass bush (see pic), which is held in place by a spring and and a washer secured by screw thru the holes in the motor cap. The main hole thru the motor cap is rounded at the outer end, and the brass bush is pressed against this by the spring. Basically, it allows the bearing to "float" to a degree, presumably to prevent alignment problems.

Nerdistan Celebrates!

There was great jubilation today throughout Nerdistan. People thronged the streets to celebrate the news that the new end cap for the Rural (see above) had been installed and tested and worked fine! This is a major step forward for Nerds!

I tried a new approach on the wires leading from the motor. As indicated below, there is danger from age and brittleness leading to the wires or their sheaths cracking and causing short circuits or even breaks. There was a specific kink point where it looked like this was happening; I thought I could see a glimpse of copper. A while ago I acquired from a car restorer's supplier (Frosts) a pot of liquid insulation - a rubber solution applied as a liquid and which then dries and hardens somewhat. I gave the dodgy place a good dosing with this, and it will I hope both insulate and give extra strength to prevent flexing of the kink at the critical point. Could get a bit of burning rubber tho' when the motor gets hot.

Incidentally, I am becoming more and more convinced that the Rural is just a Rex with an extra section added in which carries the sound head. All sound machines would need then would be a larger pulley on the motor to give a higher speed, tho in practice it would also need to be a fixed speed induction motor; the original silent Rurals had a normal motor whose speed was controlled by a rheostat. This makes a lot of sense and may explain a) where there are so few Rexes and b) why there is so much apparent variation in at least the 16mm soundheads (of which more some other time), but I don't have a basis for comparison of 17.5 machines. Maybe some were freelance jobs, with people converting their Rex's with the help of local engineers; maybe there were specialist converters - one of mine has an obviously proprietary (French) ACE sound unit. And of course, much of this and all sorts of ad hoccery would have taken place when the Germans demanded conversion to 16mm in 1941.

Once I have done one, it should be easier to do another as, with my drawings, I shall hopefully not have to work things out from first principles again. I've also bought some new equipment which should make it easier, too.

Here is the finished article, painted and ready for final fitting. I made the new inserts for the oiler holes to cover up my mistake in tapping the wrong thread. I'm really waiting to give the paint time to really harden off before fitting. Three coats of Satin black Hammerite; I baked it in the oven for an hour at v. low temp, made a pong. Dunno if this will work in drying the paint. Just before Xmas I managed to find a company who would make new geared shafts for me, which I hope to get by the end of this month. Turning my attention now to the design of new turrets to replace the distorted Mazac ones, and to the cam problem for the claw. Which is another thing, come to think of it, that had to change for sound - the silent had a claw pin to engage both sets of sprocket holes.

The Mazak problem had spread to one of the fixing lugs on one turret, and to a screw thread on the other. I had laboriously to make a fiddly little add-on bit and secure it with tiny screws to deal with the lug. The thread meant carefully drilling out a hole and fitting a small brass bush, held in place by a grub screw, with the appropriate thread cut on the protruding end. This thread was M14 x 1.5, whereas the "normal" M14 thread is 2.0. So I had to buy a special die, which I may never use again. All good, solid, bread-and-butter stuff, but not the stuff of which dreams and website material are made.

This machine is also the one where the gears were stripped and I had to get new ones made - a mad expense but.........It is now back more or less in one piece. A minor irritation is that most of the nuts and bolts appear to be non-standard. The M3 size normally has a pitch of 0.5; the ones on the Rural are 0.6, which of course you cannot buy. Fortunately, I have been able to find most of what I need in my stock of miscellaneous nuts and bolts. I have had to buy the appropriate tap and die, tho'.

You may recall that I made a new end cap for the motor to replace one that had suffered Mazac problems and caused the motor to seize. Either some over-sizing of my replacement, or other Mazac distortion in the motor fan etc has caused a problem.

