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#53937 - 11/18/05 11:54 PM Re: what's a good compass
Anonymous
Unregistered


If you read my K&M Matchcase update from Down Under post, I described having to tilt the matchcase 15-20 degrees towards south for the needle to move, and even then it does not move freely. Its pretty awkward when you walk around too.
If you hold the matchcase straight up, it looks funny with theneedle tilted so far. It just doesnot look right.
One of my friends when he went overseas took his Silva/Brunton Ranger 15 to see what would happen. In England he was pointing it on a steep angle to the ground towards North.
Recta came up with an idea that Suunto now uses which has a small magnetic needle with a pivot point that works freely anywhere around the globe inside a slot in a larger needle which uses a standard pivot point and gravity to balance it.
The needle you can see stays balanced by gravity but the smaller needle pushing it inside may have a large tilt where you are standing, and will not bind and stop working.
The Earth Magnetic feild travels between North and South, but the angle of the field varies and is not parallel to the surface, except near the equator. Near the Poles it becomes quite steep.

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#53938 - 11/19/05 12:53 AM Re: what's a good compass
SheepDog Offline
Enthusiast

Registered: 02/27/05
Posts: 232
Loc: Wild Wonderful WV
Quote:
From what I can tell the secret to a global needle is a VERY "tiltable" pivot point that allows you to tilt the compass more than you normally would.


No the magnet is mounted on a gimble over the needles bearing that allows the magnet to tip independently of the needle but rotate with the needle. The compass is still held horizontally (normally) to the ground no matter which of the compass zones you are in.
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#53939 - 11/19/05 02:17 AM Re: what's a good compass
Craig_phx Offline
Old Hand

Registered: 04/05/05
Posts: 715
Loc: Phoenix, AZ
Bee,

I keep my Suunto Comet on a 5" loop of thin braided nylon cord I got at Home Depot. Toss the metal ring. Tie one end of the cord on the end of the compass with a cow hitch. Then tie the other end to a belt loop, also with a cow hitch. Then put it in your pocket. I put mine in the watch pocket of my jeans. But it also works if it is just hanging loose into your pocket. To use just pull on the cord. In the past I had one that was not on a cord and I dropped it several times. When it hit the ground it would pop apart into 3 pieces. Now I don't have to worry. If you don't have a belt loop you could use a safety pin.
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#53940 - 11/19/05 02:21 AM Re: what's a good compass
KenK Offline
"Be Prepared"
Pooh-Bah

Registered: 06/26/04
Posts: 2015
Loc: NE Illinois
Hmmm ... I'll have to take a good look at mine again. It is nice knowing that I can take a compass with me when traveling overseas and that it will work.

I got incredibly turned around once while walking in downtown Taipei in Taiwan - all the signs looked the same and none of the streets ran parallel. I REALLY wished I'd brought my GPS and a compass that worked there. I might ask Santa for a Garmin Geko 201 for Christmas - it is small and very easy to carry.

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#53941 - 11/19/05 03:37 AM Re: what's a good compass
Anonymous
Unregistered


When I ordered my Recta I ordered with the global needle, but after 3 months waiting, I settled on the DP6 with the standard needle.
I searched and settled on the Silva 9020's because they were the cheapest global needle compasses I could find.
I have a response email from the Suunto importer so I will try contacting retailers he suggested to get an M3g to play with, and also some more Clippers.
Ive removed the compass out of the K&M Matchcase (see post K&M Matchcases- Update from Down Under) and took a few pic's of the needle tilt. I will try and post them up on Monday.
If I can get some more Suunto Clippers, which sound hopeful now. I will pull them apart and use the compass centre in the K&M Matchcase.

I got caught a few years back when I went for a quick, short trip out through some pine plantations at night and the weather closed in. I lost my vew of the sky and lost my bearings. I knew the areas South and East of my location but I didnt have a compass in the car. So I took a lot longer than the 30 minutes I'd planned. Similar feeling to your Taipei <img src="/images/graemlins/smile.gif" alt="" />
Shows how easy you can get caught out. Ive been EDCing a compass ever since and also keep a one in the car.
I also looked at the Geko, but I like the eTrex better.


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#53942 - 11/19/05 09:30 AM Re: what's a good compass
stormadvisor Offline
Journeyman

Registered: 03/14/05
Posts: 87
Loc: Ohio
Never thought of the global needle issue (new to me). I have a question now. After reading the posts here I understand how it works and for the most part why. I don't know why my Silva would not work everywhere in the northern hemisphere. North should be at a similar angle. Right?
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#53943 - 11/19/05 02:07 PM Re: what's a good compass
Anonymous
Unregistered


Quote:
I don't know why my Silva would not work everywhere in the northern hemisphere. North should be at a similar angle. Right?
I dont know which angle you ar talking about.
The angle of declination is the angle of difference between True North on a map and Magnetic North shown by you compass. Some compasses have an adjustment to tune the compass into True North so you dont have to convert anything. Your Ranger has this adjustment.
The angle of inclination is the difference between The Earth Magnetic field and the surface of the Earth.
On the Equator The magnetic field is close to parallel to the surface. The magnetic field is steep at either pole. If you get a bar magnet and lay some paper over it then sprinkle iron filings over the paper, you will see the lines of magnetism around the magnet. Near the poles of the magnet you will see some lines go straight up and away. Down the sides they will be parallel to the magnet. The poles sort of act as an entry point to the lines of magnetism.
For example if you get a compass needle that is setup for the equator so it sits parallel to the ground. Then you take that compass close to the border of the US and Canada the needle will be tilted down towards the ground on the North side. If you then take that same compass down here to the bottom of Australia it will be tilted down towards the ground on the South side.
Also the Earth is not a perfect sphere, or even in distribution of minerals and land, so the magnetic field bends and curves from that interverence aswell.
The pivot point of the needle will start to bind and stop or inhibit the rotation of the needle in some locations.
Compass manufacturer have tried many different designs over the years, some better than others. The original style Silva (Sweden) base plate compasses came in 5 different needles, Recta made theirs with 2 different needles, one for Northern Hemisphere and 1 for Southern Hemisphere before they come up with their Global Needle system.

So in answer to your question about your Silva working everywhere in the Northern Hemisphere, I dont know but I expect it would work nearly everywhere except close to the North Pole, but you may have to hold it on a bit of an angle in some places.

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#53944 - 11/19/05 06:26 PM Re: what's a good compass
KenK Offline
"Be Prepared"
Pooh-Bah

Registered: 06/26/04
Posts: 2015
Loc: NE Illinois
In a FAQ in Brunton.com they say:

Question: Does the 8099 have a global needle? Will it work anywhere around the world?

Answer: The needle on the 8099 is specific to a particular region. The three regions are: northern, equatorial, and southern.

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#53945 - 11/20/05 12:53 AM Re: what's a good compass
Anonymous
Unregistered


Thats different to their product info pages:
www.silva.se/outdoor/products/comp_voy.htm

Nothing like a bit of contradiction to fuel a debate <img src="/images/graemlins/smile.gif" alt="" />

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#53946 - 11/20/05 01:22 AM Re: what's a good compass
stormadvisor Offline
Journeyman

Registered: 03/14/05
Posts: 87
Loc: Ohio
I do understand declination and have it set on my Ranger for my location. I now see what the pupose of the "global" needle is for. I never really thought of that aspect of things. I figured that since you are following the curvature of the earth while approaching the poles you would always have the compass horizontal.

Thanks for the lesson!
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