Anyone done a hydraulic drivetrain?

[x88x]

I've been tossing this idea around my head for a while and was wondering if anyone had any thoughts on it.

The general idea is to hook up a hydraulic pump directly to an electric motor, then have hydraulic lines running from the pump to a hydraulic motor on the wheel. This would allow for a lot more flexible mounting of the motor, and none of the noise or exposed moving parts that a chain or belt drive system would have.

So, any thoughts? Anyone seen this done before? ..failed before?

 

[amberwolf]

Sounds similar in principle to the air-powered vehicles. Don't know what kind of efficiency hit you'd get, but I'm guessing it's big enough that you wouldn't want to do it unless you had really good reason not to just put the motor on a more typical drivetrain, or on or in the wheel itself.

 

[neptronix]

Done before.
Too lossy.
Also, kinda silly!

 

[AussieJester]

So, any thoughts? Anyone seen this done before? ..failed before?

Yes...on a motorcycle, diesel motor used to power the hydraulics...

Full story can be seen here

Dunno how efficient it is or how well it would adapt to e-bike use, seems like an over complex system
to gain whatever small advantages there might be over a direct chain/belt drive system IMHO
Very cool though all the same

KiM

 

[gogo]

Check out this discussion:
Magneto-hydraulic Torque Converter Wheel

 

[x88x]

Also, kinda silly!

Well of course, but it'd be fun too. Since you mention it being lossy, do you have a link to any numbers?

Thanks for the link AJ, I actually remember seeing that guy's bike a while ago, it's one of the things that started me thinking this might work. ..I think it was the same one anyway, how many diesel motorcycles with hydraulic drivetrains can there be?

Gogo, I read through that thread, and if I'm reading it correctly, it looks like a hydraulic clutch varying the position of drive magnets on a direct-drive motor, not a hydraulic drivetrain.

I wouldn't think that it would be much less efficient than a chain drive..it's just a pressurized liquid instead of a solid chain. IDK, I'll do some more research tonight after work, see if I can find some numbers on hydraulic drivedrains in other applications.

 

[mdd0127]

I have a video saved somewhere of a little two wheel drive rokon type bike with a single cylinder diesel and hydrostatic drive. I see if I can find it. It was a really well made bike. Single swingarm, 24" atv tires..I'll post it up if I can find it again.

If the hydraulics were sized correctly(read heavy), you could see efficiencies in the mid eighties but regen could also be easier....2 wheel/4 wheel drive...traction control....optimized Ackerman based wheel speeds...reversing opposites for zero turn or skid steer like the Jeep Hurricane concept..... ....the efficiency loss could be worth it in the right application. The first thing that would need to happen to make hydraulics work in electric drive systems would be designing small ultra lightweight pumps/motors, reservoirs, coolers, and lines. Most currently available hydraulic products were designed for industrial uses and in the past, industrial pretty much meant the opposite of efficient. Things are getting better a little on that front though. Now I have to go find out how far small hydraulics have come in the last few years.

I want a mini electric snow cat. I can see snowboard runs right now that I can't get to!

 

[unsane]

I got thinking about the exact same concept a few months ago and after an exhaustive search of the web I could not seem to find any readily available production drive units... My thoughts were to connect a decent RC motor to a car power steering pump but without a unit to convert the pressure into rotation its a bit hard - there are a few guys who have made their own hydro-hubs but they also have access to full workshops with CNC, lathes etc - I was looking to do this re-invented 2nd hand parts not make my own or spend big $$$

I agree this would really simplify the drivetrain and allow a lot more freedom in component mounting - there is always going to be an energy loss in each conversion of energy that takes place but I am still curious to find out just how much in this case

I remember finding some info on some French guys that went all-out building a variable flow pedal powered pump for a non-electric version of this concept - looked really good but I never saw how well it worked in practice

I don't reckon it would look silly at all neptronix... the pressure lines could be easily made to follow the frame shape and provided all the hardware could be contained within the front triangle, this would look no sillier than... say... an electric bike?

If anyone finds a hydraulic drive unit to convert the pressure into a spinning rear wheel I would love to know!

Cam

 

[mdd0127]

Nice username. Unsane is one of my favorite bands!

Also if you ever see a 9 second Grand National with unsane on the license plate running around, it's all my fault

Not hydraulic drive though.

Sorry, back on topic.....

I haven't been able to find any lightweight motors yet. Maybe it's time to design one!

 

[gogo]

Try a google search on "parker chainless". Parker has been conducting an annual chainless challenge for universities since 2005.