Have a look at these pix and I will try to explain. Each end of the motor shaft has an internal screw thread. There is also a notch cut across this thread, for a depth of about 2mm. A special washer with lugs engages with the notches, and is held in place by a screw into the thread in the motor shaft. OK so far? On the front end of the motor is a flat pulley for the main drive; at the back is the fan you see here. This is a good, secure method of fixing but, unless (which is perfectly possible) I am missing something, the relative positions of the fan and the pulley are fixed. If, for instance, I wanted to move the fan outwards to give clearance where it fouls the casing, for reasons I have suggested above, I can only do it by moving the position of the motor rotor (nice term that) relative to the casing by going right inside the motor and inserting washers at one end or the other to achieve the desired change of position. I think. If I just try to pad the fan outwards with washers, the teeth on the washer fail to engage with the notch with, as they say, disastrous results. Even a small adjustment seems to make the screw fail to tighten up properly and the fan soon spins loose.

However, I don't like going inside the motor unless I absolutely have to. The wiring is old and fragile and could easily be damaged, ruining the motor completely. Clearances are extremely tight anyway, and the motor rotor could easily hit the windings if moved much, again causing ruin. So I have attempted an alternative approach, by extending the motor shaft with the little brass thingy you see in pix 1&2 (only difference between these is showing both sides of the washer). The problem is, the extension has to be a certain minimum length - there has to be some material left between the threaded hole at one end and the screw thread at the other to keep it all in one piece! Then of course, the fan hits the cover, which in turn needs to be moved out. What is in effect a very big, thick washer seen in pic 3 is in three parts 'cos I only had a small piece of thick enough stuff. Even in alu, this was hard work as it's mostly manual labour rather than machine-aided .I still have a problem tho', in that the little brass bit tends to work loose. I am contemplating either a pin thru the screw thread to engage with the notch (tricky; drilling a tiny hole thru a screw thread without so weakening something that's only 3mm diameter anyway that it breaks.....) or some proprietary compound to lock the thread. In the end, I decided on belt and braces, and made a collar to fit on the shaft, with small screws thru into the notches in the end of the shaft to grip onto the thread of the brass extension piece. This meant boring out the fan to fit round the collar. I bought some thread fixing stuff, too, and will probably use both. At the moment, it's all still in bits as I explore getting the cam altered back to 17.5.

While we are here, you might as well see what the switch panel for the Rural looks like. I took the inside pic anyway to give me a guide when re-assembling if need be. The two pins rising towards you out of the picture carry a grid with a (variable) resistance winding for the lamp (200 or 300w); you can see the wiper for the resistance. The switch is totally simple; turn it in either direction and you get on-off-on-off an infinitum.

I thought I would prove my point about a Sound Rural just being a silent Rural or Rex with a soundhead added.

I thought that, while I was assembling a 16mm Rural, I might as well assemble it as a Rex along the way. Please excuse some rough edges to these pix; I had a very untidy background for these shots and I've been playing with removing it to various levels. Note on the back there are two small round knobs; one controls the lamp output, the other is not connected at all. Obviously, the original Rex had an ordinary series wound motor, controlled by this knob. Just add the sound unit, an induction motor with condenser and voil A Rural! This could explain why the Rex/silent Rural itself is so rare - they all got converted. One wonders if, like the Vox, the conversion was in mind right from the start. You can compare the above with the Rex pictures in Big Brother 1. I must say, I do think it's a very clever adaptation, pre-planned or not.

The lamphouse on these machines worries me. The lamp would be 200 or 300 watts, which is what is marked on the ammeter dial (tho' I've never come across a 300w). It burned upside down, like the Vox, but must have been very slim, because there is very little room between the mirror and the condenser lens. In fact, now I've actually looked, it IS a Vox lamp - same pin arrangement and the filament seems to be in the right place. I tested the voltage, but without load the lowest I got with the lamp control turned right down was 17.5v. Unwilling to risk a rare Vox lamp, I used a QI 15v 150w and, under load, the voltage fell to a much more reasonable 13.7 or thereabouts. So if I turn up the lamp control a bit, I should get exactly 15v at the 200w point on the ammeter. Don't want to try the Vox lamp until I have the motor and fan connected, too. Interesting that the Rural with Vox-type lamp was meant to be able to handle audiences of 3 or 4 hundred (it has a 100mm lens). Was there a different lamp with a different filament layout? Obviously, the same layout would not be as effective for both 17.5 and 9.5 (especially the even smaller 9.5 sound image). Maybe their eyes were just better in those days. And as I recall, when Vox lamps were re-manufactured at some point, there was a simplified filament pattern. I find these odd little byways curiously fascinating.

