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“Fluid gears” invention offers promise for improving mechanical devices

phys.org

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Re: “Fluid gears” invention offers promise for improving mechanical devices

#41

Post by formerly_proven »

Someone wrote: post #12
mcherm wrote: post #7

Ever driven a vehicle with an automatic transmission rather than a manual gearshift with a clutch? Then you almost certainly used a fluid coupling: basically two fans in a can with oil so turning one turns the other. The article is so full of hype it doesn't bother to explain how this is different from the "fluid gears" invented in 1905.

> Ever driven a vehicle with an automatic transmission rather than a manual gearshift with a clutch? Then you almost certainly used a fluid coupling Are you sure? https://en.wikipedia.org/wiki/Continuously_variable_transmis... : “The most common type of CVT uses a V-belt which runs between two variable-diameter pulleys. […] A belt-driven design offers approximately 88% efficiency, which, while lower than that of a ma…

A hydrostatic CVT is not a torque-converter transmission (which is hydrodynamic). A hydrostatic CVT is basically a hydraulic pump, control valves plus hydraulic motor. So what you would typically find on construction or forest equipment.

Re: “Fluid gears” invention offers promise for improving mechanical devices

#42

Post by MadnessASAP »

snow_flake wrote: post #27

The phys.org article and headlines are misleading, the authors did not investigate systems to actually transmit torque. From what I gather, the interesting findings are the parameters for co-rotation and counterrotation of the driving and driven cylinder, depending on the Reynolds number, distance and so on. To illustrate one of the images of their publication: https://i.imgur.com/m8P2iVw.png

That would make much more sense then what the article seems to imply (scientists reinvent a 100 year old torque converter! But worse!!). Of course that headline isn't nearly as fun (scientists develop better model for fluid dynamics in torque converter).

Re: “Fluid gears” invention offers promise for improving mechanical devices

#43

Post by ErroneousBosh »

yason wrote: post #31
ErroneousBosh wrote: post #10

Earlier quoted context omitted.

Except a fluid clutch actually works, and a torque converter works even better and has three fans inside it ;-) I can see the "passive" cylinder getting dragged around a little by viscosity but I don't see how this could transfer even the tiniest amount of power.

Yeah, and like it's name a torque converter can actually not only transmit torque as well but also convert rpms to torque. Running the engine at high rpm at standstill converts revolutions of the input shaft to torque on the output shaft, thus allowing the car to start accelerating at slow speed but with high torque, operating without a clutch. That's as close to fluid gearing as you can imagine.

Yup. You can hold the RPM steady and watch the road speed climb as the inner blades "catch up" with the outer ones.

Not as funny as with CVTs though where you can have the road speed increasing as the engine RPM decreases. Or there was a guy about 20 years ago who had a Volvo 340 automatic fitted with a Volvo 760GLT 2.3 litre turbocharged engine, which he used to compete with at drag races at the local raceway. It did not too bad against similar vehicles in its class, but it sounded pretty funny because it would just race up to about 4500RPM and stay there for the whole run, as you had a rising howl from the drive belts at the back.

Of course my car has a torque converter and two viscous couplings - the TC between the engine and gearbox, one viscous coupling that makes the centre diff act like a very stiff LSD, and of course one that works the other way (eases off as it slips) to let the cooling fan stay at a steady speed.

Re: “Fluid gears” invention offers promise for improving mechanical devices

#44

Post by dang »

snow_flake wrote: post #27

The phys.org article and headlines are misleading, the authors did not investigate systems to actually transmit torque. From what I gather, the interesting findings are the parameters for co-rotation and counterrotation of the driving and driven cylinder, depending on the Reynolds number, distance and so on. To illustrate one of the images of their publication: https://i.imgur.com/m8P2iVw.png

Can someone suggest a better (i.e. more accurate and neutral) title?

Re: “Fluid gears” invention offers promise for improving mechanical devices

#45

Post by hammock »

snow_flake wrote: post #27

The phys.org article and headlines are misleading, the authors did not investigate systems to actually transmit torque. From what I gather, the interesting findings are the parameters for co-rotation and counterrotation of the driving and driven cylinder, depending on the Reynolds number, distance and so on. To illustrate one of the images of their publication: https://i.imgur.com/m8P2iVw.png

But these things exist though. https://en.wikipedia.org/wiki/Fluid_coupling

Re: “Fluid gears” invention offers promise for improving mechanical devices

#46

Post by bwoah »

dang wrote: post #44
snow_flake wrote: post #27

The phys.org article and headlines are misleading, the authors did not investigate systems to actually transmit torque. From what I gather, the interesting findings are the parameters for co-rotation and counterrotation of the driving and driven cylinder, depending on the Reynolds number, distance and so on. To illustrate one of the images of their publication: https://i.imgur.com/m8P2iVw.png

Can someone suggest a better (i.e. more accurate and neutral) title?

Mapping out How Fluid Mechanical Spin-coupling Interactions Depend on Proximity, Confinement, and Flow State

Alternate: New Ways to Understand, Control, and Exploit Hydrodynamic Spin-spin Interactions in Applications

The article doesn't really deliver on either headline, but that's the fault of the article, not the study.

Re: “Fluid gears” invention offers promise for improving mechanical devices

#48

Post by MisterTea »

bluGill wrote: post #17
mcherm wrote: post #7

Ever driven a vehicle with an automatic transmission rather than a manual gearshift with a clutch? Then you almost certainly used a fluid coupling: basically two fans in a can with oil so turning one turns the other. The article is so full of hype it doesn't bother to explain how this is different from the "fluid gears" invented in 1905.

Many automatics these days are manual transmissions with a computer controlling the clutch. They have nothing in common with the slushboxes of old, the oil is just for lubrication.

Maybe in sports cars but the majority of vehicles still come with hydraulic autos or CVTs.

Re: “Fluid gears” invention offers promise for improving mechanical devices

#49

Post by MisterTea »

formerly_proven wrote: post #33
ROOFLES wrote: post #28

Earlier quoted context omitted.

ZF 8HP is still a traditional torque converter transmission. Most high performance or high torque applications use that design. Dual clutch automatics or automated manuals can't take it.

Virtually every truck has an automated manual transmission, every EV 2-speed is a DCT, Porsche uses PDKs etc.

Citation needed. By truck if you mean commercial truck (lorry, artic, etc.) then no, Allison still makes hydraulic automatics which are very common in vocational work the world over.

Re: “Fluid gears” invention offers promise for improving mechanical devices

#50

Post by MisterTea »

mjmas wrote: post #14
Someone wrote: post #12

Earlier quoted context omitted.

> Ever driven a vehicle with an automatic transmission rather than a manual gearshift with a clutch? Then you almost certainly used a fluid coupling Are you sure? https://en.wikipedia.org/wiki/Continuously_variable_transmis... : “The most common type of CVT uses a V-belt which runs between two variable-diameter pulleys. […] A belt-driven design offers approximately 88% efficiency, which, while lower than that of a ma…

CVT != Automatic transmission (which is generally hydraulic) https://en.wikipedia.org/wiki/Automatic_transmission#Hydraul...

Not sure why you are making this statement.

> "A continuously variable transmission (CVT) is an automatic transmission ..."

https://en.wikipedia.org/wiki/Continuously_variable_transmis...

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