Thwaites 2 Ton Two Cylinder Dumper Running On One Cylinder

[lordedmond]

It's not that relentless Stuart 


However just as things seem to be going well, there's always a 'Gotcha' to come along and nibble your nether regions 




Only alternative I can see at the moment is somehow to cut the head off the bolt in-situ, and install the new one the other way up, but cutting through a 1" bolt in a very cramped spot won't be easy.

Andrew
Get the vet over they have just the thing  embryotome would do it 


Stuart

[AdeV]

OK, this may be a bit too extreme... but let's see:

First, undo and remove the nut.
Second, gas-axe/plasma-cut a piece of the upper plate out, sufficient that you can lift the pivot up a bit
Gas-axe/plasma the bolt head off, between the pivot and the lower plate. Presumably the remnants of the bolt will then fall past the prop & out of your way. If the rest of it doesn't follow, push it through.
Weld cut-off back into place.
Install new nut/bolt the right way up.

I guess it depends if you want to cut the plate or not, it looks pretty thick to me.

[awemawson]

Well chaps many thanks for your interest and suggestions 

There was of course only one way really to do this - drop the transfer box - just get on with it and don't be a wimp  I reckoned that if I disconnected the short propshaft at the gearbox end, there should be enough travel in the splines of the other two propshafts just to lower the transfer box enough to remove the offending bolt.

So rather reluctantly I crawled under and started spannering. Propshaft was easy - there were only three loose bolts in the four bolt flange  The four bolts holding the transfer box comprised two easy ones, one that was a bit of a challenge, and one the was a nightmare - but I got there in the end and managed to lower the transfer box on the trolley jack, and prop it up on bits of timber, as the jack was needed to get the chassis on axle stands.

[awemawson]

Then,having put axle stands under the chassis I put the tourniquets back, and carefully tweaked them so that the top pivot bar assembly was in the middle of its play so that there was no strain on the big mounting bolts.

[awemawson]

This is where I should have been able just to unbolt the old pivot and pull it out. But lifes rarely like that is it 

The front bolt was fine, but the rear one refused to budge. It's nut unscrewed ok, but with loads of 'Plus-Gas', much hammering on spanners, and heating with the oxy-acetylene torch it wasn't moving one iota. Even a 14 lbs sledge hammer failed to knock it through    Having exhausted all other possibilities I decided to drill it out using the mag drill.

[awemawson]

Then the fun began. Firstly the magnet switch on the drill decided now was the time to weld it's contacts in the 'on' position.  This  made positioning it rather difficult. However, as there was a grease bore down half the length of the bolt, at least there was something for the drill to follow.

As I went progressively up in size I got to a point where the drill was wandering dangerously off centre, threatening to mar the mounting bushes. So I stopped with the bigger drills (I think I'd got up to 18 mm on a 1" bolt), and went right through with a 1/2", so leaving me a shoulder inside to put a drift against. Then I got the oxy-acetylene  torch out again and heated through the hole downwards, so at least the stuck bit was getting the flame.

A short length of rebar as a drift and the sledge hammer at last persuaded the bolt to move downwards - what a palaver 

[awemawson]

Quelle relief !

So now I transferred the adjusting / limiting bolts from the old to the new pivot, making sure that they were set to the same height as before. No idea how this is supposed the be adjusted so I thought it best to accurately copy how it was set. I then installed the new pivot, which went ok apart from getting the grease seals in place - they got there eventually but trying to squash two grease seals and slide the pivot bar at the same time was  great fun 

Then back under and bolt the transfer box and propshaft flange back, along with the steering ram. (I'd removed the ram in case the front and rear of the dumper had moved apart, as it might well have bent the ram)

[awemawson]

Now those who've been paying attention will notice I've put the rear pivot bolt in just as the original one was. Matthew is quite correct, with it the other way up you cannot get at the grease nipple. In an ideal world I would have drilled the bolt all the way through, plugged the 'nut end' and tapped the head end for a grease nipple. But time was getting on, I was knackered, and I reasoned that it would last a good few years as it was.

So lack of light stopped play. Tomorrow the steering stanchion goes back on, then the steering orbitor, and a few odds and sods like floorboards.

