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Thread: 4x10 metal?

  1. #31

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    Quote Originally Posted by kthalmann
    I'm not projecting anything, just stating my opinion on what material I'd choose if the goal was a lightweight 4x10 camera. The original poster specifically stated: "I'd like it to be metal and designed for light weight." IMHO that rules out stainless steel. If I was to design such a camera, no welding would be required. So, the relative ease of welding of stainless vs. aluminum would be irrelevant.

    I'm not attacking your post, or even responding directly to it. I was just sharing my opinion based on the original poster's requirements (which happen to be very similar to my own).

    Kerry
    The weight difference may not be all as great as you'd imagine. You can use thinner sections with stainless because it's stiffer. I had experimented at one point with a novel hinge system that I had been working on with a machinist which would do away with the need to machine the body of a view camera.

    All you needed were precision ground flats (available from a number of sources) that you put together at each corner with the hinge. The hinge could be mechanically attached or welded to the flats. After detaching the bellows, the rear body (box) portion of the camera body could be collapsed nearly flat using the hinges.

    When the box was opened and the corner hinges engaged, the box became totally rigid. The problem with the hinge system was in creating a light tight interior. We had several designs to solve that problem, and expiremented using flexible materials on the camera interior.

    Never finished it because the machinist moved to Wyoming and it became too difficult to continue with the development.

    When you stop thinking of the "right" materials and a certain way to do something (like every other design you've seen) you may end up with a new solution for the design requirements.

  2. #32

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    If I were looking to build a lightweight metal camera I would not choose stainless because it is not dimensionally stable...at least in the thicknesses that would allow it to be light weight. Stainless is a heavy metal. I know because I have worked with it for over thirty years.

    Aluminum casting would work better but this would require the ability to machine the material. Welding any metal is just asking for problems with tolerances. I would probably not choose to use aluminum either.

    I would opt for titanium. It is lighter and stronger than aluminum and stainless. It would require machining too. One of the small "all in one machines" would probably do what is needed to build a camera.

    In fact this would also be what I would use to build film holders since the ability to hold tolerances is greatly enhanced over conventional wood working equipment. If the machine can machine metal, it sure can machine wood.


    Welding aluminum is usually done with TIG or MIG reverse polarity DC with high frequency generator. The weld is flooded with argon for lighter material and flooded with Helium for heavier material.

    Welding stainless (especially light guage--22-18 ga) is best done with TIG equipment ...DC straight polarity and high frequency generator. The weld is flooded with Argon to keep the weld from having inclusion of oxygen which will tend to cause the weld to become brittle and subject to failure.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

    Visit my website at http://www.donaldmillerphotography.com

  3. #33
    naturephoto1's Avatar
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    Hi Donald,

    Most or all of the "Titanium" used in the backpacking, climbing, and I presume bicycle industry is actually an alloy with amongst other elements Aluminum. Yes it would be lighter than Steel, and generally close to the strength of Steel. However, it is generally heavier but stronger than Aluminum. Additionally, however, the Titanium alloys are expensive and more difficult to work, weld, anodize, or paint than either Steel of Aluminum.

    Rich
    Richard A. Nelridge
    http://www.nelridge.com

  4. #34

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    [QUOTE=Donald Miller]
    If I were looking to build a lightweight metal camera I would not choose stainless because it is not dimensionally stable...at least in the thicknesses that would allow it to be light weight.
    You need to explain this further. Stainless is MORE dimenionally stable than aluminum - look up the coeffecient of expansion for the metals.

    Stainless is a heavy metal. I know because I have worked with it for over thirty years.
    It's nearly the same weight as carbon steel, so "heavy" is relative, especially when used in thin sections.

    I would opt for titanium. It is lighter and stronger than aluminum and stainless. It would require machining too. One of the small "all in one machines" would probably do what is needed to build a camera.
    You need to check on the mass of metals before you make statements like this. Titanium is 60% the weight of steel for the same cubic volume. Aluminum is 40% the weight of steel for the same volume - making aluminum 20% lighter than titanium.

    The reason a final structure in titanium can be lighter than aluminum is the strength of titanium is about 6x aluminum. Meaning that depending upon the structure, a titanium piece could be up to 6x lighter than the same piece made from aluminum because of titanium's greater strength which results in thinner sections and reduced volume.

    Also, titanium is a PITA to work. It chews tools up in a hurry, doesn't hold first pass dimensions readily so it requires a lot of finishing passes. I have a 6-inch square, 10-inch tall block of titanium in my workshop. You can attempt to polish it with carborundum, Al/Ox, ceramic, etc. - it either gums up the polishing wheels or just destroys them in a spectacular shower of sparks.

    Titanium is extrememly expensive to purchase and expensive to work to a final finished piece. Magnesium alloy is a far, far better choice for any type of camera body. Way lighter weight then either titanium or aluminum and far easier to work than titanium.

    In fact this would also be what I would use to build film holders since the ability to hold tolerances is greatly enhanced over conventional wood working equipment. If the machine can machine metal, it sure can machine wood.
    Then you have no knowledge of computer numerical controlled wood working equipment - it's the same accuracy as CNC metal working equipment. Wood can be worked on metal working machinery with slightly different tooling.

    Welding aluminum is usually done with TIG or MIG reverse polarity DC with high frequency generator.
    Not quite. Aluminum is welded with "AC" (not real AC current) but with DC current and the electrode alternating between electrode positive and electrode negative. The DCEP portion of the wave providing cleaning of the oxides on the aluminum surface, and the DCEN portion providing the welding.

