The Craftmans Shop > New from Old
It's BIG, Yellow and digs holes! JCB 3CX Project 8 is joining the Tractor Shed
awemawson:
It'd be a long bouncy drive Phil :lol:
awemawson:
So it's time to sort those damaged pipes on the slew pots. I've been accumulating 'bits' over the last few days and I 'think' (well hope!) I've got everything.
There are very few videos on YouTube showing pot removal but many showing the difficulty of re-installing them - much heavy hammering and grunting. So I needed to plan a re-installation method that didn't involve many beefy blokes with big sledge hammers and hopefully relied on subtly rather than brute force.
My plan is to make two studs threaded 1" UNF that can screw in where those big bolts fit. and be counter-threaded M12 so that M12 studding can be used with a spreader bar across the rear of the cylinder to pull it back onto the new piston rings and seals. Two lengths of high tensile M12 studding ordered and I already had M12 coupler nuts that will give greater thread engagement. I should perhaps explain that an M12 Hex nut will fit through a 1" hole so the puller / pusher can be removed when finished !
Where to find some 1" UNF studs - I was about to set up to thread some when I happened on some pivot studs left over from when I had a Fordson Major tractor - they were part of the three point linkage.
Also I needed heavy wall drawn tube to make up the replacement for hydraulic feed pipe that is damaged and causing all this fuss. Original was 31/64" by 14 SWG - the nearest that I could find was 1/2" by 1/4" bore - slightly smaller bore but the flexible hoses feeding it are 1/4" so I don't suppose it will matter a jot.
OK now I need a seal / ring set for both sides which arrived this morning.
So no excuses - get a pot off ! Our satellite dish had gone wonky and while the chap was fixing it (corroded 'F-Type' plugs) I left the slew gear box draining into a sheep lick bucket.
Next job - remove the bracket from two of the pot retaining bolts as it obstructs the other two bolts - replace them but with heads protruding about half an inch. Slacken the now exposed other pair of bolts a similar distance then . . crank up the engine (keys have gone missing - use the spares !) lift the back arm up so that the bucket is just off the floor and slew boom to off side thus pressurising the near side slew pot. This pushes it off a bit until it hits the bolt heads. Cut engine - wiggle hydraulic controls to release the pressure - uncouple the hydraulic feed pipe and cap it off - remove those huge bolts then gently lever the slew pot off the piston assembly. And it's blooming heavy !.
OK one pot off - I'll do one pot at a time I think.
awemawson:
So now the pot is on the bench I can have a good look at it.
Bore looks to be in good condition. The shaved pipe seems to enter tangentially and oil flows into some sort of baffle arrangement deep in the outer end of the cylinder.
Tomorrow I need to carefully mark up where the pipe runs on the cylinder and try and replicate it - that'll be fun !
awemawson:
Today I sliced off the damaged pipe, bent a new one and welded it on . . .
. . . .sounds simple doesn't it ! Well it wasn't. Cutting off the old was easy. Cleaning up the barrel and milling a 1/2" recess for the new pipe was easy - well the fixturing took a bit of head scratching - (the clamp that seems to be on the inside of the bore is actually on a bit of soft aluminium)
What took the time was bending the new pipe to shape and welding it on. It is a very odd compound set of curves - I was doing it hot in the forge but got an approximation in the end !
Welding was never going to be easy round the 'back' of the pipe close to the cylinder wall and I'm by no means certain that it's going to be hydraulically sound - time only will tell. I can't pressurise it for testing so at the moment am relying on the 'blue towel test'. Blue workshop towel goes much darker with the slightest bit of water. Currently filled with boiling water and sitting on a towel !
pycoed:
andrew,
I know it's a bit late now, but if you can weld well enough to seal the new pipe against hydraulic pressure, wouldn't it have been easier to weld or even braze the damage on the original pipe in situ? It wasn't leaking as it was, so it would have been "belt & braces" & if disaster did occur, well you'd be in the same boat you are now? May be a thought for the other pipe, since one looked worse than the other?
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