Been working on the soundhead too. This is on the crowded top of my workbench and I have cropped off extraneous material. You can see all the salient features. The sound telescope is just lying there; it fits to the unpainted area. The original sound system was of course a photocell, plus a mirror, highly reminiscent of the Pax. The mirror is the little silver thing, bottom right. It fitted into the little black dome-shaped thing just left of it, which in turn fitted to the main body with the dome protruding into the hollow end of the sound drum. I have made instead a little bracket (seen above the mirror) and fixed a solar cell thing to it using my liquid rubber insulating stuff. The wires from this will be soldered to the wire sticking out of the main body (the wire will have to go out thru the hole opposite the end of the sound drum), then the dome has to be mounted in place and the end cap (square thing, lower left inside the armoured wire loop) put on. To minimise alteration, I have simply soldered the wire to the pins of the photocell mount and, at the other end of the armoured cable, added a phono socket to an existing hole and connected the existing wires to that. It means the machine could be very simply re-fitted with a photocell if desired.

I have finally finished re-commissioning my 16mm Rural and it works just fine. If one was to use it, there are various improvements it needs, eg shorter throw lens (one fitted is 100mm) and more light (tho' the Vox lamp works fine), but I plan to do these to the 17.5 version if I can get it converted. I do have lenses that will fit the barrel, but they come nowhere near being able to focus. It's a crude but solidly-built machine, obviously intended for heavy use in the French countryside. Here are pix. Sorry about the pink background, but it's the colour of my cinema. It's called bull's blood, tho' I think bordello red might be a better description. It was as near as I could get to real cinema colour, and it had to be very dark to avoid reflections lighting the whole place up.

Some of the things I have been up to include a third, abortive, version of the sound unit, an attempt to make the sound optic move to and fro across the track on the flat, rather than by tilting as I have done up to now. It became onvious that this would require far more, and more accurate, work than I thought was worthwhile, so I stuck with version 2, ie using an L516 optic (I refuse to believe it is from a Son [ugh!], for obvious reasons).

I have re-located the pivot of the low sprung roller after the second sprocket.

I have fitted a 110v AC to 12v DC power supply in the base for the computer fan on the side of the lamphouse. This is on whenever the projector is connected to 110v.

I have built and installed, in the space where the motor capacitor used to be, a 110v AC to 4v DC power supply for the exciter lamp. This thing cost me hours of effort and angst. As you know, I am no electronics expert and could do nothing right with this unit, building and re-building repeatedly, then having to bypass bits of the circuit board where I had destroyed the copper tracks. It was an absolute nightmare - it kept doing imposssible things like the trimmer pot which was to set the output voltage reading from low (but not low enough) at one end of its travel, via a higher voltage in the middle, then back to the number it first thought of at the other end. I finally got it done after repeated exchanges with my experts. This and the fan supply are both connected via trailing leads with DC plugs. Must find a way to differentiate or I will blow up the exciter lamp.

I decided it was worth trying the effect of tightening the springs on the sound gate (ex L516 as you know). I did this and the film kept jumping out. I was beginning to despair and to fear I would have to come up with a totally different solution. However, I first tried adding a sprung rubber roller and, finally, I have halfway decent sound, with good adjustment of the optic à la Vox.

I have done extensive other bits of fiddling, including boxing the power supply/ballast for an HID lamp and finding a way to connect it so that I can use the same unit for other projectors, changing both rollers on the top sprocket etc etc etc. I now have an even longer list of things to do to refine the sound and the physical performance of the machine. Which, if you are not careful, I shall share with you in due course.

As for the Rural Sonore, I have tried out various things. Here is a pic of a re-work of the lower sprocket film retainers; this I made several years ago.

