The Thornton Pickard Roller Blind Shutter is one of the earliest examples of what is now referred to as the focal plane shutter. Unlike the later (and more complex) Graflex style shutter, these were made to be used in front of or just behind the lens and were sold as a complete unit that could be retrofitted to an existing camera. They came in a variety of sizes and were sold for around thirty years. There were even Japanese made versions with steel casings instead of the usual mahogany. They are relatively simple units and the main problem encountered with them is curtains that are either broken or leak light, unsurprising in a unit that may will be at least 80 years old and may well be closer to 100. Fortunately it is relatively easy to replace the curtain and get the shutter working again.
The shutter consists of a cloth curtain with a rectangular hole in it that is attached to two brass axles. The axle on the right is hollow and has another axle inside which is attached to the outer axle by a long coil spring. The tension on the spring can be adjusted by winding a brass knob on the top and the shutter speed is indicated on a dial at the bottom. The axle on the left is solid and has a pulley and a cog at the top. The cog connects to another cog which has a racthet mechanism to allow the shutter to be held in place. The pulley has a string wound around it that runs across the shutter and out of the right hand side.
When you pull the string it turns the pulley, which in turn winds the shutter curtain on to the left hand axle. As the curtain is unwound from the right hand axle this motion winds up the internal spring in the axle. The ratchet stop on the large cog on top is held in place by the long lever. Lifting the lever releases the cog and the spring unwinds, which in turn pulls the curtain back onto the sprung axle. As the curtain moves, the hole in it moves past the aperture in the shutter casing and light passes through. The curtain completes it movement and the aperture is blocked again.
That’s not all. The designers placed another stop on the gear so that the shutter could be held open as well. If you moved the lever over to the “Time” position the first time you fired the shutter it would stop with the aperture open and then firing it again would close it. In the picture above you can see a small hole in the lever. This can be threaded for a conventional cable (or air bulb) release to be attached. Also note the brass knob on the right. This is connected to the inner axle and turning it tensions the shutter and thereby increase its speed. The spring next to it is another ratchet mechanism, preventing the shutter losing all of that tension.
Here is another style of cable release. Pressing the plunger pushes the cable out which lifts the little brass hinge which in turn lifts the lever and fires the shutter.
Another view of the cable release. Due to a shortage of space there is no nice celluloid disk with “Time” and Inst”. This version of the shutter only has “T” and “I” stamped into the plate that holds the sprung axle in place.
Part 2 – Disassembly
To replace the curtain you will need to pull the shutter apart. On most shutters the lensboard is held in place by a couple of bent brass pins that can be rotated out of the way. You can see these on the left of the shutter shown above. You will also need to remove a wooden baffle which is held in place by two screws at the top and bottom of the shutter. In this picture only the right side of the baffle remains, but the two brass crews on the bottom of the shutter can be clearly seen. With the baffle removed you will have a much easier time removing the shutter curtain.
Now remove the existing curtain and measure it up. The curtains on this one were glued and sewn in place. The stitching was carefully cut with a craft knife and then the curtain was prised free of the axles. On the left hand axle there is a wooden (balsa?) cover that I had to slide off first. To do this I had to disassemble the gear train on the top plate.
First remove the arm and the large cog.
Next remove the plate trapping the small cog. This cog is atached to the top of the left hand axle.
Now you need to undo the rest of the screws holding the top plate in place and remove it.
The axle can now be maneuvered out if necessary.
Part 3 – Making the new curtain
Lay the curtain out flat and carefully measure it. In the picture above you can see that the original shutter tape (the thin strips of material at the top and bottom of the aperture) had broken. The remaining piece was carefully measured to calculate the correct length of the aperture. There are two pieces of split bamboo that are used as attachment points for the curtain edges and the shutter tape. Carefully cut any stitching and prise the curtain from them, noting the distance from the ends of the curtain to where the pieces of bamboo lie. Add a little extra to the lengths for both the shutter cloth and tape as we will be gluing rather than stitching and may need more surface area for the glue to hold.
