Another conversion to S7 job turned up, in this case a Minerva Kerr Stuart 0-6-0 t.
usual procedure with these RTR models, remove the brake gear, base plate and the wheel sets.
Measure the wheel width and flange.
In this case 0.3 mm off the rear face will leave 0.7 mm of flange , ideal for the S7 profiling tool ad at the same time brings the tyre width down to a prototypical 3.24 mm
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To remove the wheels first use a scalpel to remove the cosmetic axle cover, it's brass so wont break, the Chinese use some sort of tacky glue that doesn't dry.
I use an adapted GW models puller and a slotted disc of metal on the back of the tyre otherwise there is a risk of pulling the tyre off the wheel centre.
Metal removed from the back of the wheel, 0.3 mm, and then re- profiled in the lathe. I wont go into detail with this as I told it all before.
Now the problem with outside cylinder loco's is clearance behind the slide bars but mainly the cross head.
This means, on this model, altering the leading knuckle on the coupling rods to use a flush fitting crank pin nut or retainer.
I bored the rod to take a brass top hat bush ad then counter bored with a milling cutter to a depth to suit the rim of the top hat bush.
The bush is slotted across it's face to accept a 'Romford' screw driver as I call it.
The depth of the bush is filed down to within 0.010" of the width of the rod by using a peice of 0.010" brass shim.
The leading wheels have been fitted with 10 B.A. crank pins fitted with Loctite. The bushes are also tapped 10 B.A.
Temporarily fit the rods and grind off the excess crank pin flush.
The back of the cross heads also had some metal taken off.
It is all down to just re- assembly after pressing the wheels on their axles, re-gauging with a S7 btb gauge and test running.
Edit. Nearly forgot to mention that I fitted 1mm plastic spacers between bearings and wheels to take up side play on the axles, the slotted bearings on the leading and trailing axles are fitted with the
larger portion facing outboard and the centre axle bearing has the thinner portion facing outboard.
Col.