The shape of the arms was I think dictated by some bits I had left over from an attempt to make a direct copy of the original. It works OK but reveals an area I always struggle with - spacial stuff and rotation of shapes and figuring out how a thing will work. In this case, the problem is the bottom roller. It was intended to act as a spring-loaded buffeer for the take-up. However, when loaded with film, it simply does not function, but acts as a fixed roller. I guess it's something to do with where the pivot is, so I may have to re-work this, tho' it works OK as it is.

I also finally got round to trying out the machine with the latest incarnation of the sound head. I realise that the framing could be changed by using the bit of slack in the fixing of the plate that carries the fixed front gate. This is separate from the part of the mech with the claw so moves the entire aperture, both fixed and sprung gates, in relation to the claw. This really makes my brain hurt. However, there is now some unsteadiness of the film in the gate, so clearly more work is needed. I have also done a bit of crude bending and stopped the aperture plate moving with vibration when the machine is running.The sound itself is much more promising. There's a fair bit wrong with it, but it sounds as tho it is fixable. I need to replace the switched mode power supply I have been using with a proper, regulated DC supply and do some more fiddling.

29th February

Here is an update on the Rural Sonore. I fitted a 15v 150w dichroic mirror lamp (just using the same fitting as planned for the HID lamp) and found that, although there was light visible round the various joins, it was not substantial, due in part no doubt to the light being mostly reflected forward. The latest incarnation of the sound reader was a considerable improvement, tho' a long way from being good. A change of amplifier was part of the improvement; another change and the sound was actually approaching respectable. I have also installed the power supply for the HID into a metal box; the plan is connection via banana plug leads as I intend to use the same power supply for other projectors.

So much for the good news. Now that I have been running longer bits of film, a variety of issues have crope out from the woodwork. First off, the machine keeps losing the top or bottom loop, or both. I suspect this is due to a poor film retaining set-up on top and bottom sprockets. This will have to be corrected before I can examine other issues such as the sound head itself. Associated with this are various sound defects like warbling et al - hard to know if these are wholly loop-related or not at this stage. Also, volume is low, but my once-trusty pre-amp has let me down and does not improve the sound - level up, quality way down. Another problem is that both focus and the position of the aperture plate seem to be affected by vibration and so are drifting off. Framing is also off - I get a frame line at the top of the pic but there is no framing device (tho' I have seen cases where one has been fitted) nor any significant travel on the gate itself (unlike the Home Talkie).

One other issue. I found that the motor was being very lackadaisical about starting and getting up to speed, risking damage to the film. I therefore fited a separate lamp switch (for the 15v 150w supply, as the HID lamp will be switched separately). After discussion with a friend, I doubled up the capacitor and now it goes like a rocket. I still have some residual concern that this might damage the motor. Has anyone any experience or knowledge of this?

Here is the latest incarnation of the Rural Sonore sound reader.

26th Febtuary

Here are the pix of the fully assembled lamphouse, which I think are broadly self-explanatory. You are very privileged to see these pix befpre I have actually tested it out - it may leak light all over the place (Iknow I shall have to do more with the fan) and/or generally leave me with egg on my face.

Here are a few late (Autumn 2020) additions to the pix above, showing the HID lamp in situ and revealing that the knob on the douser has changed.

25th February

I lost another week to another bug, but have since moved on a bit. I told you of my adventures with the sound reader on my Rural Sonore, but maybe not why I wanted it. More on that later. The last thing I told you was about my efforts to use a festoon lamp, with limited success. After much head-scratching with the tthing on and off the machine, I came to the conclusion that the problem lay with the Elf sound optic. I just could not get it to focus unless it was so close tothe film it fouled the sound gate, which has a raised lip. I also reverted to a standard exciter lamp. Luckily I had one that was insulated; most rely on the mech for the return path, on which keen I am not. I found an alterntive - it might be from a GBL516 or maye even a Son (ugh!). I'll do some pix for you. To avoid fouling the lamphouse, which tips back just like a Baby or an "H", I had to turn it thru 90 degrees, requiring a different lamp with a horizontal filament. The Elf telescope holder was nbg as the difference in size (my new one is a tad smaller) was too little to allow for a sleeve. So I had to machine a replacement from solid aluminium. I also put some rough shielding around the lamp to cut down on glare.

