Home of Professional Cinematography since 1996
PL Mount Safety
Published : 3rd June 2004
I'm wondering what the collective opinion is as to the safety of the Arri PL mount. I have always felt that it should have had a safety clip. The only problem I have had is that my HR 10-1 zoom vibrated out of the mount while shooting from a camera car. It was save by the lens support & 6.6" matte box. I only realised that it had come loose when I zoomed wide & everything went very soft.
However, on a colleague's shoot recently in Sydney a 10mm Ultra Prime came loose, again on a camera car, and, having no lens support or matte box it came all the way out & disappeared under the wheels of following vehicles with the obvious disastrous result.
Having seen many things vibrate loose in various situations I tend to tape whatever I can, including the PL mount, in such situations, particularly nose mount helicopter shooting. The Arri 435 instruction book has a picture of the locking tabs on the 'inside' of the mount which, although light, would put the weight in a vibrating situation on the unlocking side of the mount, aiding the self unlocking process. I always like to see them on the outside for that reason. As I said, a safety clip should have been a mandatory inclusion.
Drill a hole in one of the ears and safety wire it to a static part of the body. This is what we do on roller coaster rigs, and it works flawlessly.
Richmond, VA USA, home to 20 roller coasters!
David Wakeley of Sydney wrote :
>The only problem I have had is that my HR 10-1 zoom vibrated out of >the mount while shooting from a camera car. It was saved by the lens >support & 6.6" matte box.
This is a new one to me. I've owned two SR and 2 35 BL's over the years and have worked with dozens of other cameras from rental houses with Arri Standard, bayonet and PL mounts and have never had a problem.
Talk to Arri. I didn't think vibrating out was possible. Did you put the lens on you yourself? Is it possible that it was not twisted all the way. There should be a line on the lens and on the camera to show when the lens is on properly. I'm in the U.S so I don't know the number for Arri in Sydney but if you have a problem getting it contact me and I’ll get it from Arri here for you. I'd be interested in what they say.
Live long and prosper
Mik Cribben-Steadicam operator
David Wakeley writes :
>I'm wondering what the collective opinion is as to the safety of the Arri >PL mount. I have always felt that it should have had a safety clip.
I agree, and actually made one for the 35 III. On the 35 III the mount assembly is held onto the camera body by four Allen (recessed hex) screws.
We made an aluminium piece that pivoted on the upper right Allen screw, when facing the camera. (The factory screw had to be replaced with a longer screw.) When the mount was turned to lock the lens in place the aluminium piece was swung down against the PL mount locking ring tab. I left it on a camera we were using overseas and never made a second. Since I never had a mount loosen up in flight, the locking device seemed like overkill.
We then went to the 435 so the old gizmo wouldn't work because of the differences in camera bodies. But in principle it seems to be a straight forward matter to design something similar that would work on the Allen Screw that keeps the 435 Pl mount from being unscrewed too far.
>However, on a colleague's shoot recently in Sydney a 10mm Ultra >prime came loose, again on a camera car, and, having no lens support >or matte box it came all the way out & disappeared under the wheels of >following vehicles with the obvious disastrous result.
Ouch! After hearing that, I think I will go back to the drawing board. As I said, I've never had a mount loosen, but it may just be a matter of luck, or a function of the amount of camera usage.
>Having seen many things vibrate loose in various situations I tend to >tape whatever I can, including the PL mount, in such situations, >particularly nose mount helicopter shooting.
Me too. I also prefer the Bell Jet Ranger or Long Ranger for nose mount work. It's very reassuring to be able to see -- hopefully -- the camera and lens through the chin bubble. Not to mention being able to check for bugs.
>As I said, a safety clip should have been a mandatory inclusion. Any >opinions?
It's beginning to sound like a very good idea.
IA 600 DP
I would also worry about all sorts of screws throughout the camera. A friend of mine shot an entire day mounted on a car w/ his SR, and a lot of screws ended up loose(mag hinges, etc) There is always locktite for prevention. As for lens mount locks it would be great to hear solutions.
I just saw a shot from the top of a jetfighter's tail-the jet flying through valleys/mountain range(British footage?) All the aviation film footage is very amazing. All through the cold war development days there were some stunning images made - the Shuttle onboard cameras for instance, just think of the vibration and safety measures.
But I suspect combustion engines vibrate more than a flying plane-mounting an Eyemo and Bolexes on my 2 stroke triple yielded high vibration fuzzy images at high speed(narrow shutter would have been a good choice if they had it)Perhaps better damping in a different mount system would help. I didn't do a high speed test w/ the Eyemo(someday soon) I'm not too inclined to mount my Aaton on vehicles for long periods.
There was a "Legends of Motorsports" TV program shot around 1979-cameras mounted on F1 cars (talk about vibration...) Stunning images
>Drill a hole in one of the ears and safety wire it to a static part of the body
Make sure you drill the ear with a new Titanium nitride bit or a new cobalt bit. Otherwise you are in for the long haul drilling that stainless ear.
>Drill a hole in one of the ears and safety wire it to a static part of the >body. This is what we do on roller coaster rigs, and it works flawlessly.
Brilliant! Thank you, Max.
Ears can be purchased from Arri so you don't have the rental Cos coming after you.
Drilling them is no prob if you use a little cutting oil, like TapFree.
IA 600 DP
For putting 3's on roller coasters and heli nose mounts, I would capture one of the ears with a little loop of safety wire and spin it down to the matte box rod or the socket for the matte box rod on the dovetail. This way I didn't have to drill the ear and did not end up with a piece of loose tape flapping (I had a bad experience with flapping tape on an SR on an aerobatic biplane).
Safety wire spinners (pliers with a helical rod through them that spins the pliers when you pull the knob at the back) are on the order of $35 each and come with some safety wire - it is actually faster for me to safety wire a lens on and cut the wire when we land than to tape and untapped the mount...but that's just me.
Most motorcycle mechanics and all aviation Airframe and Powerplant mechanics have safety wire pliers in their toolboxes.
LA based erstwhile camera rigger - current VFX nerd - future old fart
John Babl writes :
>There is always locktite for prevention.
I learned about Loctite <tm> from the great Mitch Bogdanowicz, who built all the then-exotic gear for Leacock, Pennebaker and Maysles in the Olden Days. Now I never leave home without it. If you do a lot of jet travel or aerial work (or if you rent out your gear), treat your hardware to this stuff and you'll never have a screw loose.
Mitch once built me some Huey mounts I'd designed for a shoot in Vietnam. Before I left for 'Nam he gave me a tube of Loctite as a going-away present.
>I just saw a shot from the top of a jetfighter's tail
I once mounted a 16mm Arri S -- with a 5.7mm Kinoptik -- on the tip of a competition glider's tail. Well, not exactly; I built a tall tripod mount that got the camera up at the same height, but clear of the tail itself, and was strapped around the aircraft's fuselage. Used either locking nuts or Loctite on all the screws (yes, gliders do vibrate!)
>I suspect combustion engines vibrate more than a flying plane
It's said that high-frequency jet-engine vibration can loosen screws.
Dan "owns no Loctite stock" Drasin
Marin County, CA