Looking for a unique cable release!

[rdenney]

Okay, I've been called out.

First, you should describe how you will use the camera. How will you hold it, and with what finger will you release the shutter. That will dictate where the control should go.

A constraint is where the release is on the shutter itself.

Then, you should define what you expect to do to connect those two points in actual use. Do you expect that connection to remain in place when the camera is folded, and as it is unfolded? Are you expecting to have to attach a control somewhere as part of the unfolding process? This concept of use will impose requirements. A control that has to remain attached during folding and while folded will have to be routed such that it does not interfere with the folding process, and such that the folding does not damage it. Once you understand those requirements, you can lay out a path that fulfills them. That path will dictate the required radii, and the smallest of those radii will dictate the minimum radius requirement for the control mechanism.

You may also have aesthetic requirements, and you know what you expect in terms of the force and smoothness required to a actuate the button.

And there are requirements on the vibration imparted by the mechanism.

Once you know the requirements, you'll know how to evaluate what's out there very specifically.

For example, if you need a push mechanism, a cable release will need tensile stiffness. The braided cable releases provide that. If you need a push mechanism, those won't work, but the spiral-wound releases might. The spiral-wound releases also bind less when bent in a small radius in my opinion. But the more bends, the more friction, and the more friction, the more the camera is likely to move during actuation, especially if that friction is jerky. Vibration may also be an issue with a solenoid, which provides linear motion very suddenly and is thus difficult to implement without vibration, especially with a lightweight camera. A motor with an eccentric cam to actuate the shutter on the lens would be far smoother, but the trick is to find a motor that makes one revolution only per actuation.

I actually took a look at McMaster-Carr, which is an online industrial supply catalog (www.mcmaster.com) but didn't find anything small enough for this purpose. I didn't look very hard. If you go there, search on "control cables". You'll need something fairly tiny to fulfill what I'm guessing are your requirements.

The cable and actuator mechanism for the body release on a Graflex is already designed to fulfill most of those requirements, and I would see if one could be adapted for this purpose. You might have to compromise the requirement on where you put the release.

Rick "whose experience suggests that half of all design efforts should be spent properly understanding the problem" Denney

[BrianShaw]

Okay, I've been called out.

Good morning, dear boy. It's about time you dragged youself out of bed.

[Keytarjunkie]

Okay, I've been called out.

First, you should describe how you will use the camera. How will you hold it, and with what finger will you release the shutter. That will dictate where the control should go.

A constraint is where the release is on the shutter itself.

Then, you should define what you expect to do to connect those two points in actual use. Do you expect that connection to remain in place when the camera is folded, and as it is unfolded? Are you expecting to have to attach a control somewhere as part of the unfolding process? This concept of use will impose requirements. A control that has to remain attached during folding and while folded will have to be routed such that it does not interfere with the folding process, and such that the folding does not damage it. Once you understand those requirements, you can lay out a path that fulfills them. That path will dictate the required radii, and the smallest of those radii will dictate the minimum radius requirement for the control mechanism.

You may also have aesthetic requirements, and you know what you expect in terms of the force and smoothness required to a actuate the button.

And there are requirements on the vibration imparted by the mechanism.

Once you know the requirements, you'll know how to evaluate what's out there very specifically.

For example, if you need a push mechanism, a cable release will need tensile stiffness. The braided cable releases provide that. If you need a push mechanism, those won't work, but the spiral-wound releases might. The spiral-wound releases also bind less when bent in a small radius in my opinion. But the more bends, the more friction, and the more friction, the more the camera is likely to move during actuation, especially if that friction is jerky. Vibration may also be an issue with a solenoid, which provides linear motion very suddenly and is thus difficult to implement without vibration, especially with a lightweight camera. A motor with an eccentric cam to actuate the shutter on the lens would be far smoother, but the trick is to find a motor that makes one revolution only per actuation.

I actually took a look at McMaster-Carr, which is an online industrial supply catalog (www.mcmaster.com) but didn't find anything small enough for this purpose. I didn't look very hard. If you go there, search on "control cables". You'll need something fairly tiny to fulfill what I'm guessing are your requirements.

The cable and actuator mechanism for the body release on a Graflex is already designed to fulfill most of those requirements, and I would see if one could be adapted for this purpose. You might have to compromise the requirement on where you put the release.

Rick "whose experience suggests that half of all design efforts should be spent properly understanding the problem" Denney

Thank you! First off let me apologize in advance for these photos! But let's see:

I have drilled two small holes, approximately where i would like them to be. I can always mess around with it later, but it's a very tight area to be drilling holes in. The top hole is where the trigger will stick out, and the bottom hole is where the cable will enter the body.