Back now to why I am pursuing this so determinedly. Your starter for 10 is this string of pix of a fairly innocent Rural Sonore lamphouse, which does not suspect what is about to hit it.

Let me draw your attention to a couple of features. In pic 1, the notch at the top is where air from the motor fan comes in. Note the dividing wall to diect some air to the lamp and some across the gate to cool the film - another example of the superb design of the Rural. The lamp, incidentally, is a standard Vox lamp of 15v 200w. The lamphouse is pretty shallow; I have re-painted the cover, which simply slides off. Pic 2 is just a general view of the inside. Pic 3 shows past interference, probably to do with the conversion to 16mm during the war.You can see that the bracket on which the lamphouse pivots (see pic 2 for a different angle) is attached to the body by 2 screws. You can also see where it originally sat as an integral part of the main casting, to the right of that enlarged hole in the base. The front view in pic 5 shows how air is channeled across the gate. Pic 6 shows an important (to me) feature in the shape of a threaded hole. This is a relic of the earliest days of the Rural silent. On here pivoted a 2 stage douser - 1st part gauze for still, second part solid for full cut-off. A cycle-type cabe led from this thru the bottom of the lamphouse and round to a lever on the main shaft of the mech, just behind the pulley taking the drive from the motor. This originally pushed the drive pulley forwards, disengaging a dog clutch, with the pulley free to turn without driving the mech, to allow a still picture to be shown, while at the same time pulling the dowser into place. This mech had been disabled on my silent Rural and it is easy to see one possible reason why - how can you move the shutter out of the way with no means of turning the mech?

OK. I explained to you the problems I had trying to get the original sound reader to work, but I daresay I could have made it work. However, what I wanted to do was fit one of the discharge lamps described by Tony Saffrey in an article about a Specto in Group 9.5 mag, with the necessary douser, hence my long digression above. I have seen these lamps in use - they seem able, in some cases anyway, to outshine even a conventional Xenon. But this really requires a separate exciter lamp - I don't fancy scraping bits off the morror of a lamp costing £60 plus. However, this lamp is also deeper fron to back than can be fitted in the lamphouse I have shown you above. So I needed to find a way to extend the lamphouse, fit a cooling fan for when the motor is not running and fit a douser and a separate exciter lamp - all without making any new holes or other permanent alterations to the machine. This may be a personal foible, but I think there is a strong case to be made for keeping projectors as near to original as possible.

So now I have to go and re-assemble all the bits I have removed to show you where I started and do more pix.

Once more into the breach

I have struggled endlessly with the L516 curved gate and the exciter lamp holder that I have showed you in previous episodes of this saga. In recent months (Autumn 2020) I have made yet another attempt, turning the gate thru 180 degrees as it had become apparent that at least one part of the problem was that the sound gate did not line up with the film as it emerged from the gate, which I could only correct by reversing the thing. Here are a couple of pix of what may be its last incarnation.

I have also made inumerable attempts to use a flywheel, using a set-up I inherited with a machine I acquired. I remade most of the parts but still failed utterly to get the flywheel to rotate cleanly - there was always a wobble I simply could not correct.

So in the end, I decided to go back to basics and look at my most recently acquired machine which had come complete with its original sound gate/smoothing thingy. The idea is to copy it for other machines such as the one where I have been failing for so long.

