For those of you just entering 1:8 scale racing. Just a little story about shock-fluids.

In the beginning of the 80's cars were equipped with small shock absorbers 1/4 of the current size. The shock fluid used was normally a kind of transmission oil. 
These oils always changed in viscosity (thickness) during use and temperature and a stable shock oil was not there. Therefore all kinds of products were tried. 
Even STP oil was used, you then had to warm up your shocks before racing with a hair dryer before you could use them.
Fortunenatly silicone oil was introduced in the mid 80's. This type of oil has an better constant viscosity over a wider temperature range then other fluids but still is not complete temperature stable!

The thickness of the oil is officially rated in Centi Stokes "Cts". 

An other known and used American rating is WEIGHT "WT". 
This WT or W rating is a non world standard and is introduced by Associated and not comparable between brands using this W or WT rating.

Thanks to Casper who found this remark on the net about SAE WT:

"Correct measures of viscosity are centi-stokes, N/m^2, or poises, depending on how you define it.
SAE WT is not really a measure of viscosity. The SAE scale was designed for classifying motor oils. For example SAE 30/40 means that the viscoity is one value (30) at one temperature and an equivalent (40) at the engine running temperature. When the number has WT after it this meanns "winter" so that the oil will have a particular value at I think 0 degrees Celsius.
The main problem with using the SAE scale oil is that each SAE band can encompass a large variation in viscosity. For example one manufacturers SAE 5 can be anothers SAE 10 and both are within limits. Using the SAE scale oil is best only to compare one manufacturer.

An other story about WT thanks to Frédéric De Behr who found this on Wikipedia.

"Single-grade, or monograde motor oil
For single-grade oils, the kinematic viscosity is measured at a reference temperature of 100°C (212°F) in units of mm˛/s or the equivalent older non-SI units,
centistokes (abbreviated cSt). Based on the range of viscosity the oil falls in at that temperature, the oil is graded as an SAE number 0, 5, 10, 20, 30, 40, 50, 60 or 70. The higher the viscosity, the higher the SAE grade number is. These numbers are often referred to as the weight of a motor oil. The reference temperature is meant to approximate the operating temperature to which motor oil is exposed in an engine"

So, clearly, "weight" is not a measure, just a chart, and the measure is the ISO cP viscosity or cST dynamic viscosity  (at specific temperatures !), then you compare it to the SAE table.  Some charts are referenced by Wikipedia.


Concerning Cts the thinner the oil (fluid) the lower the number, the ticker the oil the higher the number. 
For normal shock absorber use, this rate may vary between 100 Cts until 900 Cts.
Nowadays we use O-ring sealed differentials, so we can use silicone oil in the differentials instead of thick grease. 
For differentials the rate may vary between 1.000 Cts (loose) up to even 500.000 Cts (very, very, stiff).

Some USA based companies are still using the "WT" weight rating, where Japanese and European companies use the better linear industry standard Centi Stokes rating. 
A lot off people think that the ratings between the "WT" and "Cts" ratings are linear but this isn't the case.

If there is a factory that can provide oil for testing we can arrange this to see if the product reaches the specification claimed or convert to Cts!

Which manufacturer use which rating?
Which manufacturers you can use same rating oil?
Only manufacturers using Cts as rating are using a world standard and can be mixed used.
Other ratings like W and WT differ from brand from brand as WT or W is not a world standard!

No one can tell TEAM TWF8 how "WT" OR "W" rating is measured!!!!! If you know it let us know! info@twf8.ws

The only and correct way to measure fluid thickness or to say viscosity is to measure the flow of fluid itself in certain time trough a hole. Simple!

So we do not weigh the weight of the oil as this is a standard value that does not change when the viscosity changes!

A special calibrated measuring device called "Ubbelohde" is a U-tube that contains a certain amount of fluid (in our case the silicone oil). The diameter of the tube and the diameter of the hole where fluid goes through is always constant and calibrated. The thicker the fluid the longer it takes to get a certain amount through. The time the passing of the fluid takes and the known diameter of the hole can produce the figures we need called viscosity.

How does the measurement works?

A vacuum sucks the oil that is in the bottom of the tube up into the front tube. As soon as the top fluid level of the fluid has passed the top (HIGH) sensor the vacuum drops automatically and the oil starts to flow back. A timer is started automatically. As soon as the the fluid level passes the other sensor (LOW) the time counting is stopped! The time it takes for the level to go from the high to the low sensor is the time we need to calculate the viscosity of the fluid.
As we know the amount of oil, the time it takes and the diameter of the calibrated hole we can calculate the viscosity in mm²/s. Then we have the viscosity in Centistokes value.
Centi Poise (nowadays called Pascal per second) is the result of the Centistokes value magnified with the density of the oil.
Normally for silicone oil this value is 0.9875 = almost 1.0

To perform the whole measurement accurate and constant we have to calibrate the whole system first. Normally this is done when the tube is placed in a water bath that is keeping the whole measurement set up on same temperature @ 22 degrees Celsius for the whole measurement. A calibration fluid is used to check if the reading is correct or need to be adjusted before the real measurement takes place.
Then the tested oil is placed into the tube and the test is performed. As not all oils are the same in viscosity, there are different tubes with a calibrated hole to get the appropriate and corresponding readings.

