I need to rebuild most of the cylinders on my JD 490. How hard is it to do myself? If I send them out, who would you recommend and how much would it be?
Fluid Power Service 716-681-8474
View attachment Cylinder Overhaul Comp.pdf Good day Dan Here is some information hope it helps. Kind regards Uffex
The biggest problem is how they hold the piston onto the rod. Now days there is a big nut on the end of the rod tightened to an incredible torque. It takes a specialized machine to take them loose and tighten them back up to the point where they don't come loose. I used to just leave the barrel pinned to the machine and pull the rod out. I'd take the rod to who ever had the machine and have them blast it loose and install the new packing. That is if the barrel was OK and the rod didn't show damage or measure out thin. Good Luck
John C. That is an interesting comment, on nut retaining torque on the end of the ram rod. I don't know what size machine a JD 490 is,but just guessing about 5 Tonne. I just replaced the plunger seals on my kh 151 (5.2) tone excavator and did exactly as you described, un-did (screwed) Ram rod seal locking nut, and pulled the whole ram seal out and took to a seal suppler to get me plunger & locking case nut seals. he said that the plunger nut at the bottom of the main plunger was very high torqued also, so I went a couple of places up the road and left the rod with a mechanic to loosen said very high torqued nut. when I went back half hour later mechanic said it was not tight at all and could have loosened said nut with 2 foot stillsons myself the nut had a cir-clip type of expanded clip on a pin that went through the centre of the ram rod that prevented the nut turning more than 1/16 th id guess without measuring if it came loose on the ram, this enabled me to get the ram rod locking nut that holds it into the ram housing off of the rod to measure up for 3 seals needed that were the hydro leak (Main inner-Wiper and small push seal. this machine is 28 odd years of age but still runs fine,All Kubotas do.
A 490 Deere is about the same as a PC120-3 Komatsu so around 12 metric tons. As I recall we used to torque the nut on the stick cylinders for the Komatsu excavators to about 3,000 foot pounds.
Garrie, your Kubota is somewhat unusual in having a locking mechanism through the nut. Most excavator cylinders I've come across have a very fine threaded nut tightened up to an exruciatingly high torque to hold the piston on. Without looking I'm thinking 2-3,000 ft.lbs. If we didn't have a cylinder removal bench we would make a plate spanner and use a couple of excavators on the nut to get it loose. See below.
Yair . . . Okay I'll be the dummy . . . can anyone explain the forces that apparently act on those nuts and work them loose? Cheers.
I'm with you Scrub as the high torque on some rod piston nuts seems a bit over the top at times . On my Grove hydro cranes everything on the cylinder is low torque value and uses set screws to lock the nuts & gland head . Rebuilt several cylinders on this thread . HeavyEquipmentForums
Scrub, effectively there are 2 types of cylinders like the assembly in the photo above: - 1. The type where the piston screws on to the rod and is tightened to a set torque using a pin wrench working on 2 holes in the end of the piston. Then a locknut (usually a Nyloc) is screwed on to the end of the rod as a belt and braces type deal. This design doesn't usually work loose but I've seen cases where the rod fails in fatigue if the piston gets regularly beaten against the head of the cylinder - using the head as a stop instead of the cylinder electrical kickouts or having badly adjusted mechanical stops in the linkage sytem in other words. In the diagram below the piston (5) screws on to the rod (8) and is tightened using the 2 holes to 600ft.lb. Then the Nyloc nut (2) is installed and tightened to 6000ft.lb. 2. The type where the piston is a slip fit on the rod up to a shoulder and the only thing holding it to the rod is the nut. The photo above is a Hitachi cylinder and is of this type. Beat the piston against the cylinder head long enough and the rod will stretch a fraction so that the piston can move a few thou' back and forth. Hey presto you have a slide hammer ...... the nut won't always work its way off but can do. Generally when you pull this type apart the nut can be loose (or maybe not at full torque rather than loose) not necessarily because the nut has actually unscrewed but the rod has been stretched a fraction.
The big issue is the pressure in the system (4,000 PSI+), the speed of the implement and the weight in the bucket. A full bucket curled all the way in and the stick run all the way out and then released a little quick and gravity becomes a demolition expert. I've seen the results of only tightening the nut to half the specified torque. Those types of jobs were real profitable.
Yair . . . Thanks for responses fellers. Cheers
Hi Nige, and as per usual you are 101% correct. Both my Kubota and the owner are some what unusual. The Boom ram on my machine is not an original Kubota 1,Breed unknown(probably a Hinze).I wish I had taken a photo of that end of the ram but did not. I only took a photo of the lock nut end seals. But it is all back together and working well. The retaining nut locker was similar to an over sized sir-clip but round regards
PS to Nige: I hope that's trick photography or smoke and mirrors of that Ran nut removal in the workshop. It might just be the light on the ram during the photo, but to me it looks like a kavendish banana bend in it.
I can imagine ......... Well spotted Garrie. What we did was to practice the remove/install process on a cylinder with a bent rod so that if we fcuked anything up it didn't matter ...... Apropos of nothing - I was listening to a song the other day that reminded me of you - "You can't call Gin-Gin Gin-Gin any more" ......... :tong :tong
Link to Youtube so everyone can have a laugh ..... https://www.youtube.com/watch?v=dCs7ZTB8LtI
That's pretty funny Nige and unfortunately all too true Before you know it we will all be debating gay marriage and talking about men called Bruce changing their name to Caitlyn Talk about cylinder rebuilds That was a doozy
No doubt about it ...youre a funny guy. Gaz.