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Converting the Accurascale Hopper Wagons to S7 by John Borkowski

This article was originally published in the ScaleSeven Newsletter 132 in May 2023

An alternative conversion using Peartree S7 wheels can be found here

Back in 1966 as young boy I remember visiting a steel forging shop in West Hartlepool. Outside the window was a railway line with freight trains serving the town’s industrial zone consisting of heavy industries including a steel sections and pipe-mill serving the large oil and petrochemical industries on Teesside and the rest of the UK. On that particular day an Ivatt 4MT mogul was shunting a series of grey unfitted hopper wagons loaded with coke and coal for heating up the metal furnaces.

Then I had a OO gauge Hornby Dublo trainset and they had recently introduced a super detail hopper wagon. Following sighting the real thing in Hartlepool I now realised this wagon would be a desirable addition for my collection. Much to my regret, I never managed to acquire a hopper wagon until a few weeks ago I received an email from Accurascale offering me an attractive deal on up to 7 individual O Gauge super detail Hoppers.

I sent off an order for the 7 differently numbered wagons and within a week they duly arrived. Beautifully packaged they are impressive models with super detail fittings and sprung axles in working W irons. My only slight reservation was the side play in the axles which was several millimetres, a bit more that was perhaps desirable for best engineering practice. I suspect this excess side play was to allow for avoidance of buffer locking on tightly radiused curved O gauge track.

The instructions had a good diagram showing the layout of the individual parts making up the complete models. This enabled me quickly to work out an easy way to remove the wheelsets and to fit replacement S7 items. I will now attempt to explain how I accomplished this task.

Following my usual practice, I decide to undertake two conversions. On the first wagon I decided to replace the O-gauge wheel sets with Slater's S7 items, and on the second wagon I fitted some machined-up Accurascale wheels made to S7 specifications. Both tasks proved relatively straightforward without too much difficulty. Both wagons run well and have joined my fleet.

To assist readers with the scope of work involved, I have taken a series of photographs some of which are reproduced here, but all of which hopefully will be put on our S7G website.

Removal of the Existing Wheelsets

  1. Detach the long plastic bar holding the axle boxes in the W-irons. This is best carried-out by using a scalpel blade to carefully ease out the tiny circular lugs holding the bar into each W iron. Please make sure that you do not cut off these lugs or damage the plastic bar otherwise it involves a difficult repair or replacement of the plastic bar with an equivalent brass bar.


  2. Carefully remove both bars making sure the axle boxes remain inside the W-irons by resting the wagon upside down on its hopper bunker.


  3. Lift one axle out of the W-iron making sure that the tiny coil springs remain in place in the W-irons.
  4. Remove the second axle out of its W-irons in a similar manner.
  5. Decide which type of S7 wheelset you would like to use.


Fitting Slaters S7 wheelsets

Two axles of Slater's Type 7122S 3’ 1” 3-hole Disc are required. These come in a single pack. These wheels are available direct from Slater's with a 10% discount for S7G Members.

Axle bearings are provided with these wheelsets. Unfortunately, the diameter of the Slater's wheels axle ends is much smaller than the Accurascale axle ends so it is not possible to use the Slater's wheels directly into the Accurascale bearings.


  1. The Slater's bearings need to be adapted and fitted inside the existing Accurascale brass bearings.
  2. To do this, the Slater's bearings need to be shortened and the Accurascale bearings are drilled out to 2.8mm. I did this by first removing the Accurascale bearings from their axleboxes and then fitting them into the headstock chuck of my lathe fitted a drill bit into the tailstock chuck.
  3. It can also be done by turning a 2.8mm drill into the Accurascale bearing held in a pin chuck or even a set of pliers with a curved aperture.
  4. Before using a drill check the outside diameter of the Slaters bearings with a vernier caliper or a screw gauge. You need a drill size that will achieve a working clearance for this bearing diameter.
  5. The Slater's bearings need to be shortened as they are too long to fit in the Accurascale axleboxes. I removed about 1.5mm by filing by hand until they fitted in a slightly drilled-out axlebox flush with the Accurascale bearing end cap.
  6. As described above, the holes in the plastic axleboxes need to be drilled out so that the longer Slater's bearings end flanges are a tight fit against the Accurascale bearings. I did this by turning the 2.8mm drill by hand carefully removing the plastic swarf and making sure that I did not drill too far to avoid damaging the front face of the axleboxes.
  7. I fitted both axleboxes on each wheelset in turn, and then filed the bearing faces as required to achieve a clean fit in the W-irons so that there was minimal clearance and a good sliding fit of the axleboxes in the W-irons.
  8. Care needs to be taken to make sure that the W-iron coil springs remain in place and the axleboxes are correctly positioned in the W-irons.
  9. As everything is coloured black it helps to carry out this work on a sunny day is direct sunlight. Reading glasses also help for the older modeller!
  10. When both axles are correctly made and fitted back in the W-irons, refit the plastic bars in the W-irons by crimping the lugs in position on the tiny W-iron holes using a flat nose pair of pliers.

Fitting Accurascale wheelsets turned to S7

This requires either a suitable lathe and an S7 profiling tool or asking someone with these facilities to carry out this work. I am very lucky to have a small Proxxon lathe and the S7 stores wheel profiling tool. This equipment enabled me to carry out this work comparatively easily, once I had made a specialist wheel-holding tool.

If you do not have these facilities, you can make contact with our S7 member Colin Dowling who carries out this work on a professional basis for a very reasonable cost. Colin’s work is much better than mine, so he is well worth using for all wheel turning jobs.

Once the wheelsets are converted to S7 they are refitted in unmodified Accurascale axleboxes with 3 or 4 brass 2.5 mm washers to limit the sideplay. I bought my brass washers online for the Western Diesel programme modifications with some extras for other uses. There are numerous suppliers on the Internet with very competitive pricing.

When the wheelsets are back in place in the W-irons, refit the plastic bars as is described in the earlier section on fitting Slater's wheels.

Selecting which wheelset to use is a personal preference matter. In my view the Slater’s wheel is little better looking than the modified Accurascale wheel, but the Slater's wheel tyre, being made mild steel, does rust easily especially when parked for long periods on track, whereas the Accurascale wheels are made of brass and can be chemically blackened if required.

I now have to convert the other 5 wagons to make up a short train for a Scale 7 Masterpiece Models Pannier, 28XX or even a Western!


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