One more time: Tachihara 4x5 front cam loosens up. Solution?

[Ulophot]

I have posted about this before and tried numerous possibilities. Here's a new thought, after having had to shoot with the camera aimed well downwards the other day and having the right-hand cam open completely from the pressure, unbeknownst to me until a two exposures had been made.

What sort of liquid might be applied to the cam and upper washer surfaces to increase friction under pressure? I could live with having to reapply it if it would last for even a day's shooting.

For those unfamiliar with the camera, the cam is solid brass, the stainless steel washer is 0.2 mm thick.

[Doremus Scudder]

Thicker washer?

Or replace the cam entirely with a stud and knurled knob assembly that you can tighten down better.

Can't think of much else.

Doremus

[Ulophot]

Thanks. Makes sense. I might have to get someone do that for me. But your mention made me think about having to figure out how to get the entending bed out to do it, and that reminded me that the back cams lock quite securely, which may result in part from the top plate through which the stud would pass being very slightly un-flat, i.e., convex top-wise, so that tightening the cams flattens the top plate ever so slightly,increasing the pressure against the ca, bottom. I'll have to see if I can figure it out. The camera came to me third-hand (at least) with some signs of misuse. I had a couple of issues addressed in an early repair but not this one.

[Ulophot]

Well, that was interesting. I discovered that the front front standard is removable when the cams are removed. I discovered that a couple of screws holding the guides for the standard to move back and forth on bed had come out very slightly. After tightening them and cleaning the bottom of the top plate that the cams press against the guides, and reassembling, I seem to have achieved a better cam tightening. Time will tell; my experience tells me this may be temporary.

My idea about the plate does not make sense, at least for me to try. It's held on with rivets and toying with it is therefore unwise. I think it's about as flat as it's going to get; so be it.

In the long run, however, since I intend to return portraits with this camera primarily (once we can get through the plague), the bed will tend to be level or not too far from it, in any case.

[ericantonio]

Well, that was interesting. I discovered that the front front standard is removable when the cams are removed. I discovered that a couple of screws holding the guides for the standard to move back and forth on bed had come out very slightly. After tightening them and cleaning the bottom of the top plate that the cams press against the guides, and reassembling, I seem to have achieved a better cam tightening. Time will tell; my experience tells me this may be temporary.

My idea about the plate does not make sense, at least for me to try. It's held on with rivets and toying with it is therefore unwise. I think it's about as flat as it's going to get; so be it.

In the long run, however, since I intend to return portraits with this camera primarily (once we can get through the plague), the bed will tend to be level or not too far from it, in any case.

Awesome!!! I had a 100 year old Korona and the screws everywhere was like that. I hated it. I wasn't a woodworker but I knew if I really wanted to baton down the hatches, I would have to unscrew it all, fill the holes with wood glue or something and screw everything back. I had not time back then or commitment. Sold it to a nice young fellow who wanted to take it to Korea.

Also, for things that need tightening, not just cameras but in general, I usually do flat washer--split washer-- nut. So maybe you can add a flat and split washer to your setup there and that could help it a little more.

[Maris Rusis]

I just checked the front and back locking cams on my Tachihara 45GF camera and note the following:

The cam handles tilt forward (toward the subject matter) to unlock the front standard. It is possible when disassembling and reassembling the cams to wrongly install them backwards so that the handles tilt backward (toward the photographer) to unlock the front standard.

The cam handles are pulled back a tiny fraction past vertical (toward the photographer) when the cam is at maximum tightness. The effect of this design is to "wedge" the cam even tighter if the front standard is pulled forward. The picture of the cam furnished by the OP shows the cam handle way past vertical. This should not be possible.

The locking cams on the back standard swing plates work the opposite way with the handles tilting back to unlock the swing. Again, maximum locking force arrives when the cam handles are a tiny fraction past vertical but this time in the direction of the subject matter.

The OP's post of 21 Feb 2021 also shows a Tachihara front locking cam with the handle way way past vertical. This should not be possible if the adjustment is correct.

[Ulophot]

Maris, thank you. Since the manual, such as it is, really gives no clue about this (or much else), I certainly defer to your expertise. I have, along my journey with this camera, tried adding more and thicker washers, without success, but I shall try again based on your recommendation. Also, according to your description, my back cams are on the opposite sides from where they should be. I'm not sure why this makes a difference, but I'll take a look into it. (P.S.: would love to see more of your outstanding work here again.)

ericantonio, thank you also, but there is no room for "flat washer--split washer...." Note that I mentioned that my washer is 0.2 mm, so thin that thy are obtainable only through hobby shops that deal with a lot of miniature modeling.

[Ulophot]

Maris, I just tried your suggestion for the front cam. The closer I get towards a more vertical closed position, the less stable it is. I tried different combinations of washers to achieve this -- not having a single one of sufficient thickness -- but even just two 0.5-mm ones gave the same result. Why yours works this way and mine not is beyond my comprehension; I am not a builder or mechanic of any kind. I returned to the single 0.2-mm washer, which lands my closed position as shown below. The cam has not reached maximum width by this point and thus still reaches a stopping point.



I know that the Tachihara 4x5 was made in a number a configurations with various modifications -- some more significant than others -- over the years it was produced, and perhaps your camera is slightly different from mine in some respect we're not including as a potential factor.

[Maris Rusis]

Interesting! Years ago I was a sales engineer marketing Tachihara camera in Australia. I got to see many of them and from unit to unit they were very consistent. I still have two 45GF for personal use. Their serial numbers are from 1993 and are only 33 units apart. And yes, the locking cams in both cameras work identically just like in my previous post.

Just for sake of experiment I added a very thin washer to one of the front cams and found the fully tight stopping place of the cam lever is exquisitely sensitive to washer thickness. Any increase in thickness means the lever stops before vertical. Any reduction in washer thickness means the lever goes past vertical to get a tight lock. I suspect Tachihara specified cam and washer as matched components.

I also discovered that the force exerted by the cam on the washer is concentrated on a very small area so a thin washer is easily bent and the cam lever has to go further to get a lock.

Amusingly, I also found using an ordinary washer with a bigger central hole doesn't work well. The high force cam looks for the edge of the centre hole and bends the metal a little bit. Again, the cam lever has to go further to get a lock.

[Sean Mac]

These were referred to as "over center" cams when I was a student.

They have to go past the point of full compression to lock.