hydro-static final drive

[floydjer]

Anyone try this in a land racing application? Seems like you could valve one to give and endless # of "gear ratios". Jerry

[Richard Thomason]

HP losses?

[Dean Los Angeles]

Start of topic . . . End of topic!

[sockjohn]

I could swear I've seen a YouTube video that claimed this was done by somebody in the fifties or sixties.

Google and Youtube search is failing me.

There have been a few CVT transmissions run, but there is efficiency loss there as well (and before anyone asks, a CVT by itself is less efficient than a manual transmission on a input to output basis, but the car as a system is more efficient in a real world driving cycle with the CVT)

[jimmy six]

Honda Civic HX models had this type of trans for an automatic. The HX from about 95 to 05 had the highest fuel economy of any of their models. My 03 HX 5-speed listed one additional MPG so I bought it 38 city 45 hwy. The dealership I bought mine from said they had no problems with the CVT's other than people wanted something that shifted gears. (most have forgotten the dynaflow). The car is very low HP, 117, so I'm sure that has something to do with it.....................JD

[Milwaukee Midget]

Anyone try this in a land racing application? Seems like you could valve one to give and endless # of "gear ratios". Jerry

So Jerry, are you talking about hydrostatic drive hubs like one sees on farm equipment, ie: sprayers, corn detastling rigs?  The beauty of that type of system would be that you can put the engine anywhere and simply plumb lines to the drive wheels, but I have no idea how fast you can turn 'em.

[Dean Los Angeles]

There are large numbers of construction and farm equipment using hydrostatic drives. The ability to shift a front loader from forward to reverse under load, rapidly, and accelerate without shifting are the benefits.

The drawbacks are very large losses in the hydraulic pump. The variable displacement axial piston drive doesn't have that much of a loss.

CVT's have the friction losses that all belt drives have.
Here is a picture of a streamliner with a CVT . . . and a rope start.
http://www.landracing.com/forum/index.php/topic,2923.0.html

LSR doesn't require much in the range of gears, it's just difficult getting the overall ratio that suits your power. This is not an area you want to be giving away friction losses. Horsepower doesn't grow on trees.  No point turning it into heat.

[Stainless1]

that CVT looks a little like a Comet clutch.... 

[Dean Los Angeles]

It could be a Comet. They make zillions of them. Comet clutches have been around since . . . Dang! Like forever!

Comet calls them torque converters. They are in fact CVTs
http://www.hoffcocomet.com/comet/oem-torque-converters.asp
Comet makes them for karts, jr. dragsters, lawn mowers, and industrial equipment.

Comet started in 1949. I'm not real sure when the first torque converter came out, but I ran into them in the early 60's. I rode one on a mini dune buggy that had a 10 hp lawn mower engine. The unit was torque sensitive, not rpm sensitive. As the load changed the ratio would shift. Smoooooth.

I rented a Dodge Caliber to see how the latest CVTs work and I was impressed. It's really neat to hit the freeway on ramp and initially hear the rpm's come up and then stay steady as the speed keeps increasing.
You'd be surprised how much nicer driving is without the interruption of shifting.



The Caliber uses the Jatco CVT2 JF011E transmission
http://www.jatco.co.jp/ENGLISH/PRODUCTS/cvt.html

[floydjer]

There goes THAT idea!!  J.B.

[JimL]

At last springs Formula Hybrid event, in New Hampshire, the University team from Taiwan gave a presentation for their hydro-static drive race car (it was not presented for judging, as it was not complete).  After the presentation we had some private discussions about the difficulties they were encountering.

Items:
- Extreme heating at high flow rates/high loads.....some difficulty keeping the fluids inside the joints, due to viscosity thinning at near boiling points.  They all said, "Many, many leaks!!"

- Good low speed power transfer, poor high speed transfer as the hyrdraulic motors were resisting "high RPM".

- I was concerned that the car cannot be backed up without flow direction control.  Pushing forward requires multiple, manual by-pass valving (we discussed concern for clearing the course in event of malfunction).  They acknowledge this problem was discovered during initial testing (especially complete lockup of their hydraulic motors when trying to push backwards).

- Accumulator design may need some creativity to handle wide flow range (they were trying to operate without an accumulator system).

I only know a little about this stuff, from "long ago" trying to keep a John Deere back-hoe working through a summer, but I'm thinking "dead end" and probably PITA in staging lanes!

Of course...unlimited power, a zillion gears in the wheel hub, could be an interesting challenge!

There sure is some neat stuff to daydream about on this board!!

