The Craftmans Shop > New from Old
It's BIG, Yellow and digs holes! JCB 3CX Project 8 is joining the Tractor Shed
awemawson:
Well things change ! The pot hadn't leaked against the very modest few inches of water head overnight but I wasn't happy about it. Took the dog for a walk to cogitate ! I decided to rig up a crude pressure test by cutting an 8 mm plate to rest over the open pot mouth with four holes corrspnding to the pot fixing bolts. Then, with a piece of rubberised cork gasket material started pumping the pot up using my plumbing pressure tester.
At 15 psi the weld started to leak - only very slightly but this is 15 psi not the 3000 psi that it will see in service. Cleaned up with a grinder, a bit more welding and gave it another test - got up to 60 psi and the rubberised cork gasket blew out :bugeye: Probably I'd not given it enough over lap . Reseated the gasket and pumped up to 60 psi when there was hissing round the gasket but apparently no leak at the weld.
At this stage I thought - this is silly - OK used slew pots in good condition aren't cheap but to go through multiple test cycles - even probably putting them on the machine and having to pull them off again if they leak - life is too short - just bite the bullet and buy the used pots. Pots ordered !
I had actually decided when I got up this morning to attempt to weld up the pipe that I'd cut off as a trial, and if it went well do the same operation on the other slew pot pipe but I never got that far, getting involved with the pressure testing. I don't regret it really - I've a lot on my plate in the next few days and weeks and this will be one less thing to sort out (but I'll still have fun refitting the replacements - they may even get a coat or two of paint. The sealing plate I made for pressure testing will double up as the 'pusher' for my refitting press !)
I may have done better to dig out my oxy-acetylene set as getting a smooth flow is for me easier but I not gas welded in years. I suppose really I should set my self up for TIG welding - but I haven't !
awemawson:
So at long last my (second hand) replacement Slew Pots arrived in a battered box this afternoon. Praying that the pipes weren't crushed I opened the boxes (total of 92 kg!) and - phew - they were OK.
fortunately the bore of these hydraulic cylinders is exactly the same as a 110 mm underground drain pipe so I was able to blank the operating end with drain stoppers, and the hydraulic pipe with a standard 1/4" BSP bung. Left them soaking in de-greaser for half an hour then hit them with the hot pressure washer. They came up reasonably clean - I'd hoped it would take the paint off but no such luck.
So when they were dry they got two applications of extremely strong paint stripper and then most paint came of with the pressure washer. Again after a drying session I removed the few reluctant bits of paint with a wire wheel, then washed them in Industrial Thinners ready for painting.
The thinners soon evaporated and they got a light coat of red oxide primer which is dry already, but I'll leave it over night before starting on the RAL 1007 JCB Yellow that they will soon sport.
. . . time to make supper . .
awemawson:
Last night the primer was amazingly hard - passed the finger nail test - so I gave it a first light coat of RAL 1007. When I came back to inspect it just before bed time to my horror I found that in one or two places the dark orange pigment had settled out from the paint forming splodges.
This morning all was dry (it is supposed to be able to over coat within an hour) and I tentatively rubbed at the splodges which also were rock hard. OK I'll try another light coat and see what happens.
Diluting the paint with the thinners it started to curdle (OK the tin is dated 2016 !) so I threw that batch out and opened a fresh pot. Diluted to thin cream consistency I gave them a blush coat (it avoids runs) followed a few minutes later by a slightly heavier one which is already touch dry and no splodges this time thank goodness.
I may give them another coat but in all likely hood actually wait until they are on the machine as they are bound to be knocked in the re-fitting process.
awemawson:
This morning I removed the off side Slew Pot and then started making my patent "Slew Pot Puller" to pull the replacement over what will fairly certainly be rather tight new seals.
As previously mentioned this device requires two 1" UNC studs counter drilled and tapped M12 to take the actual studs that do the pulling, and cross bored for a tommy bar to allow tightening up and removal.
Based on a redundant pair of Fordson Major 3 point linkage pins the turning to size proved 'interesting' Being a wear part the original pin has been selectively hardened, and even carbide lathe tools were struggling in places. Fortunately the outer end was relatively soft and could be parted off and drilled & tapped M12 but turning the body down to 1" was a bit of fun. My tommy bar cross hole had to go further out than I'd intended as the material was too hard to drill !
I had thought of sticking the original studs in the induction furnace and annealing them - but life's too short !
So one down one to go - I may get time after lunch.
awemawson:
After lunch I made the second stud - great fun turning hardened steel with the swarf glowing white hot as it comes off !
So with the two adaptor studs made I assembled the slew pot pusher as a 'dry fit' on the bench - it should work - well I hope that it does ! No idea how much force is needed but some advocate pushing them on with another digger :bugeye:
A few grandchldreny things coming up so hopefully play can recommence on Monday.
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