It is intended to avoid the very time consuming and expensive work required to balance Tornado’s coupled wheels. This was achieved by the traditional method of making weights to hang on the crank pins which represented the total mass of the rotating motion parts and a proportion of the reciprocating motion parts. Tornado’s wheels had cast in balance weights which are ‘adjusted’ by drilling holes in the back of the weights.
The actual dynamic balancing was undertaken with the assistance of Dowding and Mills (now Sulzer) at Middlesborough using their large electrical machinery balancing machine as no steam loco wheel balancing machines exist in the UK. One of our long term supporters who balanced large marine diesel engines in his youth kindly offered to produce the calculations for the overall balancing and a series of drawings to guide us as to where to drill the lightening holes. The readouts obtained from Network Rail ‘Wheelchex’ equipment which is installed in several places on main lines throughout the country to measure wheel forces (mainly to spot freight wagons with severe flats on wheels) show that the track forces produced by Tornado during testing are as predicted by the balancing calculations. The pictures below show the weights attached to the crank pins and the drive pulley required by the balancing machine, the holes drilled in the balance weights and the wheels being balanced.
For No. 2007 we are intending to achieve balancing entirely by calculation and by using built up balance weights (crescent shaped plates riveted on both sides of the spokes with predetermined quantities of molten lead/antimony alloy poured into the cavities between the spokes and plates). This was standard GWR/LMS/BR practice. However instead of using a dynamic balancing machine to determine the precise amount of lead required, we intend to do this by calculation. The starting point is the centre of mass of the wheels. The 3D CAD models will predict where this is, however as the wheels are castings which rarely turn out precisely to the shape of the drawing, we need to use other methods to determine the centre of mass. One is to 3D scan the wheels to produce a solid model from which Solidworks 3D CAD can compute the centre of mass. To back this up we will also determine the centre of mass of each wheel in the plane of the wheel by balancing it on a knife edge on the back of the wheel boss and repeating this with the knife edge at 90 degrees.
As all the other components (tyres, crank pins, coupling and connecting rods, pistons, piston rods and crossheads) are fully machined to close tolerances, their masses and centre of masses can be computed accurately, as can any material removed from the wheel centres during tyre and crank pin fitting, the existing surfaces in these areas being already machined. This removed metal will cause the centre of mass to move slightly, but this displacement can be accurately calculated. The final check on hammerblow (the minimising of which is what balancing is all about) using the ‘Wheelchex’ equipment during the main line testing.
Reg warms up a rivet – David Elliott
Ian forms the rivet head using the rivet squeezer – David Elliott
Reg countersinks a rivet hole – David Elliott
Leading brake stay nearing completion – David Elliott
A front buffer head – David Elliott
Hornblock Liners – David Elliott
Crank axle components ready for shipping from Unilathe – David Elliott
All the frame stays we have are now permanently bolted in except for the front boiler support which shares bolt holes with the outside motion brackets. Ian Matthews has continued to fit the remaining components for the footplating and splashers with permanent bolting advancing towards the middle of the engine from the back. The front sections will remain temporarily assembled until the cylinders and outside motion brackets are fitted. All photos by David Elliott unless stated.
The raised platform over the cylinders
Ian Matthews sets up a footplate closure panel behind the cylinders
The cab has been finally riveted together
The smokebox was assembled for the Convention
Buffers, chimney and whistle were added – Mandy Grant
The whistle has been made with movable stops for each of the three chambers and a temporary top with adjuster screws. When a suitable opportunity arises, we will use the chime whistle pad on Tornado to tune the whistle to the pre-war tone of C, F and A flat on 250 psi steam. The castings for the steam stand, its valve castings and the blower valve have now been delivered .
The pony truck and Cartazzi axles arrived near the end of September
Unilathe machined the crank axle webs from the forgings made by Somers Forge – Mandy Grant
The leading brake stay (which is the last of the large frame stays) is due for delivery imminently by North View Engineering Solutions in Darlington after which it will be permanently bolted in place.
The superheater header has also been ordered, modifying the Tornado pattern to allow for the two anti-vacuum valves on the P2 header. These pattern modifications are reversible such that in the future, castings for either loco can be produced.
The cab spectacle window frame castings have been cast at the South Lincs Foundry. All images by South Lincs Foundry.
These photos by Bob Hughes show Mick Robinson and Ian Matthews (re)assembling the cab after fitting the beading round the cab edge. In April 1935 the cut-out at the back of the cab side of No. 2001 was reduced to accommodate the fitting of bucket seats – this is the style adopted for No. 2007.
These photos by Bob Hughes show the ingenious process by which square sections of sandwiched metal are turned to the correct ‘almost’ half-round profile before being shaped and fixed to the cab.
Progress continues on many fronts, these images show a lot of effort being put into the frame stays, cab and sundry small parts. All photos by David Elliott.
Cab beads temporarily bolted together – finished (above left), before machining (below right)
Steve Wood machining the cab beading
Cab roof components primed
Cartazzi hornblocks permanently installed
Exhaust injector control valve casting being machined at M Machine
Machined kit of parts for front bufferbeam draw hook spring block
Front drawhook spring block as fabrication
Inside motion bracket ready for machining
Intermediate frame stay ready for machining at North View
Rear frame stay nearing completion of welding at North View
Temporary smokebox saddle stay