Proportional Electrohydraulic Systems??

[jgrreed]

I have experimented with some Parker dial-adjustable flow restrictors and I also find them to be quite effective. Very reasonably priced, too.

You've experimented with those restrictors on electrohydraulic servo on/off style valves, or mechanical style?? Just wondering if they're a good option to smooth out a servo valve.

-Jer.

 

[dfkrug]

You've experimented with those restrictors on electrohydraulic servo on/off style valves, or mechanical style?? Just wondering if they're a good option to smooth out a servo valve.

I tried them with my all-mechanically-controlled hydraulic backhoe thumbs.
These adjustable restrictors use a needle valve and work well in only one
direction.

Flow restriction with this kind of valve would work to smooth out the
movement of many kinds of implements, whether the main flow valve is
mechancical or solenoid controlled, IMO. My recent 4-in-1 project used
all 1/4" hoses and some pretty small valve orifices and that is plenty of
flow restriction (intentional!) for that application.

Backhoe swing circuits sometimes use a restrictor valve like the Parker.

 

[jgrreed]

So, after a bit of a hiatus from this project, I have an update.

Thanks to Nick at Orbit Hydraulics in Grande Prairie I now have a price on the valves the I'll need to make a go of this project.

He's come up with Parker Valve D1VW008CNKW45 for $519.18CDN each, and I'm going to do 3.

The baseplate to go along with them is part MC590M310-8A and he figures will be around 450$CDN.

What do you all think?? I figure it'll be another 1000$ or so for the controller, joystick, and switches. Maybe 4k$ total (plus my install time, I know) including hoses and fittings???

I found out that another friend of mine here in Hinton has experience with these systems (calibration, etc) as an oilfield electrician, so there's some more help with setting it up!!

-Jer.

 

[jgrreed]

Another update:

Just spoke with Steve at Otto controls. Very nice, very helpful. He's emailing me some drawings and prices for how the switches might/can fit into the face of the grip.

Brian at Scorpion controls is helping me out with the control box build and set up as well.

This just might work!!!

-Jer.

 

[quarencia]

I read through this post a few days ago and I love what you're trying to do. Here's a much cheaper and crazier idea. Would require a basic understanding of electronics, but it will work and would run somewhere in the range of $300-$500 less hoses and connectors.

Use a high-end RC servo to control a standard directional hydraulic valve. If you get a small 2-way valve that has the spring centering mechanism mounted externally (under a cup), you can remove the centering springs and greatly reduce the required control force. Fabricate a connector to hook the servo to the valve spool and obtain a suitable driver circuit to go between your control and the servo. Your control switch should be spring centered, so that will drive the valve back to center when you release the switch.

Futaba's biggest servo produces 425 oz-in of torque. With a one inch arm on the output shaft, that's a push pull force of 26.5 lbs. These servos use pulse width modulated signal for position command and use a separate wire for powering the servo. This means your control signal can be extremely low current. High-end servos for quarter-scale models are all metal constructed with metal gears and ball bearings and are highly reliable. These are used to fly aircraft that cost as much as some of our tractors. They would require a voltage drop to 6 volts for power though. Here's a link to Futaba's largest servo. Futaba Servo Someone else may make a bigger one. These run in the neighborhood of $140.
Here's some info on how RC servos work. http://www.futaba-rc.com/servos/digitalservos.pdf

You're planning to use an analog proportional thumb operated switch mounted in your joystick grip. I was thinking about a thumb operated hat to get control of two functions with one finger. Something like this small joystick hat for replacing Playstation joysticks on e-bay. Analog Controller Stick Joystick For SONY PSP 1000 Fat - eBay (item 170295562953 end time Feb-18-09 01:00:11 PST) If I did this (and I'm thinking about experimenting with it), I'd look for a more industrial grade hat.

There are PWM modules similar to the one you showed earlier that can be used to control these servos from an analog switch/joystick.

As I've looked up these components, can't help wondering why manufacturers don't use a similar (although purpose built) method. It would be much cheaper and would offer greater flexibility of design. There must be a good reason.

 

[jgrreed]

Hi,

Great ideas!! Wow, you know a lot about this stuff...... I'm assuming you're into RC planes or heli's?? I've heard that this RC stuff is not all that bad once you get a handle on it, but it's like learning another language!!! I think I'm going to stick with the pro-made valves from Danfoss or Parker. I'm already WAY out of my league in even trying to do this, so I'm going to leave the valve actuation to someone else.

I'm already on board with you on the hat switch!!!

I'm waiting to hear back form the hydraulic shop on the valves I need, as I see them as my biggest cost - likely around 500$ a piece (CDN).

Check out Otto Engineering. They have a ton of switches to choose from, including hats. They offer different levels of 'toughness', all the way up to submersion proof mil-grade. They can output analog, CanBus, PWM, and one other mode as well I think. They're the best site I've come across on the control end. They're also great to deal with when you call. I chatted with a sales guy (Steve I think) a couple weeks ago and he was very helpful in getting me drawings and price estimates on the grip I'm looking to build. Not ultra expensive either, ~80$ for a water resistant, Hall-effect 4 way hat.

I'll keep posting as soon as I have more info....

-Jer.