| Author |
Message |
    
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 111
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 30, 2010 - 04:09 pm: | 
|
I've just run into this again: an extra shutter blade in a leaf shutter.
I think the last one of these I was a Prontor with too many blades. This time, it's the Seikosha shutter in my Aires IIIL, a five-blade shutter with six blades.
The last time, I just left out the extra blade and it worked fine, which is what I intend to do here (if for no other reason that it's a pain in the ass to get that last blade in there). But I'm a little mystified about this business: is this due to paranoia on the part of the shutter designer, or by the manufacturer, that maybe some light will leak through if there isn't that extra blade there? Does anyone know for sure? |
Glenn
Tinkerer
Username: Glenn
Post Number: 746
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 31, 2010 - 04:02 am: |
|
Some repairman, in the dim and distant past, did not suddenly decide to 'slot in' the sixth blade because he had an orphan in the parts bin. If the shutters have six blades they were designed as such - sure can't be described as five bladed by any stretch of the imagination.
There is a very good book, well more a substantial technical paper, that describes the theory and technicalities of leaf shutter designs - appeared in the early 70's, well I picked my copy then. Unfortunately I cannot lay my hands on it at the moment - it is stored in the loft somewhere! Mine was in the original? German, but I recall being told that there was an English edition entitled 'Advances in Leaf Shutter Design' ? Whatever the title the subject matter covers world wide production/research.
Sorry I cannot be of more help at the moment. I do not want to 'quote' things from memory that will probably only be the half truth at best (far too much of that in this media already), so will see if I can lay my hands on the volume - but only if it's in the box I think it is!! |
Dmcrite33
Tinkerer
Username: Dmcrite33
Post Number: 23
Registered: 03-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 31, 2010 - 08:26 am: |
|
I have had shutters with the extra blade. There is not logical reason for doubling a blade. It serves no purpose. I leave the extra blade out and the shutter works fine. |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 112
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 31, 2010 - 09:00 pm: |
|
Glenn, I'm not sure what exactly you mean: this shutter has five places for blades (fixed and moving pins to hold them), even though it had six blades. Are you saying that it was actually designed for six blades? I ask because I've worked on several 5-bladed shutters like this one that only had 5 blades, all of which worked perfectly well, and all of which were the same basic design as this shutter (Seikosha MXL). Each blade overlaps its neighbors, blocking all light.
I did notice one thing when I was assembling the camera: when you look at the closed shutter, one of the blades doesn't overlap the other blades the same way as the others (over on one side, under on the other), so maybe the worry is having a loose blade that can leak light. I can't think of another reason to stick an extra blade in there. |
Mndean
Tinkerer
Username: Mndean
Post Number: 183
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 31, 2010 - 10:06 pm: |
|
I dunno guys, but I'm with Glenn here. Think about it - why would they put an extra blade in there without it serving some purpose? The extra cost in materials and design presents itself, and if it does exactly nothing, what's the value of its inclusion? I know a lot less than Glenn does about the subject, but simple logic says it wasn't done for nothing. |
Harryrag
Tinkerer
Username: Harryrag
Post Number: 168
Registered: 05-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 01, 2010 - 02:56 am: |
|
Well, every now and then this forum's participants develop their very own logic. After careful theorizing they feel they know better than the ones who constructed the shutter and conclude that there is a surplus blade that deserves to be discarded, even here https://kyp.hauslendale.com/classics/yashicaminister.html. So what? Let people find their idiosycratic way to happiness, different people have different opnions.
This topic is not new, a quick look at the archives may help to discover more recurrent reasoning about the sandwich blade.
I usually put the blade back since I read somewhere else it is there to give the whole setup more stability. |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 113
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 01, 2010 - 04:26 am: |
|
So as things stand now, nobody has come up with a plausible explanation for the need for the "extra" blade. Of course, there may be such an explanation, a perfectly logical one, but it still eludes us.
The camera seems perfectly happy with only five blades. Just for the hell of it, I think I'll shine a really strong light at the closed shutter and see if any of it leaks through ... |
Nickon51
Tinkerer
Username: Nickon51
Post Number: 120
Registered: 05-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 03, 2010 - 03:41 am: |
|
I have come across shutters with 6 blades. Likewise I don't really know the reason, but extra stabilty sounds plausible. I thought making the shutter more lightfast was the reason. The sixth blade goes on over the first one, after all the other have been put on. The blades are installed as normal and the sixth blade goes over the top of the first. It also may help to keep the blades in a tight "sandwich". If it's there in the first place, then I put it back.
-Greg |
Smasher
Tinkerer
Username: Smasher
Post Number: 11
Registered: 12-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 03, 2010 - 12:20 pm: |
|
I'd toss the extra blade; no need to lug around all that extra weight. |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 118
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 03, 2010 - 12:59 pm: |
|
Right; that extra 0.016 ounce could really make that camera a millstone around your neck.
(I don't do smiley faces either.) |