In the picture above I have cut a strip of shutter cloth the same width as the original shutter. The cloth is rubberised on one side. For the sake of clarity I have lightened the pictures a lot, which is why it appears grey. It is actually matt black on the rubbers side and gloss black on the other.
Cut two pieces of the shutter cloth and two pieces of shutter tape to the dimensions you have calculated. You will need to cut notches out of the cloth where the tape is attached. The picture above shows everything cut to the correct size and laid out in the correct positions. If anything, I could have made a little more allowance for overlap at either end of the shutter cloth.
Glue the pieces of bamboo to the rubberised side of the shutter cloth. I used contact cement which made it easier to clean up the residue once I had finshed.
The cloth is folded back over the piece of bamboo and glues to itself. The shutter tape is glued in the same way.
The finished join, shown from the rear.
Repeat the process for the other side, taking care to make sure that both sides remain parallel, i.e. that the shutter tapes is the same length at top and bottom. Laying it all out on a gridded cutting mat makes this a little easier.
The finished shutter curtain shown from the (rubberised) front. The extra bits of contact cement on the curtain were simply rubbed off. At this point I left it all for 24 hours to make sure that the contact cement was properly cured.
Part 4 – Reassembly
Start with the right hand (spring) side of the shutter. Draw a line on the rubberised side of the cloth where the stitching was on the original shutter. Spread contact cement from here to the end of the shutter cloth. Also spread contact cement on the brass axle, taking care that you don’t get too close to the ends. The sprung axle should be left in the casing for this.
Carefully wind the shutter onto the axle taking care that it remains parallel to the shutter casing. Leave the glue to set for 24 hours.
Repeat the process at the other end. It will be easiest if you take the entire axle assembly out for this step. If the axle has a balsa wood sleeve this should be removed first, i.e. the shutter curtain is attached to the brass, not wood.
Replace the balsa wood sleeve if your shutter had one and put the axle back into the casing. If the string that cocks the shutter is broken this should be replaced now. There is a hole in the bottom of the pulley which is vaguely visible in the picture above. Thread the replacement string through the hole and tie a knot in it. You can hold it in place with a drop of glue but this probably isn’t necessary.
Now wind most of the string onto the cog. The string runs through a little wire loop and then along a channel in the casing before exiting through a hole on the right hand side of the casing.
Carefully wind the shutter curtain onto the sprung axle. You will need to unscrew the spring stop at the top to allow the sprung axle to rotate freely. When you have taken up all the slack reassamble the gears on the top plate. Refer to the picture on page 2 for a rough guide to the correct orientation of the large cog. When you pull the string it should wind the curtain onto the left hand (unsprung) axle until the ratchet lever engages with a stop on the gear. At this point the shutter should be in the open position. If not simply change the orientation of the large cog a few teeth at a time until you get the correct position. If you then keep pulling the string it should wind until the second stop and the shutter should be closed again. Lifting the lever should allow the shutter to fire.
Here you can see the almost finished shutter. At this point you should try test firing it to see if the speed seems right. If it is running too slow you will need to disconnect the spring stop and wind the brass knob a few times to put more tension into the spring. This will be a trial and error process.
If you have access to a shutter tester to establish the speed you can then adjust the tension to match one of the marked speeds (these vary from model to model). Then by unscrewing the ratchet lever on the speed dial you can rotate the dial to the correct speed and then reattach the ratchet.
And here we are with the finished shutter, except that I am using a baffle borrowed from another shutter. I still need to make a new baffle, which will be cut from 3/8 inch MDF. The hole in the baffle will be the same size as the hole in the rear of the casing. The bottom of the baffle is rounded at both sides so it doesn’t snag the curtain and the top left corner is notched to leave room for the loop that the string is threaded through. The end of the string has a paperclip tied to it temporarily, originally it would have had a small metal ring or a wooden bead.