Building a Polly VI locomotive from a kit

Kit 4

Kit 1 Kit 2 Kit 3 Kit 4 Kit 5 Kit 6

Kit 7 Kit 8 Kit 9 Kit 10 Kit 11 Kit 12

6th December 2014

Kit 4 has the following parts

2 Suspension links
4 Buffer Heads
4 Buffer Springs
4 Buffer Studs
2 Trunion Brackets
2 Expansion Links
2 Rockers  (complete)
2 Die Block Pins
2 Die Blocks
2 Suspension Link Bolts
2 Eccentric Rods
4 Expansion link pins
1 Weight shaft pin
Weigh shaft arm and shaft
1 small collar
Large collar
Weigh shaft lever
kit 4
23rd December 2014

The instructions seem a little complex but when one refers to the supplied drawings it makes more sense.

The parts in question are components 53, 54, 31 and 55.

The diagram indicates that the parts 53, 54, and 55 form the Complete Rocker Assembly.

The part 53 has instead of a grub screw to hole it on has a split part which is held tight by a clamping Allen Bolt.

Similarly with part  55 it too has a slit and clamping bolt.

kit 4 plan1
The photo shows the Rocker Assembly .

Part 54 is the bar at the centre which is very nicely made with square ends so that it is locked into a position.

rocket assembly
This photo shows the part 31 into which the rocker when disassembled will enter and then be re-assembled.
kit 4 plan 2
This photo shows the location of the Rocker  on the other side.
plan kit 4 3
This photo shows the right hand rocker in place and I hope you can clearly see the split in the end of the part and the Allen bolt which pinches it together onto the square end of the shaft.

The left hand one is also now in place.

10th April 2017
Whilst preparing the loco for it annual steam test it became apparent, whilst running on air, that the was looseness in the rocker and looking closely the nut Part 32 had come loose allowing the parts to not be aligned and in fact fouled the connecting rod and brought the engine to a stop. It was apparent that movement had occurred as the squared end on one side was nearly half way through the part.

How had this come loose. Well reading through the web site I made no mention of using a nut retainer which should stop such movement.

Some brake cleaner and Loctite  Nut
retainer medium strength was purchased. The clean up needed the parts to be completely removed so the two Allen bolts were released and all the parts taken off the loco and thoroughly cleaned up. The retainer was applied to the thread and the nut tightened up ensuring that the "OIL" hole was uppermost.

The remaining parts were then replaced and also tightened up.

A check round all the nuts and bolts on the valve gear was made and as appropriate tightened up.

The loco was given a quick run on Air and then left so that the Retainer could fully develop its strength.

rocker in position
24th December 2014

Attention is now turned to the valve gear.

This is formed by 4 eccentrics  strap parts 63 operating on Expansion links parts 64.

It is important to note the the upper eccentric arm goes to the outside nearest  the frames on each side.
valve plan
The straps must be checked to ensure that when placed together that they sit nicely one on the other.

With mine I found one set did that perfectly but with the other a very slight adjustment was needed by putting the strap in my vice and then bending very gently. The error to adjust out was about 2 mm. but now both sets sit fine and are ready to be checked for burrs and then installed.

the eccentric straps
Whilst the eccentrics should have been positioned and had their set screws installed it was not done until today!

Here the eccentric straps have been fitted and note that the outside one it above the inside one and that the two of them are well in line as they need to be. eccentrics
The photo shows the second set of eccentric straps in place and oiled up.

The wheels are certainly more difficult to turn round now but then I am not using the force that the pistons will use !

The photo shows an extract from the plans with the EXPANSION LINKS parts 64 with my highlighting so that I could easily identify the parts being discussed in the build notes.
vale gear
Those supplied with my POLLY VI kit 4 did not have the Trunnion Brackets attached but they were well packed in oil / grease in a plastic pouch.

The build instructions indicate that the slot must be smoothed up obviously to make the Die Blocks operate in them easily.

The die blocks have to be filed to fit. it says "The long side concave and the other long side Convex." I am glad I have a digital micrometer to be able to identify the long side as they seem nearly identical.

expansion links
26th December 2014

The inner surfaces of the Expansion link needed quite a bit if wet and dry to bring the surfaces to a smooth state following production as was suggested in the build instructions.

The photo shows the unprepared surface

valve expansion link
The photo does not show well the cleaning up but about 30 minutes work went into improving the two expansion links
vavle expansion link
The die block has to be formed from a rectangular piece and the long sides have to be formed to a snug fit and a good sliding fit in the slot.

This took about a hour of careful filing and the use of wet and dry.

Measurement indicated that about 0.5mm off the width, so I started by bringing the top curve to shape and then filed the bottom flat so that the ends would just fit in the slot and then made the underside curve and finally adjusted both top and bottom to a nice sliding fit.

I must say that this part took a lot of time but well worth the effort as a sliding fit and not a slack fit is required.

I did find that after washing my hands that I had worn away some of the skin on my thumb something I will avoid when doing the second die.
expansion link and die
27th December 2014

Making the second die block was much easier. I first started by placing the blank on the top of the expansion link aligning the centre so the the end edges protruded about the top and then use the link shape as a guide to file.

Then the bottom was filed until the end just went onto the slot and then final adjustment was made by first filing away the centre of the bottom curve using emery cloth on curves file.

Very often checks were made to make sure where the removal of material was required.

It was all done satisfactorily in about 30 minutes.
28th  December 2014

Sorry about the out of focus picture but the Trunnion Brackets have not been fitted to the expansion links.
expansion link
The Suspension Links have now been fitted to the expansion link with their Trunnion Brackets. The tape is there to make sure the Die blocks remain in place until fitted. links and fittings
The Suspension link is identified.

On the left hand side to the loco the two arms parts 69 had too small an opening by 0.3 mm so a few swift file passes and they were brought to size.

Now both of the assemblies have been put in place but that on the right is very stiff but I hope that running on air in due course will easy the situation.

All the split pins have been inserted but now I have to locate a cutter to shorten then to about 1/4".

The tape is still there to ensure the die blocks stay in place until fitting is completed.

valve gear
29th December 2014

Now is the time to fix into place the die blocks. The piece of sheet steel that was mentioned in the build instructions was missing but soon substituted by a piece from the workshop. The Screw holding the Die Block in the expansion link was fully tightened up.

NB I have not yet cut shorter the split pins!

die block fixing
The build instruction speak of small screws set aside  from part 55 but in my parts 55 the screws were substituted for a saw cut and clamping bolt which has remained in place.

A small amount of oil was applied and a check was made that everything moved as I should.

both die blocks in place
The diagram shows the Weighshaft in parts where as in the kit it comes assembled. Also the grub screws which are indicated as holding the part 28 and 26 in place are now taper pins.

So part 28 does not need to be slid onto the it is there already with its taper pin in place.

I do need to remove part 26 so that the 1/8" collar can be slid on and up to the arm part 28.

With that done the Weighshaft can now be pushed through the Right Hand side Weighshaft Bearing and the large Weighshaft collar part 27 slid on.

Then part 26 needs to be slide on and fixed.
The Weighshaft is now installed and as expected is rather stiff to operate but I am sure that is will all easy up when the running in starts.

So other than fitting the buffers which I am not ready to do as the loco is not yet on its wheels KIT 4 is no completed
the valve assembly completed

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