 

[Hillhater]

no way can a hydraulic system get any where near the efficiency of a mechanical drive.
Hydraulic system losses include ..
Mechanical loss from the pump drive, bearings , seals, etc
Hydraulic losses from the power required to move a viscous liquid through the pipes, pumps, motors, valves etc. (less with low viscosity fluids, big pipes & Pumps)
Volumetric losses in the pump and motors ( greater with low viscosity fluids, and bigger pumps ,motors etc)
Thermal losses from the movement & compression of fluids ( can be as much as 255 in a high pressure system!)

Overall losses on commercial systems are typically 25% of input power.

 

[x88x]

Overall losses on commercial systems are typically 25% of input power.

Link?

TBH, I haven't gotten around to doing any research on this myself...moving has proved much more time consuming this time around..

 

[Hillhater]

Link?

TBH, I haven't gotten around to doing any research on this myself...moving has proved much more time consuming this time around..

Google will turn up lots, many of which get very detailed.
Wiki probably summarises it simply..
http://en.wikipedia.org/wiki/Hydraulic_machinery

When calculating the power input to the pump, the total pump efficiency ηtotal must be included. This efficiency is the product of volumetric efficiency, ηvol and the hydromechanical efficiency, ηhm. Power input = Power output ÷ ηtotal. The average for axial piston pumps, ηtotal = 0.87. In the example the power source, for example a diesel engine or an electric motor, must be capable of delivering at least 75 ÷ 0.87 = 86 [kW]. The hydraulic motors and cylinders that the pump supplies with hydraulic power also have efficiencies and the total system efficiency (without including the pressure drop in the hydraulic pipes and valves) will end up at approx. 0.75. Cylinders normally have a total efficiency around 0.95 while hydraulic axial piston motors 0.87, the same as the pump. In general the power loss in a hydraulic energy transmission is thus around 25% or more at ideal viscosity range 25-35 [cSt].

 

[dr_fruikenstein]

I haven't done a hydraulic conversion, but if you're willing to give it a try, check out the "Hydristor". Here's a wikki link on hydristors...
http://en.wikipedia.org/wiki/Hydristor

Good luck.

 

[etard]

You would think if hydrostatic drive was remotely efficient there would be at least one automobile, electric or gas, that used it with some success. My dad's old lawn tractor was hydrostatic, it seemed the biggest advantage was being able to slam it from full speed forward to full speed reverse without damaging anything, not really an advantage on a bicycle though.

What about shaft drive? It is probably about as efficient and could be run out the end of the axle.

 

[spinningmagnets]

I recall a German off-road research vehicle. 8 wheels, each on an independently height-adjustable arm. Using hydrostatic drive allowed it to be easily engineered with few custom pieces, lots of OTS. Low-speed, weight was not a concern. Lets have a look at the web...

I'm back, heres a You-Tube of a hydrostatic rock-crawler, a hydraulic motor drives the central conventional 4X4 transfer case. By doing that, a variable stroke hydraulic pump acts as a CVT, so engine RPM can stay at the most-efficient/best-power RPM as desired:

http://www.youtube.com/watch?v=mXF16-9zuCM

I've operated a mini-street-sweeper that was hydrostatic. As long as hydraulics were needed anyways, they could eliminate the conventional mechanical connection to the wheels. It had a hydraulic motor on an ATV differential to drive the front wheels, rears steered like a forklift.

Heres a 6WD off-road hydrostatic truck. Notice the lack of differential between the two rear tires, so in this type each wheel has its own motor. Lower CG, and hydraulic pressure is easily variable, but also low-speed.

 

[x88x]

Hahahaha, nice! I love the wall test in that video!

 

[Hillhater]

What about shaft drive? It is probably about as efficient and could be run out the end of the axle.

like these ??
http://www.dynamicbicycles.com/

 

[deVries]

What about shaft drive? It is probably about as efficient and could be run out the end of the axle.

like these ??
http://www.dynamicbicycles.com/

This has a very kool animation...

Nice Shaft Drive Animation

Why not drive an eBike from the left side of that crank-set. No chain to rear; cleaner & quieter setup.

8)

 

[Hillhater]

No chain to rear; cleaner & quieter setup.

8)

yes but .....
more friction losses,
lower efficiency,
more complex / expensive gearing systems,
higher costs.
more weight.

 

[DaS Energy]

Hello x88x,

We did such some time ago. Now released in Open technology.

Having hydro turbine drive to each wheel with steering by restricting water volume to specific wheel turbine.

 

[Martin A]

Hi

I've been thinking upon similar lines for powering a tilting trike. To keep things neat, hydraulics could run through the frame directly into a rear hub with no visible external drive. I realise there are efficiency losses but if one is willing to accept these, gains may be available in other areas. Try this site for more info. http://www.hydraulicinnovations.com/