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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Qidi X Smart 3 revised fan installation

I have been slowly evolving my ideas for fume filtering when using the Qidi X Smart 3 printer. I should say there is nothing majorly wrong with the fan system as shipped but there always seems to be background residual fumes even when printing PLA. The level of fumes does seem to be dependent on the brand of PLA used.

The rear fan as shipped has no HEPA filtering, it simply vents the chamber into the external air. This fan only comes on during the printing process.

I have previously posted some early ideas for improving this using readily available HEPA filters. Following some discussion with Christian, a fellow X Smart user, we worked together to evolve this further.

The first phase was to upgrade my external fan filter duct design to have both HEPA and a carbon granule filter sections. The carbon granules are sandwiched between two 10 gauge stainless steel meshes and an outer cover holds everything in place.

The result of this looked promising but the axial fan as shipped lacked a decent air flow through the filter stack. This was upgraded to a 6028 centrifugal fan mounted on an adapter plate. The Fusion 360 assembly is shown below.

Below is a simplified cross section view. The internal fan adapter plate flange and the external filter stack are bolted together through the back wall of the printer using the original fan mounting holes and M3 screws and nuts. The fan is mounted on the adapter plate using M4 screws and nuts. There are moulded nut cavities to make assembly easier. The cover plate which holds the two meshes and carbon granules in place uses M3 screws into 3D modelled threads in the corner holes.

As previously posted I had fitted a full size Bento filter to my Qidi ifast. Further discussion with Christian revealed he had fitted the Bento Mini to his X Smart and seemed impressed by the internal air scrubbing action. I looked at the design of the Mini and after some thought changed the carbon cavity filtering walls from a printed grid to using the same 10 gauge stainless steel mesh as used above. The Bento Mini printed well and I was impressed by the thought that had been put into the design. There is a version with a hanging bracket designed for the X Smart 3.

I now had a belt and braces solution – the Bento for internal scrubbing and the HEPA/Carbon filter pod on the rear extract fan. Here are some images of all the components in place and the small terminal strip to interconnect the 24V supply.

The fans used on both assemblies are the same dual bearing 6028 models as detailed in the Bento write up. These are rated at 24V @ 80mA. The axial fan originally fitted was rated at 130mA. I removed the original fan and wired the Bento and the extract fan in parallel and connected this to the original supply feed from the control board via a small terminal strip. The two fans are only commanded ON during printing.

That is my hopefully my last solution but as ever it will depend on actual performance to see whether I notice the difference in air quality. Mission creep is always possible.

As mentioned in a previous post, I designed some booster feet to fit over the existing feet on the printer. These increase the air gap below the printer to allow more air flow. If you print them in TPU they gave extra stability to the printer and reduce resonances.

Here is a link to the STL files and write ups for the simple duct, the fan adapter plate, the two stage filter duct, booster foot and also the modified Bento carbon box and lid with mesh divider walls. Note of late I have been printing with a setting of four perimeters which gives stronger modelled threads.

Thanks again to Christian in Germany who has been a great help in bringing these various mods to fruition.

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3Dconnection SpaceMouse menu changes

It is sometime since I looked at the SpaceMouse programmable menu options for Fusion 360. I only have two programmable buttons on my mine. I don’t think my brain is now capable of retaining any more than two button options. I struggle just remembering the keyboard shortcuts beyond Extrude and Dimension. The left SpaceMouse button I have set to reset the ISO ‘home’ view and the right hand one was set to the ‘change views’ pallet.

I recently upgraded my SpaceMouse driver to 10.8.17 and on checking the Fusion 360 button options I see there is now one for directly triggering the 3D print sub menu. There also seemed to be far more button options which I don’t remember seeing there before. As a result I have now reset my right button to initiate 3D print. The question is will I remember it is there ?

If you are a Fusion 360 user and haven’t got a SpaceMouse you are missing out on a whole new world of Fusion efficiency. It is a joy to use and does not take long to learn to manipulate. You could drop a hint for Christmas …. or you could look on EBay where there are lots for sale. Why people are selling them beats me.

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Myford Super 7 Large Bore depth stop

I recently had to turn a number of items on my lathe and wanted them to be consistent in length. These were long items, too long to reference with my home made Morse Taper depth stop.

In desperation I raided my Sherline CNC Rotary Table hardware kit for my coaxial tailstock clamp. This is based on the Myford tailstock winding handle but without the handle. It clamps the lathe bore to the CNC table for cutting items needing indexing such as clock wheels. Wheel cutting is quite a demanding application. There is no tolerance for slippage or you will get to the last tooth and have only half half the material that you expected left to cut … and the box of shame looms.

The clamp is quite simple – the main body is an expanding collet, this mates with an expansion cone and a centre threaded rod. The cone angle is 5 degrees. There is a knob to tighten the assembly and squeeze the cone into the body to expand its arms. The body has four slots that two pins on the cone engage with to stop rotation.