Regards, JimL

[Rex Schimmer]

I just had to comment on this subject. I am an application engineer for a company that makes the finest hydrostat drive systems in the world. We build pumps and motors that are rated at over 800 hp. The best hydrostatic drives use a pump that has a variable displacement and also is able to pump in both directions, this is called going over center. Using this type of pump you no longer need valves, the pump has two fluid ports and the motor has two fluid ports so you connect the pump to the motor and then the motor back to the pump. The oil flows from the pump to the motor and then back to the pump, this is called "closed loop" drive. There are a number of additional things that are required to make it work but this is the basis of it. Now if you vary the pump displacement the motor speed varies and if you reverse the direction of the pump flow, go "over center" the motor will reverse direction. The speed that the motor turns is a function of the ratio of the pump displacement (usually measured in cubic inches/revolution) to the motor displacement. If you have a pump that displaces 10 cu. in./rev and it drives a motor that is 5 cu. in./rev then when the pump is at full displacement the motor is turning at twice the pump speed. If you want more speed then you can have both a variable displacement pump and a variable displacement motor, which theoretically gives you an infinite speed range. (Not in real life thought!)

Our pumps are approx 91-93% overall efficiency and the motors are about the same so when you put them in a drive system you get an overall efficiency of around 83-85% plus you do loose some in the plumbing. So I would not think that they would be what you would pick for a Bonneville car. Besides our pump that transmitts 800 horse power weights around 700 lbs. The student that were building the "hydrostatic" drive car needed to do a little more research especially regarding heat, which means the system is not efficient and also up to date plumbing, the O ring face seal fittings that are used today are completely leak free. Like wise we sell hydraulic motors that will turn 10,000 rpm, not much torque but good horse power or we have motors that will only turn 10 rpm but make 1,000,000 lb-ft of torque.

Rex

[jl222]

I just had to comment on this subject. I am an application engineer for a company that makes the finest hydrostat drive systems in the world. We build pumps and motors that are rated at over 800 hp. The best hydrostatic drives use a pump that has a variable displacement and also is able to pump in both directions, this is called going over center. Using this type of pump you no longer need valves, the pump has two fluid ports and the motor has two fluid ports so you connect the pump to the motor and then the motor back to the pump. The oil flows from the pump to the motor and then back to the pump, this is called "closed loop" drive. There are a number of additional things that are required to make it work but this is the basis of it. Now if you vary the pump displacement the motor speed varies and if you reverse the direction of the pump flow, go "over center" the motor will reverse direction. The speed that the motor turns is a function of the ratio of the pump displacement (usually measured in cubic inches/revolution) to the motor displacement. If you have a pump that displaces 10 cu. in./rev and it drives a motor that is 5 cu. in./rev then when the pump is at full displacement the motor is turning at twice the pump speed. If you want more speed then you can have both a variable displacement pump and a variable displacement motor, which theoretically gives you an infinite speed range. (Not in real life thought!)

Our pumps are approx 91-93% overall efficiency and the motors are about the same so when you put them in a drive system you get an overall efficiency of around 83-85% plus you do loose some in the plumbing. So I would not think that they would be what you would pick for a Bonneville car. Besides our pump that transmitts 800 horse power weights around 700 lbs. The student that were building the "hydrostatic" drive car needed to do a little more research especially regarding heat, which means the system is not efficient and also up to date plumbing, the O ring face seal fittings that are used today are completely leak free. Like wise we sell hydraulic motors that will turn 10,000 rpm, not much torque but good horse power or we have motors that will only turn 10 rpm but make 1,000,000 lb-ft of torque.

Rex
[/quote



Hi Rex

  How about one of your pumps to drive a centrifugal supercharger or any blower?

                             JL222

[floydjer]

Let`s stir this pot a little. How about using  some form of variable speed hydraulic transmission feeding into a ring/pinion  rear? Some means of varying the input to the final drive w/out getting on/off the throttle.  Jerry

[Rex Schimmer]

Jl222,
No problem driving a blower, plus you could put a pressure transduce in the output and we could uses that at the feed back for a closed loop blower control system, i.e. you would set the boost you want and the control system would spin the blower at what ever speed required to make the set pressue and it would do this at any engine rpm that provided enough power to run the blower at the set speed. You could also program the pressure to increase or decrease depending upon what ever parameter you needed. It only requires $$$$$$$!

floydjer,
We have done exactly that on some large diesel trucks, a variable pump on the engine and a variable motor on the diff. They ran the engine at a set rpm, around 1000 in this case, and the speed was varied by the hydrostatic drive and the horsepower was controlled by the turbo boost. These got over 10 mpg wiht a 40,000 lb load.  Again the problem is that we are talking some big chunks of iron and very expensive plus you need to have some sort of control system, electronic or manual.

Just a note of history, the very first Indy turbine car that PJ almost won Indy in was 4wd and use hydrostatic drive.

Rex

Rex