    The high frequency does two things. First, it starts the arc without touching the electrode to the metal surface so you don't contaminate the electrode; secondly, a frequency imposed on the arc focuses the arc (makes it narrower) which can be useful for greater penetration. In most cases, the frequency is set between 120 Hz and 150 Hz. The Miller machines go up to 250 Hz which is almost useless - but it looks good. Kind of like a guitar amplifier volume control that goes to "11."

    The weld is flooded with argon for lighter material and flooded with Helium for heavier material.
    No. Argon can be used for welding any thickness of metal as can helium. Helium holds more heat that argon, so it can provide greater penetration, but with a narrower weld bead. It may be useful on thicker metal if the welder's maximum amperage cannot be matched to the thickness of metal. Believe me, a 600 amp TIG can weld almost any metal in a single pass with argon.

    Welding stainless (especially light guage--22-18 ga) is best done with TIG equipment ...DC straight polarity and high frequency generator. The weld is flooded with Argon to keep the weld from having inclusion of oxygen which will tend to cause the weld to become brittle and subject to failure
    Actually - it's far easier to weld thin metal with a MIG. That's why they're so popular for sheet metal repair. MIG welding thin stainless is a breeze. The problem with TIG on thin metal is the extreme heat from the arc warps the metal. A factor contributing to this is that you have to dwell longer on one area with the torch in order to melt the metal making a larger heat affected area. If you turn up the amperage to increase your travel rate and decrease the amount of dwell time on any one area - you risk blowing through the metal when the arc starts.

    Granted, TIG is the ultimate in welding controllability. You could literally weld a razor blade to an anvil.

    If you setup a MIG correctly, you have the minimum amount of heat affected area.

    Both MIG and TIG use DCEN (electrode negative) to weld stainless steel. There is no need for high frequency to weld stainless with a TIG after the arc is started. TIG welders with HF start will stop the HF after the arc is struck and stabilized when the machine is set to DC and the electrode is negative.

    For reference, I've welded stainless using a lift TIG machine with NO HF at all. It works fine, you just have to get used to the coordination required to start the arc by lightly touching the metal surface with the electrode when you activate the arc. To learn the technique, many people start with a copper plate next to the area to be welded, start the arc on the copper plate and transfer the arc to the weld area because the tungsten electrode won't stick to the copper plate.

  5. #35

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    Apparently your references on the characteristics of titanium do not follow my references. My references indicate that titanium has a density that is about one half of copper and about 60% that of iron.

    For it's weight is very nearly six times as strong as aluminum and twice as strong as iron. So taking these into account for a equal dimension of material titanium would have 60% the weight of iron (which is very similar to stainless steel)...So computing this to arrive at the same strength we would have a componant that would be 30% the weight of iron or stainless steel. Further more at that it would be six times the strength of an equally sized dimension of aluminum. So arriving at the same structural strength you would be able to decrease the structural dimension of a titanium componant to 16% that of the size of an equally strong piece of aluminum. This decrease in dimension to achieve an equal strength more than offsets the higher weight per dimension of titanium over aluminum. That is what my resources and my math indicates.

    Furthermore it is born out by my son who is a metallurgist and production engineer with Boeing Aircraft Company. Dimensional stability of a metal is a condition of it's characteristics insof as being a conductor or insulator. Stainless steel is a far less efficient conductor than a metal like aluminum or copper. This relatively poor conduction property leads to problems with dimensional stability when one is welding light guages of this metal (stainless steel). I strongly disagree with your statement about light guage metal being more easily welded with MIG rather then TIG. TIG with a continually variable amperage control allows one to alter the current over a range and gives much better control of the welding process.

    All, (read that to mean each and every instance) of the light guage stainless steel TIG welding that I have observed in over thirty years has been DC positive current. The only instance of negative current TIG has been on Aluminum. I agree that hi freq (alternating current) is not necessary to the welding process once the arc is struck. However when you do welding on really light guage metals like beer cans then the hi freq does help one heck of a lot.

    I have personally welded stainless with AC TIG and I have welded stainless with DC positive.(electrode positive) By the same token I have welded aluminum with TIG reverse polarity.(electrode negative)

    I agree that titanium does carry special considerations when it comes to machining. But by optimizing feed rates, chip loads and the flute orientation of the end mill one can come a long way to achieving acceptable results in the machining process of this metal.

    I am fully aware of CNC controlled wood working equipment. My remarks about using a machine for both metal and wood was aimed to the reduction of an investment in machinery for someone who opts to try to build their own metal camera and who presently owns no machining equipment.

    I stay by my earlier thoughts on this subject.
    Art is a step from what is obvious and well-known toward what is arcane and concealed.

    Visit my website at http://www.donaldmillerphotography.com

  6. #36

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    Quote Originally Posted by steve
    When you stop thinking of the "right" materials and a certain way to do something (like every other design you've seen) you may end up with a new solution for the design requirements.
    Absolutely. I was actually thinking of trying to make a really light camera using just standard sheet metal techniques - a punch press and a break. I think it's possible. It would be an ugly beast, but very light and not so expensive maybe. And for this, aluminum is probably not such a good choice because it wants larger bending radii than, say, stainless.

    Before I try anything like that though I want some serious time with a 3d modeling package ;-)

  7. #37
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    Hi Bruce, with all this talk of welding, and subjects metallurgical did you ever get your original question answered?
    If you havn't given up looking for a 4x10 camera have a look at fotoman on

    http://www.fotomancamera.com/prodect_list.asp?id=160
    [FONT=Palatino Linotype]Rob J-T[/FONT]

  8. #38

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    Quote Originally Posted by trebor569
    Hi Bruce, with all this talk of welding, and subjects metallurgical did you ever get your original question answered? If you havn't given up looking for a 4x10 camera have a look at fotoman on...
    Go read the post I made on 8-Aug-2006 at 1:54pm. I need movements that Fotoman doesn't have.

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