Thwaites 2 Ton Two Cylinder Dumper Running On One Cylinder

[modeldozer]

It might be easier to repair the old steering control valve, repair kits are availeble.

On assembly there is one critical step as explained on page 10 of this manual
http://www.eaton.com/ecm/groups/public/@pub/@eaton/@hyd/documents/content/dev_216975.pdf

For more info search for "Orbitrol steering valve"

Abraham

[awemawson]

I can only assume that there is a PRV built into the tipper spool valve. I can just about see a hex headed 'something' in the face where the UP and DOWN ports emerge.

[awemawson]

Modeldozer - thanks - an interesting link. The original one is a Danfoss though, not an Eaton

Now a few more facts discovered:

A/ The original is definitely an 'open neutral', ('ON' in the type number probably means this !) I can blow through from P to T. I tried linking out the orbitor so where it is in circuit is replaced by a straight though 1/2" bsp to 1/2" bsp conical connector, and sure enough the tipping ram works just as it should

B/ Before finding it was open neutral, I blocked the pipe from the 'Out' of the spool block to the orbitor with a stop end - this jams the spool block tight making the spool virtually impossible to move, and this of course is the state it's in when plumbed as per that diagram. It brings into question whether there is a pressure relief valve in the spool valve, as I'd expect it to open under these conditions 

[awemawson]

Obviously the best solution is to replace the orbitor with an 'open centre' one, so I've just trotted off to the workshop to try blowing through the ORSTA one removed from my Buchner bank mower.

Sure enough it's 'open centre'  -

I'd rejected it as it's ports were a different thread from the original so I couldn't directly use the original adaptors which were UNF. As the ORSTA is BSPP it's an easy thing just to order up the correct ones (two 1/2" BSPP to 1/2" BSPP 60 degree cone males and two 1/2" BSPP to 1/4" BSPP 60 degree cone males) which should turn up in a few days. Then, IF the ORSTA still works we should be cooking on gas 

Not been able to find any info on the ORSTA on line in English, so suck it and see !

[AdeV]

Hmm, you've got a stonking great big CNC lathe sitting there just begging to make adapters... and you've ordered them?   

Maybe I'm just making excuses for buying a big CNC lathe myself.... 

[awemawson]

Wait till you find out how long it takes to tool up and create a program for  a little job on your Mazak Ade and you'll know why 

[awemawson]

So at last the hydraulic adaptors have arrived that will let me replace the (closed neutral) Danfoss Orbitor with the (open neutral) ORSTA one 

Simple nut and bolt job and a bit of plumbing. I'm using Dowty Seals (Bonded Washers) to seal the adaptors as I find them pretty reliable, and keep a stock. Then disconnect the hydraulic pipes and cap them for safety - don't want crud in the system  Unbolt the Danfoss, bolt in the ORSTA and re-connect the plumbing. Took about 25 minutes. So nice working on things that come apart easily - well it should - this orbitor (and others!) have been in and out like a fiddlers elbow 

[awemawson]

So does it work - Oh YES 

Now I can tip without having to rock the steering back and forth  I do notice a difference in the orbitors though. This one takes more turns lock to lock than the other one, which is probably a 'good thing' as going over rough ground the implied extra steering force will be handy. (The orbitors are specified as so many cc's per rev of steering wheel, and with the volume of the steering ram together effectively set the 'lock to lock' turns ratio. However, as hydraulic rams like this one are asymmetric in terms of the volume opening or closing the ratio is greater in one direction than the other. The Buchner bank mower this orbitor came off had a double ended ram ie a rod protruding at each end which makes it  symmetrical.)

I notice that the tipping ram is weeping a bit, but I knew that and have obtained replacement seals for it. Job probably won't get done until after Christmas as I have a few hundred saplings to shift with the dumper before then.

[awemawson]

Well - holiday season, knee deep in family so distinct limitations on 'activity' but a few nice things happened recently.

First: Matthew Tinker and his son Chris visited yesterday as he's over from France for the festivities. Always nice to meet other Madmodders and chew the fat.

Second: and the is really a FIRST ! Persuaded the wife to drive the Thwaites dumper which has let me (using the JCB803) strip about 600 saplings from the river bank and start re-planting them as a hedge. I've got perhaps 55 out of 75 metres of the new hedge planted before I lost the light (and the will to live  )

Third: While doing all this My Hermes delivered a parcel with the second hand 'tipper spool' that I've sourced - it's not identical, but came from another Thwaites dumper doing the same function, so I should be able to cobble it in and cure my oil leak on the original 

Now let me point out - it's a BANK HOLIDAY in the UK yet MyHermes DID A DELIVERY - now people knock them, but so far I've never had a problem.

