I've measured the updated plenum part (10338) as it is currently installed on the latest version of the Impact M4.
Here too, the previous M3 part has been drilled out 4 mm deeper with a 6.2 mm flat drill bit, leaving barely a 0.6 mm rim as seat for the o-ring.
Surely that can't be suitable for a pressure of up to 160 bar, or am I mistaken?
To give you an idea of how thin it is, there is a plastic filler in the photo.
The hole in the top for the valve rod is 3 mm and the hole above the lower o-ring is 1.5 mm in diameter.
Because it has been drilled out 4 mm deeper, the position of the bushing is therefore completely irrelevant.
The bushing is 6 mm high, of which 4 mm has a diameter of 7.9 mm and 2 mm has a diameter of 8.10 mm.
The O-ring is 2.9 x 1.78 PUR90 (5107).
According to ChatGPT:
Minimum thickness high-grade aviation aluminum (2024-T3, SF = 2)
| Pressure | Wall Thickness (Theoretical) | Wall Thickness (Practical) | Top/Bottom Thickness (Theoretical, with 3 mm hole) | Top/Bottom Thickness (Practical, with 3 mm hole) |
|---|
| 100 bar | 0.17 mm | 1–2 mm | 1.42 mm | 2–2.5 mm |
| 160 bar | 0.27 mm | 1–2 mm | 1.80 mm | 2.5–3 mm |
If this is correct, even at 100 bar with high-grade aluminum, you are still more than double below the theoretical minimum thickness.
The part would probably have been within safety margin if it had been drilled out to a depth of only 2 mm instead of 4 mm. That way, the position of the plastic bushing would also make sense.
So if we can get exact dimeter of the main shaft hole, find flat face drill bit to drill just enough to make that flat sitting surface for O-ring, we should be good? Can you measure diameter of that space?
