DIY thumb for tractor bucket

[davedj1]

Well I dragged a fail amount of trees out with my winch and now it's time to cut them into firewood pieces (24") and I have a bad back! Luckily for me the Kubota I just bought had a third remote in the rear with dual quick connects (I have no idea why, they were on a tee) . It also came with a hydraulic top link so I figured I would use that for the ram on the thumb. I built this entirely from stuff laying in the garage. The two main arms are from a front end loader I had started to build for a Deutz-Allis little garden tractor
I ran to TSC and bought two 1/2" x 14' hoses, two swivel ends, two connectors and two 4' x 1/2" hoses. I removed one set of QD's from the bottom of the tee and ran my hoses forward and put the QD's on the front. I think it will work pretty well to lift the trees for a comfortable cutting height.
Here are a few pics, I'm for function over finish so don't critique me too badly....LOL

 

[wannabe farmer]

Nice work! Love the ingenuity! Good welds too!

 

[texasranger556]

Looks like a useful mod. I've considered something similar for my tractor.

Couple comments:
-I'd remove the tees and replace with 90s. I suspect the previous owner installed them to provide downward facing connections for something on the front of the tractor as you've done, and connections straight back for a hitch mount implement. But you can only use one or the other at the same time. Since you've removed the downward facing couplers, what you've got is effectively bulky 90s. Nothing wrong with that, but unnecessary.
-Can't tell by the pics, but if there is no support down the back of the bucket where the thumb attaches, it won't be long until the top of the bucket bends then cracks due to the hydraulic forces twisting it back and forth. Perhaps a doubler along the top of the bucket and something down the back to spread the load.

Nice work!

 

[davedj1]

Thanks guys! It got a good work out today and I can already see the top of the bucket starting to bend upwards. I think my brother has a piece of 4x4x3/8 angle iron he said I could have. I'll check that out in the next day or so.
I appreciate the comments, texasranger, I still need the rear QD's for the top link when I have the carry all/forks on the back. I'm not going to work this thing very often, a few days a year for firewood and the rear forks for moving firewood around the property.
There is a piece of 3/8x6x16 flat stock that goes down the rear of the bucket with a piece on the inside of the bucket to help it. I don't think it is the proper set up as I can see the back of the bucket flexing too
I didn't do any woodin' this weekend, got there this morning and someone had helped themselves to some of my logs! I can't believe someone would do such a thing, I was so angry. It is a public trail so I can't stop the traffic although there is very little , my buddy lives at one end and said he didn't see anyone come down out his way. I have a suspicion but really didn't think the guy I'm thinking of is that way but who knows!
Here's a couple of pics of today's haul:

What a day!

 

[ovrszd]

Yeah, you beat me to it. The top lip of your bucket isn't liking you at all bout now!!!! Better get something welded in there pretty quick. The more you use this tool, the more you are going to expect from this tool. I learned that building a Grapple on a bucket.

Good job!!!! Handy tool!!!!!

 

[texasranger556]

Sounds like you're on the right track with reinforcement!

My point with the quick disconnects is that when you attach your hydraulic top link to the tee'd connections, your thumb will operate at the same time which isn't what you want. So you'll have to remove the thumb hoses to get the top link to work as expected.

Sucks about the missing logs. Around here tree companies will deliver logs and chips for free to avoid paying dump fees.

 

[davedj1]

Sounds like you're on the right track with reinforcement!

My point with the quick disconnects is that when you attach your hydraulic top link to the tee'd connections, your thumb will operate at the same time which isn't what you want. So you'll have to remove the thumb hoses to get the top link to work as expected.

Sucks about the missing logs. Around here tree companies will deliver logs and chips for free to avoid paying dump fees.

I understand what you are saying, I don't intend to use the grapple and the back , it's the same cylinder so I'll just move it to the back when needed.
I updated my first post with a pic .of the two dump trailer loads. That stuff is HEAVY! Mostly hard Maple and some Black Birch

 

[texasranger556]

I understand what you are saying, I don't intend to use the grapple and the back , it's the same cylinder so I'll just move it to the back when needed.
I updated my first post with a pic .of the two dump trailer loads. That stuff is HEAVY! Mostly hard Maple and some Black Birch

Ahh, that would work just fine then!

 

[davedj1]

New picture of today's two trailer loads.

 

[sinisterbiker]

Nice , looking to make one for my b7100

 

[davedj1]

Nice , looking to make one for my b7100

Thank you. I am really glad I had it today, decided to get the rest of the wood home ASAP so I just cut it all to 118" and loaded it in the dump trailer.
Two loads and I was done, then I brought the tractor home I am sure I will use it for some spring cleaning of some old metal truck parts we dug up a couple of years ago while installing new septic lines...lol

 

[davedj1]

So now that my tractor is home I took the thumb off and straightened the bucket top out, picked up a piece of 4" x 4" x 3/8" angle iron and went to town.
I had to cut the two hooks I had put on the top of the bucket but I'll reattach them to the angle iron tomorrow. I can't get Imgur to cooperate so I can't get the pictures off my phone to post here but I'm working on an alternative route. Anyway it seems much stronger and less flex than before. I have not attached the back brace to the back of the bucket, not sure If I need to yet or not.

 

[davedj1]

Here are the pictures, finally got them to upload to Imgur

I'm thinking about adding a brace from the channel to the bucket in the front? Thoughts on that , just a 4-6" piece or so?

 

[ovrszd]

The amount of stress applied to the bucket is always underestimated. I used 4"x1/4" square tubing. Tore it loose from the bucket and had to add more bracing.

