TOPIC:

First of all - the Tamiya denominations #200, #300 and so on.
According to RcMart (the only source I could find) these mean the "thickness" compared water, when divided by 100.
So #200 will then be 2 times thicker than water.
But I think this division is an error. It is simply 200 times the viscosity of water...

Before I had the awareness of parts availability on the internet through PayPal, I was looking for some kind of appropriate oil to fill the Super Hornet dampers I had so I could upgrade my Grasshopper. I ended buying hydraulic jack oil.
I now noticed it was thinner than the damper oil I normally used for my RC (but that was welcome)...
How much thinner though? That wasn't easy to figure out.



What I knew was that the stuff is ISO-VG 32. Which really doesn't mean much to me.
Found this chart though that enabled me to compare the different oil denominations :


Source : www.bobistheoil...ity-charts

So it compares to about 10W-20W engine oil...
Then I found another site - and a table with the viscosity of several substances, including engine oil and water :

www.vp-scientif...Tables.htm

Measured in centipoise (cps). Apparently the standard our T-brand also uses...
So the jack oil I have should be about #100 to #140 in Tamiya terminology.



Now I'm sure there's much more sensible to be said about this foggy maze of different viscosity terms...

TRF damper oils are also measured in ISO VG grade...

Edit - VG 32 is thicker, I guess :



Something's off by a factor 2 in my reasoning (I see the obvious pattern above of course)...

I reckon Tamiya isn't using ISO VG after all..
Would have been better to call it "MG" since it's mineral based.

Researching a bit more, I see I'm opening a can of variable and definition worms again...

I'm not sure comparison across different oil types & measurement standards are that relevant - oils for different applications will have quite different properties, I guess for hydraulic oils the main requirement would be minimal compressibility, for IC engines resistance to breaking down under pressure & heat, and for damper oils .. IDK, resistance to cavitation & long term stability?

Anyone asking questions like "what sort of hydraulic oil should I use in my cars sump?" or "should I use 0W30 or 10W40 in my CVA dampers?" is I think missing some important mechanical understanding

Of course the motor oil viscosity was just an intermediate to figure how ISO relates to the Tamiya standard...
Wouldn't put it in any of my shocks.
Jack oil on the other hand wasn't such a bad (cheap) alternative, I think.

www.rctech.net/...k-oil.html

Apparently fork oil is a pretty good alternative...

www.mg-cars.net...911322.htm

Wasted a lot of precious Tam oil earlier this week. Better experiment with cheap stuff.

Edou wrote:

Apparently fork oil is a pretty good alternative...

That makes sense, it's doing the same sort of job ... from memory, 20W fork oil would be a about the same or a tiny bit heavier than the standard Tamiya shock oil (40) & 10W would be a little lighter - if Tamiya use the ISO rating & fork oil is measured on the SAE Engine oil scale that would cross check.

I got fed up of buying Tamiya oil in small quantities, so bought a couple of larger bottle of Ansmann silicone oil instead - I seem to remember that the forum discussion at the time amounted to Ansmann's 400 CPS oil being equivalent to Tamiya's kit standard shock oil (40) ... so ISO = CPS / 10 ... and Tamiya (non-silicone) oil #'s are ISO?

Jonny wrote:

so ISO = CPS / 10 ... and Tamiya (non-silicone) oil #'s are ISO?

Not exactly sure about that... at that point I realised the can's somewhat wormy.

Apparently ISO VG is a measurement of kinematic viscosity.
It is easily converted to "stokes" because the added number reflects this.
So ISO VG 32 for example will have a kinematic viscosity of 32 cST (centistoke).

Now to convert from centistoke to centipoise, we appear to come into the area of dynamic viscosity...

ehow wrote:

Stokes = Poise / (Fluid Density)

www.ehow.com/ho...poise.html

Or of course : Poise = Stokes * (Fluid Density)

So unless all densities of damper oils are the same, there would be no direct conversion possible...
Our favourite brand may be adding to the confusion by calling their oil "VG".
Now I'll have to put my hand in the wormy can (read a bit more) to see what's at the bottom.



Edit - could well be the differences between the oils are minimal and the factor is indeed (more or less) 10...

Unless damper oils are a factor 10 more dense than water I'm sort of at a loss here.
Water (at moderate temperatures) has a density of 1 g/cm3. So it translates direct from stoke to poise.
I expect damper oil to be around 0.925 g/cm3. So a bit less dense even...