New Thumb Build

[lcgoatboy]

Hello all,first time posting long time lurking. I built this thumb in the last couple of days. It works very good but the ram has developed a small leak. My question for any of you hydraulic guys is the thumb ram fully extends itself (no mechanical stopper on the thumb) relying on the end of the cylinder to stop the ram.
I'm just wondering if I shouldn't install some sort of limit or will the ram stroking out on full extension be sufficient. Right now I'm thinking this or poor quality ram??
We have only used it for maybe 10min. I can weld and fab but when it comes to hydraulic,clueless. Thankshttp://www.tractorbynet.com/forums/files/build-yourself/408928d1422413901t-new-thumb-build-imag3269-jpg

 

[LD1]

The cylinder should not need a mechanical stop. I am guessing low quality cylinder?

Nice build though.

 

[pmsmechanic]

I wouldn't worry about a stop for the ram. I'd be more worried about the need for a pressure relief for when you curl the bucket against the thumb too tightly. You maybe haven't done that yet but there will come a time when it you will.

 

[lcgoatboy]

I wouldn't worry about a stop for the ram. I'd be more worried about the need for a pressure relief for when you curl the bucket against the thumb too tightly. You maybe haven't done that yet but there will come a time when it you will.

Found out about that today from the dealer. Definitely going to do the relief kit. Thanks

 

[deerseeker001]

Welcome from Wisconsin

 

[lcgoatboy]

Welcome from Wisconsin

Thanks. Used the thumb today to cut up a load of firewood. So nice! A buddy of mine said an excavator is useless without a thumb,well I wouldn't go that far but close.

 

[skyhook]

I'm not the best either when it comes to hydraulics,
but I'm wondering, it looks like the plumbing was already there for you cylinder,
so wouldn't there already be a relief incorporated in that feed.

 

[firemanmike69]

I've installed a ton of thumbs on those mini excavators, if the plumbing is there then so is an adjustable relief valve for both sides of the circuit. It will likely be under the cab of the machine and not too easy to access or adjust, if you give me the model and serial number I can tell you which valve is the one that needs adjusting. I wouldn't worry about having a stop for the cylinder extending but I would install one on the retract side to prevent the cylinder from bottoming out when retracted all the way

 

[Xfaxman]

Thanks. Used the thumb today to cut up a load of firewood. So nice! A buddy of mine said an excavator is useless without a thumb,well I wouldn't go that far but close.

Yep, thumbs are very useful. I have one on each hand!

Need to see a picture like your first, but with the cylinder fully retracted.

 

[woodchipper]

:welcome:from Québec! Good looking thumb! As the pressure from the bucket against your thumb could be more than the rod could take without bending, it would prove wise to make sure you have a releif valve on the extension circuit. The cylinder should not leek...

 

[lcgoatboy]

I've installed a ton of thumbs on those mini excavators, if the plumbing is there then so is an adjustable relief valve for both sides of the circuit. It will likely be under the cab of the machine and not too easy to access or adjust, if you give me the model and serial number I can tell you which valve is the one that needs adjusting. I wouldn't worry about having a stop for the cylinder extending but I would install one on the retract side to prevent the cylinder from bottoming out when retracted all the way

My excavator is a TB016 Takeuchi serial #11610445. The way that I made the thumb is such that the ram doesn't retract all the way,so I'm good that way

 

[lcgoatboy]

I almost forgot that I received a new warranty cylinder from Princess Auto today. They had no problem taking it back. I gave them a full explanation of what I did and no problems taking it back but they said if the same thing happens again warranty may not happen,fair enough!

 

[lcgoatboy]

:welcome:from Qu饕ec! Good looking thumb! As the pressure from the bucket against your thumb could be more than the rod could take without bending, it would prove wise to make sure you have a releif valve on the extension circuit. The cylinder should not leek...

Yes,hello from BC! Relief,yes,I'm getting a crash course in hydraulics! I love hydraulic power!

 

[Xfaxman]

-------- The way that I made the thumb is such that the ram doesn't retract all the way,so I'm good that way

Yep, no stroke stopper needed. :thumbsup:

 

[yanmars]

Definitely get a relief system. I did not and warped/bent a 1 1/2 thick plate. Hydraulics are strong.

 

[rocketfish]

X2 on the relief! Just helped a buddy of mine take in a load of scrap 2weeks ago with a brand new cylinder on the pile. He said it had about 10 min of run time on it. It was on his thumb for a bobcat 442 excavator and it folded it right in half. Set the relief and replaced the cylinder no problems after that $300 mistake!!!

 

[skyhook]

Don't forget, lcgoatboy, if you have a cylinder rated for 3000psi and your relief is set at 3200psi,
something has to give in the cylinder, most likely, the seals.
I didn't notice whether or not you added a relief yet or using the one already there,
have you tested the relief pressure for that circuit.

 

[lcgoatboy]

Don't forget, lcgoatboy, if you have a cylinder rated for 3000psi and your relief is set at 3200psi,
something has to give in the cylinder, most likely, the seals.
I didn't notice whether or not you added a relief yet or using the one already there,
have you tested the relief pressure for that circuit.

No relief yet,I'm going to pm firemanmike69 to see if he knows if my machine already has relief install. I do know the thumb and curl cylinders have the same pressure because they fight each other.

 

[woodchipper]

The way your thumb pins are secured is not enough. Those presto pins will fly off in no time! Best to use 5/16" bolts, with nylon lock nuts.
If you don't know the rated pressure of your third function, be carefull when putting the new replacement cylinder. Its rated PSI may be too low for the third function pressure delivery. You may want to undo the cylinder lines, install a pressure guage, and plug the end of the line. Run a test and see for yourself. Industrial equipment do run at higher pressures.:2cents:

 

[jel1988]

Thumbs looks great, you don't appreciate it until you have to use a machine without one. Did you send your build to the Princess Auto projects site?