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Best oil for fluid flywheel (fluid coupling)

teletech

Aluminum
Joined
Jul 16, 2019
Hey folks, it's a bit OT, but I was hoping the PM community might have the experience and technical rigor to give me a good answer.
The item under discussion is a "fluid flywheel" which is used in the Ferret scout car from the 1950s.
Basically it's like a torque converter but without the third member so it just acts as a variable coupling. The usual fluid is in the ISO 10-15 range, and should tolerate a fair bit of heat.
I've looked at MSC/McMaster and seen several options around light hydraulic fluid and spindle oil. I also notice some air tool oil that is in the viscosity range and has a bit higher operating temperature than most of the other oils listed. I need a couple gallons and it could be I'll have to change it out fairly soon, so more like a 5-gallon pail ideally. I'm wondering what would be ideal but also what won't break me financially.

McMaster has this:
Mobil DTE21 ISO15 $180/5-gallon with temp range 0 to 150F and supposedly protects against wear
Spindle/bearing oil jugs of ISO-10 of the house brand for just $20 and is rated from -10 to 150F
Mobil Velocite No6. is $30/gallon and is rated from 25F to "not rated"
generic ISO 15 bearing/spindle oil for under $18/gallon with a temp range of -10 to 150F
"jack oil" with, I gather some additives to protect against corrosion and wear. Of course it has a lower temperature range of just -30 to +135 and is $64/gallon
Mobil DTE 10 Excel 15—Mineral Base Oil is also supposed to protect against wear and has the usual range of -45 to 150F and is only offered in 5-gallons for $177
"air-tool oil" in ISO 15 is $13 for just 20-OZ but supposedly has a temperature range of -15 to 250F and will absorb moisture, not sure if that's an asset or liability in this use.
MSC has similar offerings, the first several I checked were more expensive but found some comparable options with some digging:
Mineral hydraulic/machine oil in ISO 15 for $60/gallon or $180/5gallons
ISO 10 spindle oil which is only $50/gallon or $200/5 gallons.
ValCool Mineral Spindle Machine Oil ISO-10 is $98/5-Gallons

Below is a description of the device and it's operation:
The flywheel comprises a sealed chamber filled with hydraulic fluid (typically OM13 ISO10 light oil. ISO15 Shell Tellus Tx15 can also be used) containing an impeller(the pump) driven by the engine and a turbine connected to an output shaft. The impeller is a toroid disc connected to the engine's crankshaft.The fluid flywheel is completely automatic in action. The bowl-shaped rear casing, facing forward, is the driving member which completely encases the driven member. The turbine situated at the rear of the flywheel nearest the engine and attached to the input shaft of the gearbox, is the driven member.Sectioned and exploded diagrams can both be downloaded here.As the oil spins upwards and around in a toroidal motion it takes the energy from the driving turbine as it flows from the centre to the rim,delivering energy to the driven member as it passes from the circumference to the centre. By shaping pockets in the driving bowl or pumping turbine, the oil is thrown out as jets at high speed into the driven member.This impact, directed at a tangent, causes the driven member to turn in the same direction as its neighbour. The fluid flywheel forms a flexible coupling between the engine and gearbox.
 

bloomautomatic

Cast Iron
Joined
Oct 17, 2012
Location
Pennsylvania
Original British military spec was OM13 which is an ISO10 or 15. It should only hold 9-3/4 pints. I would call my local NAPA and tell them you need ISO10 or 15 and see what they have or can get. If they don't have it, start looking for hydraulic shops or suppliers in your area.

Make sure you're using straight SAE 30 oil in the engine and gearbox and NOT multi weight 10W-30. Additives in the multiweight are supposedly bad for the seals or something.

Since you only need about 2 gallons for the whole thing, I'd spend the money and get the good stuff.

What Mk is your Ferret?
 

thermite

Diamond
Joined
Sep 21, 2011
Location
Sol, Terra
Hey folks, it's a bit OT, but I was hoping the PM community might have the experience and technical rigor to give me a good answer.
The item under discussion is a "fluid flywheel" which is used in the Ferret scout car from the 1950s.
Basically it's like a torque converter but without the third member so it just acts as a variable coupling. The usual fluid is in the ISO 10-15 range, and should tolerate a fair bit of heat.
I've looked at MSC/McMaster and seen several options around light hydraulic fluid and spindle oil. I also notice some air tool oil that is in the viscosity range and has a bit higher operating temperature than most of the other oils listed. I need a couple gallons and it could be I'll have to change it out fairly soon, so more like a 5-gallon pail ideally. I'm wondering what would be ideal but also what won't break me financially.

