Author Topic: Pure Silicone Oil In Hydraulic Systems  (Read 429 times)

Online ozarquebus

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Pure Silicone Oil In Hydraulic Systems
« on: June 09, 2021, 03:56:56 PM »
I didn't want to hijack the thread on twodogs neautiful new Convert refreshment, so here is new topic, sure to be short lived.

 Does anyone have experience with silicone oil in hydraulic systems?

From reading lots of Convert threads, it appears there is a relationship between mpg and slippage in the slush box and some Converts appear to slip more than others.

Maybe I am wrong and it locks up at high revs, but

If so, has anyone tried to improve it other than by using different atf?

ie: adding silicone oil to ATF.

I never tried it and am not recommending adding silicone oil to the torque-converter ATF, but isn't silicone oil  theoretically one of those fluids that will flow at low rates, but get almost hard when sufficient mechanical or shock energy is applied to it. If it would still flow properly through the system, adding some could theoretically remove slippage at higher rpms.
 Whenever I get a Convert running, I might give it a try, but I have a feeling it may lock up at a low flow rate and make uneven circulation. Does silicone oil fully integrate with ATF or does it separate?  It could be guessed that it might collect in one spot and get hot or clog the pump impeller.

Any insights?


« Last Edit: June 09, 2021, 04:57:17 PM by ozarquebus »
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Offline Aaron D.

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #1 on: June 09, 2021, 04:43:35 PM »
The torque converter doesn't actually lock, and viscosity has no bearing on function.

They have to slip to produce torque. If it isn't putting out the torque it should, the fluid level is likely low. The only difference in performance with fluid type will be specific gravity-a lighter fluid will seem to slip more.

I don't think the oil you mention is going to change viscosity-but if it did it wouldn't improve performance.

Online ozarquebus

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #2 on: June 09, 2021, 05:15:43 PM »
I probably have some of my technical vocabulary wrong and silicone oil may not be the best, but let me try to illustrate my concept a little better.

Transmission fluid in the sachs transmission increases in viscosity as the shear rate (rpms) increases as in the blue linear (straight) curve below. The bottom curve in red is a non-newtonian fluid that is less linear, but is a lower viscosity than the standard Newtonian curve in blue at lower revs, yet gains viscosity quicker with shear rate (shear thickening).
 Assuming ATF is a Newtonian fluid, then a non-Newtonian fluid that resembles the red line on the graph, could theoretically develop more torque with more slippage at low rpms and achieve near zero slippage at high rpms.
The trick is to find the right fluid, maybe viscous couplng oil? I realize this would probably decrease the 6000 rpm hole shot effectiveness, but it could improve mpg at highway speeds and increase top speed on the salt flats.

« Last Edit: June 09, 2021, 05:54:26 PM by ozarquebus »
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Online Murray

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #3 on: June 09, 2021, 07:08:40 PM »

 Assuming ATF is a Newtonian fluid,

I seriously doubt it is, having something turn solid under pressure would cause chaos, the job of a hydraulic fluid is to transmit pressure, lubricate moving parts and enable cooling. If you want to go faster buy another bike, if you want better MPG buy another bike. Synthetic hydraulic fluid is used in aircraft systems to cope with the wide variety of operating temperatures, mineral is used in pretty much everything else.

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #3 on: June 09, 2021, 07:08:40 PM »

Online ozarquebus

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #4 on: June 09, 2021, 07:39:08 PM »
I agree, no practical reason to try to turn a Convert into a Hayabusa or a CT110.

It appears ATF is actually shear thinning fluid and its characteristics are exhibited as the top green line on the earlier graph. Relatively speaking, it thins out a higher speeds. The viscous coupling oil is opposite in behavior.

 What got me thinking about it was the forum member who was trying to wring the last few mph  out of a Convert on a dry lake bed. He has kind of run out of affordable gearing and tire size options. The viscous coupling oil seems like it has the desired characteristics. How hard the fluid gets may depend on concentration in a mixture with regular atf or even a hydraulic oil. I was thinking of it in terms of marginal improvement by reducing slippage within the torque converter at high speed when torque requirement is less. Sort of an anti slip mystery oil.
 It might blow, but could that risk be acceptable to somebody for another 5 or 10 mph in a record attempt?
Maybe my question should be: "How could you achieve full lock up at high rpm only on a Convert tranny?"
 Short of that my only experience is with sawdust as a transmission additive. :laugh:
« Last Edit: June 09, 2021, 07:50:32 PM by ozarquebus »
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Offline Aaron D.

