Hydraulic Hybrid Truck Conceptual Design

Tom

Marcin;

My thoughts were to start with an existing truck, like this one for $1000 with blown transmission:

https://houston.craigslist.org/cto/d/alleyton-2000-gmc-w3500-forward-box/7898859919.html

Replace the transmission with one hydraulic pump and one hydraulic motor to power it via the existing engine and differential. This would be a simple way to design the hydraulic system apart from the rest of the truck.

Of course, the power cube / 4 wheel drive thing sounds attractive, but I'd like to focus on getting the hydraulic drive train working smoothly before going further. It did suggest the following for 4 wheel drive:

Layout B — Four Motor Wheel Drive Pump: Parker / Eaton variable pump in 110–150 cc range

Motors: 4 × mobile wheel motors (100–120 cc)

Multiple closed-loop hoses

Traction control via independent motor swash controls

One thing I'd like to defer for now is integrating the 4 wheel drive and steering. Using an existing truck's steering, braking and so on is preferable for the first cut.

The prices gathered seem too high. I think alternatives / other sources can cut it substantially. It did say other pumps could work: Best hydraulic pump options for truck propulsion (ranked):

Rexroth A4VG series — ideal overall

Parker/Denison T6 series — excellent reliability

Eaton VP/PVQ series — good cost-performance

Vehicle-specific hydrostatic transmissions — highest integration

Besides, SurplusCenter sells Rexroth A4VG pumps for $800 and they sell Rexroth motors as well:

https://surpluscenter.com/piston-pump-a4vg28hwdl1-32r-nsc10n005e-s/

The beauty of the variable displacement pump is that the throttle connects to the pump and controls it's output with a feedback loop inside the pump for reliable, well controlled output.

I'd like to maximize the safety and prevent the possibility of it behaving erratically. It would be best if it works like a normal truck as much as possible.

MJ

Challenges of speed and power control for a truck with open center hydraulics: https://chatgpt.com/share/69480f12-1ea0-8010-a3cc-15a351f4209a

Please post source chat at https://wiki.opensourceecology.org/wiki/Open_Source_Hydraulic_Truck

You forgot engine and transmission in your cost estimate.

4500 lb truck is a sissy, need to pull real loads. Need 4WD.

$8k-$14k for hyd pump/motor is too much. You're now in a new class of more complex hydraulics than simple power cube stuff we did to date. Point would be to get rid of transmission. Use hydraulic motor on each wheel.

Hydraulic pumps (nonvariable) are $10/hp. Use engine throttle or multiple engines (power cubes) for speed control, not variable pumps. If you control pump through variable feature then engine is revved way up, which is not efficient. Huge efficiency would be say 1 engine on low speed, 4 engines on high power - with ability to turn on each engine as needed. 

I don't have a good affordable solution for engine. I would go with 4x 1000 cc but that is only 152 hp. We need a larger engine that is affordable.

What is the best we can do?

How about a heavy engine from caterpillar and no emission design - for off road DIY only - and as we sell some bootstrap to full emissions and our own engines?

I would do this phasing: 

1. Robust, cheap - no emissions. Work out robust speed, power, scalability with open center hydraulics.2. Invest in CNC centers, induction, and forge - make our own engines3. Develop open source high performance hydraulics.

The only way I can think of good speed control:

1. Lo/hi throttle with 4 power cubes - gives equivalent of 8 speeds2. Use 2 sets of motors per wheel: one high torque and one high speed. Select between the two. Just like in the Universal Track Unit - https://wiki.opensourceecology.org/wiki/Universal_Track_Unit3. Selecting between motors has low loss if unused motor freewheels 

Cost: 1. Pumps are $100/27 hp or $4/hp2. Motors are $150/15 hp or $10/hp3. Engine costs are $30/hp for throwaway EFI engines at 38 hp - https://wiki.opensourceecology.org/wiki/Engines#1000CC_EFI - but would need to derate engine to access low cost pump (3000 RPM) as engine runs at 3600. Forget about gear reduction. Or do 16 hp - [1] at $25/hp4. Final drive on wheels - ideally direct drive. Otherwise, go to chain - but that's a major failure point for high torque high power stuff outside of skid steers, where chain drive is normal. So practical answer is - gears etc.

Cost - Godzilla engine - https://chatgpt.com/share/6948060e-c8ec-8010-b597-8650a69e938a

No easy answer with hydraulics, really requires some thinking at higher powers. I think we would need to open source our own EFI engine using open source EFI which already exists, and then work out the high torque for wheels. Why do you suggest variable displacement pumps instead of engine throttle? Sure, but cost is $8k. Maybe start with 45 mph top speed heavy truck (8000 lb) that can also be a skid steer.  Suggestion: 1. 4 power cubes, fixed displacement system of 152 hp (4x38 hp). Add electronic controller (arduino, etc) to control throttle and engine turn-on so we have a system that functions close to variable displacement system. 2. Add RTK GPS, computer vision, remote control, autonomous driving - as a way to make up for low top speed.3. Max out, develop, document  limits of above system - commercialize it. I think that  even an 18hp x4 power cube dirt cheap system - with full electronic controls and RTK GPS etc leveraging all modern electronics and AI - could be a killer at low cost. Then we use this to bootstrap open source hardware engines and hydraulics.4. Move on to variable displacement5. Open source an EFI engine6. Open source hydraulics So in the above scenario, if we do 16 hp at $25/hp and 70 lb weight - we do the 'mother cube' concept with a lot of babies - definitely for 4 engines and see where we are at a 64 hp sissy vehicle. Potentially scale by adding another mother power cube combo to double this. Pump - 12 gpm - 3500 rpm - https://www.amazon.com/Hydraulic-Straight-Keyed-Shaft-Aluminum/dp/B07H1HDPBR - so about $10/hp Motor - also similar price - $10/hp So drive cost is $45/hp - so $7k for 150 hp. Just hydraulics are $20/hp, compared to your say $10k/150 hp for variable displacement = $70/hp. Maybe start with 150hp of Power Cube on the back of an old Ford Ranger for $7k? 70 lb per 16 hp - 700 lb for 160 hp. Hard to compete on price until all this becomes open source. Not sure where to go on this. Marcin

Top Speed

• 150 hp gives top speed of 60 mph at 7% incline - [2]