Simple Water Level Sensor for Live Steam Locos

While coming to the end of a running session of my 5″ loco at the club raised level track I suddenly realised the axle pump was not making its normal rattling noise. Water level was likely very low and there appeared very little in the glass sight gauge. My state of panic endured until I reached the filler hose.

On returning home to the workshop I resolved to try to make this alarm situation more readily visible. The common solution is to add a second sight glass feeding from the water tank and visible in the ‘cab’. My engine did not have a great deal of room for this addition.

Sacrilegiously I began to consider an electronic solution which probably wouldn’t make me popular with the mechanical diehards but the challenge appealed.

The electronic solution turned out to be a multi faceted activity. An initial bird’s nest lash up was followed by a PCB designed in Fusion 360 Electrical. The PCB was milled on my vacuum table fitted to the Tormach 440 with the Gerber and Epsilon files converted to GCode using FlatCAM. Having completed the PCB board this led to a customised enclosure designed in Fusion 360 and 3D printed in the Qidi X Smart 3.

The circuit is a NPN transistor that is turned on by water conduction between two sensor probes which in turn drives a second NPN to illuminate a flashing LED. The module is powered by a CR2025 button cell.

The enclosure consists of three parts, the base, a snap on lid and a round boss that matches the diameter of the water filling hole on the engine side tank. The two water sensing probes are made from 16 swg wire protruding from the boss.

The round boss is held in place with a M2.5 countersink screw and could be dimensioned to suit different sized filler holes. Having it as a separately printed item is also useful in that it allows the enclosure base to be 3D printed without support.

Here is are some views of the completed assembly.

It seems to work quite well and is surprising sensitive down to the last few millimetres of the probe rods. Time will tell.

If you want more details then please send me a message.

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French Model Steam Engine Gathering

5″ Gauge Activity at Montcuq

We were very lucky to be invited to this event near Cahors. A significant number of the engines were Polly designs and the owner of the track has had a long standing relationship with Polly Model Engineering.

The track has two loops and a very significant incline which tested not just the engines but also the drivers. One very encouraging aspect of the weekend was the number of young people, both male and female who were enjoying driving the track.

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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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Bad day steaming with my 5″ Polly V live steam locomotive

Last Sunday was a members steaming day at the model club.   I told all the family I would be there and to bring the grandchildren along for a ride.

I arrived early with a view to getting steam up and be ready to go … in theory.

First problem was that the connecting rods had stopped in a position that was blocking fitting the fire tray holding pin.  This immediately got worse in that the cylinders had seized since my last run.  The more experienced members told me not to worry and if I could move the wheels enough then fit the fire tray and get things warmed up.   After some rocking I managed this slight movement …. but forgot I hadn’t filled the boiler and the fire was burning very brightly.   Mad panic to get some water in quickly.

Steam pressure up to 90psi but no joy on the cylinders.   Gentle tapping on the con rods lead to heavy tapping on the con rods and lots of slide dragging back and forth on the steaming bay.   Still no joy.  Cylinders locked.

Now running out of water in the boiler.   Grandchildren arrived.  “Why can’t we have a ride grandddad ?”.   Grabbed the handpump leaver and rapidly pumped away to get water into the boiler …. too rapidly in fact and broke my hand pump leaver.   Still had a few PSI of pressure and thankfully the injector kicked in … for a short while until the pressure dropped.

How bad can this get ?

Some slight movement on the cylinders now.   Grabbed some blocks of wood and got the engine airborne so the axle pump could be used … if I could just get the wheels to fully turn.   More tapping/thrashing at the con rods and suddenly the wheels jumped into motion.   Phew.   Water now flowing into the boiler, fire good, pressure good.   Get out on the track quick and keep the grandchildren quiet.

Back home in the workshop  I made a new hand pump handle and fitted new oil port plugs on the top of each cylinder each with a M3 feed hole.   This means I can syringe oil into the valve and cylinders a lot more easily after future steamings.

It is a hobby after all but this was one of the most stressful steamings I have ever experienced – all because I was in a rush last time out and did not do the end of day drain down processes correctly because it was tipping down with rain.  Lesson learned.  Thankfully no long term damage to the cylinders.

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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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