Having worked out where the encoders fit and how they are driven by 2 driving cogs, I set about designing the exterior of the dial. This is a job I thought would be easy; the profile and design externally had been sorted out since my early sketches. 2 hours I thought. 2 hours to CAD it up and get on with the rest of it.
3 days later and an imminent deadline as good as missed, the dials are finally almost finished. It has been an absolute nightmare trying to fit everything in. I had a list of priorities which absolutely had to be achieved:
- The dials must be flush with the outer casing
- They must be suitable for assembly (it sounds stupid but it's easy to design things in CAD and fit things into conveniently placed gaps only to realise that in reality, the physical part couldn't actually be squeezed past other components to get into that position)
- They must lock into their specific cogs
- They must not fall out of the body!! (again, it sounds obvious, but this was the biggest pain in the arse to achieve because there simply wasn't enough space to do what I wanted to do)
- They must have detents, so the dial goes "clunk" as it spins and holds its position when let go
The screengrab at the top shows the cog in place and the exterior of the dial modelled. I offset a wall thickness from the exterior face to create a hollow around the ring, leaving space to work within. In the shot above you can see I have started to fill it by adding the detend ring, designed to give a soft click for each setting stop. It was calculated to have 14 setting stops, 13 for actual values (1/2000 through to 2 seconds on the shutter side, F2.8 through to F22 on the aperture side) and 1 Auto position.
The layout of components is identically mirrored around the centre plane of the camera, so both dials are designed and work in the same way, and even have interchangeable components. Working on one side though has drawbacks. I had to mess about designing and redesigning and moving and shrinking the detent ring a dozen times because when it worked on one side, the slightly different layout of adjacent components on the other side would screw it up. For example, the ring ran into the main circuit board the first time I modelled it, something I hadn't noticed on the other side where the main circuit isn't replicated.
I have no screenshots from the next problem, apart from the one above which actually shows the end solution. The problem I had was that once I had added the cog and the detent ring, I couldn't see a way of locking keeping the dial in the body. If you turned it upside down it'd just drop out. I needed to include a retaining ring somewhere, so that the dial could be dropped into the body from the outside, and then locked with the retaining ring, so it had the freedom to spin but not fall out.
Working out how to do this took me almost all day. I moved so many parts and tried so many things, and in the end there just wasn't enough space. My solutions either wouldn't fit, would hit other components, would not mate nicely with the cog/detent rings, would hit the encoders, couldn't be fixed to the dial..... etc etc. In the end I actually ended up modifying the uni-body shell. Above you can see there is an extra ring (third block in from the outside) which just slides under the circuit board, and over where the uni-body would sit. It's not easy to work it out, the shot right down at the bottom shows it off better.
Here is a shot of the dials from the outside with the markings added, bang in line with the detents inside. The outside aesthetics hasn't been compromised, even though inside it's chaos.
Above and below you can see how the final solution works both together and exploded in the same layout as the assembly order. The solution looks elegant and simple, which is good, but it doesn't really show the hours of staring and thinking and headaches that went on when trying to figure it all out.
