The Craftmans Shop > New from Old
Thwaites 2 Ton Two Cylinder Dumper Running On One Cylinder
awemawson:
It'll still be a tatty dumper, but at least it'll work :clap:
The oil seal for the input shaft of the steering orbitor arrived this morning, so I disconnected the four hydraulic pipes, capped them and got the orbiitor out and in the vice. Very close examination showed that what looks to be an oil seal pushed in from the outside, is actually a turned feature of the body , and the seal lips that are clearly visible, must be from an internally mounted seal - not entirely surprising :bang:
Having watched a youtube video of someone pulling a similar one apart I decided that that was not a course I wanted to go down !
Then in a flash of grey cells being resurrected I remembered that I had an orbitor I'd bought nine years ago as a spare for my JCB 3CX - I don't suppose that it's possibly compatible is it :scratch:
I went searching and found I actually had two different ones on the shelf - the other came of a Buchner 'bank mower' that I had got rid of years back - seems the same size but the hydraulic ports were a different thread. However the brand new, wrapped up in waxy paper JCB 3CX one had the correct port threads, but it had a small fifth port. I suspect that this port is a 'weeping port' returning any leakage back to the tank - but I had no plumbing in place to do that.
Rightly or wrongly I decided to blank it off - but what size is it and do I have a suitable bung? Well it wasn't metric, nor was it BSP or Whitworth or BSF - it had a plastic keeper in it which measured roughly 0.435" - now many hydraulic fittings use UNF - could it be 7/16" UNF :scratch:
Looking through my quite sparse UNF bolt collection there were none to be found to use as a trial - but hang on a minute, the draw bar thread of a Bridgeport is 7/16" UNF. I whipped out the draw bar and sure enough that was it.
A quick trip to the lathe produced me a nice little 7/16" UNF hex headed stopper, which went in with an 'o' ring and a bit of thread seal.
Now the time to test it, as these orbitors come with widely differing specifications in terms of the volume they pass to the steering cylinders per turn of the steering wheel, and whether they self centre or load sense. Well to cut to the chase, it went in nicely, and as far as I can tell from a quick test drive performs exactly as the original one did except that it doesn't leak :ddb: :ddb:
So that's one more thing ticked off the list. The spool valve for the tipping skip has a slight weep - nothing too bad, and as it's a very standard two way self centring jobby, if one turns up in the future at a sensible price I'll change it - otherwise it'll stay as it is.
awemawson:
A bit of Googling implies that the 'extra' small port on the Saur-Danfoss steering valve / orbitor is probably a 'load sensing' output used in systems with a load sensing feedback path.
awemawson:
I discovered a twist in the tail using the dumper today!
I was shifting the wife's compost heap 'rejects' (Clive the Gardener had heaped a load of woody trimmings that won't compost down on it) to the bonfire pile, only to discover that it wouldn't tip the skip unless you wiggle the steering wheel back and forth :bang:
I can only assume that the feed from the pump goes via the 'P' and'T' ports on the steering orbitor and onwards to the spool valve for the skip cylinder, and that the old orbitor let fluid though all the time, and the new one only lets it though when it's rotated.
It didn't stop me shifting three loads of twiggy bit and one load of pig poop, but it must look very odd as I'm tipping and rocking the wheel at the same time. :lol:
If I manage to find another spool valve I'll plumb it up differently
awemawson:
OK I've been cogitating :coffee: on this hydraulic issue and I could do will some input from any hydraulic guru's on forum :scratch:
Symptoms: following replacing the 'steering Orbitor' with a brand new but different one as the old one leaked, the steering works fine, but the ram that tips the skip only moves if the steering wheel is rocked back and forwards.
I've steam cleaned off the spool valve that does the tipping to try and trace it's plumbing, but it's extremely hard to make out markings on it however a few pictures
awemawson:
Now there is one very odd thing that I hadn't before realised. There are two return paths for the oil back to the tank. Oil from the steering orbitor returns via a filter as I'd expect, but the oil from the spool valve returns directly at a low level in the tank - very odd.
This is the circuit as far as I can tell, and a picture of the tank showing one large output going to the pump, one input at high level via the filter, and the oddity input at low level
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