I am in the process of building a thumb for my TB135 long arm and was trying to figure out what piston to buy. The thumb is going to attach to the main bucket pin so it rotates with the bucket. I need to figure out the Length, Throw to get the full range of motion, Psi, and any good vendor to purchase the piston from. Any info would be greatly appreciated. Thank you.
You could try Bailey Sales for your cylinder. http://baileynet.com/index.php
I called Bailey and they stated they could not help me with figuring out deminsions. Short of finding a part number on a piston currently on a tb135 and some how cross the numbers and demsions.
The deminsions for you thumb are an unknow because it depends on how it's built, where the cylinder will mount to thumb frame, how far it is from bucket pin pivot to cylinder attachment pivot, a number of variables that they can't know. As far as size; I would guess a cylinder no larger than your bucket cylinder would work, maybe even a tad smaller in diameter. And, again, the length would be determined by how much would be required to extend the thumb you design.
I built a thumb for the machine I have in Ireland and made the mistake of using a cylinder that is too large in diameter and the negative result of that is a very slow cycle time...
Yep, for any given flow, the larger the cylinder, the more time it take to fill that cylinder. Likewise, the smaller, the faster. That's why I would think one would use the bucket cylinder as a benchmark for size, and probably go a little smaller than the bucket cylinder. Just a guess.
Yup based on my trial and error experience I would definitely go a little smaller diameter than the bucket cylinder, maybe as much as one third smaller
I just made the assumption that there must be some formula to get the thumb as an example to rotate 140 degrees that from the main bucket pin to the end of the teeth is distance x so in turn the piston weld point must be x many inches from the main pivot point of the thumb and that info would tell you the piston length:beatsme. But I might be thinking about this too much. Is there any harm of having a piston that throw too long.:beatsme thank you for the info thus far it is really appreciated.
If the cylinder is too long it could potentially bend if the thumb curls too far so you would need some kind of stop, The best stop is the correct length cylinder which bottoms out when extended...
I'll second that. Only use a cylinder long enough to get the job done.
Digger Dan, Good point back to the drawing board :Banghead
I would suggest making/mounting the thumb grapple on the bucket pin if you can. Connect a rod to the thumb where you ram will connect to which could replicate the 'extending' part of the ram and hold the thumb in your ideal open position and mark the position of the end of the 'extending replica' on your dipper arm then close the thumb up to your desired stopping point and mark the position of the end of the replica ram on the dipper arm. Measure the amount of movement required to move the thumb from the marks on the dipper arm. You may find the replica end of the ram may not cover the full range of motion you require so you can try different length 'replicas' of the ram to get the full range of movement. This way you may be able to find the ideal length of extended movement required from your ram. Find a ram with the extension measurements as close to as possible to what you feel you require. using the measurements you marked on the dipper arm and by adjusting the potential mounting point of the ram on the dipper arm you should hopefully be able to ge the correct range of motion required. I doubt any of what I said makes sense!!!! So apologies for that, I am just trying to explain how I might try to come to a solution. However If there is a better way to do this then please inform me and others!
I just made my manual thumb into a hydraulic activated. The place where I had the excavator had a swing cylinder from a Bobcat that I purchased for a fair price. It is about the size of the bucket cylinder and extends about 24". I knew where I wanted the thumb to bottom out (end of teeth hitting bucket). I took the cylinder and stretched it out full length and positioned it on the stick to make sure it had enough clearance when the stick retracted. The cylinder was a little tight to the stick so had to make a couple of offset bushings We then welded the Bosses to the stick and then hooked the rod to the thumb. The thumb now bottoms out in the correct position, at the stroke end, but has about 4" of rod exposed when retracted. The speed of the thumb with the swing cylinder is as fast as you would want it. I also installed two pressure relief valves, just in case. I have only used it about a dozen times, but it seems to work fine. First job after the installation I used it to move some brush that I would not have bother with if I had to go out and install the manual rod.