WSR Locomotive Restoration Project
Restoring Small Prairie 4561
Restoring Small Prairie 4561
WSRA owned Small Prairie 4561 has been out of service since 1998. Restoration is now underway and although more funds will still be needed, the work has started at the WS Restoration works at Williton, managed by Ryan Pope and overseen by the WSR PLC Engineering Director, Bob Meanley
Let's get 4561 Rolling
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Having reduced the thickness of the extension frame plates where needed they were then set up flat on the milling machine table to create a curved profile where the thickness had been changed. This can just be seen above the lower handwheel. The machine spindle below the upper handwheel is fitted with a profiled milling cutter to generate the shape required.
This photograph shows the profile milling cutter in action during the early stages of this machining
Having completed the shaping of the extension frame plates the next step was to drill each plate ready for where the 4561’s front buffer beam and leading pony truck frame stretcher will be fitted.
The 8 holes on the left will be used for the buffer beam angles and the 11 holes centre and right are for the stretcher.
The all new pony truck stretcher is tried in position against one of the extension frame plates fitted to the cylinder block to confirm alignment and dimensions are to drawing. The team has fabricated the stretcher from a central casting bolted into an assembly of steel plates and angles riveted and/or welded together. The frame plate mating faces have been machined to ensure a good fit between the 2 extension frame plates to ensure they are supported the correct distance apart.
This photo. shows the assembly so far from the rear. It also shows the new rear cylinder covers in position on each cylinder
This photo. shows the assembly so far from the rear. It also shows the new rear cylinder covers in position on each cylinder
A lockdown challenge for you:
This photo. is taken from the front through one cylinder and shows the rear cover in position at the back. The central hole is where the piston rod will go. Bearing in mind that the cylinder block assembly is upside down what are the two holes to the left of the piston rod for – one in the back cover, the other in the cylinder wall?
As can be seen a frame extension (orange) is not simply a flat piece of steel plate. It is profiled to fit beneath the cylinder block but in front of that it has to be cut away to clear the leading pony truck wheels before being shaped to fit the front buffer in due course. With the cylinders upside down on the floor the LH extension is seen in position having been aligned and fitted to the block ready for all bolt holes to be reamed ready for the securing bolts to be made.
This view of the front of the extension frame shows how it is not part of a flat plate but has also to be tapered in thickness from the front of the block and joggled inwards to increase clearance for the pony truck wheels. This part of the work was done by our supplier. Apart from not wasting steel the reduction in thickness helps to keep weight distribution under control.
At the back of the cylinder block the frame extension is deeper where it will be bolted to the main frame plate in due course. In the photo. this section is still full thickness but this has to be reduced in order to provide clearance for 4561’s leading sandbox which will be fitted between the frames. This machining has to be finished in such a way as to minimise the possibility of creating any stress raisers that could cause frame cracking under heavy shunting impacts. The old extension frames are shown in the next photo. where it can be seen how this reduction in thickness has to be blended into the main part of the extension frame plate.
The old plates do show evidence of past cracking and bending under shunting impacts and the new plates are being thickened in this area to minimise this possibility in the future.
This photo. shows the back of the other, R.H. frame extension set up on our large milling machine for the thickness to be gradually reduced in a series of steps using a slab mill. Once this has been done down to finished size the plate will be laid down flat on the machine table to be profiled to removed the cut edges and provide a smooth transition from the thinner section to full thickness.
The next job was to make and permanently insert the fitted bolts and nuts for the cylinder joint. The cylinder block was then taken off the ‘coffee table’ and turned over to stand on the floor upside down as seen in the photo. One of the extension frame blanks has been placed where it has to be fitted when after machining
Each end of each cylinder bore 5 studs have to be fitted to reinforce the casting around the steam ports. Three of these studs are shown during manufacture – the one with the plain section to be fitted across a steam port. The ends are finished with square sections used to drive the studs into position when the squares are then cut off.
