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michael mott

Live steam Bagnall loco and other railway stuff

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1 hour ago, michael mott said:

Thank you for your explanation Andy I did not know that background, can you recommend any particular reading on the subject?

 

Michael

Unfortunately I have yet to stumble upon a definitive work on the subject. Most of what I’ve learned comes from various tidbits from a diverse assortment of sources, and a deep and undivided fascination with all things steam. Short of being able to dig up an old railway shop manual on the subject. Maybe if I was a bit more literarily inclined.....

 

Andy

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The shaft to hold the arms (weight Shaft) has been fitted the brackets were a bit fiddly to make. they were machined up from a couple of hard brass blanks of 7/8 diam brass rod.

 

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The end of the shaft that is bent up will form the bottom connecting point to the reversing lever that is attached to the side of the boiler so it is unfinished until the rest of the linkage is fitted. The lifting arms will come next and be pinned to the weight shaft. hence the reason for the split bracket on the one side. Once the arms are attached the shaft will not be able to be slipped out of the brackets without removing the top of the bracket on the left side.

 

Michael

 

 

 

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Another update the weight-shaft has now been finished and the arms are glued to the shaft ready to be pinned.

The arms were machined from some stress free 1144 steel bar stock.

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then a jig made to hold them in the correct relationship to each other and glued with some CA glue in order to pin them with some taper pins.

 

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The sequence shows the relationship to the rest of the valve train. next the lifting arms and work out how the gett all these bits fitted together with my large fingers.

 

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Michael 

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Happy new year to everyone.  Things are getting to be quite challenging at this stage the more parts that get made and that need to interact with other parts is becoming difficult to "get by" with small inaccuracies. The eccentric rods there are 4 of them have to be narrow enough to fit between the hanging links from the weight shaft but be able to have connecting pins held in place (in full size practice by taper pins) the previous ones I made were too wide and the space in which the straight link was pinned was too wide as well.

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These are the radius rod hangers they are OK

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disassembly (again)

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So I though I would make them over with some steel I did one as a test (didn't work out too well) so another test using some hard brass (a second failure) Then decided to rethink the whole thing and went back to the drawing board (Auto-cad) and made some adjustments to the tolerances and dimensions of the arms keeping the lengths the same as these are critical for the valve timing. and started over on the arms. They are not "perfect' but will work.

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One of the areas that I needed to change the most was the slot into which the straight link fitted the steel of the link is .075" thick and the original slot was cut with an end mill that I had that was .090" I thought this would be OK but it wasn't A friend who has built some larger model steam engines told me that you need to ensure that there is a bit of "give" in the gaps and linkages in order that things do not bind because the axles are sprung and move in a couple of planes (basically in a twisting motion when moving over irregularities on the track) I found out that there is also a limit to how much "slop" one need to build in.

 

I used a slotting saw the second time around and made the fit much closer. I also simplified the shape a little from the Actual shape of the full size loco, in order to simplify the manufacture of the part. I used my old grinding vice that I made as an apprentice as it allowed me to hod the part more easily than the regular milling vice.

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After the slots were cut I used some filing buttons to shape the ends.

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The split large ends of the eccentric rods were thinned down a little on a temporary faceplate jig. I used the same plate to trim up the straight link hangers that were made from some free machining hex steel.

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I am going to have to make a special jig to assemble the links to the radius rods and the eccentrics before putting them as sub assemblies into the frames. I take my hat off to the watchmakers in the crowd.  

 

Michael   

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Watching a craftsman at work in any area is always such a pleasure! I can’t imagine the amount of satisfaction it brings you. Especially when you perfect areas you weren’t satisfied with. You must spend as much or more time planning and building in your head than with your hands and those ”a ha” moments must feel great.

 

Keep it coming.

 

Kurt

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