Pentaflex 16mm cog repair

[Gareth Blackstock]

So recently I bought a Pentaflex 16mm camera, exactly the same, apart from cosmetics, as the Pentacon AK16, and as per the advertisement, it was not working and in need of repair.  When I opened it up, it had what appears to be a very common ailment of Pentaflex 16mm cameras.  One of its Bakelite cogs had lost some teeth and therefore a side or bottom mounted motor would not be able to drive the camera.  It seems that when people who do not know the camera try to manually get it to "turn over" or actuate the movements to see the mirror move, they fail to unlock the drive and inadvertently break off a few Bakelite cog teeth.

So, I contacted a person with a 3D printer, sent them a could condition cog to copy, and they were able to print off lots of cogs for a fee.  I re-installed the plastic cog into the camera and it works very well.  The repair is pretty straight forward, no electrics, no calibration, and a touch of lubrication.  I am pretty impressed with what a 3D printer can print, I imagine there are lots of little bits and pieces from old cameras that have since broken and essentially killed the camera as spare parts are non-existent.  3D printed parts might be a good lifeline for fixing old cameras.  

I used Envision Engineering of Queensland, Australia WEBSITE LINK

Below is a link to the cog repair details on my website:

https://canon-s8-repair.yolasite.com/pentaflex-16.php (at the bottom of the page)

The below image shows the printed black cog, the dark brown Bakelite original, and a broken cog mounted on its metal spindle.

[Gareth Blackstock]

This picture shows a mock-up of how the cogs sit on the camera body and their relation to each other

[Gareth Blackstock]

And this picture shows the finished assembly, ready to be placed back on the camera.  

[Nicholas Kovats]

Well done! 

[Simon Wyss]

1. It’s not Bakelite.
2. I praise your inititative.
3. Technically you miss the point that cog wheels made from fibre-reinforced composite can hold some oil and so keep the gear train lubricated.
4. You are so right about people who force things.

[Gareth Blackstock]

Thanks for the feedback,

I'm curious Simon, what is the name of the cog's material? I acknowledge Bakelite is a harder type of material, but it's a lot easier to say than "fibre-reinforced composite" I think regarding the lubrication of the gear train, that you are mistaken with the Pentaflex.  Early East German industries utilised numerous materials, I never took time to research the various ones.  Sometimes I imagine they used whatever was available.... and cheap.  

Judging from the inside of the camera, there is only 3 lubrication points, all spindles.  The fibre-reinforced composite cogs all appear to run dry.  There is evidence from the metal cogs in the camera that they likely had a light smear of grease applied, but these cog do not contact the fibre-reinforced composite cogs.

[Simon Wyss]

I must clarify. The Pentacon AK 16 alias Pentaflex 16 is a Bell & Howell design through and through. It has a precursor at least one patent period older.

FRC gears are used in such cameras as the Paillard-Bolex H (1935), Miller B De Luxe (9.5 mm, 1938), Revere 88 (1940), and many more. The material needs to be oily, else it’s worn down in short time and that is exactly the reason for the damage you encountered. Had it been oily the teeth would less likely have broken away.

[Mark Dunn]

3 hours ago, Simon Wyss said:

I must clarify. The Pentacon AK 16 alias Pentaflex 16 is a Bell & Howell design through and through. It has a precursor at least one patent period older.

FRC gears are used in such cameras as the Paillard-Bolex H (1935), Miller B De Luxe (9.5 mm, 1938), Revere 88 (1940), and many more. The material needs to be oily, else it’s worn down in short time and that is exactly the reason for the damage you encountered. Had it been oily the teeth would less likely have broken away.

My Steenbeck has a number of cogs which appear to be made of this sort of material but they appear quite dry- I have greased them on occasion and it doesn't seem likely that they would get oiled often if at all, and the user manual doesn't mention it. Should I be thinking about oiling them? I should mention that the machine was made in 1975 and they show no signs of wear.

Edited March 31, 2023 by Mark Dunn

[Gareth Blackstock]

Thanks for the added info Simon, what type of oil would have been used? Or would it have been a grease? Although the camera gears and cogs I have show no wear, I would be interested to see what lubricant can be used... I am unsure why the Pentaflex has these types of cogs/gears, I doubt the factory would want to keep the weight down, they already weigh a ton... and there are plenty of metal cogs/gears in the camera... Odd.

