The Tale of my Old Dumper, Part Three

A 1960’s Thwaites Orion dumper rated to carry 15 hundredweight or ¾ ton load

The next component that I needed was a so-called ‘’spool valve’’ with is basically a device with a hand operated lever that ports the hydraulic oil to either end of the hydraulic rams according to operator input. Now I know a little about these valves as I have a tractor with them and so the only issue was to find a suitable one.  There are various types available, the two main ones being ‘open centre’ and ‘closed centre.’ The difference revolves around what the valve does with the supply oil when it’s in the neutral, or at rest position. The closed centre valve blocks the flow of oil completely and so you need a rather complex variable displacement pump or a pressure relief valve as the system would otherwise rupture.  And the open centre valve ports the supply oil straight though to the return port thus completely dumping all pressure produced by the pump. That was the obvious one that I needed so one was ordered. Again, the smallest available and a budget component made in Italy was used. When it arrived I was a little disappointed as the valve body and handle were all to the same side of the mounting lugs and while I could still make it work it would mean the bird’s nest of hydraulic pipes and the valve would all be on show and looking a mess on the top of the dumper. A quick perusal of the destructions showed me that by dismantling the end of the valve I could reposition the handle through 180 degrees and so problem solved.

The spool valve fitted. The two pipes at the top are hydraulic supply and return lines. (from the pump and to the tank) The four lower pipes are actually just two pipes in effect as they are supply to either side of the ram, as there are two rams I determined that here is a good location for ‘T’ pieces to split the supply.

One more little job, which probably wasn’t strictly essential but I like to keep things well engineered, was a filter for the hydraulic oil. I decided upon fitting one in the return line as that could simply comprise a spin on canister type as there’s very little pressure there and thus dispensing with the need for some robust casting designed to survive at 3000psi. I found a spin on filter head on ebay and a suitable spin on filter advertised at 10 microns. 20 microns available too but 10 is better – right? I didn’t worry too much about that.

Simple standard hydraulic filter head and spin on filter. Cheap and effective.

We now come to fabricating parts and assembly of components so I thought I would branch off for a little while and introduce you to my two main machine tools that adorn my workshop and a few other things. The first one is a very old Colchester Student lathe, capable of turning 6.5” radius and 24” length jobs, manufactured sometime in the 50’s I think. It has several speeds and revolves at 1000prm maximum which is quite frightening when you have a heavy lump in it spinning  right by your nose, but  the slowest is at a mere 45 rpm.  It has a screw thread cutting gearbox for both imperial and metric, a 3 phase reversible motor, coolant/cutting fluid tank and pump, tail stock, three and four jaw chucks, automatic traverse on the carriage and cross slide and usefully, an adjustable compound slide so tapers can be produced. These machines were designed for industry and were also often found in schools when metalwork was taught before the H&S lot became involved and kids started to prefer computer games. Many thousands will still be in use today, working for a living all over the globe mainly in places where CNC machinery is still just a dream.  I think I paid about £800 for it years ago, and it’s probably worth than now, unlike the Chinese crap from Machine Mart that’s made from chocolate. It will outlast me with ease.

My Colchester Student lathe, not pretty as it has much paint battle damage but it is fine mechanically.

The second tool is a vertical milling machine. I admit to mostly using it as a pillar drill, as can be seen from the fitted chuck in the photograph but I have used it for many milling jobs in the past. It came from a friend who was moving up to a larger Bridgeport machine. Manufactured by a Swedish company, Modig and started life at a British Aerospace company at Lostock, Bolton which I think is now involved with missiles. Again it’s a three phase machine with a two speed motor and 4 speed gearbox resulting in 8 speeds. It has done very little work and is almost new underneath the standard layer of dirt that seems inevitable in my workshop. They are rare in the UK, I’m not sure why British Aerospace decided upon this machine, but it works really nicely and is a good size for me. I’m not sure of the age but certainly more modern than the lathe.

My Modig vertical mill.

I’ve mentioned that both of these machines have three phase motors and unfortunately our property, like most UK domestic properties only has a single phase supply. Installation of three phase probably costs about 20K, retrofitting the machines with single phase motors could be possible but you lose the reversing facility which is vital for some operations. Fortunately one solution is fairly simple and cheap and that is via a static phase convertor. I have an elderly one which creates an artificial phase induced by the motor and third phase produced by capacitors but only for starting. When running at speed the motor just uses two phases so there is a reduction in power output, but for non- production work and light jobs you never notice this. Modern ones are available that are far more compact and efficient using electronic technology but why swap something out that does the job well enough?

Elderly Transwave phase converter, still in production today and British.

Finally, a fairly standard 160amp MIG welder, a cheap thing, but does the job. It will be stretched and working at full capacity for most of the welds are on 10mm and 12mm plate, I do have another conventional arc welder capable of dealing with heavier stuff but the MIG is cleaner, easier and quicker and becomes the weapon of choice if adequate. In the time honoured tradition, the 13 amp fuse in the plug has been wrapped in tinfoil to stop it repeatedly popping when used on full chat, but don’t tell anyone.

Mig welder from Machine Mart. Note the ‘’Hobby Weld’’ refillable CO2/Argon mix shielding gas bottle that you purchase.  A number of companies offer this service thus no longer the  need for the hideously expensive disposable bottles or the other option to pay rental charges to BOC or Linde Gas.


© text & images Cardinal Puff 2023