A typical 060 is about 120lbs so make a guess on the extra length factor.
Re top heavy: biggest danger might be the day you try a small position adjustment and it decides to flip over until stopped by the chimney.

The problem is going to come when you add the boiler and the CofG of the swivel point needs raising. It will need plates on the ends of the frames at a new distance away from the buffer height datum. So you will have to raise and lower the loco with some other support and jacking system. Also, when you are finished what will be around 100kg needs to be removed from the frame and easily placed on a trolley with rails. 100kg is a four person lift without mechanical assistance.

I built a wheeled trolley, with rails on top, then strong vertical supports that bolt to the trolley frame with vertical screws (like a lathe feed screw) to raise or lower a block at each end. Each block has a large pin about which a friction clamp can rotate. Affixed to the clamp are plates to allow CofG adjustment. One of the plates grips firmly to the end of the loco frames. The decorative buffer beams can be left off until the loco is in its final build stages.

The photo shows my assembly supporting a 45kg 0-6-0 with wooden clamps around the buffer stocks. More recently the same frames, with adjusted CofG have supported a 100kg Britannia but with steel clamps around the frame ends. With the CofG adjusted to within a few mm the loco can be turned by hand.

I only post this in case it helps you plan ahead.

Norm

Sorry Duncan ! But I would not be happy with my loco hanging on 4 5mm bolts ! Noel

Hi, my two 500 Kg chain blocks have a 6mm bolt holding the hook to the chain, and have both had close to the 500 Kg on them, the older one having had that many more times than the other one.

Regards Nick.

Being an adgerent of the Victorian “Brick mausoleum” school of engineering, I would feel happier with two 8mm bolts at each end.

If the supports are too strong, no problem, but the converse means danger and trouble.

Again, with safety in mind, with the loco becoming more and more out of balance as build proceeds, I would advocate rotating by means of a single start worm and wormwheel.  That way, even off balance, the single start worm will prevent the loco rotating out of control.

Howard

OK, as requested, but this is a bit beyond what the OP was looking for.

The uprights are steel box section with a milled out slot in one side. Welded cross member at the bottom and bolt on stretcher at the top to allow assembly. The central steel carrier runs vertically in those slots and takes any side or twist thrust to keep the screw thread unloaded. A welded pin in that carrier has a split aluminium clamp gripping it. The screws allow grip adjustment. The drilled steel plate allows height adjustment to enable loco rotation along (near to) its CofG. It is important that the mounting to the loco is rigid and does not impose any downward twist. The towers could be half the height shown and would still allow full rotation.

One photo shows a mounting clamp that is attached to the loco front frame stretcher with buffer beam and stocks removed. The other shows a long steel tongue that goes into the rear loco drag box.

Hope these are of some interest.