Thinking about adding a (?hydraulic?) thumb to my full size backhoe

[Aruba1]

Unfortunately I don't. The reason because it isn't finished yet :laughing:
It's one of those (many) projects that I haven't found (or rather made) the time to finish up. I have it about half welded together at this point and it is sitting in my garage. I'm actually a bit nervous that it is going to be TOO heavy for my backhoe. I think I may have "overbuilt" it a little bit too much, but we'll find out......someday.

Do you have a 3rd function valve for your backhoe?

Tell me about it, too many project, too little time to do anything and still acquiring more projects , the story of my life.

No, I don't have a 3rd function valve but I already have everything in do the install but I have not got around making the drawings yet. If you have CAD drawing and you would like to share, please send me a PM. In regards to your build, you should be fine and I would not be too concerned with the weight of the thumb. How heavy is it? Its a big machine: Overbuilt = Good.

 

[Piston]

It will weigh somewhere around 350 lbs I believe, that is just me figuring the weight of all the steel using online calculators.

What are you using for the 3rd function? I bought a diverter valve that I'm planning on using, but I'm not really sure which would be the best circuit to tie into, any ideas?

I'm happy to share my drawings, I drew it up on sketchup. I imagine someone that is smarter than me could convert it to a CAD file, bring it to a shop with a CNC machine or computer aided plasma cutter, and have them cut out all the pieces exactly. I simply cut them all out using the torches.

I can't send you the file through a PM though, so send me your email address and I'll email you the .skp file (and anyone else who wants it as well)

 

[Aruba1]

I think the weight on your thumb is just fine, see some other thumb that are equivalent of yours, they also weight around 350 lbs: Hydraulic Thumb 18"x45" for Excavator 19000 23000 lb by USA Attachments | eBay
Unused 2010 CP Paladin Hydraulic Thumb Accessory for John Deere 310 G Loaders | eBay

I purchased a single spool off a damaged loader on ebay and I will be using that (I paid $25 that included shipping). Once I finish cutting and installing the thumb I will be focusing on which circuit to use but I'll check to see which one would be best to tie too, most likely I will be using one of the 2 largest cylinders on the backhoe. I would love to see some pics of your cut outs, I may just go that route also and skip the CNC. I'll send you my email shortly. Thank you...

 

[Piston]

I'm looking for some hydraulic help with this project. As I mentioned earlier in the thread, I'd like to tie the thumb cylinder in with the same valve that operates the outrigger. I am going to use a diverter valve for this. Before I do it though, I have some questions regarding the way this would work, or if it would work.
Here is the valve I have already purchased: https://www.surpluscenter.com/Hydra...GPM-DOUBLE-SELECTOR-VALVE-12-VDC-P15544-1.axd

Does anyone have some input on some of the below quotes/questions for me?

The outrigger is the way to go, as long as the pressure stays on the leg on the switch over.

Will the pressure stay on the outrigger cylinder, when I switch over to use the thumb cylinder?
What happens if I turn the machine off? Let's say I have the machine up on the outriggers, with the rear tires off the ground so the outriggers are holding the weight of the backhoe. If I shut the power off, will the solenoid valve open one way or the other, allowing the outrigger to bleed down?




Can anyone advise if the quote below is correct, in the way it is explained? I'm not entirely sure how the switch/solenoid/cylinder work together. I suppose the main thing I'm concerned with is the outrigger losing pressure/retracting when I either switch over the toggle switch to the thumb cylinder, or shut the power off completely.

=================

you have 2 hoses going to the out rigger. to either contract or expand the cylinder on outrigger. same goes for the hyd thumb.

the diverter valve you picked up. does it mean,
---you just flip the switch "up" no need to hold switch and switch should automatically go back to center. and then use the outrigger lever to lower or rise the out rigger.
--- and then if you flip the switch "down" switch goes back to center, and then you use the outer rigger lever to expand / contract the hyd thumb

does above sound correct?

does the divertor valve you are using, act like 2 3way valves. and you just need to flip the switch for a quick second and that is all that it takes to switch between out rigger or hyd thumb? or does the switch needs to stay on in the up or down position, so hyd oil goes to the out rigger or hyd thumb?