 

Gareth

[Aapo Lettinen]

1 hour ago, Gareth Blackstock said:

 I am unsure why the Pentaflex has these types of cogs/gears, I doubt the factory would want to keep the weight down, they already weigh a ton... and there are plenty of metal cogs/gears in the camera... Odd

Cheaper to manufacture and lower running noise are possible reasons. Additionally I would expect the composite gear to wear down more easily than the metal ones so it might save the metal gear from being replaced... Instead of changing both gears you would only change the composite one and the metal gear does not need to be replaced ever.

Personally I think it is most probable that they just wanted to make it cheaper to manufacture. Krasnogorsks etc. cheaper cameras are full of these composite gears as well.

On higher end ones like cp16r the composite gears are only used on specific spots to reduce running noise and the other gears are meral

[Aapo Lettinen]

and there is of course the additional benefit that one can direct the most probable fault point to the easiest replaceable part if making that easiest replaced part the physically weakest one.

Ideally the gears which mount to the axles would be durable metal and the "free-spinning" intermediate gear would be plastic or composite material. Then, if something is about to break, the easily replaceable plastic/composite gear loses teeth instead of the difficult to replace and expensive metal ones.

If done right, one could make such a system so that the users can replace the broken intermediate gear by themselves very quickly (and have spare ones with them all the time because they are cheap) and the system would continue working in couple of minutes instead of needing a huge disassembly, possible special tools and lots of extra work and time which would ruin the whole project

[Simon Wyss]

Tough times for me. Although having explained exactly why and how FRC gears are in use everybody tries to evade the fact and rather bring other ideas. If one studies the oiling system of the Pentaflex 16 one will understand that oil will run along shafts to eventually reach gears. It is well made, oil is being pulled up by the movement of the teeth one over the other. The only drawback is that oil can’t be applied without removal of the RH side cover.

There’s no difference of cost in the making of metal and FRC gears, you need a milling device, a controlled movement of the work, and a controlled movement of the tool.

With a Steenbeck editor the same, the composite gears should be oiled, not dripping wet, just a bare minimum. Once or twice a year a few drops of a sewing machine oil, wiped over with the finger. Make sure no oil comes in contact with a belt. V belts, by the way, like a tender rubbing with talcum. Yes, all mechanical devices need maintenance. Door locks, water taps, typewriters, cinema projectors, a Merrow.

[Dom Jaeger]

Those gears are made from fibre reinforced resin, very common in motion picture cameras from this era. They are used in the mirror drive gear and intermediate mag drive gear of Arriflex 2Cs and the sprocket drive gears of Arriflex 16Sts, among many other cameras. One of the names for this material is Tufnol.

They are very commonly used as spur gears paired with a steel gear, in order to dampen noise and vibration. The material is very strong and wear resistant, but has some elasticity, allowing it to be uniformly shaped against the steel gear. For slow speed applications like movie cameras they are usually run either dry or with a light application of grease, oil is normally used for higher speed applications. On the Arriflex 16St for instance, the bearings for the fibre gears have oil tubes leading from an oiling well, but the gear teeth themselves are dry. On a 2C the gears are greased. I’ve yet to see them worn. Whether the East Bloc used the same quality of material as Arri I don’t know.

3D printing gears will solve the problem in the short term, but I’d be curious to know how the gear will last over time, or under more load like higher frame rates. We 3D print a variety of things where I work, but invariably the only gears that work well are ones with fairly low force applied, or very intermittent use. Using a stronger material like nylon or higher resolution printing can help. The other problem is dimensional accuracy, which can introduce issues with vibration or binding etc. But the science of 3D printing will only improve.

[Gareth Blackstock]

Well there is some pretty good info here, thanks guys.  I have a couple of questions though- For Simon:

On 3/31/2023 at 5:13 PM, Simon Wyss said:

Pentaflex 16 is a Bell & Howell design through and through. It has a precursor at least one patent period older.

Which Bell & Howell design or camera was the Pentaflex copied from? I was under the impression that it was quite a unique design.

[Gareth Blackstock]

Another question for Simon: 

On 4/1/2023 at 2:22 AM, Simon Wyss said:

the oiling system of the Pentaflex 16 one will understand that oil will run along shafts to eventually reach gears. It is well made, oil is being pulled up by the movement of the teeth one over the other. The only drawback is that oil can’t be applied without removal of the RH side cover.

I am curious about your statement on the Pentaflex maintenance requirements.  The Pentaflex has one maintenance oil port, coloured red, accessible from the outside of the camera.  In the inside of the camera there are more, not coloured though.  As far as I am aware, older cine camera makers required owners to occasionally maintain or at least apply lubricant to their cameras, in specific holes only, usually coloured red. 

