Fluid Drive questions

[Worden18]

Fellas, at the moment I can't find my Meadowbrook manual.  Even if I had it I'm not sure I wouldn't be inquiring for some help anyway.

When me and some friends pulled the engine years ago for the rebuild, I'm certain we pulled the transmission out first from underneath, and then everything forward of the transmission came out still assembled.  I think I remember my engine builder pulling the fluid drive unit off of the back of the engine, but I don't remember how everything was assembled. Is the clutch between the fluid drive and the transmission?  That's a pretty silly question but I still need it answered.  The reason I'm asking this is because I want to know more how the whole unit is put together (meaning engine all the way back to the rear axle).  I understand that the fluid drive unit is connected to the crankshaft, and supposedly the rear impeller of the fluid drive is connected to the drive shaft.  Well how does the transmission fit in there between the fluid drive unit and the drive shaft?  Does the drive shaft go through the transmission and into the fluid drive unit?  Also, can the fluid drive unit be unbolted from the engine underneath?  Where is the clutch in the whole assembly?  Could the fluid drive unit stay in the car without being connected to the engine?

[Bryan]

37 minutes ago, Worden18 said:

Fellas, at the moment I can't find my Meadowbrook manual.  Even if I had it I'm not sure I wouldn't be inquiring for some help anyway.

When me and some friends pulled the engine years ago for the rebuild, I'm certain we pulled the transmission out first from underneath, and then everything forward of the transmission came out still assembled.  I think I remember my engine builder pulling the fluid drive unit off of the back of the engine, but I don't remember how everything was assembled. Is the clutch between the fluid drive and the transmission?  That's a pretty silly question but I still need it answered.  The reason I'm asking this is because I want to know more how the whole unit is put together (meaning engine all the way back to the rear axle).  I understand that the fluid drive unit is connected to the crankshaft, and supposedly the rear impeller of the fluid drive is connected to the drive shaft.  Well how does the transmission fit in there between the fluid drive unit and the drive shaft?  Does the drive shaft go through the transmission and into the fluid drive unit?  Also, can the fluid drive unit be unbolted from the engine underneath?  Where is the clutch in the whole assembly?  Could the fluid drive unit stay in the car without being connected to the engine?

I have a 48 Dodge with Fluid drive. Pic 5665 is the FD  Correct picture order is 3rd, 2nd, 1st, 4th 5th. It always knocks them out of order.  Engine, FD with flywheel, then clutch, then transmission. Don't wobble the plate on the FD.  Carbon seal on the inside which is easily damaged.

Edited June 13, 2022 by Bryan

[tom'sB2B]

Crank mounted to fluiddrive assembly 

Edited June 13, 2022 by tom'sB2B

[tom'sB2B]

Clutch and pressure plate assembly mounts to the back of the fluid drive unit.

[tom'sB2B]

The bell housing covers the fluid drive and clutch assembly. The main shaft of your transmission slides through the throw out bearing and fork, through the clutch assembly and into the fluiddrive/ flywheel. The transmission then bolts to the bell housing.

[Merle Coggins]

As they showed above, and as you already surmised, the Fluid Drive attaches to the crankshaft and rotates with the engine. Inside there are a pair of impellers. One is connected to the FD housing and spins with the crankshaft. The other, the turbine, is connected to the output, which is the clutch plate. This acts like a flywheel on a conventional engine and the clutch attaches to it. As the rotating speed increases the input impeller drives more oil against the turbine impeller to increase the output torque to the clutch plate. The clutch will then drive the input shaft of the transmission which will in turn supply the power through the selected set of gears to the transmission output shaft to drive the driveshaft, supplying power to the differential. 

[Dan Hiebert]

This might simplify it.  The fluid drive unit takes the place of the flywheel in a standard drive line.  Everything else is the same, except the transmission in fluid drive cars has a longer input shaft.

 

You can remove the fluid drive unit from the car, it is a bear to do.  You can see in Bryan's photos how much room you don't have.  You do have to remove the transmission and clutch first.  

 

 

[Dodgeb4ya]

Here is a cut open FD coupling...

The fixed crankshaft half of the vanes is spun by the crankshaft spinning oil against the opposite output side of the vanes... thus causing that output side of vanes to spin which then turn the clutch and transmission.

 

 

[Worden18]

Thanks to everyone who has responded so far, and double thanks for the pictures.  It really helps without having to lay underneath my car, which I really don't want to do at the moment. I should have taken more pictures and notes myself when I took the thing apart years ago.  

 

So here's another question / observation.  The compression of the engine itself must be the worst enemy of the fluid drive and clutch plate spinning more freely than what is possible?  When you let off the gas pedal and decelerate, things slow down.  But the engine is dragging it down because of the compression.  You need the explosion of the gasoline to push the pistons up and down, thus spinning the impellers and making the car move. What I'm getting at: let's say the engine is removed, but everything else is still there from the fluid drive on back.  If you had any enormous heavy flywheel attached to the fluid drive unit, and you spun that sucker and got it moving, there wouldn't be much resistance to slow that flywheel down, correct?  If the resistance was little, in theory you should be able to put the car in gear and move forward, yes?  