So a few pictures to prove it happened. Firstly Penny driving the dumper with the first batch of saplings

[awemawson]

And here is the spool valve - it looked for all the world like a wrapped up Praying Mantis - but fortunately it wasn't - it was a spool valve 

Same number of ports that seem to be marked up with similar functions. In slightly different places, and I've a feeling the bore sizes of the ports aren't quite the same - though it may just be a case of swapping over the adaptors. For instance the two ports to the steering ram look to be 1/2" BSP whereas the original is 1/4" BSP - needs further investigation

[awemawson]

Just a little bit of progress today as my times been taken planting all those saplings into a windbreak hedge in very wet sticky muddy conditions where your boots get pulled off your feet and you loose the will to live  Still they are now in and at least I don't have to worry about watering them 

I decided I wanted to investigate the new valve before pulling the old one, so first step was to undo that attached 1/2" bsp pipe, and effectively that's ALL I've done as it put up a lot of resistance. I wanted to prove that it was the output from the main Pressure Relief Valve returning oil to the tank when rams were at their limits of travel, but the nut on the end of the hydraulic pipe was unbelievably tight. Ended up removing the relief valve (as that WAS what it was) complete with pipe, and applying gentle heat from a blow lamp and liberal applications of 'Plus Gas. If you look at the flats on the nut you can see it was very close to being 'rounded off' before it came loose.

Anyway, apart from a physically different layout it looks to be ok. So so long as I can get the operating rod in line with the spool as I mount it, it shouldn't be too difficult - just hopefully drilling new holes in the existing mounting bracket to correspond with this valve, and swapping the pipes over. But as the return to the tank from the PRV is to the base of the tank I may well have to drain it first. Might possibly be able to clamp it but in the end no bad thing to drain the tank I suppose.

Again a few pictures to prove that it happened 

[mattinker]

First: Matthew Tinker and his son Chris visited yesterday as he's over from France for the festivities. Always nice to meet other Madmodders and chew the fat.

I got back yesterday, very nice to see you again, have a bit of a chin wag and see progress in the flesh as it were.

Thanks again, all the best and a happy new year!! Matthew

[awemawson]

 OK I think I can finally draw a line under this refurbishment. 

I managed to fit the replacement tipping ram spool valve. It had a totally different mounting lay out, so I had to make up an adaptor plate taking the original valve's mounting points and presenting tapped holes to suit the new one. Fitted nicely and I managed to get the operating rod in the same alignment as the original, just having to shorten it a bit.

Now the hydraulic ports were another matter. The original was BSP all round. The second hand replacement had a very odd coupling that I've not been able to identify -  20 tpi, but an o/d of 0.758" with a deeply recessed conical seal. No matter, the body of the valve was tapped 7/8 UNF on all ports, so it was a matter of sourcing 7/8" UNF conical male to 1/2" BSP conical male adaptors for input and output, and 1/2" BSP ones for the A & B ports of the tipping ram. All went together nicely, and I even got 'tip' and 'retract' the right way round on the spool valve (50/50 chance !)


So I thought that I'd replace the weeping sealing in the tipping ram itself. I put the skip into 'full tip', then extended the fork lift tines above it and secured the skip to them with strops. This let me safely disconnect the hydraulic pipes to the cylinder and knock out it's pivot pins - heavy bu@@@r

I've had the seals waiting for some time but have been putting the job off. The outer end of the rod is a design I've not encountered before, with the end cap retained by a heavy C ring. All the was visible from outside was a large circlip preventing the cap sliding into the cylinder. Turns out, you remove the circlip, push the end cap inwards leaving the C ring in its groove, then remove the ring. Clever design.

Replaced the piston and rod seals, put it all back together then cleaned it up and sprayed a couple of coats of zinc rich primer followed by satin black, as I did with the steering ram. Back on the dumper and it works a treat.

In a fit of enthusiasm I decided to sort out the 'rotating skip'. The skip sits on a massive thrust bearing, and is prevented rotating by a large pin that is spring loaded upwards, and released by a foot pedal. It's never worked in the nine years I've had it. If you managed to release the pin, it would stick down and be a problem relocating. After a bit of cleaning up, cooking with a propane torch, and jiggling about, it freed off enough to withdraw it and give it a good greasing.

This has allowed me to rotate the thrust bearing and re-pack it with grease. Easy enough to turn it unloaded, not sure what it will be like with 2 ton of rubble in it 

So - that's about it - well I've a wheel and tyre to replace as one on the front  axle is off a one tonner and a bit narrow - I've got the replacement (good old eBay) - just a case of doing it

[Spurry]

Excellent write-up Andrew. Shame it's come to an end, but I bet you're pleased. 
Pete

[Dumperman]

Hi there has anyone got a thwaites alldrive 4000 with petter ph2 engine?

[awemawson]

Yes !

[Dumperman]

Have you got any pictures of the engine throttle set up on your engine?
The machine I’m working on I’m not sure it’s all back in the right place.

Thanks

Chris

[awemawson]

Chris,

All my pictures are embedded in this thread if you look 'up page'