From September 2006 we measure all oils with a RHEOMETER.



Serpent oil (04-01-2005)
rating W Cts

20

107
25 207
30 370
35  626
40 1070
45 1449
50 2250


We tested this oil supplied by Serpent Benelux on 04-01-2005 in our labaratory and compared them with a calibration oil.of 100 Cts.

Conclusion:
  Serpent oil is way of linear with Cts rating


Xray silicone oil with Rheometer
09-10-2005

Rating Cts
100 106
150 179
200 248
250 292
300 354
350 381
400 441
450 475
500 542
600 625
700 702
800 799
900 913
1.000 1020
Differential usage  
2.000 2490
3.000 4270
5.000 9000
7.000 10500
10.000 13000
20.000 30000
30.000 39600
60.000 65000

Use the values above for your benefit and as a guideline.
Xray oil provided by TEAM Xray Slovakia


Kyosho

rating Cts
250 244
300 302
350 351
400 411
500 506

Use the values above for your benefit and as a guideline.


Associated silicone oil measured with Rheometer
09-10-2005
rating WT Cts
10 108
15 --*
20 208
25 286
30 373
35 454
40 525
50 707
60 725
70 960
80 1040

Use the values above for your benefit and as a guideline.
* The value 15 Weights we measured was like water thickness and is probably a filling fault at the factory.
Altough the contents was silicone oil it was to thin for the 15 WT spects and can not be used for the shocks.
Associated oils were provided by Kendall Bennet from A-mainhobbies and Tony Penzincka from Tony Screws


Trinity silicone oil measured with Rheometer
09-10-2005
rating Cts
30 337
35 376
40 505
45 497
50 658
55 568
60 799
70 757
90 974

Use the values above for your benefit and as a guideline.
Trinity oils were provided by Kendall Bennet from A-mainhobbies and Tony Penzincka from Tony Screws


Losi silicone oil measured with Rheometer
15-12-2005
rating Cts
15 110
17.5 158
20 243
22.5 243
25 294
27.5 345
30 381
32.5 397
35 459
37.5 477
40 546
45 657
50 886
60 844
70 970

Use the values above for your benefit and as a guideline.
Losi oils were provided byVolker Gerdes from BUGGY-SPORT.INFO


xceed

 

Xceed RC just released a full range of silicone oils for use in geardiffs and shocks.

High quality lab-checked and verified silicone oil. Packed in 50ml easy squeezable bottles, with special top for precision filling of shocks and diffs.

Available now, range 300cst up to 200.000cst in total 13 grades.

TWF8 inhouse chemical analist, Jacco Koch, tested the consistency of the total range.


Ultimate rc shock oil
Ultimate Racing brand was created in 1999 by Modelix Racing with the main goal in mind of offering high quality alternatives and solutions to the 1/8th nitro racers, with the advantage that has been designed by experienced racers. After a few years, Ultimate Racing has become a brand synonymous with racing in the 1/8th scale nitro market.

The distinctive feature of the Ultimate Racing products is that have been designed with both professional racers and beginners in mind, so the result is a wide range of high competition products that can also be easily used by beginners.
ultimate oil pic


SILICONE SHOCK OIL AND TEMPERATURE

Although everybody thinks silicone oil is not affected by temperature, we can wake you up out of that dream. 
When the same test is done @ 12 or @ 32 degrees Celsius we get other values!
Test result from our laboratory provid us with the following fist rule:

When temperature is 10 degrees Celsius lower or higher the viscosity decreases or increases by 5%. Example:

200Cts @ 12 degrees Celsius is 210 Cts
200Cts @ 22 degrees Celsius is 200 Cts
200Cts @ 32 degrees Celsius is 190 Cts

Silicone shock oil measured in Centistokes at various temprature in Degrees Celsius
Shock oil temperature Losi 40 Trinity 40 Associated 40
5 754 688 747
10 677 622 685
15 605 555 598
20 539 492 536
25 501 467 502
30 455 420 456
35 409 377 410
40 373 345 375
45 345 320 346
50 319 294 319

 

 

Team TWF8 special thanks goes to Jacco Koch our Chemicals specialist from The Netherlands for testing the fluids and the pictures.


Click here and see how to mix your silicone shock and diff oils in the right percentages.