On my Bobcat E60 I have an aftermarket two spool solenoid valve for the auxiliary hydraulic circuits. Currently there are simple push buttons on the joysticks for control. Obviously this makes for very jerky movement of the attachment since it's either off or full flow. I'd like to convert it to proportional control but I'm not sure how to do that. I know I will need joysticks with slide or rocker style switches (not sure of the proper term). And I assume I'll need a pulse width controller. But I'm not sure if I'll need different solenoids on the spools. Any ideas of where to source the parts I'll need to do this? Thanks
You could do what you suggest but it's going to take quite a bit of engineering to make things both fit, and be ergonomically useful. Yes, the solenoid coils must be matched in resistance value to the output of the square wave generator circuitry. The main control unit for a proportional controller is a center null rheostat which is shifted one of two ways from the null to a maximum value from zero and this increases, or decreased the on/off times of the desired output of the square wave generator. I don't know your application but I wouldn't rule out "soft star" hydraulic valves for your application. These are dampened in spool shift and many times eliminate the "all or nothing" engagement and lesses shock loading. They seemingly would work very well in slowing the engagement of an auxiliary attachment I'd think.
Good day There are some other solutions that you may have overlooked, such as using a pedal on the deck or dual function the bucket control see the link. H2 ThumbDualBucketControl1.pdf drive.google.com Kind regards Uffex
Thanks for the advice. I hadn't heard of soft start valves. From what I gathered in a preliminary search is that they replace the relief valve. Is that correct? Uffex, that's some good info on adding a circuit. I tried calling Hydraulic Circuit Technologies in Georgia yesterday hoping they would be able to sell me a kit, or even just some parts. But they said they don't have any technical info for my machine and can't help me out (even though I mentioned that the two spool auxiliary valve is a generic add on valve). It seems like dealers must have a source for things like this when they have to add auxiliary circuits to a machine that didn't come with them from the factory.
Good day Glen I suggest you make a decision on how you would like to operate the thumb. If you go to the website excatech.org look at the alternatives you will find a document "Thumb questions & answers" it may well help you figure out the best way to go. Once you decide you can give us a line a [email protected] we can steer you through the install using of the shelf parts. I would recommend that you avoid proportional control unless you are electronically minded. There are easier ways to achieve the same goal. Kind regards Uffex
"Soft Start" hydraulic valves tend to incorporate a small "RC" network, (timer) to designate the time delay to full opening and/or closing so the action is "ramped". This lessens the harshness of the application, or engagement. Some are adjustable, some fixed in delay. They act much like a manual valve that you slowly stroke/engage full on, or full off in position. Usually have nothing to do with a relief section which is either a cartridge assembly, or a shim adjustable affair incorporated into the system. I used two soft start valves with D03 mounting pattern on a matching manifold to power drive motors on my shop gantry. Also a manually actuated pressure compensated speed controller to make this crane traverse the shop floor fast, and then very slow such as when placing a cab or hanging engine assembly into a chassis when "finesse" is required. With these valve incorporated, the application of hydraulic engagement is very easy.
Thanks Uffex, The machine already has two sets of lines/hoses installed, and a two spool solenoid valve controlled by push buttons on the joysticks. I use it with a tilting cleanup bucket and a rotating grapple. It works quite well for both of these, except being quite jerky when the machine is at normal operating RPM. I am looking for a way to have better control of these auxiliary circuits to allow for finer movements of the attachments.
If your only trying to slow down a thumb and make it less jerky I would try installing a restrictor valve. They make them adjustable so you can dial it in to where you like it
Thanks for the explanation, I think I understand better now. Sounds like this would replace the valves that I am currently using? As opposed to being an add on to the circuit
Another good option to look at, thanks.
Sometimes, but not always. Many times it is just the solenoid package that shifts the spool you would replace. I like either "Yuken", or "Eaton" valves myself as very well supported.
Years ago we softened the thumb action by installing a pressure control cartridge in the pilot circuit that controlled the thumb actions. It took a special sub plate but used the standard solenoid valve setup.
This is exactly what I was hoping. But, I will need to find out where to buy them.
I may have to look into this as a secondary option. Thanks
Good day It is possible to improve some solenoid valves installing a one way restriction, may be worth a thought. Kind regards Uffex
If you could attach a photo of the solenoids package itself and some identifiers, I can do some research also. Some things can be rather inexpensive to incorporate, some quite expensive, but need to know what is being worked with to start.
Good day Consult your nearest Rexwroth - Bosch dealer or catalogue for more details. Kind regards Uffex
I will definitely post some pictures. I thought I had taken some pictures when I installed the valve block and solenoids about a year ago but I looked through my phone and computer and can't find them. I need to tip up the cab and remove some panels to get access for pictures so it won't be tomorrow but I'll try to get them soon. Thanks
Well maybe I'll have some downtime now to check out that solenoid valve while I'm waiting for welding/line boring.
Finally got a chance to get some info on the valves.
Real standard valve used with hydrastatic drive or action. Blocked center with spring return to center, electric solenoid shifted four way valve. A "soft start" valve would be an easy installation replacing the original valve.
Thanks. So you are recommending replacing the whole valve block unit, or just the spools? Soft start would be better than what I currently have, but I was hoping to convert this valve so that it can be proportionally controlled with slide switches on the joysticks. Are these solenoids capable of holding the valve partially open if connected to a proper controller? I thought about testing it out with a potentiometer to see if I can vary the flow rate with different voltages applied to the solenoids.
No, they will not work as you are asking. They receive full voltage for operation from a switch or function, and the full engagement, (spool shift) is slowly actuated. It is not immediate shifting of the spool as your current valve offers. Removal of voltage causes the spool to recenter blocking all ports. Some are dampened in return to center; many are immediate return to center.
Ok, so that helps me understand how soft start valves work. Can you help me understand how proportional valves work?
In the "soft start" valve: The resistance capacitive time constant, (RC) is changed accordingly to the amount of delay desired in the circuit design. This is a design feature not normally adjustable by the end user but can be externally adjusted for application and delay if designed so. This is much the same way your delay feature on windshield wipers operate but slightly altered to slowly apply full voltage to the circuit shifting the spool. Proportional controls usually utilize a square wave generator circuit and vary the off, and on times of the output voltage on both sides of the "null point" which is felt in the circuit as a varying voltage. This square wave voltage output can be applied to either side of a coil energizing the coil and driving a slug, or a electrical circuit in a given direction.
Good day Mat The easy way to understand is to compare it with a florescent light. It uses's less electricity than a lamp that burns power all the time by switching on & off the power, which results in a flicker from the florescent tube. A proportional signal does much the same, mostly with five volts. The period that it remains with power will cause the spool to remain open, the control is by a chip which in turn will be signalled from the slider switch on the control lever. Without going into lengthy text explanation, it is the best I can do. Kind regards Uffex
Good day Attached if you like detail. Kind regards Uffex