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Saracen vision block clamp


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This is the clamping plate that (via compression) holds the front vision block in place. There was a rusty broken threaded rod that passed through a clearance hole in the right hand wedge and threaded into the left hand wedge. The head of the threaded rod is located on the outside of the vision block housing. This is as I believe it to be assembled.


I am a bit confused as to why it should work, I can see that as the threaded rod is tightened the left hand wedge moves towards the centre of this plate resulting in a clamping force on the vision block. But there is nothing pushing the right hand wedge towards the centre of the the plate so surely the vision block is only being squeezed on the left hand side, or have I missed some vital point?


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Do you have the "Vision block, keep plate assembly FV811056"?


There was a mod issued in March 1976 to modify it to prevent the swing bolt slipping out of engagement & releasing the keep plate.



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Nic I have a diagram of the modified plate but there are no measurements other than the relatively minor adaptations.


It refers to the IPC 12559 Amdt No.4 Plate H13, Item 32. I have that it doesn't include Amdt No.4 although it has some before & after.


It suggest the whole thing was a pain in that the IPC had to list a new item & a blue EMER was issued indicating that it had "immediate priority" to be carried out.

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I replaced the vision blocks in my Mk 5 Saracen, about 18 months ago.


There should be a hand wheel on the threaded rod coming through the housing, and that provides the clamping force on the other side of the wedge - the threaded rod pulls the wedges together, which due to the inclined plane on the base, lifts them up and clamps the block.




Let me know if you have any other questions.










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Thanks Terry, that's really helpful. I'll have to fabricate the hand wheel but the photo clarifies exactly what's needed. I only managed to get hold of the shorter (side) vision block from Richard Banister which I was going to use, with some slight modification to the housing, in the absence of getting the correct vision block. I gues it begs the question, where did you get the front vision block from?


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FYI, the old one had a crack in it and the plastic between the glass layers had degraded, so you couldn't really see through it. Once replaced, I thought that the best thing to do was to see just how bulletproof it was. One of the guys in the RAAF took it to work and they shot it during a range day with 1 x 7.62 NATO and 2 x 5.56 NATO. It shattered, but held together quite well.

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