There has been a few threads about hydraulic thumbs on HEF. So I thought I would share my progress and hopefully help someone else that is anticipating doing it also. As the title says, I finally converted my manual thumb to hydraulic. This was something I have been wanting to do for a long time. The backhoe is on a Case 680 series tractor. It can dig to 16 feet. I plumbed a Parker #DS12 six way diverter valve into the RH stabilizer circuit. I chose that valve because the spool and handle can be rotated to any position to accommodate different mounting positions of the valve body. It functions great. Better than I had hoped. The stabilizer works normally.
Next was the hydraulic cylinder layout. The cylinder base mount is located close enough to the thumb so that the piston is 1 inch from bottoming out in the barrel when thumb hits the travel stop I put on it. The cylinder I chose is a 4 inch bore, 2 inch rod & 28 inch stroke. It is almost identical to the bucket cylinder. These 2 images shows how I determined the base mount size and location on the dipper. I had to be careful that the cylinder fittings were well away from the dipper when extending the thumb.
The base mount was made from 1"thick x 9" x12" steel plate that I cut diagonally. There is 1" bar welded in the center of it to prevent any damage from twisting forces created by the cylinder. That bar serves another purpose. It is a few thousands of an inch from the cylinder base mount. My previous thumbs suffered a lot of damage(elongated) to the mounting pin holes from handling extremely heavy loads. That bar will eliminate any chance of that happening.
Finally, the thumb and the modifications I made to it. It is a new Titan 32" extreme duty thumb. It replaced the first extreme duty one on this backhoe. I mentioned earlier that I had some very disappointing damage to the pin holes from normal use of the thumb. I bent the pins that came with the it as if they were made out of copper. I replaced them with grade 8 bolts and that eliminated any more bending. There is just to much clearance in the way the thumb is made to avoid twisting it when picking up unbalanced loads. So, I bought some 1/2 inch wall pipe and made spacers and pin bushings with my chop saw. The bolts required a small amount of polishing to get them to slide in the homemade bushings. Can you imagine what would happen to the thumb without all those mods ? The bolt (pin) that is tack welded is the travel stop that prevents cylinder from bottoming out.
Nice, just curious...what did you pay for the valve?
$90.00 US on eBay included shipping. The vendor is Hydraulic Warehouse.
Looks good. The hose with the red zip tie looks like the outer wrap is a little funky. Not sure if you're finished or not but I would round the corners on the plates where the cylinder base mounts to make it look a little tidier. If you ever wanted to remove the cylinder, sure enough you'd whack the back of your hand on the sharp corner. I'd try to get some weld on the inside of the mounts and the ends of the plates. Not being welded could act as a starting point for a crack. Maybe 1 to 1-1/2" of weld on the inside and then wrap around the ends. Are you worried about having a separate relief valve for the thumb? Have read on here that the bucket can push the thumb or vice/versa and cause problems. Nice looking garage too!
Yeah, Dave, I am not really finished yet. I'm capable of doing nicer looking welds than some of those. I used some real old rod and it was giving me grief. When the weather gets nice out I'm going to a dig hole and I will lay the boom in it so those welds on the thumb mount will be horizontal. I just don't much vertical stuff any more and those beads show it. As nasty as they look I had good penetration and I peened the crap out of them with an air chisel with a pointed bit in it. Good idea about trimming the points on the base mount. Those pins will get removed occasionally. There are times the hydraulic cylinder will be in harms way when picking up big stuff and transporting it. Such as tree stumps and big pieces of concrete. I'm planning on putting quick couplers on the cylinder fittings to enable removal it and the thumb in a few minutes. I'll take look at that funky looking hose today. I think it may be just dust from laying on the shop floor. Thanks for the observation of my shop I built it two years ago with no help from anyone except for the steel roof sheeting. I hired two two laid off pole barn builders to lay the steel sheets. They did a beautiful job and were completely done in 5 1/2 hours ! I was 77 years old at that time.
So say if you have the machine up on the stabilizers, so there is pressure on them. There’s no problem switching over to the thumb? My backhoe has a 4 in 1 front bucket circuit that I was thinking of using for a thumb. I was also curious about relief valves. I’ve heard of some people damaging their thumb cylinder.
The stabilizers work just the same as they did before the diverter valve was installed. I can extend the stabilizer completely and then switch the convertor valve to the thumb cylinder and the stabilizer does not move and holds up the machine as it usually does. The only problem I think using your calm bucket valve would be where would you locate the diverter valve so it would be handy to use. The other thing would be the loader valve location would create a need for longer hoses to reach the back of the backhoe. I highly recommend using a stabilizer circuit for a thumb. The relief valves in the loader or backhoe valve bank will not protect the thumb cylinder from damage when using the thumb. They only protect the cylinders when they are dead ended with hydraulic pressure. That is normal on all hydraulic cylinders. AFAIK ! Until I find out how to install relief valves in the thumb circuit I will need to be extremely careful not to put to much pressure against the thumb cylinder with the bucket cylinder.