McMaster has this:
Mobil DTE21 ISO15 $180/5-gallon with temp range 0 to 150F and supposedly protects against wear
Spindle/bearing oil jugs of ISO-10 of the house brand for just $20 and is rated from -10 to 150F
Mobil Velocite No6. is $30/gallon and is rated from 25F to "not rated"
generic ISO 15 bearing/spindle oil for under $18/gallon with a temp range of -10 to 150F
"jack oil" with, I gather some additives to protect against corrosion and wear. Of course it has a lower temperature range of just -30 to +135 and is $64/gallon
Mobil DTE 10 Excel 15—Mineral Base Oil is also supposed to protect against wear and has the usual range of -45 to 150F and is only offered in 5-gallons for $177
"air-tool oil" in ISO 15 is $13 for just 20-OZ but supposedly has a temperature range of -15 to 250F and will absorb moisture, not sure if that's an asset or liability in this use.
MSC has similar offerings, the first several I checked were more expensive but found some comparable options with some digging:
Mineral hydraulic/machine oil in ISO 15 for $60/gallon or $180/5gallons
ISO 10 spindle oil which is only $50/gallon or $200/5 gallons.
ValCool Mineral Spindle Machine Oil ISO-10 is $98/5-Gallons

Below is a description of the device and it's operation:
The flywheel comprises a sealed chamber filled with hydraulic fluid (typically OM13 ISO10 light oil. ISO15 Shell Tellus Tx15 can also be used) containing an impeller(the pump) driven by the engine and a turbine connected to an output shaft. The impeller is a toroid disc connected to the engine's crankshaft.The fluid flywheel is completely automatic in action. The bowl-shaped rear casing, facing forward, is the driving member which completely encases the driven member. The turbine situated at the rear of the flywheel nearest the engine and attached to the input shaft of the gearbox, is the driven member.Sectioned and exploded diagrams can both be downloaded here.As the oil spins upwards and around in a toroidal motion it takes the energy from the driving turbine as it flows from the centre to the rim,delivering energy to the driven member as it passes from the circumference to the centre. By shaping pockets in the driving bowl or pumping turbine, the oil is thrown out as jets at high speed into the driven member.This impact, directed at a tangent, causes the driven member to turn in the same direction as its neighbour. The fluid flywheel forms a flexible coupling between the engine and gearbox.

Same general era, Chrysler had - AFAIK - three DIFFERENT systems called "fluid drive". Our 1950 Dodge Wayfarer 2 Dr and 1951 Dodge Meadowbook 4 Dr had the simplest one.

Same deal you have just described with a conventional clutch and 3 speed manual transmission inline.

One "could" come off the throttle, brake at a stoplight .. in top gear or any other gear - use the throttle-only, leaving the mechanical clutch engaged, then waddle (slowly, if in a higher gear!) off the line when the light changed.

Mum - just learning to drive, winter of 1949-50, loved it as being more forgiving about de-clutching - or forgetting to do - and for pulling off the line, steep uphill, or in snow and ice - than the 1939 conventional-clutch Chevy.

Dad - who had sold his fully-automatic transmission 1941 Oldsmobile when he found the storage garage was renting it out whilst he was away on active duty, loved it in stop & go traffic, also for its light touch on snow and ice, and for its extra low-end torque - once pulling a core driller's off-road truck, drill rig on it, out of a mud hole. Mind.. all three axles on the truck were trying their best as well, so it wasn't exactly magical.

That one was plumbed to share the flathead six engine's lube oil. For "cooling" or at least stabilization of temperature? Or just to insure it was not run dry?

One of the OTHER variants was in a 1950 Chrysler a neighbour owned. It was coupled with what seems to have been "a form of" Wilson pre-selector transmission, as he would upshift the conventional-sized column-mounted lever, but the shift didn't execute until he came off the throttle to provide vacuum.

A cousin had another variant back of a flathead straight 8. '48 or '49 Desoto, IIRC. A crackerjack mechanic, he ran on and on as to how it worked, vacuum lines and cylinders, valving, etc.. but WTF?

I was only vintage of 1945 meself, hadn't yet learnt enuf to push my apparent age back the other 120 years, so it didn't all sink-in very clearly!

