Hydraulic motor sizing - weird project

[cmaas]

I'd guess you'd be way better off financially and mechanically less complicated to just use a small engine powering one variable volume pump that provides power to two wheel motors that drive the two ground tires, and with diverter valves, power the stern drive with the same pump and a smaller hydraulic motor.

Well that's not nearly as much fun.

Since to purpose of this barge is to transport the electric car from one island to another for grocery shopping I'm set on using it for the power source.

 

[MossRoad]

Seems like it'd be simpler, cheaper and more efficient to skip the hydraulics and make it purely mechanical.

Use the roller drive diff output to turn a salvaged automatic transmission (for the torque converter to act as a clutch) which operates the front drive axle.

Also if there's not enough weight on them you might have traction problems with wet front tires on a 23% slope.

Yep. He could turn around and back up the hills.

 

[MossRoad]

Well that's not nearly as much fun.

Since to purpose of this barge is to transport the electric car from one island to another for grocery shopping I'm set on using it for the power source.

:thumbsup:

 

[cmaas]

I'd also be leery of casters on a +5000# vehicle, weight balance, and the ability to get enough weight over the casters to provide steering force VS sinking into soft ground.

Good point. I hope to stay on the gravel or pavement. In theory the casters don't need any weight on them though. The drive wheels are doing all the steering. Of course I don't want this thing doing a nose dive going down hill so there will be enough weight on the casters to avoid that, I hope.

 

[cmaas]

Seems like it'd be simpler, cheaper and more efficient to skip the hydraulics and make it purely mechanical.

Use the roller drive diff output to turn a salvaged automatic transmission (for the torque converter to act as a clutch) which operates the front drive axle.

Also if there's not enough weight on them you might have traction problems with wet front tires on a 23% slope.

There are a lot of ways to skin this cat for sure.

Two things to keep in mind: The wheels need to retract out of the water so I'm not dragging them around; If I don't steer with the separate motors on the drive wheels I'd need to set the rear wheels up to steer. That can be done - like tie them to the sterndrive - but it is a new element to deal with.

Good point about the traction. I will have the torque - otherwise I'm not going anywhere - so I figure it's a matter of choosing the right tires and weight distribution.

 

[MossRoad]

You could use the front steering axle off of a 4wd pickup or Jeep and power that with 1 reversible hydraulic motor.

Then you'd only need to power 1 variable volume hydraulic pump to provide infinite speed control in both forward and reverse to that reversible motor on the steering axle.

You power that VVpump with the spinning rollers from the drive wheels of the electric car set at a specific speed and cruise control set.

That takes care of your ground drive and steering.

If you want to go with one hydraulic motor on each drive wheel instead of the above mentioned, then you'd have to figure out how to steer them. You could do either two VVP's, one for each motor, or some valving arrangement.

Either way, the pumps and motors to provide that kind of torque and power will be expensive if you can't salvage them from something else.

With a hydraulic motor, you could power a manual transmission and get gear reduction to a differential.

Man, there's all kinds of what if's in how you could go at it! :laughing:

Anyhow, good luck with your project. Sounds fun. :thumbsup:

 

[oldnslo]

Cmaas,
On the counterbalance question. Each motor will require two one on each work port. These valves free flow in indirection and are piloted open in the other or restrict flow when pilot signal is lost. I.e. going down hill.

On your design I presume the tires and motor will be under water especially when launching and landing. Will they also be in the water while traveling on the water? Is this salt water or fresh water. Not to beat a horse to death but you might want to check into the rules on hydraulics used in submersible applications in your area for any special requirements on oils, seal requirements, etc.

If using open loop system yes you can run multiple functions off one pump. If running full speed majority of the time a simple fixed displacement pump is the most economical. If running at slower speeds or doing turns on a frequent basis a variable volume load sense pump would create the least amount of heat and waste the least energy.

110 percent agree on the devil is in the details and if you size something incorrectly or miscalculate traction could be an expensive learning curve. Any good reputable hydraulic shops in your area the tspecialize in mobile equipment? They could potentially provide some ideas for you also.

 

[4570Man]

Seems like it'd be simpler, cheaper and more efficient to skip the hydraulics and make it purely mechanical.

Use the roller drive diff output to turn a salvaged automatic transmission (for the torque converter to act as a clutch) which operates the front drive axle.

Also if there's not enough weight on them you might have traction problems with wet front tires on a 23% slope.

