hydraulic drivetrain 1

[jdsewell]

i recently read in design news about ford and the epa working together on a hybrid hydraulic drivetrain for automobiles. through web research, to purge my ignorance on the subject, i discovered several industrial uses as well as the epa's patent. this system has me very intriqued. why hasn't someone used this before (in automobiles)? as with all things viewed from the outside (ei not having worked with this design) it strikes me as the ultimate drivetrain. what are the advantages/disadvantages?

 

[tschmidt]

I have to admit not knowing the details of the hydraulic hybrid drive system. But I have worked on electric hybrid drive systems for buses. The pluses are generally that you can recover the energy normally lost in braking, you can run the engine at it's most efficient and/or cleanest points, you can have independent motors at each wheel, the list goes on. The negatives are mainly the initial cost due to the increased number of components, the higher level of complication, balancing the loss of efficiency in the hydraulic (electric) system versus the gains achieved on the engine side, and customer acceptance. In general these systems work best in vehicles that experience a duty cycle with lots of stops and starts, like the city transit bus program I worked on.

Hope this helps,

 

[ferreiro]

Hi One of the reasons that this type of drive has not been used in road auto has been the cost and lack of competent people who would be able to maintain the systems.In the industial side of the industry/mining the systems are used on underground fel.
only real problem that has cropted has been the hydraulic maintence knowledge of the maintence staff. When a failure has taken place outside hydraulic eng have had to be called driving up the cost of the maintence bill.
Otherwise a very good system.
if you need more info i will see if i can get you from the manufactures.
regards

 

[butelja]

Ford has a system called "Hydraulic Launch Assist" which is used in the F-350 Tonka show truck. I don't know if that is the system you refer to. Details can be found at:

http://www.ford.com/en/ourVehicles/...s/ford/fordMightyF350TonkaConcept/default.htm

 

[jdsewell]

the system i'm talking about is losely based on current automotive hybrids. a high rpm internal combustion engine powers a hydraulic pump. the pump pushes fluid to the wheels for forward motion. at the same time, hydraulic accumulators store energy from braking, much like the electrical regenerative braking. the reason this drivetrain intrigues me is 1. it simplifies the drive train. no more energy shafts and u joints etc. 2. it strikes me as being more efficient. i have not crunched any numbers to confirm this. does anyone have an opinion on that? i would be very interested in hearing from experience.

 

[butelja]

It probably is more efficient in stop and go city driving. However, in steady state cruising on the interstate, the pump/motor combination would be less efficient then a conventional drivetrain. There may be a weight penalty, and there certainly is increased complexity as compared to a standard system. The accumulators could also present an extreme hazard to improperly trained service personnel.

The system you desribe is a series hybrid. The HLA system in my earlier post is a parallel hybrid mated to a conventional drivetrain.

 

[truck]

To the above I would add the following considerations to run through:

- package considerations for
- motors which will have both depth and diametral
considerations to be reckoned with
- large diameter, high pressure jounce hoses to provide
motor power at the wheel ends (hydraulic hoses tend
to fall in the semi-rigid category)
- hydraulic routing for large diameter, high pressure
tubing on the chassis which will protect from rust
(steel lines) and abrasion.

- performance - more requires larger components (motors,
flow, etc.)

- component size vs. vehicle mass as above

- overall system complexity - you go from developed
components (engine, trans, axles, etc.) to a system
which is 'new' to the application (on highway, country
road, moderately high suspension travels, etc.)

None of this is prohibitive, but greatly complicates life Truck

 

I first heard of this hydraulic hybrid from Popular Sciences article on the Tonka Truck. The article says that with the accumulator tank fully charged it adds another 600 lb.-ft. of torque, giving it enough power to let it drag race competitively with a BMW roadster. I am wondering if it is possible to use this for aftermarket racing applications.

 

[ProEpro]

The hydrlic drive trains that are in use are for things like earth moving equipment. They are slow heavy and ineficent at what would be considered moderate speeds for cars. The advantages for that application are.

Easy to multiply torque
Works well for things that are loaded to the point of stopping
Might be better able to handle massive amounts of torque
Packaging can be easier with no drive shafts.

For street cars no system that has the motors at the wheels will provide suitable ride and handeling.

The Ford system on the Tonka truck is only good for a couple of seconds. I do not think that such a large, heavy and potentialy dangerous system would work well in the aftermarket.

Even if it never works it shows that someone at Ford is creative and smart.

 

[ivymike]

probably a contractor

 

[gbent]

Agriculture also uses many hydrostatic drives. Some of the advantages for agriculture are: 1) Allows full engine power (and RPM) for other processes. Sometimes propelling the equipment thru the field is secondary. 2) Allows precise control of ground speed with speed ranges between 0 and 20 MPH. A transmission is also employed to give sufficient speed ranges while the engine is at full rated RPM. 3) The design of the equipment is driven by the desired task. The drivetrain can be added almost as an afterthought.
For highway vehicles, the system is heavy, has high inertia, high cost, and very poor efficiency compared to conventional geartrains.

 

[ProEpro]

I recently saw a hydralic motor in a very strange place. The Lincon LS, Thunderbird and maybe the Jag x-type use a hydralic motor to drive the fan for the radiator. It has it's own pump resivor and everything. I was told it was done for NVH but I would be surprissed it it was quieter. they switched back to electric for next years model.

How would you react if you mechanic said you were low on fan fluid?