Thanks for the thoughtful reply John.
I didn't mean to say that the hairspring should be used to correct the
unbalance, but that the guy at Independent Instruments claimed that
there was NO hairspring in a Vario, and that it was returned to zero by
a counterweight only. This I found hard to believe.
I agree with all you say regarding other problems, but I have checked
the plumbing for leaks, so don't think that is the problem. On the other
hand I have no idea what they have done to the innards of the poor old
vario. Maybe it is completely screwed up (another technical term).
Wouldn't surprise me :-(
The guy who claimed there was no hairspring also told me he couldn't
calibrate it because his test system only showed feet per minute, not
Metres per second !!!! Where did he do his instrument technician
training.....
I am not an instrument technician, but I am an engineer, and the above
left me gasping. Needless to say I won't be going back to that repair shop.
John G.
--
John Giddy
5/287 Barkers Rd
Kew, Victoria, 3101
AUSTRALIA
tel/fax: +61 (0)3 9818 4524
John Wharington wrote:
Hi John,
I can't help you with the replacement instrument, but I can give you my
impression of the zero error.
As I understand it, zero errors appearing over time in mechanical varios
is due to minute changes in the mass of the paint on the needle over
long periods of time. The needle basically gets lighter as remaining
volatile elements of the paint gradually escape.
I agree with Independent Instruments that a hairspring would not
normally be used to correct this zero offset error, what would be
required is adjustment to the counterbalance on the other side of the
needle. Otherwise you would have the needle affected by acceleration
(e.g. it would read too high or too low when circling).
Before you throw out the vario, try checking the installed system for
leaks, as it is possible that the vario wasn't sealed or the baffles
were damaged during the repair; and it is also possible that the old
tubing used to connect it to the static source may have hardened over
time and will not seal now. If I were you, I would cut an inch off the
static tube and try that.
Disclaimer: I'm an aerospace engineer, not an instrument technician.
John Wharington
On Mon, 2006-04-24 at 13:24 +1000, John Giddy wrote:
I should add that the panel is cut for an 80 mm diameter instrument.
No flask is needed, as a serviceable one is already mounted in the glider.
John G.
--
John Giddy
5/287 Barkers Rd
Kew, Victoria, 3101
AUSTRALIA
tel/fax: +61 (0)3 9818 4524
John Giddy wrote:
Further to my last post on this topic, it now seems that the vario I had
"repaired" at Independent Instruments is stuffed (technical term). The
original problem was just a zero error, which I was loth to fix myself,
as it was not easy to remove the glass to get at the movement. The error
seemed to be a balance one, rather than a spring setting.
When I got the vario back from Independent Instruments, it was reading
zero OK, but was entirely dependent on gravity for the restoration
force. When I took it back to them, they maintained that there was no
hairspring in such instruments, and that gravity was always used as the
restoring force. I had my doubts, but, not having any qualifications in
the instrumentation area, I felt I couldn't argue. Now that the
instrument is mounted in the glider and a test flight done, we have
determined that the vario doesn't work.
I know I should take it back and complain, but I would rather just get a
replacement and forget the whole mess.
Does anyone have a secondhand working Winter Variometer for sale please?
I don't want to fit a modern electronic vario, as the glider is a
Bergfalke II-55, which would have been fitted originally with a
mechanical vario.
Regards, John G.
John Giddy
5/287 Barkers Rd
Kew, Victoria, 3101
AUSTRALIA
tel/fax: +61 (0)3 9818 4524
John Giddy wrote:
Thanks for that Ian.
I don't know, but I suspect that Independent Instruments may be under
new management, as I didn't see the old gentleman and lady there on
any of my four visits over the last couple of weeks.
They always gave great service, but I am not sure the current lot have
the same dedication to quality.
Cheers, John G.
Patching wrote:
Good question John,
We had the same experience. I was going to send my ASIs' to Adelaide
but it is actually cheaper to buy a new one from Wade Air in NSW. I'm
not sure about the other instruments.
The big question is just how old are the instruments?
I am slowly replacing mine with new ones.
Cheers
Ian P.
Kookaburra Precision Soaring Team
----- Original Message ----- From: "John Giddy" <[EMAIL PROTECTED]>
To: "Discussion of issues relating to Soaring in Australia."
<[email protected]>
Sent: Friday, April 07, 2006 5:59 PM
Subject: [Aus-soaring] Instrument repair
Hi All in Victoria,
Where do people go for repair/calibration of instruments such as
ASIs, Varios, Altimeters etc. ?
I have been using Independent Instruments at Moorabbin, but my last
experience has not been entirely happy, and I would like another
possibility...
Cheers, John G.
--
John Giddy
5/287 Barkers Rd
Kew, Victoria, 3101
AUSTRALIA
tel/fax: +61 (0)3 9818 4524
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