Question for the knowledgeable folks on this site. Considering swapping out the offset/side shift boom on my pc75uu2. Reasons - I rarely use, and have not been in a situation in the last year where I had to have it - used it because It was convenient. Second reason is, I was going to start redoing the next stick pivot pin and cylinder pin and maybe the first shift joint. When I look at all the joints in that boom I am amazed that it still feeling as tight as it does! Helps that I redid all the pins and bushings on the bucket end last year. I have found a boom that is 12 inch longer pin to pin than the current boom. Pretty sure the length will not change the stability much - I would be losing 500 lbs off the boom just in the forward section of the current boom according to the weights given in the manual. 300lbs on the knuckle, 135 on the side shift cylinder, 75 on the support rod, plus the big castings at each end of each section. I guess my main question is how does the extra boom length affect the actual digging force, lifting abilities etc. Any other concerns? Thanks for any insights!
Does it have the computer controlled safety so you can’t hit the cab?
Yes - it has all the parts - but was disabled when I bought it, and I went ahead and removed all the wiring wiring from the potentiometers, cleaned the wiring loom up and have put it in a box. Did not want to deal with it - I am the only one who runs it. That is the other thing I was thinking - a foot longer boom may keep the bucket from ever having the opportunity of getting in the cab.
Well the conversion is started! A Komatsu PC90-1 is the donor boom. Uses the same width at the boom base and the same pin diameter. It is 12 inches longer, and as close as I can calculate 470lbs lighter. The cl of the boom pin to the cl of the boom cylinder mount are also the same, however the pin holes in the boom are larger, so I put bushings in those. Worksing on rebending the steel lines on the boom now, and then will get hoses made. Will update when I am further along.
Got steel hydraulic lines reconfigured And added steel lines for the thumb. This was more work than anticipated! But came out well. Just need to clean up n paint. The guy that was helping me suggested we purge the original lines with the gas from the mig welder tank while heating and bending them to keep the scale out of the inside, seems to have worked well.
The stuff is all seamless tubing without any coating so you shouldn't get any scale at all. Anything in them will come out in the return filter and it's more likely to be dirt than any metallics. Nice looking job by the way. What did you used to bend the tubing?
The new lines were bent with a very nice tubing bender that my buddy has, not sure on the brand, has dies up to 1inch, and you crank a handwheel- has three speeds depending on the gear reduction needed for the size tubing you are bending. Also has degree indicator to help you get the bend angles you are after. It went well, but still took a lot of time by the time I made all the brackets. Thanks for the compliment.
Well it’s finally out of the shop! Seems like projects like this are never ending- always something else you see you need to do. But snows gone and frost around my place is mostly gone, so time to put it to work. Put all new seals in the arm cylinder, painted boom, added led lights to the boom, also installed some flush mount leds to the house. The only thing I am a little concerned about is the height of the arm cylinder mount location on the arm. The cylinder bottoms out on the top of the boom just before it’s all the way in. So I am planning on cutting the end off and raising it a couple inches in the near future. It’s usable as is, but have to pay attention- not something I want to have to deal with long term.
Good job, looks great!
Nice job. I've seen the cylinder issue on long sticks in the past. I usually cut off the cylinder base bracket and moved it back enough that the barrel didn't hit on the boom.
Thanks guys! John C. So by moving the cylinder base bracket back you are making it so when the cylinder is extended it is at the end of its travel before the barrel goes low enough to hit the top of the boom? One thing that concerns me about raising where the cylinder rod end mount is on the stick - it will increase the leverage force. Which may not be a good thing as the arm was not designed with that in mind. But I guess if it breaks- I can find another one!
When I move them back it lost some close up curl. The bucket wasn't able to touch the from of the track frames and the boom wouldn't set down as low when putting it on a trailer on the truck. When I loaded them on a trailer for them to be moved I pulled the cylinder to stick pin and the boom was able to settle all the way down. After the first two I guess someone complained to the engineers who designed the fronts and I never got another one. In looking at the distance between the boom pin and the stick to cylinder pin it looks to me like it is short from what I'm used to. It may be the angle of the photo but you might check it against a machine sitting in a lot somewhere.
I agree John, it is short. The way the cylinder mounts on the offset boom, the cylinder follows the stick angle as it goes in n out, so it doesn’t need to be as tall. But with this conventional style boom mount location, it really does need to be taller. Planning on rainy it 3 inches. But will try and find some similar size machines and measure them
Raising it I think should take care of the issue of the barrel hitting. It will be interesting to hear the difference in length between the boom to stick pin and the stick cylinder to stick pin and the stick to boom cylinder pin. Nice work!
