Hydro Oil conversion

[DuckHole]

If your remaining bubble doesnt shrink on you I would call your mod a success. It looks really good. That oil can be found at any hobby shop that sells R/C cars. I race 1/8 scale nitro buggys and have TONS of this stuff in different weights for the shocks. I just ordered my first Gshock yesterday and wanna do this mod so bad when it arrives. Anyway thanks for posting your experience and photos!

[tfar]

Can you point me to such a shop in Austin? I have no idea where to find that stuff locally. Gun shops should sell the low density variety as it is used to oil guns but it's not what I'm looking for.

EDIT: This link contains charts on RC silicone shock oil as it is called in the RC world. Most mfrs give a WT rating. And as usual with American mfrs (rant, rant,) these weight ratings are not coherent among brands and not coherent as compared to the cSt standard for the most part. A 40wt for one brand can be 1000CSt whereas for another brand it is 500cSt. This link helps:
http://www.rcrcr.com/index.php?optio...eral&Itemid=46

If possible, try to find oil by Mugen-Seiki or Kyosho as they label in linear cSt steps. GS Racing does that, too.

At the very bottom of the page there is also an interesting chart telling you how viscosity changes with temperature. The standard rate is given at 25C. This is probably pretty close to the temperature in your watch except in very hot summer or winter conditions.


Till

[RayT]

strangest mod yet imho...different strokes

[tfar]

Here is another converter:
http://www.offroad-cult.org/Special/...wt_convert.php

It's approximative but indicates that a 500cps/cST rating equals around a 40wt and a 1000 cps/CSt rating is around 73wt.

This should give you a good reference what to look for. I'm pretty sure anything between 300 and 1000cps will be fine. cps is not quite the same thing but corresponds number for number to the cSt rating, as far as I understood.

Till

[freeman]

I have the feeling that the best way to do the mod, if possible, is to heat the oil at the highest temperature you need the watch to operate, and then do the plunging. That way the oil will for sure not expand more than it already did during the heating.
Only thing to check is if it's easy to close the case while the oil is hot. And also if it can be done fast enough to prevent the oil to cool down during the process of closing the case.

[tfar]

I have the feeling that the best way to do the mod, if possible, is to heat the oil at the highest temperature you need the watch to operate, and then do the plunging. That way the oil will for sure not expand more than it already did during the heating.
Only thing to check is if it's easy to close the case while the oil is hot. And also if it can be done fast enough to prevent the oil to cool down during the process of closing the case.

Very smart thinking! Good idea. Thanks! You'd close the case while the watch is submerged. So no cool down will happen. This means you have to put at least one hand in oil that is around 60C hot. I have some VERY thick silicone (ironic) kitchen gloves that will allow me to do that.

Can't wait to do that mod. If it works well I might do it to other watches. I could imagine the GW-M5600 where the display is very close to the glass would look absolutely stunning.

Till

[freeman]

Very smart thinking! Good idea. Thanks! You'd close the case while the watch is submerged. So no cool down will happen. This means you have to put at least one hand in oil that is around 60C hot. I have some VERY thick silicone (ironic) kitchen gloves that will allow me to do that.

Can't wait to do that mod. If it works well I might do it to other watches. I could imagine the GW-M5600 where the display is very close to the glass would look absolutely stunning.

Till

Don't forget one important instrument to do the mod : your camera :)
Hope it'll work !

[tfar]

The coefficients of volume expansion you saw probably have units of inverse Kelvin or inverse degrees Celcius--same thing, since it's the change in temperature that matters. The change in volume is equal to the coefficient of volume expansion times the original volume times the change in temperature, so the final volume is equal to the original volume times the quantity 1 + the coefficient of expansion times the change in temperature.

Here is the graph from the clearco site:
iscosity Specific Gravity Pour Point Flash Point Viscosity/Temp Coefficient Thermal Expansion cc/cc °C Thermal Conductivity g/cal/cm/sec °C
50 0.960 -55°C 285°C 0.59 0.001060 0.00036
100 0.966 -55°C 315°C 0.60 0.000960 0.00037
200 0.968 -50°C 315°C 0.60 0.000960 0.00037
350 0.970 -50°C 315°C 0.60 0.000960 0.00037
500 0.971 -50°C 315°C 0.60 0.000960 0.00038
1,000 0.971 -50°C 315°C 0.61 0.000960 0.00038


0.000960 is the thermal expansion factor. Once you are in the 100cSt range that doesn't change until you get to 100,000cSt! The lowest used by a member here was around 200 cSt the highest 10,000. For expansion it seems to not matter.

Let me see if I understand your explanation correctly. I presume an oil fill volume of 5cc (cubic centimeter) for ease of calculation. It is probably also pretty close to reality. A G-Shock measures about 4x4x1cm = 16cc. The volume inside the watch is probably half that, 8cc. Most of that is taken by the module. So fill volume would actually be close to 5cc, I guess.

Here goes for a temperature differential from 25 to 60C, thus factor 35:

5cc x (1+ 0.00096x35)= 5 x (1+ 0.0336) = 5 x 1.0336 = 5.168

This means an expansion of about 3.4% for a temperature change of 35 degrees C. So you see a direct relation between temperature change and expansion percentage. Basically every ten degrees of temperature change will give you 1% of expansion.

Let's play it safe. Normal temp 25C. Highest temp 80C. Difference 55C. Maximal expansion 5.5%. 5.5% of 5cc is 0.275cc.

1 cubic centimeter is 10x10x10mm. Here we are dealing with at most one third of that. Thus 10x10x3mm. That is one friggin' big bubble!

It would fill half the display in surface area and about half the case depth. Much bigger than even the biggest bubbles we have seen.

Perhaps my calculations are wrong but I don't think so. Do we have science times who can verify that the approach and execution is correct?

This means that either the entire bubble thing is over-rated because those little bubbles wouldn't really help or something else is wrong.

There is another thing I'm thinking of. When we close the watch it's airtight. No air in or out. If the watch is filled with oil all the way. And the oil has a temp of 50C when we fill it. It will then try to contract by 2.5% when it cools down to 25C. But can it contract? There is no air in the case. Does that even matter. Would the watch so to say implode instead of explode. During diving the water temp may be around 10C. So that would mean a contraction of 4% of the 5cc volume, i.e. 0.2cc. There will be an under-pressure in the watch. However, I'd think that a watch that can withstand an over-pressure of 20ATM can deal with that.

We need a darn physics prof or engineer!

Till

[tfar]

Don't forget one important instrument to do the mod : your camera :)
Hope it'll work !

Should I hydro my camera???

Till

[freeman]

Should I hydro my camera???

Till

This is called hydromania :)
I'm not going to try to check your calculations sorry... but I was thinking that all this can be checked : by heating the oil, filling a glass of 10 cl (for example) with hot oil (80C), and then let it cool down to room temp : then check the volume. Then we'll see the percentage of expansion in real life.... In fact since you want the watch to survive at low temps, the volume difference should be even multiplied by 2 : or put the glass in the freezer.
Concerning your second point : I don't think we have a problem there : if the oil doesn't fill all the case it simply should shrink but without causing a significant enough depression inside the case to make it implode : the depression should be negligible. In high pressure (deep water), the pressure of the water causes a much more significant force on the watch which is then likely to implode. But the presence of enough oil inside it is exactly what should counter the water pression and will prevent the watch implosion.