I noticed that one of the hydraulic lines for the ram has suffered a bit, so if I have the correct fittings I'll crimp up a new one.

... so now it's time for a bottle of Ibuprofen and a wee dram as I have aches in places I didn't know that I had 

[awemawson]

A relatively easy morning today. I bolted back the steering stanchion, installed the steering orbitor and checked that it all still worked. Then removed the temporary 'tourniquet'  brackets, and bolted back the floor.

[awemawson]

While I was fitting the steering orbitor I noticed that it's shaft oil seal was weeping. Seems to be an externally fitted 1" shaft 1 3/4" o/d of perhaps 1/4" or 3/8" thick. I ordered some up but carried on installing it as it's only 4 bolts to drop it off in the future when they arrive.

Also the pipes to the steering ram were pretty horrid - as they were previously fitted they were squashed at a difficult angle against the floor. Having raised the orbitor a bit they fit much more comfortably, but needed replacing. Fortunately I had the correct fittings and hose in stock so crimped up a new pair.

With the new stanchion arrangement the wheel is perhaps a bit to far forwards - I may have to work out how to move the seat forwards a bit.

[mattinker]

Nice to see, as usual!! I like the one bit at a time paint job.

I might pop in for a cuppa between xmas and the new year. All the best, Matthew.

[awemawson]

Be good to see you again Matthew 

[appletree]

A relatively easy morning today. I bolted back the steering stanchion, installed the steering orbitor and checked that it all still worked. Then removed the temporary 'tourniquet'  brackets, and bolted back the floor.

How do steering wheels end up that shape? and does it hurt? we had several of the same machine inner fleet a number had the same steering wheel.

[awemawson]

I have always assumed that it's the constant exposure to weather releasing stresses from the moulding process that distorts them. Works ok as it is and a new one is £45 

[Spurry]

Andrew
This will be a mighty posh dumper by the time you have finished.
Pete

[awemawson]

It'll still be a tatty dumper, but at least it'll work 

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 

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 

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 

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 

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 

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. 

If I manage to find another spool valve I'll plumb it up differently

[awemawson]

OK I've been cogitating  on this hydraulic issue and I could do will some input from any hydraulic guru's on forum   


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

[awemawson]

Now here come the assumptions 

I am ASSUMING that the old orbitor presented resistance to flow when not being rotated so that pressure was available to operate the tipping ram. (*)

I am ASSUMING that the new orbitor only presents resistance to flow when being operated, hence the tipping working if the wheel is rocked (*)

Now buying a new orbitor is out of the question as they are hundreds of pounds, so what's the solution?

If I were to insert a 'pressure maintenance valve' on the output from the orbitor is it likely to work.

Comments please from any hydraulic guru's



(* See later posts - this is INCORRECT - it's the other way round, the new one is 'closed neutral' and the old one 'open neutral'

[appletree]

Just keep on rocking

[smiffy]

Just a thought but where is the PRV, is it built into the tipping valve or is there a separate  stand alone PRV   For the tipping ram to work from your diagram the P and T ports in the orbitor would have to be closed. If the flow went from the pump to the tipping valve and then to the orbitor  and then returned to the tank the system would work but priority would given to the tipping ram , not ideal but workable.The system can only work with one return  unless there is a priorty valve fitted in the system somewhere. Mike

[awemawson]

A bit of 'google research' shows that there are two or more varieties of steering orbitor. Centre closed and centre open. In the neutral position the centre closed variety blocks P to T whereas the centre open variety, which I think I must have fitted, passes oil from P to T unless the wheel is turned.

I suspect, but yet to be proved, the solution is to fit an inline pressure release valve between the out port on the spool valve, and the P port on the orbitor. This way the spool valve will have pressure to operate, and when the wheel is turned so will the orbitor ...... I think ....


Again ... informed comments welcomed ......

[smiffy]

This would depend on the tipper spool, is it open centre or closed centre . From your diagram it should be open centre.It could work if you feed from pump to p port on orbitor , t port to tipper spool  and tipper valve to tank but this is dependant on where  the prv is .Mike