A Cracker locomotive

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ozzie46:

Arnold, that's a cracking looking little cracker there. :D :D :D :D

Very nice

Ron

saw:
Good work :thumbup:

DaveH:
Arnold,

Quite a little violent finger engine, like the 'free wheel'. :thumbup: :thumbup: :thumbup:

Cracker is coming along very good, the dome looks good. :thumbup: :clap:
:beer:

DaveH

arnoldb:
Ron, Benni, Dave - thanks Gents :beer:

:D Sometimes a work week that's gone badly makes for a great weekend... I had some crises thrown at me during the week at the office, with a result that I could not get around to do the prep that was needed for this weekend's work, so I got shop time :ddb:

First order of the day was to start on the safety valve. I turned a bit of 8mm hex brass down to 6mm and threaded it M6x0.5 to fit the treads in the boiler bushes. I still have not been able to find a decent M6x0.5 die nut, so I just used the "thread cleaning" nut I have supported by one of my tailstock die holders to thread the workpiece:

Parted off to a suitable length, I chucked it up in reverse, and started drilling... First 2mm right through, then 5.5mm to a suitable depth for threading M6x0.5 - which was duly threaded. Then I used a 5mm end mill to flatten out the bottom of the hole:

A bit more drilling, this time 3mm diameter and about 3mm below the bottom of the flat section. This is a lot of faffing around - I'm out of 3mm stainless steel balls to use in the valve, so now it's on to a pop-style with O-ring. That'll teach me to run out of balls :lol: The (nearly) finished safety valve body on the boiler, with the 5mm flat barely visible around the 3mm centre hole:

Next the adjusting nut; a bit of brass round turned down to 6mm, and a 1mm hole poked through the centre:

Then threaded M6x0.5 on the outside and parted part-way, and off to the rotary table on the mill to add some 1.5mm slots around the outside; these will allow steam past the adjusting nut:

After some more lathe work to turn the valve itself I had all the bits together for the safety valve; the O ring from a kit, the "brass" pin (actually coated soft steel) from a packet of Cheap 'n Cheerful Chinese design-your-own jewellery stuff, and the spring from a cheap disposable lighter:

A stainless or bronze spring would be better, but I couldn't find any; older style tire valves had some nice springs, but the new ones are not suitable... Fortunately, if the spring corrodes from steam vapour, it will reduce the safety valve's operating pressure.

Then I soldered the pin to the valve and assembled the lot after trimming a section of spring off. A quick check with the compressor showed that the valve works nicely, which I hadn't expected on my first try with this type of valve; it was easy to adjust to open at 35 psi and repeatedly re-sealed properly without leaking. Assembled it looks like this; it still needs final setting while on steam, but the adjustment range is good so I added a little loop to the top of the valve spindle to make it easier to test manually that it's not sticking:

The hex valve body was definitely not pleasing on the eye, so I made up a quick mandrel and turned down the body a bit:

On to a bit of planning... It was high time I sorted out what I wanted to do about the smokestack and cab. This engine will be used quite often to "play" with and show off, and while it is roughly based on a real model, it's more of a fun toy than a model, and it should look the part. I scrounged around a bit and found the extra pipe reducer I bought "in case" when I built the burner for the Little Blazer; it looks quite pleasing as a smoke stack... Some recycled ciggy packs to mock up a cab - I'm not quite happy with that yet, but to get a rough idea. I'll only finish the design of the cab once I finished the rest and have the loco running, as I don't want the gas tank and regulator difficult to get to; this engine must be easy to run:

At least, having decided on the smokestack, I set up the boring head in the mill and faced off the end of the copper fitting to conform to the boiler outside diameter - clamped down using a tightish-fitting bit of bar in the bore to prevent the milling vice from flattening it:

While I had the boring head set up and to the correct dimension, I messed around with some hardwood - that will become the boiler mountings:

Utter laziness - milling down wood on the mill :doh: :lol: :lol: :lol: :

How about a reprieve then? - I used my mitre saw to saw off the needed bits:

Ended up with these - there's a bit of wood that splintered out on the one, and I hadn't noticed until too late :doh: :

With the stack soldered on (I used electronics solder for that), things are starting to look up:

Time to start messing (albeit very carefully and safely!) with the gas supply system... I haven't been able to find jets as specified locally, and the only gas filler valves I can find comes from these cheap pencil torches:

If only the body where the filler screws into were brass! - Alas, it is aluminium and useless. The filler uses a thread for which I don't have taps - measured across the thread it's 5.4mm. The pitch appears to be 0.5mm which is fine. This leads me to believe this is M5.5x0.5 ??? - so I'll have to make a tap. I'll play around with the torch first; maybe it's jet will work as well, which will save me the bother of having to make my own or wait for months for delivery from overseas.

:beer:, Arnold

saw:
Nice I just love this project :drool:

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