GeckoSub Mirage Evo - And Adventures in 3D Printing Speargun Parts

[Diving Gecko]

Blowing O-rings Out Of Their Grooves

@Zahar mentioned this as being a risk and it has indeed happend to me on this very build. Back when I was using the original bushing which looked like this:

Looks like a perfect fit for an 8mm bore (or rather ~8.1mm), right?
Well, Mares designed the bulkhead for this gun to be 9mm...:

Which I think is a bit strange as that's an unneeded 0.5mm gap all around the bushing which is not healthy for the o-ring.
On top of that, as mentioned, the groove seems to not have any free space, either.

When I used this bushing in a Mirage system with a 9mm bore, the o-ring was blown off. But when I made my own bushing with a bigger OD resulting in taller walls around the o-ring, it stayed put. Not Mares' fault as it was never intended as a Mirage part but nonetheless, an 8mm bushing in a 9mm bore almost sounds like they decided to increase the bore to 9mm after having manufactured 1000s of 8mm bushings...

 

[tromic]

New Bulkhead In The Making - Part 2
I took yesterday off, but back in the workshop today. Last time around, at the end of Op 1 which are all the features I can reach from the front side, I hadn't programmed two of the chamfers perfectly. So, they stopped short when they were close to the filleted sealing lip for the power regulator valve.

I considered just finishing those chamfers in hand but I had a go at re-indicating the part in the vise and it went well
View attachment 60858View attachment 60859

The chamfers look almost perfect, just one little weirdness on the shooting barrel bore edge where it meets the sealing lip:
View attachment 60860

You can kinde see how it's ever so slightly higher, so maybe the Z-offset was not exactly the same. Anyhow, that little blemish can be ground and polished and overall, I think the finish looks great. Especially the inside bore walls come out very smooth.

I also engraved a version number on it so I can keep track of it down the line. But I got lazy and just used a 45d chamfer tool to do it. I have some tiny engraving tools, I have used to greater effect before.

OK, on to Op 2 which is all the remaining rear features.

David, I noticed that the lip edge may be too sharp, high, and could cut the rubber seal at a pressure of 35 bar...?
I tried to calculate the equivalent diameter of the air regulator opening, as if it were round, and I got 10 mm..? I didn't check so I might be wrong...