I took a picture of the oil route holding the motor mounts as they would be on the camera.  The cog circled in red is the one that has an oil maintenance hole.  So I think here you are correct, that oil from the maintenance hole will eventually flow down to the bottom cog, but I think more as a side benefit, not an engineered design.  

Also, after having used my Pentaflex a few times, certainly running it without film, I have not seen any oil travel up the cog system.  I would have noticed a change in colour of the FRC cog.  To get oil to travel upwards, you need either a different viscosity or a "sticky" oil.

Also, there are many areas of the camera's internals that are entirely free from any lubricant, and there is no evidence of dried old grease.  Nor is there build up of oily dust.  I consider that as these cameras were very expensive in their day, and well made, that if they were intended to be fully lubricated, then I would see some evidence of it.  I have opened a few old cameras and found lots of old built up lubricant.  

This is from a Pentaflex 16mm user manual I translated ages ago "The camera, engine and cassette oiling is required by the manufacturer or the authorized repair shops after 50 operating hours. The camera drive is provided with non-resinous, low viscosity, cold-resistant oil. For this, a few drops are sufficient."

I am inclined to believe that the Pentaflex was designed to be a dry running camera, oiled only via maintenance hole, and if during a service, then only the cog area.  If you have access to a Pentaflex service manual I would be keen to hear what it dictates.  perhaps to allow cine cameras to be used in cold climates, lubricants were minimally applied to prevent the lubricant freezing.

[Gareth Blackstock]

On 4/1/2023 at 11:52 AM, Dom Jaeger said:

3D printing gears will solve the problem in the short term, but I’d be curious to know how the gear will last over time, or under more load like higher frame rates. We 3D print a variety of things where I work, but invariably the only gears that work well are ones with fairly low force applied, or very intermittent use. Using a stronger material like nylon or higher resolution printing can help. The other problem is dimensional accuracy, which can introduce issues with vibration or binding etc. But the science of 3D printing will only improve.

Thanks for the fibre info, Dom. Very helpful. Regarding the printed cog I will be running the camera with a load of film and also at high speed as I am now curious to see how well the printed gear will manage.  The first batch of gears I ordered came back with a bind point, and after investigating the issue, I realised the original fibre cog I sent to be copied had the bind point.  The second batch is better. 

Cheers, Gareth

 

[Simon Wyss]

I spend a lot of time doing research on film motion-picture equipment and how it was developed. From the Pentacon AK 16 I have abhorred a long time, it appeared ugly to my eye, not well balanced between small magazines and a large body. Now that a client had sent me one I have to deal with it and guess what I found during the past two weeks alone: like other cameras this one simply popped up in 1952, all of a sudden it was there, precisely thirty years after the first model of the Zeiss-Ikon Movikon 16.

To help understand what I’m laying out awkwardly let me point to the Movikon K 16. That desing tells clearly: Kodak was not far away. America wasn’t that far away.

Pentacon was formed in 1952 as the successor to Zeiss-Ikon. While taking measurements of the FFD that lie around 44,1 mm I read that the Praktiflex SL stills camera has the FFD of 44 mm. A number of 50 mm Biotar (besides Schneider and other lenses) that fit the Praktiflex were already around, so perhaps that had led to the AK 16 specification.

Fascinating I find a correlation of mount diameter and flange focal distance. With the Bell & Howell Eyemo it’s 1.5 inches. Here we have 45 mm H 9 vs. not 44,45 mm which would correspond to 1.75 inches but a little less.

Now the oil bores. I find them so large and so numerous that I picture Dresden just didn’t grasp the opportunity the designer had given. Felt torches could easily be plugged into the holes, pressed in by small leaf springs screwed down in the vicinity, and fed by felt lines in wire coils. A neat oiling system could be installed that would make the camera a very robust thing. Mitchell had oil wickets on the shafts of the moving register pins that leave a whiff of oil on the steel all the time. Accordingly a very narrow fit can be made.

Pentacon’s fits are less tight. In only one place 0,01 mm play is admitted, the runout of the mirror shutter. There are some surprising specialties in these cameras, for example a rigid film canal. No active lateral film guidance. I measure 16,02 mm width on the specimen here. Then the anomaly of the position of the transport claw relative to the aperture. A variable shutter in addition to the mirrored shutter which rather appeals the amateur than pros. In the professional realm fades and dissolves are generally introduced in postproduction by the lab.

