17 Oct
2012
17 Oct
'12
5:58 a.m.
On 10/16/2012 01:48 PM, Tony Duell wrote:
Hmm, I think it might be to keep the HDA artificially pressurised at high
altitude so that the heads still fly. Either [partially] block the
breather, or just push enough air into it to counter the losses.
I was initially surprised that every[1] drive has the valve if that's the
case (rather than just a plug for the vast majority which will never need
it), but perhaps the valves were so cheap that it makes more sense just to
fit them, rather than make a separate part and still have to supply the
valve to customers wanting to use the HDA at high altitude.
[1] although pressurising at the factory to check for seal leaks might be a
useful exercise (but in absence of any other need for valves there could
just as easily be a valve on the test rig rather than every HDA)
cheers
Jules
On Mon, 15 Oct 2012, Tony Duell wrote:
However, the Micropolis 1200 certainly has a breather filter. The air
holes for it are clearly visible on the top of the HDA.
The schrader vavle is on the underside, alongside the motor PCB, brake
solenoid, etc. I haev yet to find a convincing reason for it being fitted
at all. Any suggestions? I have no idea what it's for. The HDA cannot
be presurised in normal use,
there is a breather filter. One suggestio nwas that clean ar was squred
in there when the HDA was made, forcing any resitual dust onto the
brether filter. Any other ideas?
If there was not a breather, and if you pressurized slightly, then
any leakage would be outwards, keeping dust from entering