Cool! There's lots of uu machines for cheap that guys pass on because they are different. Good to see this swap! The orange confused me for a minute though!
Yea, not fond of purple/Blue! And Komatsu Yellow just looks anemic to me. So I picked Allis Chalmers orange! Still need to paint the bottom frame, but it’s low priority as it’s always got some dirt on it.
Have not figured out how to use that quote function correctly- only the first paragraph is John C !
Nice job, I would never own a knuckle boom machine, the resale here in aus is not good ether so worth all the work i think. Just how much is the cylinder hitting the boom? Roughly what distance would the cylinder pin have to be moved so the cylinder just missed? The only reason i asked because u could make a couple of custom offset bushes for the cylinder ends that could easily lift 125tho both ends.
The cylinder has approximately 3 inches of travel left when the barrel cylinder touches the top of the boom. So from what I can figure, I need to raise it a minimum of an 1 inch to clear the boom at full extension. I was going to do exactly as you suggested - make a 1/4 smaller pin on both ends and make offset bushings. But looking at the geometry it was not going to be enough of a change to keep it from hitting. The easiest option really would have been to find a cylinder with a little less travel rather than using the PC90-1 cylinder. But I had this cylinder already.
What you could do is have a spacer machined to install inside the cylinder on the rod.
Yes I actually asked the hydraulic shop that put the new cylinder seals in to do that. But they called after they had it apart and said due to the cylinders cushion design, it was going to be complicated. I did not go and look at what they were talking about, happened to be out of town at the time. Took there word for it and told them to leave it as it was and just put the seals in.
I hadn't thought of it having a cushion. Basically that is just something that blocks the hole for the oil to go through before the piston hits the end of the cylinder. I guess the slug might get in the way. The other idea is to just cut off the eye and enough of the rod to shorten the stroke. The problem I had doing that is that it also shortens the stoke in the opposite direction. I'm sure you will figure out a way to make it not hit the barrel.
Got the 3 inches added! Here’s some pictures of it ready to weld
Almost done welding Preheated, 5 passes with .035 wire, 27 volts pulling 250 amps. Burns in real nice. Starts are seem little cold, but if you starts right on the edge that hot it all runs off - I do not claim to be a welding wizard! Ground the ends/ starts all out and then welded across the ends with stick repositioned. Will post finished pics Monday. Pretty happy with how it came out. Cylinder Barrel still touched just before cylinder bottom out, but, stick is curled to were the bucket will touch the bottom of the boom. Not a place where you would normally curl to except when hauling.
Good looking machine, did you make the side cover?
Yes I did. It was missing when I bought it. Built that last year right after I bought the machine. Machine was a bit of a basket case cosmetically! But the engine ran/ runs very strong and the hydraulic pump had just been replaced. None of the cylinders leaked externally, and all the under carriage was in good shape. So figured for the money it was worth the effort to get it back in good operating condition.
It looks pretty good from here. Did you get any pull when you welded the ears. Are you planning on line boring when you are through with the welding?
Yep, it definitely pulled, that’s to be expected with that much weld in my experience! Did not line bore. Got out the big rosebud and some grade 8 all thread, hardened nuts and washers. Heated the ears up along the weld lines a dull red and pulled them back in alignment till the pin dropped through. Took three tries, but was much faster than setting up to bore. As well I feel it’s good for the welds to post heat them, I think it helps prevent cracks/brittleness.
Top picture is after adding 3 1/4 inches. Bottom is before Not the same angle, so hard to see exact differences Hindsight- should have done 4 inches, that would have been perfect. Certainly will be ok though, and MUCH better than before!
That is nice work.
Thank you!
Finally found a grapple with rigid rotator I could justify buying! Spent the last week getting it plumbed and the mounting bracket manufactured. So far really liking it for moving/stacking logs.
Nice job! I have a PC75UU that I would like to add a thumb too. How did you suppy hydraulics to the thumb you added?
Thanks, Added a solenoid operated selector valve to divert the side shift oil to the thumb. Have a switch in the cab to select wich function. After I swapped booms I had that circuit available to run the grapple, and added another solenoid operated valve on the stick to divert oil to the rotator. This is activated with a momentary switch I installed in the top of the joy stick. After using for a few hours it’s pretty smooth and quick, I would I believe prefer a trigger type switch though on the front of the joy stick.
Built a new stinger so I can move my gooseneck trailers around without having to go get the truck. Decided why not hang the logs in it from the grapple and limb right into the trailer, worked, but actually found it to be better just to set the log in the trailer, limb it n then remove the log. Works slick!