The basic concept is of a thin metal strip held by a spring onto the sprocket edge of the film, which is riding on the curved block(pix 4-6). This is best seen in pic 5. The actual execution, however, is far from simple. A long screw passes thru from the front of the block to a small shouldered thingy (not at all sure what to call it), which provides a lug for the spring, tension of which can be varied by turning the thingy. This in trun seems to require rather precise work to provide an axis on which the arm can pivot, while being loose enough to allow the arm actually to pivot, so that the length of thread on the long screw seems to be critical. One end of the steel strip fits into an amazingly narrow slit in the spigot at the very rear of the arm (pic 7 extreme right), and a tiny screw passes thru the strip. The other end of the thin strip has a similar arrangement. The slit in this case is in the shaft that carries the film guide roller, which isn't a roller at all but is fixed and forms the outer guide for the film at the beginning; after that, the film is left to sort itself out. I must say I was very sceptical about this arrangement but, reasoning that it must have worked at least tolerably in the early days decided to give it a go and see. All the 16mm conversions I have seen, incidentally, have a completely different set-up.

I have managed to fabricate a couple of blocks but haven't gotten any further yet, partly because I wanted actually to test the original before doing any more and partly because it looked very difficult. Was there a correct type of steel needed for the thin strip? How on earth was I to cut one with smooth enuff edges? Could I match the spring arrangement? And, most of all, how could I reproduce the tiny slits?

I was forced to address some of these questions quite early on; close examination revealed that there was a tear in one edge of the strip in the only original I had. I was not prepared to risk the horrendous damage that would occur if it got worse. So I was forced to make a new strip before I could go any further. In the end I made one by sandwiching the strip between straight edges for cutting and drilling. I then had to make a second because the first was slightly too short and did not allow the film guide at the front end to fit into its recess. Yet another critical dimension. I am pondering using two separate pices to simulate the slit for the strip, but I am not looking forward to the manipulation of tiny parts that will be involved.

This was only one part of the problem. I was never fully satisfied with the exciter lamp arrangement I had devised - there didn't seem to be enough light getting thru to the screen. So I decided to have a go at something I have frequently pondered, ie whether an LED could do the job. With my lamentable lack of electronic knowledge, I then had to try to learn what I would need to do. This was not helped by the problem of getting info about the LEDs so as to figure out what resistance would be needed. They arrived with no info at all; it was on a website apparently but even this varied between suppliers and terminology was inexact, inconsistent and variable. One is supposed to just know this stuff, it seems. In the end I proceeded by the tried and trusted method of trial and error. The one consistent piece of info was the working current an LED needed - fortunately, peak current is much higher than working current so there is some leeway. So I tested various resistors, starting high and working down. I think I ended up with 150 ohms for a 5mm LED with a light output of 30,000 millicandles. I can write these things but it don't mean I understand them. I mounted this thru a block of aluminium which in turn sits on top of a Vox sound telescope mounted in a sleeve in the holder for the original telescope. On testing, the new metal strip in the old block worked well and gave no problems with the film and sound was encouraging; however, the sound seemed very sensitive to focus and position, neither of which are easily adjustable with this set-up. I am now pondering using a full Vox-style st-up with its integral focus and postion adjustment, probably by reproducing the relevant part of the Vox sound head/drum assembly and stealing a telescope and its holder from an unsuspecting Vox. (I once tried to make a replacement holder - they often get cracked/busted). I didn't completely succed but got far enuff to see how it could be done if I nneded to. Must dig it out again - I did see it around quite recently. And I have several unused telescopes I acquired in France as spares.) Remember, there is limited space between the top of the original sound telescope and the bottom of the lamphouse so I could not fit an LED on top of that. My alterations to fit the HID lamp ruled out fitting the LED inside the lamphouse, so I have not yet considered in detail what may be possible on that front.

I have spent much of the last two days doing exactly what I was suggesting, ie building a mounting plate for a standard Vox sound telescope unit. Both it and the LED exciter work well. As indeed does my fingers-crossed repair of the sound smoothing unit. Must copy both asap. Will do you some pix. And here they are.