This photo. shows one cylinder end with the 5 studs in position and the ends dressed off. 3 can just be seen within the steam port and 2 between the cylinder bore and the steam chest below.
A close up view of the steam port showing the studs in position.
This photo shows one new extension frame plate on the milling machine preparatory to being set up for machining to size.
This photo shows the old extension frames which have been retained to act as patterns for the machining. The new plates will be thicker to resist cracking and/or bending when 4561 is next in service.
Having set the cylinders up the first check made was that both castings were sitting flat on the ‘table’. This was done between each casting and the ‘table’ top using a feeler gauge which was 0.002” thick – i.e. two-thousandths of an inch.
These photos show the joint between the cylinders secured with temporary bolts. In the centre is the hand tool made to skim the casting surfaces around each bolt hole to ensure that the fitted bolt heads and nuts when inserted can be tightened evenly onto the casting surfaces.
A further alignment check was made using a straight edge across the cylinder end faces and the edges of the cylinder flanges. The straight edge is an 8 feet long steel bar which has been ground true over its length which is kept solely for this sort of work. This check was also done using feeler gauges to ensure there were no unacceptable gaps compared with the GWR standard tolerances for machined parts.
Having prepared the two cylinder castings they were separated for the joint faces to be cleaned up ready for the application of the jointing compound. The photo shows the area involved.
This photo shows one of the cylinder faces liberally coated with the jointing compound.
The two castings were rejoined on the ‘table’ and the same alignment checks made to confirm all was well before the bolts were tightened. The photo shows the cylinder flanges with bolts in place and evidence that the jointing compound has squeezed all around the joint.
Machining of the surface table to form a level datum for assembling the cylinders has been completed and the resulting block mounted on a welded steel framework. It is now referred to as the ‘coffee table’ although it is considerably more substantial than these normally are!
A quick reminder that we still need more funds to help with this work so please give what you can.Donate now
Two photos that show the new cylinders having been set up on the ‘table’ with temporary nuts and bolts through the central flanges to hold the two castings steady. Once Ryan is satisfied that these are correctly aligned he will make and fit new fitted bolts for these flanges to hold the two cylinders together in service. Note that a small screw jack has been set up under each cylinder casting to take some of the weight to assist making any movements needed.
Work on the horn blocks and stays has now been completed and all have been fitted as can be seen in the photo. of the mainframe. This has enabled adjustment of the frame stands to leave clearance for the fitting of the spring hangers, two of which can be seen in position painted in light green primer.
The new cylinder castings have been brought into the workshop ready for work to start on joining them together. The photo. shows the two castings each of which consists of one cylinder plus half the locomotive’s smokebox saddle. The two halves have to be joined by bolting through the central vertical flanges front and back for which a set of 10 fitted bolts and nuts are to be made. The blanks for these have been cut and initial machining undertaken as seen in second photo.
In order to align the cylinders accurately they will be set up using a known level flat surface table with square sides to act as a datum base. This is shown in the photo. under preparation on the horizontal milling machine where one side is being machined square.
Once the cylinders have been joined the next step is to fit 4561’s new extension frames and front bufferbeam. The two partially prepared extension pieces and the buffer plank have been brought into the workshop in readiness.
During October Ryan and Don visited the South Devon Railway at Buckfastleigh to discuss the possible needs for steel plates when work resumes on 4561’s boiler and firebox. These plates have now been delivered and are seen in Williton yard.
Ryan has made good progress with fitting the horn stays. This photo shows the RL Horn with its stay as fitted. The upright mating faces of the horn block and horn stay are machined at an angle of 2 degrees from the vertical such that when the retaining nuts are tightened these faces become the register for locating the stay. A gap is left between the bottom horizontal face of the horn block and the matching face of the stay. This allows for adjustment when 4561 is in service should a stay show any signs of loosening under the pounding this part of the main frames have to sustain when the locomotive is working.
