Hy-Mac 480 excavator restoration

Jeremy Rowland enjoys a trip to see the superb results of an exacting and expert, ‘nut and bolt’ Hy-Mac 480 excavator restoration.

The Hy-Mac 480 was the first excavator model that was manufactured by the Rhymney Engineering Company in South Wales, and sold and distributed by Peter Hamilton Equipment Ltd. The machine was based on an American Hy-Hoe design, and was the first all-hydraulic excavator to be manufactured in Great Britain.

Tony Flint has just completed a full ‘nut and bolt’ restoration of one of these pioneer Hy-Mac models, and I went along to see it; the machine in question carries the serial number H4810159, which links it to a purchase date of March 9th, 1963. It was delivered to Scottish Land’s depot in Newcastle.

Unrestored debut
It was advertised for sale in Classic Plant & Machinery magazine some years ago, but was finally purchased at a Cheffins auction in April 2016, by Clive Hurt. It then made its unrestored debut at the Chipping Steam Fair later that year, after which it was taken to Tony Flint for full restoration.

Machinery restorations of any kind aren’t simple jobs, and this one presented more than its fair share of problems. However, before the restoration even started, one of the track drives failed, which turned out to be due to a broken drive chain. But, already spotted by Tony at the 2016 Chipping event, was a far more serious issue with the excavator.

Steel channel had been welded around the front and both sides of the machine, indicating that at some time in the past the upper frame had ‘broken its back’ – something that would cause far more issues during the restoration. Another visible defect was the cracked dipper arm but, with those two exceptions, the machine was a viable candidate for restoration.

As with previous, full restoration jobs, the excavator was totally stripped down so that the really hard work could begin. All the hydraulic components were fully refurbished, including the triple, in-line gear pump, spool valves, rams and track drive motors. The brakes used on the Hy-Mac 480 aren’t automatic brakes like the ones fitted to the later machines.

In this case, after a full investigation, it was discovered from a Girling brake specialist, that the brake cylinders (including the master cylinder), were the same as those fitted to Jaguar cars of the period. The brakes are operated by pumping the brake pedal then, once applied, turning a gate valve to keep the pressure in the system and hold the brakes on; the brakes are simply released by unscrewing the gate valve.

‘Broken back’ fracture
The excavator’s upper frame was stripped, which revealed the true extent of the ‘broken back’ fracture. She was in a very bad condition. All the previous attempted repairs had to be removed first, after which the frame was sent away for specialist welding. While this was happening, attention turned to the undercarriage. The drive systems and rollers – along with the idler wheel – were all refurbished, with new bearings and bushes being fitted.

The Hy-Mac 480, like all early Hy-Mac tracked machines, was fitted with a cast navvy pad-type undercarriage, similar to those fitted to track-driven cranes of the same era. However, the problem is that, on this type of undercarriage, the pads tend to wear where they are linked together, which was the case in this instance. All the pads were bushed and had new pins fitted, then the first real problem arose, because a previous owner had removed two old track links from each track to compensate for the wear (which had now been rectified), so the tracks were two pads short on each side.

Naturally, you can’t purchase new track pads off-the-shelf nowadays, and finding good, used ones is nigh-on impossible. So, the only answer was to have four new pads manufactured. These were made from solid steel and machined out; I must say that they are first class, and you’d struggle to spot the new replacements from the originals.

The dipper arm, which had cracked quite badly, was also sent out for repair; once again, a bodged repair by a former owner had to be removed, at which point the true extent of the damage became evident, then the repair could be made. Once the repaired upper frame returned, the restoration took a turn for the worse, as it was discovered that the frame damage had caused diesel to leak into the main, hydraulic oil reservoir. This proved to be a trying time for Tony and Strutt Engineering, who carried out the welding work on the excavator; the issue with the leaking tank cost much time and effort to finally sort out.

 

 

 

 

 

 

 

 

 

Finishing touches
The engine bonnet covers received lots of attention, with new panels being fabricated and nicely finished with the chrome ‘tee’ key covers. The excavator benefited from all new hydraulic hoses, including some of the steel pipes, and the electrical system received a new wiring loom.

The Hy-Mac 480 isn’t a full 360° slew machine, but slew is accomplished via two hydraulic rams that pull the upper works around via two chains and sprockets – the chains were renewed and the two rams rebuilt. The cab had to have a new floor welded in – fully expected on a machine of this age – although the original cab glass was retained. The excavator was finished with a high-quality paint job in the early yellow livery that was seen on the first Hy-Mac excavators. I’m sure you’ll agree that this is a first-class restoration.

 

 

 

 

 

 

 

 

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