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.

Links to similar or related post are listed below : –

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.

Links to similar or related post are listed below : –

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.

Similar or related subjects : –

Verified by ExactMetrics