You really wouldn’t even need the transmission or clutch. The car already has those functions. If the rollers the car sits on were direct drive to the raft wheels it would be simple and work fine.

 

[cmaas]

Cmaas,
On the counterbalance question. Each motor will require two one on each work port. These valves free flow in indirection and are piloted open in the other or restrict flow when pilot signal is lost. I.e. going down hill.

On your design I presume the tires and motor will be under water especially when launching and landing. Will they also be in the water while traveling on the water? Is this salt water or fresh water. Not to beat a horse to death but you might want to check into the rules on hydraulics used in submersible applications in your area for any special requirements on oils, seal requirements, etc.

If using open loop system yes you can run multiple functions off one pump. If running full speed majority of the time a simple fixed displacement pump is the most economical. If running at slower speeds or doing turns on a frequent basis a variable volume load sense pump would create the least amount of heat and waste the least energy.

110 percent agree on the devil is in the details and if you size something incorrectly or miscalculate traction could be an expensive learning curve. Any good reputable hydraulic shops in your area the tspecialize in mobile equipment? They could potentially provide some ideas for you also.

Thanks again. I really appreciate your giving this some thought.

The tires and wheels are under salt water when launching/retrieving. Otherwise they are on pivoting legs that retract. Except for the high pressure this is the same as outboards and sterndrives relying on seals to keep the oil out of the water, and vice versa, but I take your point and will check into it. Metal corrosion is a constant battle in this environment. I try to keep trailers outboards etc. rinsed off but steel components can have a very limited life here. Even galvanized.

I've got the name of a hydraulic shop in Seattle that does a lot of work on commercial fish boats. I need to find a knowledgeable place for mobile equipment but there's not a lot of ag stuff in this area. I wanted to get some basic knowledge (which you are helping to give me) before I contacted a hydraulics shop. Didn't want to sound like a complete idiot!

Re. traction, weight etc. A lot of what I can do to work on this design is learned empirically. Like mimicking the load weight and traction using my little tractor in 2wd towing a loaded trailer on the 23% hill that my amphibious barge needs to climb. I can compare that to the torque and speed numbers my engineering student calculates and see how the real matches the theoretical.

I may end up putting bigger tires on the drive wheels and will definitely make them as wide as I can get. But bigger diameter means more torque needed at the wheel. Other comments on this post are making me think I should increase the weight those drive wheels carry by moving the wheels back some to carry more load.

 

[cmaas]

You really wouldn’t even need the transmission or clutch. The car already has those functions. If the rollers the car sits on were direct drive to the raft wheels it would be simple and work fine.

I couldn't figure out a way to make those drive wheels (1) on a differential that I could retract out of the water (2) keep that diff, and the cv joints it would need, from rotting in the salt water, (3) Connect a direct drive to those wheels and the sterndrive (propeller) that moves the barge.

I figured that since I need hydraulic cylinders to lift wheels and ramps anyway I might as well size it up to run a couple of motors.

Earlier design ideas had direct chain drive but that meant only one drive wheel which I'm pretty sure won't get me up the hill.

It's all a matter of trade offs and compromises. In the end I just hope to have something that works okay, doesn't take forever to build and doesn't cost more that three times what I estimate.

 

[oldnslo]

cmaas,
Salt water does add another layer of concern or complexity. I believe that every wheel motor I have ever seen has cast iron housing so corrosion protection will be required.

Why could you not make two wheel chain drive. Separate drive motor for each wheel with chain final drive. Could provide gear reduction so use smaller lower cost motor and also keep them out of the water.

I would definitely make this a true 2 wheel drive since driving out of water one tire should easily be on a little mud and spin out.

Good luck on cost being less than three times your estimate and five times longer to build. This is how most of my projects end up...

Have a safe and Happy Thanksgiving

 

[cmaas]

cmaas,
Salt water does add another layer of concern or complexity. I believe that every wheel motor I have ever seen has cast iron housing so corrosion protection will be required.

Why could you not make two wheel chain drive. Separate drive motor for each wheel with chain final drive. Could provide gear reduction so use smaller lower cost motor and also keep them out of the water.
I would definitely make this a true 2 wheel drive since driving out of water one tire should easily be on a little mud and spin out.

Good luck on cost being less than three times your estimate and five times longer to build. This is how most of my projects end up...