If I understand correctly, you are considering adding a brace from the "front" edge of the channel downward inside the bucket and welding to the bucket vertical back?? I didn't say that very well.....

If so, yes that will help considerably. Maybe add two, one under each hinge pedestal??

The idea is to keep the assembly from rolling backward.

Trust me on this one,,,, it's much easier to over build now while everything is relatively straight rather that tear it loose from the bucket and then try to repair.....

 

[davedj1]

The amount of stress applied to the bucket is always underestimated. I used 4"x1/4" square tubing. Tore it loose from the bucket and had to add more bracing.

If I understand correctly, you are considering adding a brace from the "front" edge of the channel downward inside the bucket and welding to the bucket vertical back?? I didn't say that very well.....

If so, yes that will help considerably. Maybe add two, one under each hinge pedestal??

The idea is to keep the assembly from rolling backward.

Trust me on this one,,,, it's much easier to over build now while everything is relatively straight rather that tear it loose from the bucket and then try to repair.....

Yes, you understand correctly. I have a piece of 6" wide by 3/8" that extends down the back of the bucket and was bolted through with another piece on the inside to help back it up, I have not bolted it back up yet. Maybe I'll incorporate the front braces to tie into the rear one?
You are right about forces, hydraulics are no joke. My bucket was actually pushed up and back from using the thumb, I chained the thumb down and managed to get the bucket pretty much back to it's original shape then some clamping and hammering with a bfh to get the angle lined up. There will be no work done on it today as I woke up at midnight feeling as though I had ingested a box of razorblades and they are stuck in my throat! I hate being sick!

 

[ovrszd]

Sorry to hear of your illness Dave. I'm extremely Blessed in that regard. Haven't had a cold in the last 7 years. Can't remember the last time I had the flu, guessing over 20 years.

Yes, I'd add the front braces. Better overkill than failure.

A bfh is my "go to" tool.

 

[davedj1]

Thank you sinesterbiker.
Here are the last two loads I brought home in 118" lengths (dump trailer is 120")

I'm going to add two more teeth to the bucket, one on each side of the grapple, The two on the ends of the bucket work well for longer lengths but I'm thinking two more for shorter stuff (big rounds). The ones on there stick out 8" , I'm glad I didn't make them any shorter.

 

[Dave M7040]

I admire your ingenuity and fabrications skills.

Plse let me point out one hydraulic aspect so you can at least consider it.

Many backhoes have thumbs to act like your grapple.

The thumbs are usually fixed and not hydraulically powered.

There is a good reason for that.

At this point, to better explain myself I need to wander a bit.

If you connect a pressure gauge tee'd into the push line for your grapple, you will read the pressure of the relief valve setting on your tractor. Lets say 2,000 psi to keep things simple.

I again will use a simple number (4 square inches) for the number of square inches on the piston in your grapple hydraulic cylinder. Therefore your push force will be the system pressure of 2,000 psi x the piston area of 4 sq inches which equals 8,000 pounds of push force.

If you disconnect the retract hose from its quick coupling, you now have fluid trapped on one side of your cylinder's piston.
The area of the piston, when you subtract the area of the push rod shaft, will be less than 4 sq inches, more like 2 square inches.

Now this 2 square inches is having to use a much higher hydraulic pressure to keep the piston stationary. You have 8,000 pounds of push..
The piston is not going to move because fluid does not compress.
You have 2 square inches of area

So you have 8,000 pounds of push being resisted by 2 square inches on the retract side of the cylinder's piston. 8,000 divided by 2 square niches means the pressure on the retract side of the cylinder will be 4,000 psi. The tractor's hydraulic pressure has been amplified 2 x

When you use a control valve to extend or retract a cylinder, the relief valve only provides protection when the cylinder is moving and the control lever is not in a neutral position.
Once you release the valve lever the fluid is trapped and can rise to very high, even damaging levels..

Consider the backhoe bucket thumb. You add a hydraulic cylinder to allow you to easily adjust the position of the thumb. As the thumb closes, the bucket is stationary. The fluid in the bucket cylinder has no where to go. As the thumb squeezes against the bucket you can have serious hydraulic amplification taking place. The relief valve cannot protect the fluid in the circuit being amplified.

I am not an expert in either grapples or thumbs so my words are cautionary. Perhaps putting a few hydraulic gauges into the circuits on a temporary basis will let you know if you can be at risk of damage.

This photo is of a hydraulic double acting cylinder for a front mounted plow on a small tractor.
Look closely and notice the snap ring hanging off the push rod and the cylinder end partially out.

The owner was trying to center the plow blade. When it would not move right, he increased to full rpm's and tried again. At that moment the end of the cylinder was forced out.

This next picture is of the damaged groove for the snap ring. The line for the retract side of the cylinder was not properly seated in the quick coupling leaving fluid trapped in the retract end of the cylinder. When the pressure was amplified, the snap ring destroyed its groove and the cylinder end came out.

This is an area where cross over relief valves might have a use. They are usually found on pickup truck plows to relieve pressure if the blade hits something solid.

Dave M7040

 

[davedj1]

Dave, I'm not sure I am comprehending all that at the moment as I just came to from a nap and I'm under the weather but I will review it in a day or so when the old soft computer hard drive is a little fresher. Thank you. I do understand the crossover relief valves in pickup plows, I've rebuilt several Meyer brand pumps.

 

[davedj1]

Dave, something I just thought about as I was re reading what you wrote the other day. In your example of a backhoe bucket and thumb one exerts force on the other. In my thumb application this does not happen as the thumb moves with the bucket tilt and not against it. I'm guessing the only way I would have increased pressure on the cylinder would be if a large log was drooping thereby pushing against the thumb?