The Lima class 33 is readily available secondhand and makes an excellent general-purpose workhorse for a British H0 layout. The model dates from the 1970s, and this write-up shows how to rebuild the engine into something more realistic, with a modern mechanism. The total cost of the project will be about £50, plus the cost of a donor engine. The donor engine will ideally be a non-runner and cost only a few pounds to buy at a swapmeet or exhibition.
The body of the prototype is 8’ 10” wide, which scales to about 31 mm in H0 scale, but the Lima model is about 33 mm wide. Looking at the fronts of the cabs on the model, the cab windows are near to the right shape and size but the window pillars are too wide.
The excess width of the Lima model is very noticeable when you look at the model at the ends and from above. If you try to reduce the width by the full 2 mm, you really need to tackle the width of all four window pillars at each end, and this will make for quite a fiddly job because the pieces of plastic you trim out are so small. It will also run the risk of losing the shape of the cab front, which Lima have captured rather well.
My own approach here is to reduce the width of the body by about 1.4 mm instead of the full 2 mm, leaving it 0.3 mm too wide each side. This is too small to notice when the engine is coupled up to a train, but it makes for an easier job.
This is an account of how I modified my engine – the original approach was devised by the late Malcolm Carson, and I have drawn on other useful techniques from other members of the British 1:87 Scale Society. I am writing for a person who has probably added detail to a RTR model in the past, but not chopped up a model into pieces before. It might be said, “this is not for the faint hearted” but truly, it worked out much easier than I expected. The only tricky bit in the whole project has been finding somewhere to buy the buffers.
And so . . . if this is the only Lima H0 class 33 you possess, have a good look at how the parts look when assembled by Lima. This will help when you come to put the model together again, because several parts like the lamps and the glazing will fit different ways. Taking a few photos now, before you have a pile of bits, won’t do any harm at all.
1. Unclip the body shell, push out the four lamp lenses and lift out the window glazing.
2. Drill a ring of tiny holes around the roof fan, join the holes together and drop out the fan. Clean up the jagged hole in the roof - I used some aluminium oxide paper rolled into a tube shape to do this, but a proper tapered reamer would be better.
3. Take a length of 1.5 mm thick styrene strip and cement it firmly along the centre line of the roof, passing over the large hole where the fan was and stopping a few millimetres short of the horn enclosures at each end. This strip is a cutting guide, and it makes the whole narrowing job much easier. Leave this strip overnight to set completely hard.
This is the end of the first session.
There are three important “secondary dimensions” for this project:
0.6 mm, the width of a standard junior hacksaw blade
0.4 mm, the width of a fine coping saw blade
Next to nothing, the width of a cut from a craft knife blade.
4. Put the body vertically into the vise. Use the junior hacksaw to make two cuts, one each side of the horn enclosure and vertically down the cab front. It is best to stop the first cut short of the bottom of the cab, so the body holds its shape while you make the second cut. Then finish off the first cut. The junior hacksaw blade makes a cut about 0.6 mm wide – this width is important. It must be a less than half the width of the styrene strip glued onto the roof, but ideally only 0.1 mm or so less. Make sure the cuts do not touch the edges of the horn enclosure.
5. Using the coping saw, join the two saw cuts behind the horn enclosure and lift out the centre section of the cab front. Mark the back of the piece so you know which end it belongs, and then do the same cutting out at the other cab.
6. With a really sharp blade in the craft knife, score two cut lines along the roof, tight against the sides of the styrene strip. Gently work the knife deeper and deeper until you can fold and snap the body into three sections – the two sides and the sacrificial strip from the middle. The styrene strip will keep the cuts parallel with each other, even if it isn’t perfectly straight.
7. Using a fairly coarse, flat file, clean up the cut edges of the two body sides. They should need very little cleaning up. There will be some raised burrs on the top of the roof created by the knife blade, but it is best to ignore these for now.
9. Cut a bulkhead 30 mm wide from 1.5 mm styrene. This will reinforce the body structure when it goes back together. Make sure the body is consistently 30 mm wide inside (this gives about 31.5 mm outside), make sure the two halves are in perfect alignment, and then install the bulkhead and flood all the joints with solvent.
Don’t touch anything again until you are sure the joints are set solid. The model looks pretty awful now - with two huge holes at each end, it has lost all the appearance of a class 33, but this will go right at the next session.
10. Offer up one of the cab offcuts to its cab. You will see it needs hardly any work to make it fit – perhaps a tenth of a millimetre to be removed from each vertical edge, and a little more at the top beside the horn enclosure. Use the flat file to work the edges, a little at a time, until the offcut fits snugly. I did virtually all of the fettling on the offcut – there is hardly any material to work with beside the cab windows attached to the sides.
11. When the cab offcut is a snug fit, put it into place. Because of the curving geometry of the cab front, it will be slightly too tall, but fix it in place with the correct alignment of the moulding lines above the windows. This leaves two tiny steps in the handrail below the windows, and a small protrusion at the bottom of the cab, to remove later. Secure the assembly with a rubber band around the body.
12. Wait for the solvent to set, and then rebuild the second cab in the same way.
13. Cut a square of 0.25 mm styrene sheet (this is thin enough to curve into place and stay put) and fix it below the large hole in the roof. Glue the fan removed at stage 2 on top of this square. You will need to remove the rubber bands holding the cabs together to check the alignment of the fan against the centre of the model, so once again you have a wait until the solvent from the previous step has set. Patience.