NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Another artificial horizon
From: Stan K
Date: 2014 Jan 2, 16:56 -0500
From: Stan K
Date: 2014 Jan 2, 16:56 -0500
Brad,
As it stands now (without any cleaning), the settled position is not consistent. Just a few trials were enough to determine that. I'll try again after cleaning, but this is a device I really don't expect to use. As I said, it weighs more than I do, and the slightest breath of air starts it rocking. I suppose I could make a cover for it, but then I might as well use the Davis AH that was also in the box when it was given to me. Yeah, I know. The water in the Davis AH ripples when the cover gets hit with wind. So I'll build a cover that doesn't sit on the water pan. Right, that'll happen.
Happily, living about 30 minutes from Long Island Sound, my classes have never had to use an artificial horizon.
Stan
As it stands now (without any cleaning), the settled position is not consistent. Just a few trials were enough to determine that. I'll try again after cleaning, but this is a device I really don't expect to use. As I said, it weighs more than I do, and the slightest breath of air starts it rocking. I suppose I could make a cover for it, but then I might as well use the Davis AH that was also in the box when it was given to me. Yeah, I know. The water in the Davis AH ripples when the cover gets hit with wind. So I'll build a cover that doesn't sit on the water pan. Right, that'll happen.
Happily, living about 30 minutes from Long Island Sound, my classes have never had to use an artificial horizon.
Stan
-----Original Message-----
From: Brad Morris <bradley.r.morris@gmail.com>
To: slk1000 <slk1000@aol.com>
Sent: Wed, Jan 1, 2014 11:27 pm
Subject: [NavList] Re: Another artificial horizon
From: Brad Morris <bradley.r.morris@gmail.com>
To: slk1000 <slk1000@aol.com>
Sent: Wed, Jan 1, 2014 11:27 pm
Subject: [NavList] Re: Another artificial horizon
Hi Stan
The reason I asked about the auto settling is that the coefficient of friction of the materials at the interface, combined with the down force, 'may' overcome the last angular motion.
I say may, because its going to be two opposing forces. One working towards level, creating a torque at the interfaces. The other frictional force working to resist that torque. If the frictional force overcomes the torque, the AH will not settle in the level position.
Before trying the experiment again, thoroughly clean the grooves, knife edges and flats. Leave no particulates behind!
Brad
On Jan 1, 2014 8:57 PM, "Stan K" <slk1000---.com> wrote:
Brad,
Nothing on the instrument, and the box just says "Springfield Power Squadron", the previous owner.
I set it rocking and watched it for a while. The axis with the knife edges in grooves settled much more quickly that the axis with the knife edges on flat surfaces, but both axes were a bit off. I tried adjusting it with the Allen screws. It was getting better, but I ran out of patience after a couple of tries. I then noticed that there was some scum on the glass, which should probably have been cleaned off before screwing with the screws.
Stan
-----Original Message-----
From: Brad Morris <bradley.r.morris---.com>
To: slk1000 <slk1000---.com>
Sent: Wed, Jan 1, 2014 6:32 pm
Subject: [NavList] Re: Another artificial horizon
Hi StanAny markings on the box or instrument?Self leveling AH. Have you performed any experiments to determine how good it levels? Set it rocking and wait until it stops (leveled) and then determine how level it actually is.BradOn Jan 1, 2014 6:12 PM, "Stan K" <slk1000---.com> wrote:
I originally sent this message in November 2012, expecting it to elicit much discussion. Instead, there was only one response, and that was four months later, so I suspect something went wrong. Since there has been much discussion on artificial horizons recently, I thought I would try again to drum up some "business".
Stan
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Since there has been some discussion of artificial horizons lately, I thought I would show one that someone, I don't know who, put a lot of effort into.
The first photo shows a top view. The outer diameter is nine inches. The left and right pivots are knife edges resting on flat surfaces. The top and bottom pivots are knife edges in grooves. There is a bubble level for each axis. The reflecting surface is black glass.
The second photo shows a side view, where the lead weight, which has lost some of its black paint, can be seen. It weighs more than I do. It also shows the stand.
The third photo shows the case. Blocks in the lid prevent movement during transport.
The fourth photo shows the lead weight. It can be seen that coarse leveling was done by drilling out some of the lead.
The fifth photo shows the stand alone.
The sixth photo shows the device in its case. In the lower right corner you can see an Allen wrench. Fine leveling is done with four Allen screws around the periphery of the circles, two for each axis. Once it is leveled there should be no reason to play with these adjustments again.
If you start the axes rocking, they take a good ten minutes or more to settle, so the leveling works nicely if you stabilize manually, but it needs to be sheltered from the wind.
Stan
