K3s Progress 2012 to 2013
As promised in the last instalment, the next part of the locos is the pony truck. Gresley was very fond of swing links for side control of bogies and pony trucks and
the A1 Pacifics and all the pony truck engines were so fitted. The riding of the Pacifics was not particularly good with the single bolster design used and they tended
to be over sensitive to track irregularities and all the engines ultimately had the bogies modified to spring side control. The pony truck engines must have been
considered satisfactory and this may have been due to the adoption of a double bolster design, but in the mid to late 1940s some derailments of V2s occurred
which were blamed on the swing link arrangement, and the pony trucks on this class were changed to the spring controlled type already in use on post Gresley 2-6-0s
and 2-6-4Ts. That poor maintenance of both locomotives and track at the time was the real cause of the problem was clear and none of the remaining 450 or so swing
link engines was modified, testimony to the design, which remained in service to the end of steam.
The side plate of a pony truck complete with horns and spring hanger brackets.
The horns are almost identical to those fitted to the tenders, the fabrication of which was shown earlier.
The only modification is the cut out for the spring hanger brackets in the top corners.
The fabricated main stretcher incorporating the bosses for the top bolster swing link pins.
Views of a truck frame during erection with the pressed steel stretchers and back plate riveted and bolted in place, and the radial arms fitted.
A bogie axlebox on a full size locomotive, a view from the inspection pit. This is typical of LNER type carrying wheel axleboxes and shows the oil seal around the axle,
the oil feeder box and the generally filthy state these components attain in service and on which the maintenance people have to work.
A detail of the bearing coil spring.
In preservation these circular section springs have replaced the 'Timmis' section springs, a cruciform section, originally used, and now unavailable.
The top of the box with the spring bearing bridge beams above.
The locomotive number 60007 can be seen stamped in the face of the box with LT above for Left Trailing.
These are the miniature bridge pieces for the K3 and H4
A closer view
The wheel sets and axleboxes were made much as shown earlier for the coupled wheels and these photos show the frames primed and with the wheel sets fitted
Once the spring hangers, shock absorbers and temporary coil springs were fitted a visit to Exhibition Park was required to check clearances on the
tightest curves of the railway. No problems there, even with the unfinished coupled wheel profiles.
The bolsters were castings on the full size locos but I needed to make the top bolsters from the solid and the photo shows the initial stages
after drilling the main holes and hacksawing the blanks roughly to shape. Pins through the bearing holes provide clamping and references for milling
The two top bolsters after profiling
A bolster in the four jaw chuck with necessary packing for drilling the centre pin hole
A bolster with the brass rubbing plates fitted
Bolster and bearing pad before silver soldering.
The stepped pin accurately locates the components and provides a reference for final machining
Bolster during silver soldering
Back in the lathe for finish machining after drilling through the temporary location pin
The bottom bolster is a fabrication and after drilling the main bearing holes the four side plates were mounted in the machine vice for profiling
Stages in profiling, final finishing by hand
The bottom bolsters after fabrication.
The outer plates are separated by a curved plate and angles and plates attached to the sides form the transverse rubbing plates.
The centre bearer is a close fit on the top bolster.
The top and bottom bolsters brought together
The bottom bolster set up for machining the side bearers that need to be a close running fit in the pony truck main frame stretcher
A view from above the main frame showing the top bolster in position where it slides transversely across the pony truck stretcher.
The bolsters placed in the pony truck frame showing their location in the main stretcher
The loco and the pony truck are connected by pairs of short links that carry the vertical load and by being angled generate the transverse forces
that steer the loco through curves.
After machining a suitable piece of MS plate to the desired thickness holes were drilled for the pins and the corner radii.
This plate is for 12 links and there was another for the remaining four
The plates were cut up into the sixteen individual links
Milling the link sides in batches of four using the pin holes as a register
Four links ready to have their ends rounded
The ends being rounded by progressively machining flats around the circumference
Four complete links
All the bolster components for the two locos. The long pins have an oilway drilled through the centre so that oil can be fed from boxes on the footplate.
The other link bearings just have oil holes as they are more accessible
Views of the completed pony truck with the working springs and shock absorbers in place and the addition of the life guards and dust shields
The frames with the pony truck in place
My original intention was to fit steel tyres to the driving and coupled wheels, but when I had machined the wheels I didn't make the final step to machine down the wheel centres
to take the tyres as it looked like a lot of work to make the tyres and at the time I deferred the decision. Tony Wall who made the wheels for TSMEE's 7 1/4" passenger cars
persuaded me to put on the steel tyres, so I drew them up in CAD and he made them using his CNC machinery. A tyre is seen on the bench marked up for location and internal diameter whilst in front is an edge view showing the profile to GL5MLA standards.
The wheel sets being machined between centres, each to match a specific tyre plus about 7 thousands of an inch for the shrink fit - a thou per inch plus one for luck.
Note the wheel nearest the lathe headstock being machined to avoid chatter caused by wind up in the axle which occurs if the other wheel is machined
The wheel faces also needed reducing and this was done with fine cuts to avoid chatter
A tyre ready for fitting
Checking the internal diameter
A tyre on the hearth ready to be heated. A gap is left between the fire bricks for the crankpin
The tyre being gently heated with a gas torch
The expansion of the tyre is gauged using an internal micrometer set to the wheel diameter plus 10 thou, the temperature colour is just around pale blue.
When the gauge clears the inside of the tyre the wheel set is quickly lowered in and left to cool
The process is repeated for the other side
A crank axle laid on the horn gap with tyre in place
Before the wheelsets where returned to the frames, I remembered there was a little job that needed doing.
The leaf springs are suspended under the axlebox by a clevis and the pin needs to be retained somehow.
Often this is done with split pins through an extension to the pin or a transverse pin through the middle.
There is little space for either of these methods and access is restricted so LNER engines had an open ended metal box dropped over the clevis to prevent the pin from escaping.
These photographs show the process of bending up the box from strip steel, silver soldering the join and machining to fit the location.
A spring with the box in place
61962 on the TSMEE stand at Harrogate 2013 alongside Ian Spencer's hansom V2
1009 on the GL5MLA stand the same weekend.