4mm A Broad Gauge Buffalo

adrian

Flying Squad
Forgot to say - when using the silver solder paste even if it contains flux I would still apply a layer of easy-flow flux over the top of the silver-solder paste.
 

Dave Holt

Western Thunderer
Thanks for the advice, Adrian.
I used silver solder paste but without the additional flux. I think the flux included in the paste is probably OK with non-ferrous metals but not for steel.
Dave.
 

Ian@StEnochs

Western Thunderer
Dave,

All the crank axles I have made have been soft soldered with 188 solder and bakers fluid flux. Albeit 7mm scale and all steel parts. So far none have come apart in service.

I chose to soft solder because of the difficulty in cleaning up after silver soldering, Acid pickle is a bit difficult to source. However I have obtained a safer pickling solution, ‘Picklean’ from Cooksongold which comes as crystals to dissolve in water. It works ok on my test piece so I am going to risk it on a crank axle.

Last night I made the crank checks for two axles and over the weekend I hope to make the remaining components and perhaps assemble them. This time I am going to use silver solder paste and miss out the wire reinforcing.

Ian.
 

Brian McKenzie

Western Thunderer
I chose to soft solder because of the difficulty in cleaning up after silver soldering, Acid pickle is a bit difficult to source.
Ian.

A solution of Citric acid, mixed from powder bought at the supermarket works well for me - overcoming past difficulties. Be aware that it can also dissolve tiny steel components if left soaking overnight as I once did.
Not sure if it is really necessary, but I also clean silver solder rods before use, by running it through wet 'n dry paper held in the fingers.

-Brian
 

garethashenden

Western Thunderer
Back to the crank axle. I have four shiny new eccentrics and I have a question about their fitment. The instructions say that they fit together in pairs, but I don't think that's correct. I have a photo I took of the Dean Goods in Swindon, then the two ways of positioning the eccentrics. My main concern is if I put it together as it should be, will it work correctly at the other end?

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garethashenden

Western Thunderer
After a bit more research, it will work. I just need to be careful that the eccentric sheaths can pivot on the expansion links. If there is a little play here and between the expansion link and the valve stem everything can move as it should. The kit design allows for the eccentric sheaths and expansion links to be firmly riveted together. If that is done the expansion link will move in and out, rather than wiggle around.
 

garethashenden

Western Thunderer
I have constructed a new crank axle. It’s much sturdier and the mechanism runs well. I also replaced the gearbox. 54:1 is now 120:1 with the expected improvement in slow speed performance.
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I have reworked the brakes in a way that allows them to be installed or removed as a unit, an idea I borrowed from Will L. on the Scalefour forum.
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The handrails have been added, although not photographed. The final thing for this update, that I’m feeling rather pleased with, is the injector. I haven’t been able to find anything like it commercially, so I had to fabricate it. The first attempt was about 50% too big. This one looks about right though. I’m using some London Road castings for the bit that goes into the boiler up front. Just need to make the other side now…
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