=============

 

[BukitCase]

I bought two of these

12 VDC 13.2 GPM SAE 8 DOUBLE SELECTOR VALVE

for front hydraulics on my 580B - one will be used for a grapple (yet to be built) and the other to articulate a Samurai sickle bar cutter for doing hedges, etc -

Mine actuates BOTH sets of ports with one solenoid, yours will actuate ports SEPARATELY if you want - but for what you want to do, I would wire both solenoids in parallel to one momentary switch on your BUCKET circuit control lever - that way, one hand on the bucket lever, with no switch, bucket curls. Switch, and thumb operates while bucket stays put. You will need both pairs of ports, one for pressure and the other (depending on whether you're extending or retracting the thumb) for tank return. That's why you'll need to wire both coils to the same switch.

By doing that, you can pre-position either the bucket OR the thumb, then use either one to grab stuff. Or, you could "sneak up on your load" by alternating bucket-thumb-bucket til you have it the way you want.

If you still want to use your outrigger circuit, it'll work - those valves block off whichever port is NOT actuated, so wherever your outrigger is, it will STAY there til you switch BACK to using that control for the actuator. (Leaks being the exception)

Not sure about YOUR hoe, but my Case has MUCH smaller ports on the outriggers (3/8 instead of 3/4) so, for THAT reason, the outrigger circuit might be your better choice - the lower flow would give you a LOT better control/finesse.

HTH... Steve

Missed one point - if you use the outrigger, THAT should be the DEFAULT (as in, no power applied = outrigger) - most that should happen, if you shut the hoe off with your finger on the (momentary, remember?) button, you might get a small "twitch" in the outrigger...

 

[Piston]

Steve,
Thank you for the helpful advice/info! It clears it up a bit for me. Now you mentioned one thing that I was thinking about doing, but decided not to. I'd like your opinion if it's a valid reason or not.....

This valve I purchased can be wired to operate either BOTH ports at the same time, or just a SINGLE port at the same time, meaning one OR the other. Soooooooo....... After a little thinking, I thought it would be pretty slick to wire it to my bucket curl cylinder, so like you mentioned, I could operate it by switching back and forth between the thumb, and the bucket curl simply by hitting the switch....OR, I could flip the switch (actually it would be 2 switches if I wire it this way, to have the "option" to use it either way) and have both functions work at the same time. This would allow me to curl the bucket closed, and at the same time, the thumb will be closing, sort of like both cylinders extending at the same time to "pinch" something.

The reason I decided against this, is because the diverter valve I purchased is only rated for 15GPM flow. My backhoe's pump puts out 30GPM. I thought if I had the diverter tied into the bucket curl function, I'd never be able to get more than 15GPM (half) of hydraulic flow.

So, I guess my question is, is that a big deal? Will my curl function be too slow if it is only getting 15GPM max flow? vs the 30gpm it could get otherwise? I'd have to have a ridiculously slow curl cylinder, the issue is, I don't know if that is significant or not?

Hope that makes sense? and thanks again for the help.

 

[J_J]

Since your tractor is closed center hyd system, all valves are connected in parrallel.

So if you operate the curl with one lever, you can also operate another valve with lever or a solenoid valve at the same time, and the flow will divide between the two valves.

If the two cyl size, and ports and hoses are equal, then the flow will be equal.

So if you have 20 GPM, and you open the valves to two equal cyl, curl and thumb, then each cyl will get about 10 GPM for the time the lever/switch is operated.

The data says you have 30 GPM total, but about 19 GPM is for the attachments, and the other is for steering I believe.

Your tractor may have two pumps or one pump with two sections.

 

[BukitCase]

Sorry, didn't notice you had one of those weird green tractors that insist on doing everything DIFFERENT (including being painted yellow :=)- I've not spent any time studying closed center stuff since all 3 of mine are open center.

JJ definitely is the man for your JD stuff, don't have one, don't want one, open center stuff is complex enough for me... :confused2:

 

[J_J]

I think I would use one of these to control the thumb and set it where you want and close the bucket using the lever on the BH valve.

12 VDC 10 GPM CC DA SOLENOID VALVE

http://baileynet.com/hydraulics/dir...age=ProductDetails&line=SV3B&baileyno=220-321

You will also need a subplate for the solenoid valve.