Cylinder Re-Seal questions and knowledge
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  1. #1
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    Question Cylinder Re-Seal questions and knowledge

    Going to be working on the outrigger cylinder of my Komatsu Backhoe, has a slight drip and I don't like drips. I've done a lot of cylinders over the years on the various 4 backhoes I have owned, but this one has me scratchings my head over a few things. The service manual shows the piston nut is 65mm (2-9/16) so I need to get a socket first. Largest breaker bar I have currently is 3/4" drive. Nut is to be torqued to 2400 ftl/bs. I'm thinking a 8' cheater bar on a 3/4" drive breaker will twist the end off before I get my 2400 ft/lbs. Looking if any of you knowledgable individuals agree, before I fork out the cash for a 1" drive bar. Secondly the service manual calls out for light grease on the threads in addition to red Thread Locker. I was always under the impression that Locktite with grease/oils just didn't work. Don't know whether to just use grease and torque down, or whether to just use locktite and torque???

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    Quote Originally Posted by cudafamily View Post
    Secondly the service manual calls out for light grease on the threads in addition to red Thread Locker. I was always under the impression that Locktite with grease/oils just didn't work. Don't know whether to just use grease and torque down, or whether to just use locktite and torque???
    I was under the same impression. Personally I'd probably skip the loctite at first and be prepared to tighten the nut again. If that became a pattern then I'd break it back down.

    What size backhoe? Ive worked around quite a few of their pieces and don't ever recall a hex on the rod gland. Gotta be fairly small?

    Sent from my SM-G981V using Tapatalk

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    I had lots of experience with locktite at work. If you want it to bond you have to degrease the threads, dry, and then apply the locktite. Forget the grease until locktite has cured. We would apply grease or oil to threads we did not want to bond by accident. With that much torque I doubt if locktite would make much difference. An outrigger would be a noncritical cylinder. Check your rod for scratches/defects. Buy the best rod seal you can. Torque the nut on machine. There is a chart for torque that prescribes how many degrees or hex flats to turn after making contact for desired torque.

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    A box wrench with cheater pipe slid over it would be a good alternative to a socket.

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    If you can reliably convert the torque to angle, I'd use a slugging wrench.

    The math isn't hard, but you need good measurements to do it.

    Sent from my SM-G981V using Tapatalk

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    I wouldn't worry about trying to torque it if it was mine. I would use loctite and slug it tight with a 10 pound hammer. There are lots of things that can go wrong when trying to exert 2400 foot pounds with a 12 ft cheater, and they are liable to run into hurt.

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    I have a radical suggestion. Grease the threads and torque it much as gbent suggests. Then clean (down to metal) and degrease a few spots around the cylinder/nut interface and use a few dabs of JB Weld as an external threadlocker. Easy enough to remove the epoxy blobs in future if it ever needs another overhaul.

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    Komatsu wb140-2N. Heavier than Case, JD and Cat. 19500 GVW so not that small

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    Quote Originally Posted by Cole2534 View Post
    I was under the same impression. Personally I'd probably skip the loctite at first and be prepared to tighten the nut again. If that became a pattern then I'd break it back down.

    What size backhoe? Ive worked around quite a few of their pieces and don't ever recall a hex on the rod gland. Gotta be fairly small?

    Sent from my SM-G981V using Tapatalk
    No its the nut on the piston not the gland.

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    Quote Originally Posted by cudafamily View Post
    No its the nut on the piston not the gland.
    Ooooh. Kk

    I'd slug it.

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    Quote Originally Posted by cudafamily View Post
    Komatsu wb140-2N. Heavier than Case, JD and Cat. 19500 GVW so not that small
    WB140 here as well, nice machine. Personally I'd degrease, apply locktite and then just tighten it solidly and not worry about and insanely high torque spec. If the nut loosens you might get a little bypass leakage, minor irritation and even if it fell off entirely it would only be an issue on outrigger retract, not suddenly drop you and tip you over into a ditch.

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    Seen some mighty messes where a doubled up cylinder (loader/excavator) loses a piston nut ,nut rattles round in the cylinder worked by the paired cylinder,then belive it or not,is speared by the threaded rod ,backwards ,and all holds together ......yes ,everything in the cylinder is wrecked .....happened in a D9H at Lees,old Lee fired everyone in the workshop,on the spot.Seen it in Bobcats too.

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    If I were doing it and didn’t have a wrench, I would burn a hex out of a piece of 3/4” or 1” plate and weld a handle on it.
    I have built many cylinders and I wouldn’t put locktite on the threads, just get it real good and tight.
    And I sure wouldn’t put JB weld on the outside of the nut.
    Pull the barrel of the cylinder off of the piston leaving the rod end on the outrigger.
    Flip the rod over to the outside now you have a good way to hold it. Pin is probably frozen in anyway.

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    Did just that to reseal the rams on a Hough 500 loader......to undo the nuts ,torch cut 6ft long spanner from wearplate,and undid the rod nuts by using the power of an excavator,plus heat ...as I could smell Loctite when it was hot.......Nuts were loctitied ,then done up using a torque multiplier to around 4000 ft lb.......Bitter experience is that unless earthmoving parts are done up to massive torques ,the whole assy will come to pieces with maximum damage.

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    Quote Originally Posted by john.k View Post
    Did just that to reseal the rams on a Hough 500 loader......to undo the nuts ,torch cut 6ft long spanner from wearplate,and undid the rod nuts by using the power of an excavator,plus heat ...as I could smell Loctite when it was hot.......Nuts were loctitied ,then done up using a torque multiplier to around 4000 ft lb.......Bitter experience is that unless earthmoving parts are done up to massive torques ,the whole assy will come to pieces with maximum damage.
    Recall we're talking about an outrigger cylinder here, nothing is doubled and it is not doing any constant high impact cycling moving dirt, it's just lifting the machine off the tires and holding it there in extend.

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    I’ve had the same problem, manly torque more than I can manage, bloody big cheater was my helper, even the 3/4 torque wrench didn’t go up to some of the requirements, crazy if loosening was an issue why not use castellated nuts or somthing,
    Mark

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    On the topic of how to deal with fasteners requiring high torque values- don't forget the possibility of a supernut.

    Hand tighten the collar, torque all the little screws. They're slow, but you can achieve high preload values with low torque.

    If m reading this chart right, and did the math to get your preload at about 265kn, then you'd need only ~50ft-lb on the wrench.

    capture2.jpg

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    Point of information....Loctites are very oil tolerant....a simple wipe with a gloved hand,loctite smeared with gloved finger ,do up a 4"x12tpi thread so treated,and torque it up.....its never going to loosen in service,and be a solid effort to undo..........By the way ,if you use a torque multiplier,dont waste money on impact sockets,cheapies just split ...Koken are the only ones to stand up to the job.


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