:)

"Later on"... ISTR finding that these torque converters were generic goods built such that choosing the "fluid" characteristics was an OPTION related to selecting the "converter stall" RPM, degree of lockup, eg: specific performance curve for a given application.

Seals compatibility issues aside? Can't much harm these simple critters.

"Try it and see" approach as to which fluid best serves might do yah?
 

johnoder

Moderator
Joined
Jul 16, 2004
Location
Houston, TX USA
More on Fluid drives and antique Mopars

Engine oil served in my 1953 Imperial to make the fluid coupling function, and it had the semi automatic Bill describes above

Scan01.jpg
 

thermite

Diamond
Joined
Sep 21, 2011
Location
Sol, Terra
More on Fluid drives and antique Mopars

Engine oil served in my 1953 Imperial to make the fluid coupling function, and it had the semi automatic Bill describes above

View attachment 297912

"Antique?" Only if it had wooden wheels and brass trim.

"Back in the day..", MOPAR-style.. when a Dodge was a Plymouth with lockwashers.. a DeSoto was a Dodge with weird stuff MOPAR needed to test more, a Chrysler was a DeSoto with fewer risky bits, and an Imperial was a Chrysler that had actual padding under the upholstery and carpet and wider, softer tires!

:)

PS: "Genuine" Wilson-pattern pre-selector lived-on for a time in city bus service.
 

dkmc

Diamond
Had a '53 Yale forklift with Chrysler IND30 Flathead 6 connected to a 2 speed manual trans via fluid coupling. Used Dextron ATF in it without any issues for 20 years. The neat thing was, you could 'adjust' the stall RPM depending on how much fluid you put in the coupling.
 
Last edited:

teletech

Aluminum
Joined
Jul 16, 2019
Original British military spec was OM13 which is an ISO10 or 15. It should only hold 9-3/4 pints. I would call my local NAPA and tell them you need ISO10 or 15 and see what they have or can get. If they don't have it, start looking for hydraulic shops or suppliers in your area.

Make sure you're using straight SAE 30 oil in the engine and gearbox and NOT multi weight 10W-30. Additives in the multiweight are supposedly bad for the seals or something.

Since you only need about 2 gallons for the whole thing, I'd spend the money and get the good stuff.

What Mk is your Ferret?

It's a fairly early Mk1 but someone added a turret (which I removed).

I'm leery of just asking a local shop for oil, hence digging into the properties of oils. At the moment I'm pretty interested to know about the Velocite #6 and it's "not rated" for maximum temp and if that's not a high enough value I'll look hard at the Enerpac oil, it's spendy but with a top end temperature of 350F it's a top contender.

Indeed, the rumour is that the Rolls engine is designed to sacrifice some oil as part of the lubrication process. When multiweight burns it apparently leaves really abrasive residue, hence the prohibition.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
Id certainly be using an ATF ,if hydraulic oils are so crazy expensive....the Wilson transmission is mostly bands with just one clutch ,so ATF will be OK for the trans too.........Incidentally ,the RR motor had no rear oilseal ,just a slinger and reverse worm ...........I bought a heap of trannys for both Ferets and Saracens,long before the vehicles were sold ......all went for scrap ,as owners of the vehicles generally had zero mechanical ability ,and couldnt do anymore than pose........Heed the advice about filling ,if over filled the expanding fluid will bust the seal.....Both busses ,trucks and cars had the Wilson trannys .....in the Daimler busses ,they were know as "shin kickers",as the pedal would drop to the floor as the band grabbed ,then come back with great force as the slack was taken up ......hence the ritual of "pumping up the gears"
 

teletech

Aluminum
Joined
Jul 16, 2019
Id certainly be using an ATF ,if hydraulic oils are so crazy expensive....the Wilson transmission is mostly bands with just one clutch ,so ATF will be OK for the trans too.........Incidentally ,the RR motor had no rear oilseal ,just a slinger and reverse worm ...........I bought a heap of trannys for both Ferets and Saracens,long before the vehicles were sold ......all went for scrap ,as owners of the vehicles generally had zero mechanical ability ,and couldnt do anymore than pose........Heed the advice about filling ,if over filled the expanding fluid will bust the seal.....Both busses ,trucks and cars had the Wilson trannys .....in the Daimler busses ,they were know as "shin kickers",as the pedal would drop to the floor as the band grabbed ,then come back with great force as the slack was taken up ......hence the ritual of "pumping up the gears"
I eventually found some log-splitter oil of about the right weight and for a good price. I'm pleased to report my fluid flywheel leaks very little, for a thing made in England and with oil inside it that is! The wheel-stations are a bit more of an issue I'm afraid and I'm collecting seals to do those. I also don't notice the compressing on that one cylinder coming up, so I'm hoping it's just a rusty valve from having sat for so long. I can't say I'm particularly looking forward to finding out how hard it is to do a valve job on these beasts.
 

