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JLTRT Class 40 Conversion to S7 by Richard Carr

The original Western Thunder source for this article is here: JLTRT Class 40 Conversion to S7 by Richard Carr

I'm taking a little break from the 9Fs and tidying up a few loose ends, two of which are a pair of JLTRT Class 40s that I bought on eBay back in 2019. Both are finished in BR Blue; one is 40075 a discless disc head code example and the other is 40135 in its final configuration with water tanks removed. The paint work and weathering finish on both locos is excellent. Both, of course, are finescale so the little job now is to convert these to S7.


When I collected the locos from the seller at Kettering I did ask why he was selling them and he replied that they wouldn't stay on the track, the pony wheels regularly derailed, fortunately I have a solution to that problem.


40135 is powered by a pair of ABC power bogies, these aren't going to work with conversion so the first thing is to remove them.


This just involves undoing a few screws and removing the pick-up and motor wires from the decoder.


Bogie frames removed.

Some progress has been made so I now need to get some S7 wheels ready for the first loco.

The S7 Group have been producing diesel wheels for a few years now and they are nice. They are made by Slater's but with a few tweaks for S7 and aimed at specific loco types. The 3 foot 9 inch wheel that a class 40 needs is really aimed at a class 47 so comes complete with the 4 lifting holes, but you won't be able to see those once the wheels are behind the bogie frames.

I have, though, identified a few issues with these wheels; not so much with the wheels but with the axle and the axle screw.

Here is a wheel fitted to an S7 axle with the screw fitted you can see that the screw cannot go fully home it should be flush with the boss of the wheel.


This means the wheel is lose on the axle end and you can pull away from the axle like this.

That isn't something anybody wants.


To fix this I find that 3 things are needed, first the square end to the axle needs to be shortened by 0.7 mm so it looks like this.


You then need to thin the neck of the screw, I do this by putting it in a mini drill and taking a file to it to just thin the area where the tapered head begins, I then shorten the screw by about 2mm.

Have any other S7 members had a similar problems, can't we get Slater’s to sort this out?


I have had a similar problem when thinning standard O wheelsets down to S7 standards. My solution has been to countersink the end of the axle on the lathe. This retains the square but gives space for the head of the screw. Sometimes the countersink needs deepening too but I do that on the vertical drill. I have two countersink bits one I use only for the brass and the other for the steel.

The latest Slater’s screws have quite a thick head so I usually turn a wee bit off the face so that they sit flush or just proud of the wheel depending on prototype. The hex socket is much better than on the old screws and doesn’t give me the same problem with the key slipping.

If the threaded bore is not long enough for the screw and you don't want to cut the screws down then you'll need a 6 B.A. tap but check that the counterbore is long enough for the tap first!

To be continued.....! Top