This shows how to arrange the trunnion for either the sliding version or the folding only version. In the latter mode screw the trunnion directly to the base unit with wood screws and use a another larger wood screw as the back pivot. If you have already made the camera back incorporating the pivot rod channel but now want to change your mind, you can still use it but not bother about the extra work needed making the trunnion work the other way.
If you want all the features, this is how you make the trunnion. Once it is cut out and you have drilled hole A, heat until it is red hot then plunge it cold water. Lay it face down and hammer out the raised section using a tool like the one in the picture.You can make a punch like this by putting a suitable piece of metal rod an electric drill held in a vice and using it as a lathe and a file as a tool, shape it as shown. Then all you need is a thick piece of metal with a hole to match the thin part of your punch and a large counter sink to force the brass into the right shape. Once this is done you can go ahead, fix the pins, and make the rest of the trunnion.
The Standard Field camera arranged for using a short focus lens. It also shows how all the pieces you have made fit together. In use, normally the back is pushed to the end of the baseboard, and if maximum extension is needed, the front standard can be pushed right to the other end. Then the focusing platform can be racked right out for using longer lenses or doing close-up work. My standard design will extend to approx 320 mm and close to about 65 mm.
Now you have a base and back unit made, the next thing is the front standard. I designed it to provide the rising front movement and swings, as well as the ability to fold forwards as the camera is closed. You do this by sliding the front along the focusing platform up to the back and then loosening the two locking knobs so that it can move partly into the recess provided in the focusing platform. It may be necessary to lower the rising front slightly to get it to the closed position.
The unit consists of two slotted brass supports, their stays, and a wooden frame. This last unit has a recess for attaching the bellows on one side, and on its other side, a recess for the lens panel. The lens panel you intend to use dictates the frame size; I make mine 122mm wide by 122mm. I use the 12mm size wood and build the frame from 20mm wide strips. When made into a frame this gives a central opening of around 70mm which is big enough for most lenses. It also a big enough to fit in the necessary recesses, I mentioned, back and front. The back one needs to be about 110mm square for the front end of the bellows and the front one 100mmx 97 mm to suit the Linhof sized lens panel. The two sides need another shallow recessed slot cut on their outer edges to give clearance for the side support locking bolt heads.
You will now need to make your front standards. They should be 12mm wide and 155 mm long and slotted as shown on the plan. I have been criticized in the past for making them from 1/8 in (3 mm) thick brass. Some say thinner metal would look better but this camera is foremost a working machine, and thicker means stronger. Nothing is worse if the camera front waves in the breeze or moves out of alignment when you cock the shutter or adjust the diaphragm.
The next bit is the base for the front. This is a rectangle of brass with angle pieces fixed into it at each end so it forms a stretched U with square corners. It is of course possible to bend up this from one piece of metal, but using angle pieces can make a neater job. Your front supports pivot on 5 BA bolts from the inside of this, so its width must allow for their combined thickness, plus that of the lens panel frame .This will work out about 116 mm but should be checked as you proceed. It should also be about 40 mm wide. The diagram should help make this clear. Make the two front bracing struts next from 1/16 in (1.5mm) brass. They pivot on more 5BA bolts but this time on the outside of your base unit. The top end of this strut fits over the locking bolt, which can then ride up and down the slot on the main support. The whole front can swing and lock in any position, as well as fold forward when you shut the camera. Check the arrangement in the insert diagram opposite.
A word about locking bolts; you need them in several different parts of the camera. The one each side here is 2B brass cheese head bolt. File their heads to provide shoulders to form a flat bit that can ride in the slot to prevent the screw turning as you tighten the locking knob. The remainder of the bolt head rides in the recess cut each side of the lens frame. Again, the insert diagram will show you what I mean.