ramsay1

Stainless
Joined
Aug 19, 2003
Location
port allen, louisiana usa
Hello everyone: Don't know if this really fits but I worked on Twin Disc torque converters years ago and they take a light fluid in the turbine section... Some, in fact, use diesel fuel for torque fluid... We had both.. One used diesel from the fuel tank pressured by a belt driven pump on the engine, the other had its own sump and in this one we used Velocite #6 or Shell Diala ax, as I recall... Very light fluid it is.. Cheers from Louisiana.. Ramsay 1:)
 

Limy Sami

Diamond
Joined
Jan 7, 2007
Location
Norfolk, UK
I eventually found some log-splitter oil of about the right weight and for a good price. I'm pleased to report my fluid flywheel leaks very little, for a thing made in England and with oil inside it that is! The wheel-stations are a bit more of an issue I'm afraid and I'm collecting seals to do those. I also don't notice the compressing on that one cylinder coming up, so I'm hoping it's just a rusty valve from having sat for so long. I can't say I'm particularly looking forward to finding out how hard it is to do a valve job on these beasts.

I thought it was and checked - AFAIK they used the Rolls Royce B60 which is a 6 cyl version of the B40 used in the Austin Champ - and they did.
IIRC (it's over 45 years!!) there's nothing special about those engines - just well made and again IIRC were fitted with hardened valve seat to run on anything almost from Brylcream and Creosote to Blue Streak rocket fuel so will have no problem with the unleaded / ethanol weasel piss they call petrol today.

Just make sure you can source the parts first - oh and you might want to be sitting down when asking the price.

I found this Rolls-Royce B range engines - Wikipedia
 

James H Clark

Stainless
Joined
May 11, 2011
Location
southern in.
I remember back in the late fifties, working in a service station, when a customer had us change the oil in the transmission of his late 40s' Dodge or DeSoto and specified 10 wt. non-detergent oil for the transmission and fluid drive. Ah, the good old days when it was only straight detergent or non-detergent oils.

JH
 

ratbldr427

Stainless
Joined
Mar 21, 2006
Location
jacksonville,fl.
I had a 53 Dodge with a small Red Ram hemi in it(Small meaning displacement not od!) The trans when you wanted it to shift into high you let off the gas and waited for it to clunk, hence most people around my area called them clunk- amatics. All of the early automatics had fluid couplings.I think the 55 or so Buick Dynaflow was one of the first torque converters followed by Pontiacs Jetaway? The early hydramatics were fluid coupling.

I think the op is overthinking the oil type.If it were mine Atf would be my choice and not worry about it, it is what it is designed for. As running it low to increase the stall that is a very good way to start a fire. When the oil cavitates it over heats and foams which can come out the vent and spill on the exhaust as well as over filling. Has happened on the early automatics.
 

CalG

Diamond
Joined
Dec 30, 2008
Location
Vt USA
There are only three lubes needed to run 98% of all lubricating fluid requirements.
ATF
UTTO
Motor Oil.

Skydrol falls in the 2% beyond the rule.
 

ramsay1

Stainless
Joined
Aug 19, 2003
Location
port allen, louisiana usa
I remember back in the late fifties, working in a service station, when a customer had us change the oil in the transmission of his late 40s' Dodge or DeSoto and specified 10 wt. non-detergent oil for the transmission and fluid drive. Ah, the good old days when it was only straight detergent or non-detergent oils.

JH

When I was a teen, my aunt had a 1950 DeSoto with fluid drive.... First one I ever saw and drove... It was pretty nice.. That car was20 years old and everything including the old vibrator radio still worked just like new.....Cheers; Ramsay 1:)
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
There was another hydraulic converter used on some of the mid 30s Leyland busses,called a Lysholm Smith,it was true torque converter and had several elements and could give considerable torque multiplication for starting and acceleration....In this era heavy busses had a four speed crash gearbox and a big clutch of around 17-18" dia for long wear....Fortunately the diesel motors were so flexible ,you could lug the motor down to 350 revs in top gear,and pull away without changing down.
 








 
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