Nice Job! Seems like a 4" cylinder is overkill for the task. So the diverter is a manual valve you change positions on then use the stabilizer handle to operate the thumb? Does it stay in which ever position you put it in or is it spring loaded to the default? If you don't mind a couple suggestions? Get that hose clamp off and find a better way to contain the 4 hoses in the first picture. It is sure to cut into the hoses. Next time you make bushings try using DOM tube. Get it the the correct diameter and wall thickness and you won't have to clean it up. This is what the hydraulic version of the Titan 36" thumb looks like. https://www.palletforks.com/skid-st...lic-backhoe-thumb-36-inch-weld-on/122986.html
Might be worth a look at not having all 4 hoses bunched together. Two separate bundles and keep them together with some spiral plastic hose protector or maybe a short piece of old rad. hose or suction hose. The 2 hoses for the stabilizer will move the most. Maybe take the hose clamp off and work the stabilizer up and down to see what the hoses do. I don't know how close the cylinder gets to the cab when it's all the way up to see where the hoses could go. I think the larger thumb cylinder will give you more leeway if you clamp onto something a little tight. All that said I am thoroughly impressed! I can hardly get out of bed right now with my bad back and you're 79 welding and hooking up hydraulics. I tip my hat to you sir! You are the definition of young at heart. Bravo!!!
Nice Job! Thank You NH! #1 Seems like a 4" cylinder is overkill for the task. I matched it to the bucket cylinder so it could withstand the forces of said bucket cyl. #2 So the diverter is a manual valve you change positions on then use the stabilizer handle to operate the thumb? Does it stay in which ever position you put it in or is it spring loaded to the default? Yes it stays in either position, no detents. Slides effortlessly and smooth as silk. If you don't mind a couple suggestions? #3 Get that hose clamp off and find a better way to contain the 4 hoses in the first picture. It is sure to cut into the hoses. That is on my list when it get warmer out. Along with making those nasty welds look purty. #4 Next time you make bushings try using DOM tube. Get it the the correct diameter and wall thickness and you won't have to clean it up. It is DOM tube. I polished the grade 8 bolts for an awesome fit in the pipe. Speedy Metals is where I bought it. #5 This is what the hydraulic version of the Titan 36" thumb looks like. https://www.palletforks.com/skid-steers/backhoe-attachments/thumbs/hydraulic-backhoe-thumb-36-inch-weld-on/122986.htm I saw those offerings a long time ago when I was shopping for my first thumb. Way to wimpy for anything I would use it on. This is the third thumb on the same backhoe. The first one was not an extreme model and it bent like wet pretzel.
Thanks go to a fellow member (uffex) for posting some valuable information in the excavator forum in regards to backhoe thumbs. This is his post. "Good day JHead To be correct providing relief is only part of the issue you must refill the opposing chamber to prevent cavitation, attaching the file with the information is to large for the site, however if you go excatech.org - library - adapted applications - thumb ? & answers. I hope you will find the information helpful there is much more of the web site, any questions please drop me a line. Kind regards Uffex" I went to that site and found all the answers to my concerns about the pressures a thumb cylinder undergoes when the bucket cylinder is pushing against it. I may not need a relief valve because my thumb and bucket cylinders are nearly identical in size. If that is the case then I can remove the temporary hose clamps on my hydraulic lines and bolt them down properly. This is the page in that document that addresses the relief valve.
That pretty well covers it,
Tinkerer, what does your thumb look like at full extension? On the Titan page they have what they call a manual and it shows this When I bought mine there was zero info included and the web site had nothing then. Now they have this, which is not the way I did it but too late now. Thinking of redoing it hope to get a bit more travel. Can you post a pic of yours at full travel? Thanks, Joe H
I looked at that Titan thumb and it is way too wimpy for me to consider using. I'll post a photo of mine fully open later today. I wish we could post cell phone videos. I won't do You tube videos. Google requires tooo much personal information.
Here ya go Joe ! The bucket is full open. The thumb is fully extended. I could have used a cylinder with a longer stroke on the thumb, but I didn't think I needed any more travel on it. It works quite well for me the way it is.
Thanks for the pic. It doesn't go any further than the fixed edition of the Titan thumb, I guess that's where that fancy multi jointed linkage comes in. More thinking required for mine. Joe H
A fixed thumb extended any further than my hydraulic one would extremely limit what you could do with it. Look closely in the picture how little the bucket can retract. And that is with nothing in it such as a rock or tree. As I mentioned -- a cylinder with a longer stroke will extend the tine farther. I cannot imagine a need to extend one further than mine. But, to each his own. For me a fixed position thumb is next to useless extended further than a 90° angle to the dipper. Bear in mind I used one like that quite a bit. Quite often my fixed thumb needed to have the tine pushed into the dirt to be able to pick anything up with the boom extended nearly flat. I had to reposition the tractor to avoid that.
Fixed position sucks, although still better than nothing. I think with it fixed I end up having the bucket in a less than ideal position that with hydraulics could be avoided. Get the bucket in position then close the thumb would work much better than trying to fight the bucket and whatever onto the thumb. I've been thinking having more thumb movement would be the answer but I can see that it isn't necessary if the bucket moves first. Joe H
I built a thumb for a Case 580K with extend a hoe. It worked like a charm, but the third valve on the loader I had rerouted to supply the thumb apparently didn't have port relief. It wasn't a long while before it bent the rod. At the time, 15 years ago, the guy at Cassella Hydraulic added a one piece relief valve. Both hoses from the supply went to this relief, two hoses connected the valve to the ends of the cylinder. That worked well until a mishap. It was a "welded T cylinder" The but end of the cylinder pinned on a 4" wide tube welded to the butt end. The pin sheared on one side causing sideways thrust, bending the rod. Best picture of old thumb: Only picture I found of the first thumb. Next prototype was a very different design & is still working fine. This was a much better functioning thumb. This picture with the reinforced 12" bucket. Great rock handler!