Since both, the 1.4 and the 2.1 have the same casing I want to tell you my "problem" here in this thread:
In the moment I use this C mount to Canon Adapter https://www.amazon.de/gp/product/B00VIVXL2E/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I'm using some quite heavy lenses on my Chronos. Having this super tiny C mount hole expanding to the Canon Adapter with this "giant" lens on it, it looks very worrying from a structural point of view.
Do you know if there are more "stable" adapters on the market... maybe some which use the for screw holes next to the lens hole??
I just know this from my Moravian Astro Camera... they have some Canon adapters that can be screwt directly to the casing ...
Or can you just prove me, that this tiny c mount thread is more than enough to hold a big 1kg lens on it's own?
So, third try then...
I tried to Upload an image of an Heavy C-Mount Lens, but since i now wrote an Lenghty Post twice, and ended up with an error-Page when trying to preview (with my text all gone...), i will just use Links now...
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https://www.engineeringtoolbox.com/metric-bolts-minimum-ultimate-tensile-proof-loads-d_2026.html .
Here is an List with proof Load Rating of different Bolt Sizes. C-Mount is Basically just an 25,4mm (1") 32TPI Fine Screw Thread, so, even given the Fact, that it is Hollow on the inside, it should still be able to hold a lot of weight (easily 50~100kg or even way more according to this link). This is for Steel Bolts though, smaller/ Cheaper lenses and adapters are Aluminum, more Premium Ones or Very big/ Heavy ones are made from Stainless Steel..
I had an 16-160mm 1.6 Tarcus Brand C-Mount Lens once, dont have it anymore, this was a Very heavy and big lens. Propably over 2kg, and never had any problems with the C-Mount.Since i can somehow not post the image right now because of error pages, here is a link to the Fattest and Heaviest vintage C-Mount Lenses i could find for the Moment (Most of them Wont cover the Chronos 2.1 Sensor, keep that in mind!):.This one Has 5lbs Weight!:
https://www.ebay.de/itm/SUPER-16-ANGENIEUX-ZOOM-SUPERSPEED-1-9-15-150MM-LENS-C-MOUNT-BMPCC-MOVIE-CAMERA/291640944665
https://www.ebay.de/itm/Angenieux-10-150mm-T-2-3-C-mount-S16-Cooke-BMPC-Red-Alexa/184071216674
https://www.ebay.de/itm/Schneider-Kreuznach-Tele-Variogon-1-4-80-240mm-C-Mount-w-hood-and-case/264631424263 .
I can just agree, what tesla500 said, dont do way too crazy Stuff including high-G and Physical Shock with it, and you should be fine, mounting about anything to it you would propably ever want to mount.
However, most bigger and heavier Lenses Do come with an Tripod Mount built in, if it has one, use it. Also, if your Lens is heavier than your Camera, Handle, Hold, Lift, and Mount the Whole Rig by the Lens.
This is just an general Reccomendation for any camera System, not just for C-Mount but also applies here.
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Yet anothe Point i want to make:
https://en.wikipedia.org/wiki/Flange_focal_distance
Look at this list of Lens mounts, C-Mount is now almost 100 Years old! and Thats for a reason.
It did stand the Test of time, and has proofen it self.
This is the Oldest Lensmount, for which new Lenses Are Produced up to this day, and no end in sight.
Again, As tesla500 Said, it might look not like much and too small, but it is quite the serious Mount!
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I am also pretty Happy, that they went with this combination of the CS-Mount and the four-Hole Box-Mount, because, unless about any other Camera of this kind, it allows you to mount about every lens ever made, including almost any Mirrorless Lenses known today (Electronic Focus-By-wire Style Lenses are a problem, but i mean just beeing able to physicaly mount the Lens itself while maintaining propper Flange Distance is quite a big thing!).
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If you still feel the Need to mount the Lens more sturdily, search the internet for those Rod-Type Supports they use in Professional Cinema.
Supports for different size Cameras and Lenses Are Available, if you search a bit, also Rods at different Lenght.
Even More Stable/ Serious Solution would be to use an Adapter which uses the four M4-Hole-Mount on the Front of the Chronos Camera Body.
I and a few other People on the Forum can Make one, if you still feel the need, or just find sombody to make one for you, for example a local Machining Shop. Its still just a Pice of Metal at the end of the Day.
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EVEN MORE Sturdy would be to just Modify the Lens and get it Rehoused or get the Mount itself changed to just mount directly to the four Holes on the Chronos, this way you dont have anything between the Lens itself and the Camera.
If that is still not enough, also support it by Some Kind of Cage (Highly Required, if you for some Reason end up needing to use big and/ or heavy Lenses in high-G /Vibration/ Physical Shock situations)
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Hope this, as requested, was enough to proof to you that C-Mount will be able to handle Lenses of 1kg and beyond just fine. Maybe dont use your Camera Rig as An Hammer or as a Mounting Point for your Heavy Lifting Equipment, but everything else should be fine
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#EDIT#: Reformating of the Post to make it easier Readable, Text itself remains unchanged. Also finally Added the image of the 16-160mm Lens