Having finished the particular job in hand I put away the Sherline clamp and thought it would be useful to make a second version of the clamping collet dedicated as a lathe depth stop. I was rummaging in my metal stock for material to make this when the light bulb came on …. why not 3D print it? When the clamp is used as a depth stop there is no rotational stress. It just acts as a stationary reference stop that sits down the lathe bore.

I copied the dimensions from the Sherline version and input this into Fusion. I printed the body, the cone and a knob (with an M8 embedded nut). The centre rod is M8 studding which passes through the collet body and then screws into the cone and then protrudes onwards to set the depth in the lathe bore. You would think that there needs to be a nut to lock the studding to the cone but the cone cannot rotate as it has the two locating pins. Providing the studding is stopped from rotation while the knob is tightened, the depth should be set solidly. A lathe depth stock is rarely an accurate setting tool but just a repeatable reference. The accuracy of the final cut is catered for by the tool position set and the various lathe DROs.

Printing this was a lot easier than cutting it from metal. No messing setting cutting angles etc. Here is the Fusion pictorial view and cross section.

After using it a couple of times I ended up putting a spring and two M8 washers between the body and the knob to maintain a slight pressure on the cone. The spring keeps the locating pins engaged in the slots on the body as the assembly is pushed in place down the spindle bore.

I also added a ‘top hat’ on the end of the M8 rod (not shown above) to give a larger surface area for the work piece to bear against. This would also stop wobble of the threaded rod as the spindle rotates.

Attached below is a ZIP file with the body, cone, top hat and knob STL files. You will need some M8 studding, an M8 nut and some short M3 stubs for the anti rotation pins in the cone. If you add the spring then two M8 washers will be needed. All the threads are modelled in the STL files but will need cleaning up post printing. I printed in PLA+ and had the prints set to four perimeters. I superglued the two M3 studs in place. The tops of the studs should not protrude beyond the unexpanded body surface otherwise they will bind on the inside surface of the spindle bore.

Things now went a little bit off piste …. I had forgotten that the end of the lathe spindle has a threaded section that mounts the bearing pressure collar. The exposed thread is normally protected with a plain collar. The thread is M35 x 1.5, something very easy to model and print via Fusion 360. Below is the relevant exposed thread with the protector collar removed.

Another light bulb came on (getting to be competition to Blackpool you might think). Why not make things very much simpler?

I modelled a boss to screw onto the M35 thread with a central core to fit down the spindle bore (26mm) and with a central M8 tapped hole. I also printed another through hole M8 knob, a M8 top hat and a new blind M8 knob. I now had a much more simple depth stop.

Here is the Fusion image of the boss. This would have been very difficult to cut as one piece in metal but very simple as a 3D print.

Here is a close up view of the final assembly with the top hat out of shot at the far end of the M8 studding but shown in the second image. The knob on the left grips the end of the studding to allow easy adjustment of the position of the top hat. The inner knob locks the studding in place against the boss. Both knobs have embedded M8 nuts. (Note the bend on studding is a photographic distortion).

Two solutions for a depth stop. The second option is peculiar to the Myford and the first solution more universally adaptable to other lathes. The following download ZIP file contains the STL files for both versions and there is a second ZIP which has the Fusion 360 model for those wanting to tweak. Either version will make a useful addition to the workshop tooling.

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3D Printed Brass Threaded Insert Soldering Iron Stand

A simple solution for holding a soldering iron when inserting brass threaded inserts into 3D printed items

NOTE – This is a revised posting with a modified write up.

When faced with adding threaded holes into 3D models I am faced with three choices.

The easy option is to model the threads in Fusion 360.   This is fine for a ‘fit and forget’ single fastening but for repeated screw insertion and removal the modelled thread will begin to wear.

My preferred solution is to use embedded nuts in the plastic or leave an open hex cavity to fit a nut into after printing.   Some jobs do not have enough space to use the embedded nut technique so brass inserts are the next choice. Brass threaded inserts come in a number of sizes and geometries and are available from Amazon and other sources.  The inserts are melted into the printed medium with a soldering iron or other such heat source.

Having had mixed success with a handheld iron I pondered for a while with Fusion 360 whether I could make a jig to improve insertion repeatability.   This led to some internet searching and finding a couple of solutions.   The first one was via Clough42.   He showed a heavily engineered solution supplied by Naomi Wu.

Naomi’s product was impressive but seemed to be way over the top.   Next up was a site by Valera Perinski.   His site is remarkable and oozes all manner of 3D printed objects, one of which was just what I was looking for – a simple insert punch.

Valera’s design, while simple, looked elegantly functional. I downloaded the STLs.  Valera offers these free of charge with a comment that he would appreciate any contributions. A contribution was duly made. Thank you Valera !

My modified version of Valera’s design is shown above and is described in the attached ZIP file along with the my versions of the 3D print STLs.

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