I thought I'd post another contraption I just made.
I think I'm up to number 27 so I'll just go with that.
This one started with an internet discovery that just drove me bunkers. It all started when I found this design by Rodrigo Silva on Printables (
https://www.printables.com/model/117669-ps-compact-camera-lens-conversion-adaptor-to-m39-l)
It's an M39 mount that allows you to adapt lenses from point & shoot cameras. The original concept seemed really nice, so I proceeded to print it. That's when I started running into problems; this thing is super hard to print!
Once I got one that didn't jam-up like the others, which is a common problem with this design, I did some tests and discovered other shortcomings. It's pretty hard to assemble, hard to collimate, hard to operate, doesn't have a working rangefinder connection that won't risk breaking the camera and it only focuses down to about 9 feet.
To me that was completely unacceptable. I normally would have just chucked the part in my PLA recycling bag but the idea of saving those lenses was too great, so I began obsessing over the whole thing. And for those of you who know me well, you all know this can't be a good thing.
With all it's downfalls, the original design had something going for it; namely an adjustable lens core. So, I started with only that and began sketching and drawing it in 3D.
I measured the lens draw on my Industar. I measured the thread size. After the first thread fitting test, I discovered that M39 lenses are not exactly 39mm diameter! That wad a surprise, so I measured the lens and the camera instead. Once I got the thread working smoothly on the camera, I moved-on to the next part.
My first prototype looked promising, but there was a problem with the focusing helicoid; it needed a whole bunch of turns to reach infinity, something I found unacceptable. So I moved to a coarser multi-start thread that required less than half a turn to reach infinity. Lets just say I was happy with this win.
I also added a flange to the part so that it would smoothly contact the rangefinder follower without any issue.
Now came the lens carrier. It took me a few tries to get things right but now it worked flawlessly.
Finally, I designed the focusing knob. I wanted something different, so I opted for using a timing gear as it has soft rounded edges which are easy to grab.
This one was a bit hard to design properly as I needed to set the thickness so that the lens would stop turning when the lens reached infinity. It must have taken three or four times to get it about right.
Not it was time to wear everything in so that it moved smoothly. And I did get a few scares when the lens core would regularly jam inside the focusing helicoid. But with really sore fingers, I managed to get things smooth enough for a first try.
So, I had to devise an assembly procedure for this thing as it's all held by CA glue. I mounted the helicoid in the LTM mount, backed it off a bit to put a few dabs of moly grease. I put CA glue on the focusing mount so I could put the grippy part on it... major faux-pas as it just made the threads rough. While I did manage to force it on, I knew there had to be a better way.
Now came the lens holder's turn. I had to collimate the whole thing and it involved repeatedly taking the mount on and off the camera to adjust things... not something acceptable to me. So I was thrown into making a special collimating box for testing... not an obvious thing to do.
But eventually I had the first prototype done. Which I modified for the second one, and the third.
I made some custom lens caps for them.
I now feel like I'm probably at the 90% mark when it comes to design satisfaction.
I now have re-designed the lens core so that it can be adjusted with a special screwdriver, re-adjusted the grip so that it reaches infinity more easily and reliably, added text and so on.
I also discovered 1000 ways to kill my computer in the process, with each re-calculations taking close to 10 minutes.
So, here you have the prototypes numbers 2 to 4 from left to right and the final result.
And now I can't wait to see what they can produce!
