Help Me Identify this Compass

[JamesBon92007]

So....some questions (if I get stuck with it)

1) Since I still have a working Supertilt Hose mount
a) I have found a module from XS Scuba that will work for about what I paid for this ($30-ish). Are there any others?
b) Can just the 'capsule' (as in the attached photo) be bought, since the housing/bezel is good? If so, where ?
2) Should I just not worry about using the mount and go find an 'OK' compass of any brand ?
(I only need a compass occasionally and have a precision one on my Vyper Air. Would probably prefer CLIP mount)
3) Anyone got and old one they want to sell (PM me if so).

Thanks.

I have a console that I custom fit to an Ikelite compass many years ago. The compass leaked out it's oil. I tried several other compasses but none fit. So, before I ditched my console and built a new one I decided to try this:

Portable Plastic Outdoor Camping Tool Liquid Oil Filled Emergency Gear Compass | eBay

It just happens to be exactly the right size to fit my old Ikelite housing. It does not glow in the dark. I think I paid 78 cents for mine (the price has come down!). I've had it on 10-20 dives down to as far as about 90 feet with no problems. This may not be the same seller I got mine from but I always check their approval rating before I buy. I will go down to about 98.5% if it's coming from China.

My local dive shop actually carries replacement compass modules that are similar but those are the only ones I've seen other than the eBay Chinese modules. The dive shop's modules appeared to be the same.

 

[james_bond_007]

...

Portable Plastic Outdoor Camping Tool Liquid Oil Filled Emergency Gear Compass | eBay

It just happens to be exactly the right size to fit my old Ikelite housing. It does not glow in the dark. I think I paid 78 cents for mine (the price has come down!). I've had it on 10-20 dives down to as far as about 90 feet with no problems. This may not be the same seller I got mine from but I always check their approval rating before I buy. I will go down to about 98.5% if it's coming from China....

How can one go wrong for $0.72 (today's price) ...including shipping ?

 

[Scared Silly]

OP - just file a claim with eBay that the item was damaged. Anymore they have a pretty good policy of not letting sellers screw over buyers. Just recently dealt with something similar.

 

[The Chairman]

Oil in a compass serves two functions: It's a needle dampener preventing magnetic hysteresis, and since it's also non compressible, it stops the housing from being deformed the housing.

 

[james_bond_007]

OP - just file a claim with eBay that the item was damaged. Anymore they have a pretty good policy of not letting sellers screw over buyers. Just recently dealt with something similar.

Already did. Need to wait a week and see if the seller responds.

I'm not too worried...just disappointed I didn't get a 'cool' vintage compass that worked.

 

[james_bond_007]

Oil in a compass serves two functions: It's a needle dampener preventing magnetic hysteresis, and since it's also non compressible, it stops the housing from being deformed the housing.

The fluid (not necessarily oil) is also is used to prevent freezing of a compass.
Albeit, this may not apply to scuba compasses in temperate waters.
(Maybe it applies to ice diving, but since I have no experience in that area, I cannot speak to that issue.)
I had understood that older, non-pressurized aircraft that flew at high altitudes used compasses with 90/10 alcohol/water to keep them from freezing EX: B-17 (maybe just a myth ?).

Not sure what you mean by this:
" It's a needle dampener preventing magnetic hysteresis,"

I understand about the damping. The fluid is essentially the "D" component of a classic PID (proportional/integral/derivative) controller, where the fluid (damper) is 'smoothing out or preventing' the oscillations that would occur without the fluid, thus preventing or minimizing overshoot/undershoot.

But I am not seeing how fluid applies to magnetic hysteresis. To me, magnetic hysteresis occurs when, after applying a magnetic field to say, another magnet (or compass in our case) , and then removing it, the original magnet does not return to the original position, despite not be subjected to anything (including friction) other than the initial conditions.
So I am not sure how the fluid would be involved in any sort of 'magnetic' hysteresis.

The only thing I can think of is that if the static coefficient of friction (Fs) between if the spindle about which the card spins and the card is large enough, and the dampening factor too small (i.e. fluid is not viscous enough allowing overshoot) or too large (i.e fluid too viscous and causing undershoot) the card can stabilize/settle too late (spin past/overshoot), or too soon, (never get to/undershoot) the true direction. But to me, this would be due to the friction between the card and the spindle that cannot be overcome by the force of the magnetic field/compass rather than due to magnetic hysteresis.

In other words, there is so much friction at the point of mechanical rotation that the force of the compass, due to the Earth's magnetic field, cannot overcome Fs and properly turn to the correct position. This, IMHO, would just mean we have a cheaply (lower precision) made compass, rather than seeing effects of magnetic hysteresis.

Can you help me understand where you believe magnetic hysteresis comes into play with the damping fluid ?
(and I'm not trying to be a 'wise guy', I just what to know what you were getting at )
Thanks.

 

[JamesBon92007]

Already did. Need to wait a week and see if the seller responds.

I'm not too worried...just disappointed I didn't get a 'cool' vintage compass that worked.

On top of that, if you pay with PayPal you are usually covered for just about anything that goes wrong. They even refunded my shipping costs when I returned an item recently. I actually came out 30 cents ahead.

Yes, the 72 cents includes shipping. I bought a couple extra at that price. Vintage is nice but I have other compasses if I want to look cool

 

[The Chairman]

Can you help me understand where you believe magnetic hysteresis comes into play with the damping fluid ?

We're saying much the same thing. Here's a link that covers the importance of oil in the compass: Compass Fluid

 

[james_bond_007]

We're saying much the same thing. Here's a link that covers the importance of oil in the compass: Compass Fluid

Thanks.

While a PID controller typically applies to a closed loop system, with proper choices of coefficients, it can sometimes be used to model an open loop system.

 

[james_bond_007]

UPDATE:

Ebay
1) Ebay denied my claim, due to the Seller's claim that, because I tool the compass out of the boot to inspect it, I had disassembled it.
2) I appealed - I explained that the boot was like a 3rd party case for a cell phone; if you take the phone out of the case, it is not considered disassembling the phone. I also gave her links to separate boots and compass modules being sold on Ebay
3) I won and received reimbursement
4) I then tried to write a negative, but not nasty, review on the Seller. I only discussed his reluctance to negotiate with me. I was willing to give him some $$$ for the boot. Ebay automatically removed it.

Compass:
5) I found the leak in the compass, glued it, drilled two tiny holes in the side, filled it with 1:1 babyoil/mineral spirits (baby oil alone was too thick, mineral spirits alone began lifting the paint from the dial) using a hypodermic needle, and glued the holes shut using Loctite Extra Strong Super Glue Gel. This type is rubberized and gap filling. It has a 1/16" bubble, but works (tested to 60').
Hardest part was 1) cleaning the oil off the compass by the drilled holes using Dawn w/o getting water in the compass and 2) gluing the holes shut over the 'cleaned' surface

Why? Just wanted to try. I will buy a new module when this fails.

NOTE: when testing the compass on the table, I put an M-1950 compass nearby. It affected the compass severely (caused dial to rotate up to 180 when the compass was more than 12" away). More sensitive than any 'land' compass I have used.