Building a Polly VI
locomotive from a kit
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
Weigh shaft lever
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.
|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.
|This photo shows the
part 31 into which the rocker when disassembled will enter and
then be re-assembled.
|This photo shows the
location of the Rocker on the other side.
|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.
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.
|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.
|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.|
|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.
|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.
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
|The photo does not show
well the cleaning up but about 30 minutes work went into improving
the two expansion links
|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.
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.
Sorry about the out of focus picture but the Trunnion Brackets have not been fitted to the expansion links.
|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.|
|The Suspension link is
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
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.
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!
|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.
|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 shaft.as 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
for Kit 3 Click
for Kit 5