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Converting a Dapol Class 08 Diesel Shunter to S7 by Colin Dowling

The original source for this article is here: Converting a Dapol Class 08 Diesel Shunter to S7 by Colin Dowling

This Dapol loco has proved popular with some S7 modellers and I now have the fifth example on my bench for conversion.

Start by removing the coupling rod crankpins, be careful with these as they are fitted with some sort of thread lock fluid and I have already had one shear, spares should be available from Dapol having spoken to them at Reading. (I had to mill the remains out with a 1mm cutter!)


Next remove the brake linkages, these are plastic mouldings and are held on with some form of waxy glue.


Remove the clips from the base of the axle boxes and the five screws retaining the baseplate.


The wheel sets can now be lifted out….


....and the wheels and cranks and spacers pulled with a wheel puller. Use a plate behind the wheel or you'll be in danger of pulling the tyre off the centre!


With the wheels in a set of soft jaws on the lathe remove 0.018" (0.44 mm) from the back only as far as and including the balance weights, the backs of the spokes are nicely profiled and there's no need to remove material from the boss.

Just an extra note, when deciding how much to remove from the back of any wheel that already has a flange on it, always leave 0.7mm min width of existing flange to give enough meat for the S7 profile tool to work on regardless of how wide it leaves the tyre (so long as the tyre is not reduced to below prototypical dimensions, 3.26mm ); take too much and you're b******d.

(The wheels appear to have steel tyres and Mazak centres?)

This should leave a wheel with a prototypical width of 3.26mm, but please measure the wheels first and then work out how much to remove as I can't guarantee Dapol’s consistency.

I use an AGH profile tool on the tyre, the wheel must be held by mandrels bearing on the tyre only with the revolving centre.

Turn up some axle spacers 1.50mm (0.060") thickness x 6mm dia. bored 4mm dia.

Edit: The axle spacers can be dispensed with and the axles shortened by removing 1.6mm from each end. But please do take your own measurements to double check.

When the cranks are re-fitted leave off the brass spacer that is originally fitted, the cranks will act to limit any side play by bearing against the axleboxes.

With the spacers between the wheel and bearings, use the S7 back to back gauge (31.25 mm). but before pressing the wheels fully home set the quartering by eye (R/H lead), this is quite easy using the spokes and balance weights as a guide.

Refit the cranks using a thread locker such as Loctite etc. noting the position relation to the balance weights.

This shows L/H side wheels looking from the cab.


Here's the R/H set.


Refit axle sets making sure the current collectors are not caught on the wrong side of the wheel.

Refit plastic clips in the axle boxes.


Refit base plate, brake linkages and finally the coupling rods and crank pins with a drop of thread-locker.

There is just enough room for this conversion between the frames; you will not do it without turning the backs off the wheels.


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