Thank you!
Thank you!That's a great idea! Building a large-format leaf shutter is a challenging but rewarding project.
Thats interesting! I found (probably) your post and picture of that shutter/lens assembly. Thanks for sharing it.Hmm. OP, are you aware of the AGI F.135 aerial camera? It uses 5" roll film, has two very strange leaf shutters that hold 38/4.5 Biogons. Not a stereo camera, the shutters fire alternately, the film is advanced after two shots. The shutters embody a few ideas that you might want to consider.
The shutters' blades are metallized mylar, are probably lighter than the equivalent steel blades. Less inertia.
The shutter is opened/closed by a pair of opposed solenoids that extend when energized. The open solenoid whacks a lever that opens the blades, the close shutter whacks the lever to close them.
Thats cool idea! It would be able to have good maybe felt material light seals too, if the motor pulls the slide and not just gravity and tilting the camera possible.One thing you might consider is a guillotine type shutter, but using your electric driver (stepper motor with ,lead screw or solenoid) instead of the gravity fall common in homebuilt guillotine shutters.
This doesn't absolutely require a very fast travel; like a focal plane shutter, exposure time is mainly governed by the width of the slit -- but if you drive with a stepper, you could have a fixed width slit and vary the drive speed instead.
You mean that square body sinar db shutter? Ive googled some pics from insides of that, but coudnt find pics of the mechanism how is the shutter leafs moved in that.
But ive already kinda gone with this 5 leaf desing that seems to be most popular in shutters.
This probably woudnt work or anything moving, or portraits though? Hard to simulate in head, how it would go, but I get the feeling something weird could happen.
I wonder why its done using two solenoids? I know that normal solenoid just pulls even if put to reversed polarity. Shop's sell push/pull solenoids, Maybe those have magnet inside a coil, like a speaker. I dont have one to explore.
without a close solenoid the shutter has to be closed using a spring
I have diy 5x7 camera that is built so that it can fit almost everything, so that will be used.My question is what format?
There are various options, first as mentioned already the Sonar/Copal shutter, I bought one in January at a camera fair for £20. O assume the seller thought it needed repair as it did not work with a cable release, It just needed the special extra long throw dedicated cable release and works fine.
I'm lucky I have large Thornton Pickard roller blind shutters that fit all my large barrel lenses, and also a large Gitzo leaf shutter with flash sync, these are front mounted.
Another option is a focal plane shutter, I have two half plate shutters that can be rear fitted, also a dual shuttered TP Triple Imperial, focal plane shutter for high speeds to 1/1000, and behind lens roller blind shutter for slower speeds.
Some years ago I bought a box of Graflex parts from Paris, off a member here. He had stripped down Quarter plate Speed graphics to use the focal plane shutters between large lenses and his camera's lens board.
Ian
I am sure it might work too, with the rotary disk thing built ultra light so that it wouldnt knock tripod over when accerelating/slowind down.Just to trow it out there, have you considered a rotary shutter? Seems simpler to build than a leaf shutter and can probably achieve higher travel speeds than a linear travel curtain shutter, because it can accelerate before reaching the aperture (which is also possible with a linear shutter, but would make it quite unwieldy).
Yeah, theres no hope pulling the shutter back closed with a spring, or it would reguire huge solenoid and spring.The reason for an open and a close solenoid is simple - without a close solenoid the shutter has to be closed using a spring. The solenoid, of course, has to overcome the spring to open the shutter. The spring tension has to be such that its force is enough to close the shutter in the required time. For small shutters this isn't much of a problem, for large ones it is.
Yes, for sure! But with bigger size and 2 of them. The shutter needs to be built first and then its easier to see what kind of force it needs to move.Many generic solenoids have a spring-mounted plunger. This type is likely adequate for this shutter project.
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Thank you! Hmm, I have a goal to make the shutter go about 1/30s or shorter. The 5 leaf design should allow relatively small/light invidual blade size and mass.So far it looks nice. I'm guessing the shutter will be slow due to the length of the blades. Rotational inertia proportional to radius squared!
Problem with 20 or so lightweight blades woud be friction. I'm curious to see how it turns out. Nothing wrong with a slow shutter for Large Format photography.
That pin thing is very true, I thought a lot about a design where every leaf had a 3mm thick piece of hard aluminium plate riveted around pin areas, to prevent pins eating into leafs.It's not the pins that will break. Shutters that move quickly have small brass rivets crimped into the shutter blades, else the pins will wear out the holes in the blades and at the same time the blades will cut grooves in the pins.
Brass is usually used with aluminum, along with a lubricant, when making a sliding surface. I have never seen a steel/aluminum bearing surface, my guess is that galling will be a problem. The best interface is hardened steel and sintered bronze; the bronze will be oil impregnated.
If you are looking for push-pull solenoids you will need to look into linear motors, sometimes called 'voice coil motors.' If you want to use them without a restoring spring you will need a feedback system for positioning. The moving part of the motor is a magnet, in a speaker the moving part is the coil, or you can have a moving coil and a field coil - all just like DC motors.
Solenoids are unstable - the force increases very quickly as the solenoid closes. The force/distance relationship isn't linear like it is with a spring. There are special solenoids made for positioning but they are really voice coil style motors that only generate force in one direction; the construction is different in that the force is proportional to current and position.
Yes and no. The famous example is an aluminum engine block and steel piston rings as in the General Motors Chevrolet Vega. General Motors tried several times to be cheap/sophisticated by depositing a layer of nikasil (nickel/silicon carbide) on the cylinder bores. In combination with engine overheating (GM also decided big radiators were too expensive) the nikasil coating failed and the piston rings promptly ate into the cylinder walls. The proper solution is to have iron sleeves in the cylinders - then all is good, and if the cylinders do get scored then replacing the sleeves is a lot easier than re-boring the block.Steel and aluminium bearing surfaces are used in car engines a lot.
if the cylinders do get scored then replacing the sleeves is a lot easier than re-boring the block
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