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #5 on: June 10, 2021, 05:58:58 AM »
I probably have some of my technical vocabulary wrong and silicone oil may not be the best, but let me try to illustrate my concept a little better.

Transmission fluid in the sachs transmission increases in viscosity as the shear rate (rpms) increases as in the blue linear (straight) curve below. The bottom curve in red is a non-newtonian fluid that is less linear, but is a lower viscosity than the standard Newtonian curve in blue at lower revs, yet gains viscosity quicker with shear rate (shear thickening).
 Assuming ATF is a Newtonian fluid, then a non-Newtonian fluid that resembles the red line on the graph, could theoretically develop more torque with more slippage at low rpms and achieve near zero slippage at high rpms.
The trick is to find the right fluid, maybe viscous couplng oil? I realize this would probably decrease the 6000 rpm hole shot effectiveness, but it could improve mpg at highway speeds and increase top speed on the salt flats.



Shear doesn't play a part in your torque converter. A viscous coupling is a completely different thing.

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #6 on: June 10, 2021, 08:37:18 AM »
 This is really a theoretical question at this point I am no expert, of course, but it seems like shear flow rates of the fluid in a torque converter would make a big difference and perhaps the primary variable at play.
 Don't heavier or lighter hydraulic oils make a difference in torque converter behavior? Wouldn't a Shear Thickening Fluid, such as viscous coupling (silicone) oil, which in effect gets thicker with force applied quicker than other oils make some difference in torque converter function?
  If shear rates have nothing to do with a torque converter function, what is the action for transmitting the rotational energy from one impeller to the other in the donut? Isn't shear rate of a fluid a critical component of overall dynamic viscosity and isn't viscosity important in the torque converter fluid?

'not trying spread heresy over the sacred design of the Sachs Torque converter within the I-Convert.


just trying to understand if a non newtonian shear thickening fluid, such as silicone oil, could be used to reduce high speed slippage in a torque converter under load.

 
John
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Offline Aaron D.

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #7 on: June 10, 2021, 05:22:17 PM »
This is really a theoretical question at this point I am no expert, of course, but it seems like shear flow rates of the fluid in a torque converter would make a big difference and perhaps the primary variable at play.
 Don't heavier or lighter hydraulic oils make a difference in torque converter behavior? Wouldn't a Shear Thickening Fluid, such as viscous coupling (silicone) oil, which in effect gets thicker with force applied quicker than other oils make some difference in torque converter function?
  If shear rates have nothing to do with a torque converter function, what is the action for transmitting the rotational energy from one impeller to the other in the donut? Isn't shear rate of a fluid a critical component of overall dynamic viscosity and isn't viscosity important in the torque converter fluid?

'not trying spread heresy over the sacred design of the Sachs Torque converter within the I-Convert.

It makes no difference up to the point it impairs performance. The driving force is specific gravity. Torque transmission comes from the energy of the working being flung at the vanes. Shear rate is irrelevant.

If the fluid is thick enough and the fluid level is high enough, it won't work as a torque converter at all.


just trying to understand if a non newtonian shear thickening fluid, such as silicone oil, could be used to reduce high speed slippage in a torque converter under load.

Offline chuck peterson

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #8 on: June 11, 2021, 08:16:27 AM »
Congratulations! You’ve discovered what kept my mind busy for a decade…

I still haven’t figured it out

Converts…

Who would have ever thought they would keep riders so busy?

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Online Murray

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #9 on: June 11, 2021, 10:20:34 PM »
This is really a theoretical question at this point I am no expert, of course, but it seems like shear flow rates of the fluid in a torque converter would make a big difference and perhaps the primary variable at play.
 Don't heavier or lighter hydraulic oils make a difference in torque converter behavior? Wouldn't a Shear Thickening Fluid, such as viscous coupling (silicone) oil, which in effect gets thicker with force applied quicker than other oils make some difference in torque converter function?
  If shear rates have nothing to do with a torque converter function, what is the action for transmitting the rotational energy from one impeller to the other in the donut? Isn't shear rate of a fluid a critical component of overall dynamic viscosity and isn't viscosity important in the torque converter fluid?

'not trying spread heresy over the sacred design of the Sachs Torque converter within the I-Convert.


just trying to understand if a non newtonian shear thickening fluid, such as silicone oil, could be used to reduce high speed slippage in a torque converter under load.

Most hydraulic oils are the same, the only thing that varies is the temperature range they are designed to operate in.

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Re: Pure Silicone Oil In Hydraulic Systems
« Reply #10 on: June 17, 2021, 03:06:08 PM »
I know for a fact that Silicone brake fluid attacks Brembo seals, so Italian engine/gearbox seals might be a concern.
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