The first two pix m show the bracket, made from a chunk of 6.25mm/0.25" aluminium bracket I had lying around. The part with the through slots in sits at the top level of the sound unit, which originally had 3 screws (two of them in line) holding down a curved bracket for the original sound telescope. The back corner is cut away because the picture head unit is at the same level and its base gets in the way. The slots were to allow for easier fitting and easy adjustment. The first thing you will notice is that there is a blob added at one side. This is because the intrusion of the picture head that required the corner to be cut off led me to assume that the vertical and horizontal parts needed to be cut to the same width. When I came to try to fit the Vox sound reader shown in pic 3, one of the screws fell just beyond the edge so I had to add a bit to make room for the screw hole, which in fact falls right on the join between plate and blob. The second thing you will notice is the grooves to fit the back of the Vox sound reader into, one being a deep rectangular section, the other a rather shollower V groove. Pix 3-6 show the alu block I set up as a test bed to try various different values of resistor without undoing the rest of the wiring. The hole in the bottom fits over the top of the Vox sound telescope tube and is held on by a screw (front of pic 4). In a thru hole sits the 5mm LED. I have some 10mm I must try some time. I used the same power supply as I had fitted for the earlier version of the sound reader which I assume delivers about 4v into load but which registers 9.5 without load.

Update January 2021

I have continued working on the sound unit. I have made a new block to take a 10mm LED and I seem to be getting somwhere with the sound. It has been too high-pitches, sharp and distrorted and I suspect the problem now may be too much light. I have fitted a red filter in the sound telescope which seems to help a bit; I am now considering a diffuse LED rather than the water-clear I am presently using. Then there is the photodiode to consider - maybe that might help. I know results can be better because I also have the unaltered (apart from replacing PEC with diode) machine upstairs, which gives markedly better sound. Maybe the Vox sound slit is just too small. All of this messing about with the sound is to accommodate an HID lamp rather than the orignal 15v 200w or a modern 15v 150w dichroic. I am also getting a lot of hum - there are plentiful possible sources for this eg switched mode power supplies for the fan and exciter, or it could be a characteristic of LEDs or the various 110 volt trannies (one each for projector and amp). So some way to go yet before I can declare this over.

I have bottled out re the sound unit and have not attempted to emulate the spring strip of the original, though the other machine retains it. Instead, I have adapted the design slightly to include a runner roller to do the smoothing. Here are some pix, including one of the complete set-up. Mechanically, it all seems to work OK.

You will see on earlier pages some stuff about guide rollers for the lower sprocket - here is a repeat of one of the pix.

The sprocket turrets and these guide rollers seem to take a bit of a battering on the Rural. The turrets suffer from Mazac disease and the rollers seem to have been replaced in many cases. The approach shown in this first pic looks terribly Heath Robinson, but it does have a couple of useful points - it has a "wrap-round" so it is difficult for the film to leave the sprocket (just like the Vox) but in this case with the lower roller sprung to smooth things out a bit between take-up and sprocketand back thru to the sound head. But it don't look right.

This more recent attempt (pic 2) is based on half of a roller frame I discovered among my bits and pieces. That gave me the shape of the curved sides and the location of some of the guide rollers. I then had to fix axles for the rollers that also served to hold the frame together and make sure the rollers rode in the correct position, and make rollers to an exact size. A long and fiddly job but it does seem to work. It does however need a fairly complete turret to work. As you can see, it still does a wrap-round, albeit in a different way, though I would still in principle like a sprung roller before the take-up.

The above is just a string of pix of turrets on some of my machines that I took for a friend. The one in pix 7 and 8 looks good but is not very successful. The best one appears to the one in Pic 2

January 2021

Here's a bit of detailed restoration sort of stuff - it's about the 17.5 Rural.
The original silent Rural was introduced in 1927, too long after 16mm to have much chance in markets outside France. In 1933, a piece of clever engineering added an extra layer to the existing two tiers to create the Rural Sonore. Then in 1941 the Germans demanded that all 17.5 machines be converted to 16mm. Some did survive as 17.5, but most were converted. The original Rural silent had only 500' capacity - a single reel. The sound machines had longer arms, to suit the 1000' (2 Reel) spools that became the norm for features and the like. This was not good enough for 16mm of course, so yet more adaptation increased capacity to 1600', which I think will be just enough to take a 2000' spool, to make life a bit easier for projectionists showing 8 and 10 reel features.
I am gradually getting to the point. I wanted the bigger (1000') spools for my 2 silent Rurals, so when I acquired some 16mm versions of the Rural Sonore it was party with an eye to stealing their spool arms as well as various other common parts. Given that some of the 16mm machines came without arms, the net result has been a shortage of said arms, so I am having to re-condition those I have got as best I can - and not all of them are complete. The one I have just been dealing with has the take-up assembly missing from the lower arm. I have therefore stolen one from the now-unused 500' arms and in the process discovered a style of friction brake I had not previously seen. Yer tiz.