Now we come to the rising/falling front movement. This is where the whole lens frame slides up and down between the two main supports. Two brass strips with thin lips, angle sectioned brass with one side almost cut off, are screwed to the back of the lens board, holding it to the supports in a sliding fit. Another two brass strips screwed to the front holds it in check that way. The actual lock is the bar located at the base of the lens board frame across the front. Long 5BA bolts that pass freely through the lens frame at the bottom from back to front link this, and a similar one at the back. The bolts are tapped into the back bar to prevent them turning. Tightening two small knobs make these two bars grip the side supports and hold the lens frame tightly in position. The final part of the lens frame assemble is the top sliding bar used to hold the lens panel in position. This is simple to make and the plan as the picture shows.
There is now only one more section needed before the front unit is complete. This is the means to attach it to the focussing platform. Remember the brass tracks fitted inside this platform. Well, you will now need a rectangle of brass 3mm thick, that is the same width as your front and that fits snugly between these two runners. Below this, you need another piece of metal the same width but overlapping each end by 5mm. With the base piece in position, drill hole in the middle through this and the two new pieces and fit a 2BA countersunk headed bolt, tapped into to the lower piece but free to pass through the other two. Assembled the base unit, add a locking knob. Tightening this will lock the base unit to the focusing platform at any position along its length. If it does not make it firm, bend the ends of the bottom piece up slightly so that it grips the runners as you tighten the knob.
To fix the back, already made, to the baseboard, you will need to cut a channel the width of your locking boot head, down each side. This is where a Router comes in handy. This channel serves the same purpose as the one on the sides of the lens frame; to provide clearance for the head of a locking bolt. Over this channel fit two slotted strips as per the plan. The slot must be just wide enough for the 2BA locking bolt to pass freely (say 4.5 mm). The next two pieces to make are the brass trunnions; dimensions are on the main plan. Their purpose is to join the back to the base unit. The trunnions ride in the slots on the base when you add two metal pins to fit the slot, one at each end to keep everything steady but still free to slide. The trunnion locks onto the base by a 2BA bolt filed as before and set in the middle. This and the two pins, mentioned earlier must be in line. Do not forget to put the locking bolt in place before screwing the slotted pieces home. I sometimes do away with the pins and use two locking bolts each end instead of the central one. It is a slightly 'belt and braces' approach but does guarantee the whole thing stays in place, once locked, without any tendency to rock. I like my camera backs and fronts to be very stable once set in position.
The back itself pivots on the long rod that passes right through the bottom of the body through the channel you made earlier through to the other side. I have provided this with a locking provision as well. The reason is, when this is slackened, it gives the back a small amount of movement on a vertical axis. It works better if you countersink the hole in the back of the locking knob and treat the trunnion as I suggest under the diagram opposite. This turns it into a ball and socket joint, in a limited way, and provides enough movement for you to twist the back in its tracks if the picture-taking situation requires. This feature is something that escaped the attention of a magazine when reviewing one of my cameras, but is very useful in some picture taking situations. The final part of this hinge unit is the slotted stay that allows the back to fold down onto the base or provide a tilting movement for the camera back, if you need to correct distortion. Again, in the interests of rigidity, I make this from 1/8 in (3mm) thick brass.
Clearly if you only need the back to fold, you can do without the locking rod, the channel down the bottom of the camera back or treating the trunnion as I suggest. Instead, screw the trunnion pieces directly to the end of the baseboard and simply use another screw put into the camera body as the pivot for opening and closing the camera and the tilting movement. That, and as I said earlier, not having to bother about organising the slotted brass pieces screwed to the sides of the base can save a lot of time and effort.
General arrangement of the front assembly with exploded view and the way it is put together. The close-up show how they are fixed to the base. The other insert view is of the way an ordinary 2BA bolt is turned into a locking bolt. A bolt is gripped in the vice and two sides of its head are filed away flush with the treaded part but leaving about 1.5 mm of the original head intact. The shoulders you have formed will slide in the any slot that will fit the screw thread and prevent it from turning. What is left of the original head enables the bolt to be used for locking purposes, when a threaded knob is added, without pulling through the slot. These bolts are used whenever necessary on the camera.