 

If your engine is spinning 2,500 RPM, are the impellers in the fluid drive spinning the same rpm?  It just seems awful fast.

 

Edited June 14, 2022 by Worden18

[MarcDeSoto]

Your question has me a bit confused.  You can't drive the car without the engine in place.  I do know that when you want to upshift from 3rd to 4th gear, you let your foot off of the pedal for a second which takes pressure off of the transmission gears so it can upshift.  Also the 1st and 3rd gears are free-wheeling.  So if you are going to go down a steep hill or mountain, you would put the transmission in second gear for engine braking.  I do know that the propellers turn at the same rpm as the crankshaft.  2500 rpm does seem fast.  I know the car idles at 450.  I'm not sure what the engine speed is at 60 mph.  

[Dan Hiebert]

I can see what Worden18 is getting at, and there would indeed be resistance to slow that flywheel down.  That would be provided by the FD oil.  The FD unit does not work like a gyroscope or perpetual motion doodad.  Yes, you could spin it up, which would take effort to overcome the viscosity of the FD oil, but as soon as you removed the torque it would bog down until it stopped, rather quickly.  The engineers of old figured out just what viscosity was optimum for the desired effect.  At some point, the impellers are spinning as fast as the engine, I have to assume the engineering was done with the unit to ensure it doesn't spin faster than input.  The fluid drive unit only eliminates the mechanical connection between the engine and the clutch.  It does not provide any additional energy.  The advertisements, owners' manual, etc. extol the drivability virtues of the arrangement, although "power" isn't one of them.  Interesting discussion here.  All the paperwork says what it does and how but getting one's head around why it does it can be intriguing.   

[Merle Coggins]

The compression in the cylinders is what gives you engine breaking when you lift off the throttle pedal. You also get some engine breaking with a FD unit. It’s all spinning at relatively the same speed when you are motoring down the road. When you let off the throttle, to coast, the momentum from the car now drives the clutch through the transmission. This now makes the turbine impeller force oil against the input impeller which tries to spin the engine. So you still get similar engine breaking as you would in a conventional clutch/trans. vehicle. At lower speeds, and engine RPM, this effect is much lower.

Another factor that comes in to play with FD equipped vehicles is that the FD unit itself makes for a much heavier flywheel on the engine than a conventional flywheel/clutch setup. This makes the engine RPM’s drop more slowly when you let off the throttle.   

[greg g]

There was an idea years ago that cities should have bus fleets powered by flywheels.   That is the bus would have a heavy flywheel and transmission similar to the friction disc of a snowblower or some riding mowers.  The fly wheel would be spun up while the bus was stationary at its stop.  Since the bus would only go a block or two between stops, the energy stored by the mass of the fly wheel would be more than sufficient to cover one or two shops.   In the case of the fluid drives mass upon deceleration it acts similarly imparting inertia into the drive line, hence the free wheeling aspect.

[DonaldSmith]

Uncle Arthur told my dad that if he got a flywheel big enough, and spun it fast enough, it would spin forever.  Perpetual motion.  My dad, the engineer, knew that friction would slow it down, but could not argue the point.  My dad wondered how Arthur could be so dumb.  Uncle Arthur wondered how long before my dad realized he was pulling his leg.   Oh, and if you get a wagon with the front wheels smaller than the back wheels, the wagon would be pointing downhill, and would roll forever.     

[Doug&Deb]

Cars equipped with fluid drive can be bump started but will roll if parked in gear. At some point the viscosity takes over. 

[kencombs]

7 hours ago, Merle Coggins said:

The compression in the cylinders is what gives you engine breaking when you lift off the throttle pedal. You also get some engine breaking with a FD unit. It’s all spinning at relatively the same speed when you are motoring down the road. When you let off the throttle, to coast, the momentum from the car now drives the clutch through the transmission. This now makes the turbine impeller force oil against the input impeller which tries to spin the engine. So you still get similar engine breaking as you would in a conventional clutch/trans. vehicle. At lower speeds, and engine RPM, this effect is much lower.

Another factor that comes in to play with FD equipped vehicles is that the FD unit itself makes for a much heavier flywheel on the engine than a conventional flywheel/clutch setup. This makes the engine RPM’s drop more slowly when you let off the throttle.   

 

7 hours ago, greg g said:

There was an idea years ago that cities should have bus fleets powered by flywheels.   That is the bus would have a heavy flywheel and transmission similar to the friction disc of a snowblower or some riding mowers.  The fly wheel would be spun up while the bus was stationary at its stop.  Since the bus would only go a block or two between stops, the energy stored by the mass of the fly wheel would be more than sufficient to cover one or two shops.   In the case of the fluid drives mass upon deceleration it acts similarly imparting inertia into the drive line, hence the free wheeling aspect.