All in all I have the impression of purchased design, adapted to assembly by only partially trained persons (as a mechanic I see not so well made pinned fittings), and the decision in favour of the turret version where a single lens port model can easily be had. A fresh narrow front and two flat sides.

[Mark Dunn]

29 minutes ago, Simon Wyss said:

Pentacon  Dresden

One of mine from a visit in 2012. Old and new. The Ernemannturm at the Pentacon factory by Högg and Müller, 1923, now housing the technology museum.

An exemplar of the Neue Sachlichkeit (New Objectivity) architectural style.

Edited April 4, 2023 by Mark Dunn

[Gareth Blackstock]

Well Simon, you undoubtedly know more of the Pentaflex than myself, it is very rare I take a vernier to a camera as I lack service manuals and specialised servicing tools, most often I have to find my way and attempt to detect how things work.  It is interesting what you say about it's design origins and contemporary camera developments. 

On 4/5/2023 at 2:04 AM, Simon Wyss said:

the Pentacon AK 16 I have abhorred a long time, it appeared ugly to my eye, not well balanced between small magazines and a large body.

And yes, the camera is certainly an ugly ducking.  It makes me wonder if the designers tried really hard to make a boxy, poorly balanced, over weight camera or they simply had no plastic available for manufacture, so steel was it.  The following is a quote from http://www.lusznat.de/cms1/index.php/kinomuseum-muenchen/gerhard-fromm-s-sammelblaetter/ak-16-pentaflex-sammelblatt

“She is really not beautiful, she is not small either, as a lightweight one can cannot say, nor running-quietly, …was produced in the early 50s. Clean mechanics, the camera and the motors are beautifully crafted … are from the Pentaflex 16 program and stand out in terms of workmanship and appearance. When the name changed around 1960, the look of the camera was also changed. Instead of leather, a matte-greyish plastic and elastic material was used and the camera was painted in grey hammered finish… A loud camera that seems neither suited for hand-held or on-the-shoulder, just designed for a tripod. An unwieldy black box, so to speak, where you can start one of the even more unmanageable motors at the bottom or right side and insert a cassette at the top” 

However, while the camera in your opinion is poorly developed, poorly designed, poorly appointed with a turret instead of single mount, and poorly machined, I believe the camera exemplifies norms of the time in East Germany and the Soviet Union.  A time when few industries had advanced R&D, had difficulty accessing modern materials, and likely had workforce's plagued with little motivation to do more than the minimum, I think these cameras are diamonds in the rough, what they lack in bells and whistles, they make up for in their indestructibility...  If you drop one, it'll keep working, they will run in freezing conditions, can be operated by anyone, and are not plagued by circuitry boards that oxidise... don't rely on computers and can run on a motorcycle battery.. and I think for the amateur film maker, these types of 16mm cameras are ideal, cheap, easy to repair, high quality standard lenses, and very robust.... all for less than $250 in any currency..... 

 

"They're boxy, but they're good" 

 

 

                  era is certainly an ugly d, 

[Simon Wyss]

I don’t agree with everything you write, for instance I find many parts that are, quite startlingly, of better quality than what was common with the Zeiss-Ikon/Pentacon stills cameras. A lot of problems occured during manufacture of the Contax, Praktiflex and other models well into the late 1950s. Not so with the AK 16.

One freedom that camerapeople got with it is left or right eye at the ocular because it is located behind the camera body (not exactly centered, though). It was only in 1973 that a first (western) 16-mm. camera afforded a swing-over viewfinder system for left or right eye view. On an Eclair Camerette 35-16 (1950) the finder tube can be pulled out to allow for left eye sighting.

Not good is the use of velvet pads near the film loops. Those are already rather tight and then a braking action from the velvets never helped a trouble-free transport. The magazines or cassettes on the other hand are geared, there are no wire springs or belts. But, one of a number of buts, eleven steel gears per mag. plus a ratchet on every spool spindle make noise.

Another freedom of the design is for larger mags. Basically, any magazine size can be made and put on, up to 1200 ft. There were eight film manufacturers behind the iron curtain,

1. Agfa-Orwo, East Germany;
2. Foton, Poland;
3. Fotochema (Foma Bohemia), Czech Rep.;
4. Forte, Hungary;
5. Fotokemika (Efka/Efke), Croatia;
6. Azomureș, Romania;
7. Svema, Ukraine;
8. Tasma, Tatarstan.

Foton and Forte made amateur lengths only, the other plants up to 1000 ft. Of course was it not at all easy to procure every raw stock in all these countries. The heydays seem to have been late 60s, early 70s.

Edited April 8, 2023 by Simon Wyss