XRAY - Model racing cars

After talking to a Hydrualics guy yesterday here's the deal: their is no formula for converting Centipoise to SAE WT because of "Shear" and "Fixatropic" effects on the oil viscosity. Also, of the chart that he referenced the effective range of SAE Wt oils is huge. Like this:

10WT can be anywhere from: 85 - 140CPS
20WT can be anywhere from: 140- 420
30WT can be anywhere from: 420-350

This basically is on the same page with KenPro's post. WT (at least within the RC industry and those suppliers of shock oils that use WT for a viscosity measurment) appears to be an internal rating system standard to only that particular company.

All this being said, I also researched suppliers of Silicone oil aka: Dimethyl Silicone. There aren't very many and of the US maunfacturers I found (3) they all sell their oil in CPS. Which means the buyers (Losi, Associated, etc.) are buying in CPS and then labeling their packages into their own "WT". Hopefully that makes sense.

In anycase, unless you can get them to give up their own idividual CPS=WT charts you will not find an accurate conversion.

MyFileHut.com still isn't working so below is the conversions that I work off of. These are based off of Gene Hickerson's conversions and are refereneced on TWF8

WT. = CPS
10.0 = 100
15.0 = 150
20.0 = 200
25.0 = 275
30.0 = 350
35.0 = 425
40.0 = 500
45.0 = 575
50.0 = 650
55.0 = 725
60.0 = 800


CPS = WT.
100 = 10.0
150 = 15.0
200 = 20.0
250 = 23.4
300 = 26.7
350 = 30.0
400 = 33.4
450 = 36.7
500 = 40.0
550 = 43.4
600 = 46.7
650 = 50.0
700 = 53.4
750 = 56.7
800 = 60.0

This is my chart showing the ambient temperature effects on the oil. It's tough to read because the formating on this forum doesn't support an EXCEL file but maybe some of you will find it useful.

TEMPERATURE-VISCOSITY CHART

TEMP.
C F
42 108 90 135 180 225 270 315 360 405 450 495 540 585 630 675 720
37 99 93 139 185 231 278 324 370 416 463 509 555 601 648 694 740
32 90 95 143 190 238 285 333 380 428 475 523 570 618 665 713 760
27 81 98 146 195 244 293 341 390 439 488 536 585 634 683 731 780
22 72 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800
17 63 103 154 205 256 308 359 410 461 513 564 615 666 718 769 820
12 54 105 158 210 263 315 368 420 473 525 578 630 683 735 788 840
7 45 108 161 215 269 323 376 430 484 538 591 645 699 753 806 860
2 36 110 165 220 275 330 385 440 495 550 605 660 715 770 825 880
CPS# listed in bold is the "purchased" viscosity.

Example: If you have 200CPS and your running at 36 degrees F that would be like using 220CPS oil or virtually the same as using 250CPS on a 108 degree day (225CPS).

OH!!!!, lastly....

the easiest thing to do is get oil rated in CPS. Then you don't have to worry about it. Use up what you have and replace it with oil that uses the world standard in viscosity measurment, like XRAY oil

xray 600 isn`t kyosho 600 so something is totaly wrong...
I think xray 600 is more like 450 kyosho

So ....XRAY

400w is ...400 = 33.4wt

an Losi marked 35wt is 35.0 = 425


which looks to me the losi 35wt is thicker by 25cps

am I reading this right... ???

I got this chart from Team Losi in the early 1990's :
10wt=100cps
15wt=150cps
20wt=200cps
25wt=275cps
30wt=350cps
35wt=425cps
40wt=500cps


Everything else is an educated guess.

I appreciate everyones help on this topic, but the next most important question still needs to be answered by Xray.

How is Xray oil measured?( drum roll please....)

Auto2 - Yes I can see a need for some kind of a sheet that shows the steps. I treat oil as an additional tuning accessories. Yes it can be and is expensive but they are just as important as the additional swaybars,shock pistons etc etc. It sure is nice knowing that you have the full compliment of oils as there will be a situation when your going to use it all.

It appears that some Team Xray drivers are sending oil in to get it tested versus the international rating system... Until those results get back I am afraid I cannot answer the technical aspect of your question...

And the question that's now on everyone's mind is why in the world do RC companies like associated, losi, and XRAY just make up some rating system out of the blue?

Why don't they use the international standard?

It's like instead of saying the chassis is 3mm thick, you come out with an ad saying it is 3.5 "frugomeisters" thick. It's actually ridiculous if you think about it.

I've pondered about this particular issue long before this thread started. It would be nice to see one of these manufacturers come out with a reasoning for it. Until then, I'm starting to think the reason they all use made up numbers (with in house formula ratings) is because the oil you get is not actually accurate enough from bottle to bottle to legitimately make the claim on the bottle in an internationally recognized standard.

For instance, in my original example, if you make a 2mm chassis and claim it is 3mm, anyone could check it and prove you wrong and you could even be in a heap of legal trouble as well. But if you claim it is 3.5 frugomeisters thick no one has a reference to measure your claims but you yourself so that protects you.

just wanted to bump this back on the first page. Any updates?