Have a safe and Happy Thanksgiving

Two wheel chain drive would work. It make things a little worse for corrosion - now I would have wheel hub and bearings, sprocket and chain added to the mix. Though I can get stainless steel chain and I can make stainless sprockets. (when I looked into it ss sprockets were stupidly expensive. Maybe there's an alloy version that would work). Short duration salt water submersion is really no different than salt water splash so the motor would still be subject to corrosion. Fresh water rinsing is really a good idea. I have toyed with the idea of setting up a permanent rinse system at each wheel. Just quick connect the garden hose to it after a trip. But like you say the gearing would be a real benefit to chain drive so I am not discarding the idea completely yet.

I'm starting to think something like two 45cu in wheel motors run by a 6cu in gear pump might be what I build this system around. I could belt drive the pump off the 3,000 - 4,000rpm propeller drive shaft and engage it using an electric clutch.

Got any thoughts on using an oil cooler? I'm thinking that they must restrict the flow somewhat but haven't been able to find out anything about that. I would like to reduce weight wherever I can and if I can carry less oil by using a cooler I'm willing to consider it.

Happy Thanksgiving to you too!

 

[oldnslo]

Oil colors are for low pressure return line so sized correctly they only add 20 - 30 PSI. But again not sure how these stand up to salt spray though.

I believe Hydac has a decent website for their heat exchanger product line and are focused on the mobile industry with both DC electric & hydraulic motor fan drives. This could provide some idea on size and weight Vs heat rejection capabilities. The huge factor is how many HP or BTUs do you need to remove the oil. Starting point Rule of thumb is figure 20 - 25% of input power.

 

[MossRoad]

One more question... why do you need the barge to drive on land?

 

[cmaas]

One more question... why do you need the barge to drive on land?

Lots of good reasons. Starting with in the Summer it's a lot easier to find a parking spot at the launching ramp parking lot than to find dock space. At both ends of the trip. In winter the barge will be out of the water in bad weather so I don't need to worry about it getting banged up at the dock or what's happening to it if its hanging on a mooring in a storm. And no bottom paint or scraping barnacles.

It means we can basically drive to the store on the next island over and not have to lug bags of animal feed and groceries etc. up and down the dock ramps.

That's what I tell my wife anyway. Really the deal is you can pick up one of these little electric Fiats pretty cheap. They are a blast to drive. I wouldn't be surprised if I could beat a Porsche 911 to 50 unless he dropped the clutch. Besides I think this project is going to be a really fun and interesting challenge.

Happy Thanksgiving

 

[LouNY]

I like your barge idea.
But would it be easier to install long folding ramps on the barge.
Unfold when grounded out drive the car off, hook to the barge and tow it like a trailer to the parking lot.
You would need a small power source to power the ramps in and out and possible a winch to pull the barge to the car when it was safely secured.

 

[cmaas]

I like your barge idea.
But would it be easier to install long folding ramps on the barge.
Unfold when grounded out drive the car off, hook to the barge and tow it like a trailer to the parking lot.
You would need a small power source to power the ramps in and out and possible a winch to pull the barge to the car when it was safely secured.

Your idea has merit for sure. My goal is to drive from my house to the grocery store on another island and back home without getting out of the car, except to go into the store. We're trying to figure out ways to keep living on a remote island as we get old. And a helicopter isn't in the budget.

The picture is of us bring the Fiat over a few of days ago on a steel barge I built. That barge mostly gets used for a hay trailer these days.

 

[cmaas]

I have tested the Fiat powered barge in the water. Now it's time to start on the hydraulic wheels.

I plan to use two hub mounted motors on the front wheels. You can see the retractable leg with hub motor in the photo. Those hub motors need to have speed and forward/reverse control for each motor.

I'd like to have a control for those motors with me in the car but can't really drag those hydraulic hoses in there. I'm hoping I can use a switch (joy stick?) that controls a proportional valve. Is that how its done?

 

[Patrick Herd]

Dana Brevini have proportional control valves which will do what you want and can be electronically controlled remotely: Mobile valves HPV310 Series | Brevini Fluid Power I can probably help you find a Brevini project engineer near you. Disclaimer: I'm not an employee, just a happy customer.

 

[cmaas]

Dana Brevini have proportional control valves which will do what you want and can be electronically controlled remotely: Mobile valves HPV310 Series | Brevini Fluid Power I can probably help you find a Brevini project engineer near you. Disclaimer: I'm not an employee, just a happy customer.

Thanks! I will have a look.