Another Pennsylvania A3 Switcher

[matthew-s]

Looks AMAZING!  Congrats.

I think you are the first person who I’ve followed to make the box. Looks sharp.

And as far as time consumed …. compared to [ahem] some of us, you are flying!!
Enjoy the journey.

[JCvdW]

Thanks Kim and Matthew! It took me close to two years to build the tender, so I guess it will be at least four years or so to build the engine. A box to protect the tender in the mean time is probably not a bad idea.

I made an indirect start on the engine by first making the headlights for the tender and engine. I was wondering how to make the curved aluminium reflector, until I consulted Kim's build. Using pre-calculated X and Z DRO coordinates for a ball nose cutter gave excellent results!



The same technique was used with a 3mm ball nose cutter to round the tops of the top covers, as these will be very visible.

The lenses were made from 1mm thick clear polycarbonate sheet, which I could cut with my CNC router.

Two headlights ready for painting:



I modified the inside of the headlights behind the reflector to make room for a PCB that carries a coin battery, a push button toggle switch and a LED. A small hole on the side of the headlight gives access to the switch with a piece of paperclip wire. No need then to route wires from external batteries and switches.

Here is a 3D model of the layout:



Now I just need to figure out how to layout a PCB. I noticed that Fusion 360 now has an Electronics module...

And then I can start to fill in the bits underneath the engine headlight!

[Kim]

That's pretty clever for the headlights!   Looking forward to seeing how you workout the PCB and all.  Very cool!

Kim

[JCvdW]

Thanks Kim. I hope it works out!

The headlight detail provides a nice sense of realism to the tender:

[JCvdW]

First order of business on the engine is the main frame. Cold rolled bright mild steel flat bar was milled to size for the side frames. The X-axis travel on my RF-45 clone milling machine was just enough to mill the length of the side frames in one go.



The blanks for the two side frames were then bolted together for all subsequent operations.  To avoid tedious hacksawing, the cutouts for the fire grid were drilled out.



Eventually the two side frames, pedestal braces and rear axle boxes were complete!



Due to carelessness, an M2.5 tap broke off on the foot plate. Impossible to remove, the broken tap was drilled out from the opposite side with a 5mm drill. An M6 plug was then made from silver steel (drill rod), screwed into the foot plate with Locktite. I am now wondering if the Locktite will be able to handle the heat of the fire?



A 2mm drill bit was initially used for the M2.5 tapped holes. This was then increased to a 2.1mm drill bit, to reduce the risk of breaking another tap in mild steel. This resulted in much easier tapping!

 I also noted that tapping the drill rod was much easier than tapping the cold rolled bright mild steel. This made me realise that I should pay closer attention to the type of steel alloy I am using in general. Softer steels will extend cutting tool life, and cutting tools are getting more expensive by the day. Kozo suggests using brass all over, but it is prohibitively expensive.

Any suggestions re preferred steel alloys to use, will be appreciated.

The M3 holes in the end of the side frames were drilled and tapped on the lathe by clamping the side bars onto the vertical slide mounted on the cross slide.





As always, it took much longer than anticipated, but I can finally reproduce Kozo's photo of the completed main frame!

[crueby]

The main frame came out great!   

[peatoluser]

yes, the images in the last post are now viewable

[Kim]

Great work on the chassis! That's looking very nice.   

I also used steel for most of my A3 Switcher build.  I used 12L14 when available (round or square rod) and 1018 for rectangular bar.  The 12L14 is much easier to machine, but only seems to come in round and square cross sections.  I'm in the US, so these are numbers used for steel here.  Sorry, I don't know what similar material would be called in South Africa.

Kim

[JCvdW]

Thanks Chris and Kim for the kind feedback.

The equivalent to 12L14 in South Africa, is En1A. This is however very scarce, and when available, mostly in round sections.

So I will have to make do with the tougher/harder mild steels available here. With solid carbide milling cutters getting more and more expensive, I decided that indexable carbide insert cutters may be a better option. To be able to use these cutters on my RF-45 clone mill/drill, I thought it would be a good idea to stiffen it up a bit, by fixing the column to the brick wall behind the mill. The idea  being not to put any side forces on the column, but to simply add a support that clamps to the column and use the mass of the wall for extra rigidity.







Surprisingly, the extra support resulted in a noticeable increase in vibration! I could use my IPhone as a vibration sensor to do some comparative measurements:



ChatGPT suggested adding extra mass to the base of the machine. Easiest was to add two 40kg bags of swimming pool filter sand:

 

The sand had the desired effect, and suddenly using the clamp reduces vibrations even further:



The combination of 80kg sand and the clamp resulted in noticeably less vibration.

The new Iscar cutter with indexable inserts works quite well on mild steel. Time will tell if the inserts work out cheaper than solid carbide cutters.

Carrying on with the foot board for the A3 Switcher, the bending jig used for the stairs on the tender, was modified to allow for the two 90 deg bends in the vertical parts:



The foot board after silver soldering. The front bumper was used as a fixture during silver soldering, with extra washers between the foot board and bumper to prevent the bumper from sucking away too much heat.



The front axle box took quite a while to be carved out of a block of steel, but eventually the axle boxes and bushes are all complete.



And now it is finally time to start machining the driving wheels for the engine! Four years ago, I made some wax patterns of the drivers and had them investment casted, as described here: https://www.modelenginemaker.com/index.php?topic=10915.msg252914#msg252914

[Kim]

Your vibration reduction looks successful! 

As does the foot board!  And your cast drivers look really great!  I didn't go the casting route, but you sure made a nice set of drivers that way! 

Kim

[JCvdW]

Thanks for the comments Kim! I still remember following along as you fabricated your drivers. What a feat, and they came out great! At the time I could not even spell "silver solder" yet.

I closely followed Kozo's instructions to machine the drivers.

After the second chucking:




And after completing all the lathe work:



The drilling jig that was used to accurately drill the crank pin holes came in handy later to hold the pump and lubricator eccentrics to locate and drill the holes for the set screws.






And finally the drivers, axles, eccentrics, crank pins and side rod pins are complete. Could not resist putting them all together for a family shot:



The 11mm axles were turned from 12 mm silver steel. It took a few attempts to hit the correct diameter for a snug fit in the drivers and axle boxes. Using wet and dry sanding paper to remove the last 30 micron turned out to be the answer. This was also the technique used for the crank pins, which were turned from the scrapped axles.

Next up are painting and quartering the drivers. But I first need to test the 2 component automative paint that was used on the tender, to see if it can handle to heat of the engine.

[Kim]

The drivers came out really nicely!  You must be pleased with those! 

Kim

[Roger B]

Your vibration reduction system worked well   

The frames and wheels are looking good