Boss,
How I answer complex notes is to do a cut and paste then interlace my comments within.
Thanks for your thoughts.
I did actually wonder about the dissimilar metal issue here.
(Good, it shows your paying attention to how the world works.)
And the fact that brass will tarnish too.
Plus the fact that the contacts are not a phosphor bronze 'springy' material.
Will the brass relax enough to cease making contact?
(Don't know. Lack of experience.)
Probably the best thing to do when changing batteries is to use a pencil eraser to shine up the contacts before putting it back together.
(Cleaning metals is always touchy.
An eraser is usually a good idea until you get into the super tiny, then a small crumble could end up being an insulator.
Murphy shows up everywhere.
For putting a shine in metals I like an item called a 'glass brush'.
This will leave a surface sterile. Look up
https://www.eraser.com/products/component-preparation-equipment/industrial-fine-eraser/
Stunningly good tools.
And a can of dry compressed air to remove the glass chips.
Fixed a lot of gear with this alone.
Brings up fresh metal and removes all trace of oxides.)
The brass I used is a sheet brass, that seems to b treated so it doesn't tarnish too much... the sheet I had is years old and is still shiny.
(That's weird,
I don't know what to make of it.
Brass and oxygen always turns colors.
On the other hand if it's working and you need more, then finding that material again may be a bit of a challenge.)
Regarding the screws, you are right, they can strip out. I put a warning in my instructions to not over tighten them.
(Good idea,
I too made up an instruction sheet for my batteries.)
But surprisingly, they hold very well. We will see how stable the printed plastic is over time.
Hopefully they won't split apart a few years from now... if they do,
I guess I'll be refunding people their hard-earned cash.
(At some point we are not responsible for clients equipment and what they do with it.
Years most likely not. Six weeks, yeah. It's an ethics call.)
The better screw to use would be to use a screw with plastic threads.
(Two way radio makers use something like a tiny wood screw to hold circuit board to cast aluminum chassis.
I can see that ripping out little tiny amounts of plastic with each twist.)
This is a #1 screw and I don't think the plastic threaded parts are made that small.
(I guess you run the openings through with a tap.
Learned that small threads don't print well.
For the samples in the photography I used a .4mm extruder, should I need to make more will be switching to a .2mm.
I usually print a tap hole and run the tap in and out to form the threads.
This requires a thicker shell.
So for this battery holder,
I print at 100% infill to give this as much bite as possible.)
I think one of the appeals with my approach is the re-usability of it. It would be hard to justify the price for a one-time battery.
(I have run into some resistance here.
Mine are not cheap given the level of hand labor involved.
I prefer to sell them in groups rather than one at a time.
On the flip view, the price is about right given inflation from when the OEM was making these things.
Weren't they a four or five buck battery in the 80's?)
Especially since the cells we're putting in there are not the same as the original.
(I think they were mercury cells, and today there is a national allergy to heavy metals.
Unfortunately they have a long history in electronics.
Mercury rectifiers, Mercury batteries, and switches.
Hard to find a liquid metal that's a replacement and non toxic.)
The original had something very similar to a 625 battery, but not as tall. It must have been a custom made cell.
You cannot stack three normal 625 cells in that size package. Because I'm using smaller cells, it's capacity is less than the original, an therefore its life is shorter in use.
(Based on no data than a gut feeling I am hoping for a service life of between 250 to 500 exposures.
That's a lot of film.
Hopefully they will last longer.
The test camera I have has an issue and I can see that the iris is physically bent and won't move, so taking current readings is pointless.
For the moment I tall clients that this is a 'by guess and by golly' number.
I don't have any good way at this time to get facts.
That's the news.
Mike