This photo shows how the upright faces of the stay are machined. The normally vertical spindle of the milling machine has been set over at the 2 degree angle to cut the stay face as it is traversed past the cutter. This is a separate operation for each of the 4 upright faces of the stay.
Here we can see the other 4 horn stays which, having been fitted and marked for each of their particular locations, have been put to one side pending the next operation. So far these stays have been fitted using one stud in each horn block but to complete the installation a second stud is required in each horn block, i.e. a further 12 studs have to be made and fitted.
There has been a lull in progress over the last couple of weeks owing to other priorities in Williton Works taking up Ryan Pope’s time. However volunteers John Ayres and Ray Rolt are making steady progress with screw cutting the horn stay studs and their final fitting. This photo shows the Left Driving horn blocks and studs being fitted – these may be compared with the blank studs previously seen in the update of 25th September.
Now here’s a challenge for you. There are many parts of 4561 still to be refurbished which you could help with. This photo shows some of the plate and pipework awaiting attention. Ryan would like a couple of extra volunteers to work as a team to sort out and clean the parts on hand so that they can be examined to determine what refurbishing work is needed. No particular skills are needed but you could learn as you go along and have the satisfaction of making a contribution to this Association project.
To find out more about helping with the 4561 project contact Ryan Pope at ryan.pope@wsrestoration and if you’re new to volunteering on the West Somerset Railway, please email email@example.com to find out more.
This Photo shows the Right Driving horn with both horn blocks snugly in place and bolted to the frame plate. The domed heads of the 14 fitted bolts, 7 each side, have been given a coat of primer to protect them against corrosion. A square shanked horn stay stud has been fitted to the underside of each horn block for alignment when fitting the horn stay. These stay studs have yet to be finish machined with a screw thread beneath the shank for bolting up the horn stays in due course.
Horn stays are fitted across each pair of horn blocks partly to retain the axle boxes but also to tie the lower edges of the frame plate together. This Photo shows the 6 new horn stays which were cut from thick steel plate prior to being machined with a square hole within each of the recessed sections. Each stay is identified with its position under the horn blocks in the frames and has been fitted over the appropriate stay stud shanks in order to mark out where the recessed sections needed to be located. Each has been rough machined but has yet to be finished to suit the underside of its horn blocks in such a way that limited adjustment can take place in service to compensate for wear and tear in service.
Away from the frames work has been steadily progressing with painting the 5 wheelsets shown here. The 2 smaller, or pony wheels are from the leading and trailing trucks, the others being the main driving wheels. All have been primed with one pony set having been given its first coat of black paint. Unfortunately it has been found that the main driving axle (far right in photo.) has to be replaced as its axle journals have worn below scrap size. Arrangements are to be made for supply and fitting which will have to be done off site. If you would like to contribute to the cost of this work you can do so HERE
Having fitted the bolts to 5 sets of horn blocks so far the final 14 bolts are seen here during manufacture. The two on the left have their shanks rough turned and their screw threads cut while their heads have yet to be domed. The remainder have already been done and now await their shanks being turned to finished sizes with the required tolerance to suit their individual holes in the frames.
Although we have access to the majority of the original drawings we need for the overhaul, many railway drawings were produced of assemblies. Where specific parts are needed, separate detail drawings of the particular items have to be produced either to ensure clarity in the workshop or to pass to our supplier when parts have to be bought in. An example are the two expansion links which have to be replaced for which the drawing shown here has been produced. This shows the finished product but needs to have some machining allowances added when we have finalised the production process to be used and can place an order.
Work has also started on producing the studs that are required to be fitted in the underside of each horn block and used to secure the horn stays when fitted. These horn stays which are the next items to be machined and fitted, straddle the gaps between each pair of horn blocks to retain the axleboxes in the frames. This will become clearer when we have a photo to show you.
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WSR Locomotive Restoration Fund, West Somerset Railway Association, The Railway Station, Bishops Lydeard, TAUNTON, TA4 3BX.