The friction is provided by the four little "brushes" bottom left. The springs fit in the transverse holes thru the adjacent disc, which holes are partly exposed as seen. The brushes fit one either end of the springs, and the disc, spring and brush unit fits into thehole provided in the pulley wheel bottom right. The rest is obvious.
Experience in recent weeks testing a Rural Sonore makes me feel that this friction mech is necessary for correct functioning of the machine. The drive to the take-up is a standard wire spring belt but it needs to be thick and fairly stiff to work. This in turn means that the springing is too stiff to rely on the flexibility of the spring to avoid ecxess stress as the film comes over the bottom sprocket, as many small projectors do.
I very much doubt that the assembly has ever been taken apart since 1927 as it was so filthy and it took a bit of work to remove the accumulated gunge of the years.

26th January 2021

Although it's a bit esoteric, this is after all just a blog about what I have been doing, so...........

This is the sound unit for a 16mm Rural Sonore. I am looking at the possibilities of conversion to 17.5 by running the film thru the "wrong" (for 17.5) way, not so much because of the sound unit but because of the problems with the claw and cam. My previous attempts to dismantle one of this design failed because of the difficulty of getting the sound drum out, which is held in 2 ball bearings and did not want to shift. In the end, I 'it it wiv a 'ammer (cushioned by a piece of wood). Note the clever design which provides a big space for the motor capacitor and the sound drum, exciter (from the projector main lamp) and photocell, all in a single layer which could mount directly between the silent Rural's base and mech sections. This 16mm version obviously followed on from an original design for 17.5. Below is a pic of my 16mm (working) Rural Sonore with a similar soundhead, which may make the above easier to understand.

As usual, the paint was coming away in large areas, with some aluminium rust (you know, that white stuff that so often appears on elderly alu etc castings), so I decided to strip it back. This reveals how rouigh and ready the casting is in places. The fettling (this is, I believe. the correct technical term for machining the rough bits from raw castings) is precise only where it needs to be, eg in the tube that contains the bearings - Pic one far left. Elsewhere, it was a lower standard - see pics 2-3. In fact, pix 3 and 4 make me wonder if the square section and the twiddly bits were made separately (which would be a lot easier to cast) and welded together after. The problem is that one cannot realistically re-paint over the old - it just looks scruffy, but duplicating the very thick paint finish that hides the multitude of underlying sins is a problem. Hand painting never looks right, but spray is pretty thin and shows all the dodgy bits. There is also the question of adhesion - one of the reasons so many old machines tend to lose their paint finish is that alu etc needs a special etch primer for the paint to stick, and the correct procedure was not always followed. I have a Vox that is almost bald because I was able to flake the paint off with little effort.

Pic 5 shows the bits that survived to now. The sound drum - necessarily very small because of the design - is basically a single unit comprising the shaft with drum, 2 ball bearing and a spacer to go between them. The ball bearings had seized up, but improved with soaking in white spirit and oiling. I spose they would work, but I would ideally like to replace them. I have however discovered that while bearings with a 10mm centre, 26mm outside diameter and 8mm thick are ten a penny. Unfortunately, these ones are 25mm diameter and a preliminary search has completely failed to find any. Usually in the past I have easily been able to source replacements on various French machines as they have been standard metric sizes.
The tube for the photcell is obvious in the pix, but the little cone thing, which has a curved mirror placed across its axis, puzzles me as I have seen only direct reading versions before. It must have worked tho'. The pressure roller for the sound drum is really crude - mounted on an arm that is just a piece of steel twisted to the required shape.

BB1 BB2 C Home Talkie Super Rural