 

And the downside of all that Inertia is a much slower spinup when accelerating.   IMO, that is what makes the FD equipped cars feel slower than normal in acceleration,   more so than the slippage in the coupling itself.     Oval track cars use lightened flywheels to enhance acceleration.   but a lightened flywheel on the street, especially in a heavy car feel gutless from a start due to the loss of that stored power (inertia of a moving flywheel).  Can require a lot of clutch slipping to overcome.

[Dan Hiebert]

15 hours ago, kencombs said:

 

 

   IMO, that is what makes the FD equipped cars feel slower than normal in acceleration,  

"Majestic" acceleration is my go to description...?

[Worden18]

On 6/14/2022 at 7:43 AM, DonaldSmith said:

Uncle Arthur told my dad that if he got a flywheel big enough, and spun it fast enough, it would spin forever.  Perpetual motion.  My dad, the engineer, knew that friction would slow it down, but could not argue the point.  My dad wondered how Arthur could be so dumb.  Uncle Arthur wondered how long before my dad realized he was pulling his leg.   Oh, and if you get a wagon with the front wheels smaller than the back wheels, the wagon would be pointing downhill, and would roll forever.     

The flywheel would do better in the vacuum of space!

[LeRoy]

On 6/14/2022 at 12:23 PM, Doug&Deb said:

Cars equipped with fluid drive can be bump started but will roll if parked in gear. At some point the viscosity takes over. 

I wondered if you could bump start a fluid drive, makes sense to me that you could.

[DonaldSmith]

Fluid dive with 3-speed standard transmission - Shift into first gear and push the car until it starts or reason suggests backing off. 

 

Fluid drive with semi-automatic transmission - put the transmission in the "power" range and push the car.  After getting up to 8 miles per hour, the transmission should shift into second, which should bypass the freewheeling function.   Keep pushing above 8 mph until the car stars or reason suggests backing off.  

 

(For engine braking with the semi-automatic transmission, shift into the "power" range, and the transmission will shift into second gear, again avoiding the freewheeling effect.) 

[Worden18]

Bumping up this thread.  

How much HP is actually making it to the wheels?  My engine had to be bored out .030, so I'll assume it has a bit more power...maybe 110HP?  I really don't know.  Is half of the engine's horsepower making it to the wheels?  More than that?  

 

Also, anyone know what peak torque is?

 

Thanks!

[greg g]

My 56 230 was rated at the factory at 125 fly wheel hp at 3600 rpm.  It was bored .030 adding 5 cubic inches.  The head was milled .040,the block was cut .010.  It runs a 3mm thick solid copper head gasket.  Dual carbs in a Fenton intake.  Stock cam single exhaust 2 inch I'd from manifold to rear.  Muffler is single in, single out dynamax turbo flow. Stock ignition at 6 degrees btc. Flywheel lightened and balanced. The machinist calculated the compression ratio at 8.6 to 1.  The car was mounted on a chassis dynometer when it had about 3000 miles on it.  In third gear at 3300 rpm, it put 127 hp to the rear wheels.  I did not go to 3600 where the factory did peak hp as the speedo was at apx 64 mph at 3300. The printout shows  219 lbft of torque at 1820 rpm.  This pull was done on a Mustang rolling dyno in the automotive facility on the campus of the college where I worked.  The set up, pull and results were done by students under faculty, and Mustang dyno representative supervision.  Accurate? Who knows, it is what it was. The run was done inside at around 75 degrees running on 87 octane 10% ethanol gasoline with air filter in place.

 

I think member Robin Wheathersbe and maybe one other did dyno runs recently before they participated in the Penndine Sands timed speed runs in Wales.  Both are running setups similar to mine.  Be interested  in seeing their numbers.

Edited June 28, 2022 by greg g

[Worden18]

Amyone know offhand what the OD of the Fluid Drive impellers are?

[James_Douglas]

On 6/14/2022 at 9:23 AM, Doug&Deb said:

Cars equipped with fluid drive can be bump started but will roll if parked in gear. At some point the viscosity takes over. 

As small point but one that is worth mentioning...

 

The Fluid Drive power transmission has nothing to do with the fluids viscosity. It has to do with the fluid velocity. I was corrected in this idea by the VP of Engineering at the corporate successor of Gyrol.  He told me that water would be the best fluid in a fluid coupling as long as one had sealed bearings. But since out units need oil...

 

The base viscosity best for a fluid coupling is ISO-10 if the bearings are in very good shape, else use something a little bit thicker like the ISO-32. What is critically important is the Viscosity Index which is the stability of the fluid to stay at its base viscosity when it heats up.  

 

James