Replacement Whistle on Polly V Steam Engine

Spluttering Banished to be replaced by a Banshee

It had become a standing family joke on steaming outings that my Polly V whistle left a lot to be desired.   Quite often it would do nothing more than a feeble splutter.   The Polly V kit supplied whistle is fitted under the running board on the left hand side of the cab.   The pipe run is long and somewhat tortuous.   I had insulated the pipe to reduce feed loss but this made little difference.   The whistle valve also had a gentle leak and was very stiff to activate.   All in all not a good setup.

A recent article in Engineering In Miniature (EIM) by Richard Wightman (September 2022) went into detail about a whistle and valve combination he had created.   The whistle was fairly conventional but very compact.   The steam control valve was unusual in that he used a standard tyre Schrader valve.   This tweaked my interest and I set about upgrading my Polly V locomotive using this technique. Here are some Fusion 360 images and shots of the new valve and whistle mounted in place on my Polly V.

Here is a blow by blow description of the process as a PDF download.

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Lempor Nozzle added to Poly V 5″ steam locomotive

Lempor Modification to my Poly V

This post was corrupted when converting from Classic Editor to the new Block Editor and has been re-created.

I have made mention of my Poly V 5″ gauge live steam locomotive elsewhere on my blog.   With lockdown having restricted running the engine on the Club track, the loco has sat idle in the workshop.

The locomotive has always been a struggle to maintain steam over a full running day.  It starts off enthusiastically but then begins to struggle.   This is frustrating and also embarrassing when I have to push it round to the steaming bay.

I was sent some notes on Lempor Draughting to change the blast characteristics in the smoke box.  With time on my hands I spent some time on Fusion 360 drawing up a possible Lempor assembly.   This is shown below.   It consists of four nozzles each having a cumulative aperture area equal to the original blast nozzle as fitted in the Poly V.

The assembly was quite tricky. I bought in a new standard nozzle from Poly and then modelled it and the new sub nozzles in Fusion 360 to create the toolpath to mill out on the CNC, The new nozzles were created on the lathe and the mating butt flats machined on them in the mill. It was very fiddly. I wired them together and silver soldered them in place. Here is a picture of the finished assembly before fitting.

Because the new blast is diverging I had to increase the height of the petticoat. I did this experimentally by fitting a small grub screw at the back of the smoke stack to grip the petticoat as I moved it up and down. This resulted in the petticoat being almost at its maximum height. One idea suggested by a club member was to make this adjustment on a cold morning with the smoke box door open so you can see the blast pattern.

My subjective conclusion is that the engine now steams from cold much quicker and it runs very well (providing I keep the fire level high in the firebox….). Whether this is the new blast pipe or the Rosebud grate or the coal or a combination of all three is difficult to judge. It is certainly a different engine and a pleasure to drive.

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