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Meikon a7RII zoom adjust

Started Nov 26, 2018 | Discussions thread
daveco2
OP daveco2 Contributing Member • Posts: 953
Re: Meikon a7RII zoom adjust

That looks great. Do you have any more details on how you did this and how it is working? Wondering how you attached the adjuster making sure it is waterproof at depth.

I tested the assembly by pulling a vacuum, giving a one atmosphere inward differential, equivalent to 33 ft of water depth.  No air leaks while rotating the zoom adjust.  I also submerged it in a tub of water, but of course, that didn't show any leaks either. Have not dived with it yet.

The rotating adjuster rod is attached through a Swagelok fitting normally used for gas pressure and vacuum use. I've had these fittings up to 3000 psi and down to 10^-6 Torr, and have used them as a rotating seal under these conditions. A disassembled sample is shown in the top figure of the picture below, and the assembled part in the bottom figure. The body has an O-ring seal. The rotating seal is made with a nylon ferrule about 1/4 inch long that is swaged against the rotating shaft. Teflon ferrules are available for more free rotation, but I prefer the tightness of the nylon.

I made 2-D and 3-D CAD drawings before cutting any metal. The parts fit had to be good to fit within the space available. The housing with arc saddle required use of a fly cutter in a mill, which can be dangerous. It is bolted to the case extension from the inside and sealed with epoxy, requiring a good fit to start.

I don't recommend this project unless you have a home machine shop and lots of experience operating it.

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Sony RX100 Sony a7R II Sony a7R III
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