Last night I couldn't sleep so I pulled out one of my favorite how-to-use-a-map-and-compass books for some late night reading.

With that in mind I pulled out some of my compasses this morning only to find:

My Brunton 8099 has a large bubble in it.
My Brunton 8096 also has a large bubble in it.
My Brunton 15TDLC's needle actually points to the south instead of north, and it is tilted downward a bit.

Sigh. I haven't got a clue what happened to the 15TDCL. It worked fine just a few in July (last I used it). All my compasses are stored away from nasty fields. I even keep them separated from flashlights, batteries, and the like.

The truth is that I knew the 8099 had the bubble - I'd written Brunton about it last July and they said they'd fix it at no charge. I just hadn't gotten around to sending it in yet. Now I need to send three compasses in.

Befoe we start bashing the 8099, I actually have a second 8099 (long story) that I'd sent in for a bubble repair a few years back and it remains bubble-free to this day ... and I REALLY like the 8099. I find it sooo much easier to sight bearings than with the 15DTCL ranger-style compass.

Ken K.

Normally if a compass' needle is tilted it is not a global model and is out of the zone it was built for; there are several different zones and normall compasses are made to work in a specific zone.
Bill

I know this is true, but I don't understand the science of it. Why do normal compasses only work in specific zones and what makes "global" compasses different?

Jeff

Not always the case. I've had the same thing that happened to Ken's happen to a LOT of compasses. I kill a compass in about three years that way. It can be 30 year old military surplus, and in three to four years, it will be inverted.

Well, maybe if you were something like plasticraven or paperraven, that wouldn’t happen!

…

I know… I know… I just couldn’t resist.

Here's a good explanation

http://www.dougritter.com/global_needle.htm

The way I understand it, depending where you are on the globe, the needle doesn't always point parallel to the surface of the earth. It could point up or down to some degree. The global needle allows it to pivot without affecting the pointing direction.

Speaking of broken compasses,

Does anyone know is Silva (I can't remember if they own Brunton or what the deal is) will replace/repair broken compasses?

I have 3 Silva Ranger 15's that all have significant bubbles in the capsule caused by a crack. I think I broke then all the same way by having them in my chest pocket while driving the snowmobile, you hit something hard and compresses the compass against the handlebars.

Thanks,

Mike

The 15TDCL was built for the US, and worked fine up until July.

You know, I did see funny lights in the sky last July ... oh wait, that was Independence Day. Never mind.

Explanation: http://www.utm.utoronto.ca/~w3gibo/How%20to%20do%20field%20studies/properties_of_magnetic_field_at_.htm

Vector Explanation: http://www.ngdc.noaa.gov/seg/geomag/geomaginfo.shtml


Inclination Map: http://www.ngdc.noaa.gov/seg/geomag/icons/wmm2000i.gif

Compass Inclination Zone Map:
http://www.wide-screen.com/support/FAQsuunto.shtml#Anchor-60059

Brunton says that the 8099 is made for three regions: northern, equatorial, and southern.

The Brunton 8099 type compasses are seriously flawed in design in my view. A bubble of any sort will prevent the compass card from rotating....effectively making it useless. That coupled with its tendency to form bubbles at the drop of a hat has relegated mine to the storage box....after 3 capsule replacements it just is not trustworthy.

A bubble in a needle compass will most likely not make the instrument useless....that to me is the reason to not use any of the Brunton compass card type instruments.

Silva = Brunton. Their repair replacement has been top rate for me. Just do not get an 8099