I plan on holding the camera with my index finger closest to the trigger. Pretty straightforward



Here's a view from the bottom of the camera that shows how I want the cable to go, I think this would work best for folding:



And a profile view:



The folding of the camera will make both the contour of the cable and the placement/size of the trigger very important...which is why I'd like to keep the cable as bendable and the trigger as small as possible.

I'm thinking it might even be a good idea to attach a small light spring to the point where the cable comes closest to the front door...that might help keep its shape and keep it inside the camera when it closes. On one of my donor cameras, the bellows had little slots for the flash sync cable. That might also be a possibility although I can see the problems with that idea when the bellows are folded flat.

[rdenney]

Definitely look into a Graflex with a body trigger. You'll need a Pacemaker, rather than Anniversary or earlier models. The Pacemaker Graphics (both Speed and Crown) had body trigger on the lower right, with a very thin Bowden cable leading to a coupling mechanism on the side of the front standard. That mechanism has a lever that reaches out and touches the shutter release. The body release is complicated by it being switchable (on Speed Graphics) between the front and rear shutters, though it doesn't affect the cable arrangement. The cable is thin (much thinner than a standard cable release) and flexible enough to fold into the camera.

The only parts that would require some fabrication on your part are the trigger and the mounting for the actuator. The actuator mounting would be easy--forget the cable release socket and align it to push the finger release on the shutter directly. You might have to turn the shutter to the appropriate clocking to make that happen. The mechanism on that end is pretty adjustable.

The trigger will be harder. I've never had a Graphic disassembled enough to know how the body release attaches to it, but I can't imagine that it would present more of a problem than machining a film-holder back for the Polaroid or aligning the rangefinder. There will be some sort of bell crank to turn the push of the button into a pull on the cable. Note that this is a pull cable, not a push cable like most cable releases, and that helps with binding and friction.

A 3x4 Pacemaker Speed or Crown might be the place to look for a cheap carcass with a working cable. These are not particularly adaptable to easily available current films and sell for much cheaper than do 2x3 and 4x5 cameras.

One more point. If you have room inside the body, you might be able to use a bell-crank to attach your trigger to the cable, instead of turning a cable release around to go through your two holes. A bell crank would need a pivot between the two holes if you want to transmit a push as a push, or a pivot well to one side of both holes (maybe at the bottom of the camera) to turn a push into a pull. That would eliminate your tightest radius.

Rick "pretty sure the Graphic cable will be long enough" Denney

[Keytarjunkie]

Thanks, maybe that's the way to go. Again I don't have a lot of money to be spending here but I'll look into it.

[Daniel Moore]

If I wanted a button release with a very short throw, not pull , I'd seriously go the electric solenoid route rather than mechanical.

If one insists on mechanical, the way to reduce the mechanical throw is via gearing or leverage; the way to convert from throw to pull is via a bellcrank. No matter what is wanted it can be engineered. Whether it is worth it or not is a very different story!

Does this electric solenoid type already exist? I need exactly this for one of my projects.

[rdenney]

Does this electric solenoid type already exist? I need exactly this for one of my projects.

Once again, Graflex to the rescue. They used solenoid shutter actuators on many of their press cameras, so that photographers could fire the flash and release the shutter using a button on the flash unit. It's the small can that is mounted on the lens board of many Speed and Crown graphics.

Finding one that works might be a bigger issue.

Or you can buy a solenoid and create your own operation. Here's one place that sells them, and they do provide some detailed data. You'll have to do a bit of research, but the control circuits for a captive tubular solenoid are pretty simple. If it's a push solenoid, you apply voltage, and it pushes. Remove the voltage, and the return spring pulls it back. By minimizing the voltage, you can reduce the shock of the movement, but that also reduces the force. Force won't be an issue, but size and stroke will be.

http://www.solenoidcity.com/solenoid...oidcatalog.htm

Solenoids work by using an inductive coil wrapped around a magnet. Applying voltage to the coil creates a magnet of opposite pole to the magnet on the pushrod, which repels it, forcing it to move.

Rick "noting the term 'solenoid' really refers to the shape of the coil" Denney

[BrianShaw]

Once again, Graflex to the rescue. (snip) Finding one that works might be a bigger issue. (snip)

Graflex solenoids come up on Ebay quite frequently. They are also quite reliable so they are a good bet.