Discussion in 'Steam Traction' started by Flying Phil, Dec 24, 2018.
Great news! The bogie wheel looks very good.....but which one is my spoke?
Phil, just like you to put a spoke in the wheel = thank you for your contribution....!
The Institute of Engineering Designers had a great article about the 'New Build' Lyn in the July/August edition.
It prompted me to write to the editor to comment about the smokebox design and how things in the modern world required attention to detail that did not matter in the 1890's. In the September/October edition my letter was re-produced - getting a bit more advertising for the Project.
The design for a welded Tender Tank has escaped. I hear the 'Rivet Counters' groan - "Its got to have rivets - lots of them".
Well, yes, the rivets ARE an important feature - about 800 of them - all expensive.
Holes need drilling - 2 or even 3 per rivet, all lining up perfectly.... And then you have to heat the rivet up, pass to the person inside the tank, who pushes it through the hole, and then suffers the percussive effects (yes even wearing ear defenders) of the riveting hammer forming the head on the outside of the tank. Its dangerous, requires skill, and its expensive - what company wants to build such a tank? I hasten to add that a quote was received - about twice the expected cost!!!
So we have designed one stuck together with electric glue and fitted with pseudo rivet heads - these being cunningly attached by studs welded in place, and the semi spherical dummy heads screwed on. Still an expensive exercise in creating something that looks the part.
And I will say to the 'Rivet Counters' - the pattern for the placement of these 'Dummies' is an approximation - realise that Gorton, Sharp Stewart, Kitson & Co, Neilson & Co, Nasmyth-Wilson, Vulcan Foundry and several others who produced these ML&SR/GCR Tenders - ALL had differing rivet locations and sizes - I make no claim as to the exact accuracy, but the drawing I have worked to is a Gorton Works .
Thanks for the update Legrandanglais
Looking forward to seeing the tank built. I suspect it would have cost as much to weld the dummy heads in place or to studs, rather than screwing onto welded studs?
Are there any tenders of that sort that are flush-rivetted? the sheer cost and number of operations that are added to the process for no engineering reason would seem to me something I would do a lot to avoid.
If you took that attitude to it’s logical conclusion, you wouldn’t be building a new example of a 120 year old piece of engineering.
Indeed, it sounds to me like an excellent compromise to me; you retain the character of the original while employing a cheaper and less laborious construction technique.
If you take it it's logical conclusion the other way, you wouldn't be able to build it - "steel? we'll have none of that new-fangled nonsense, wrought iron all the way..."
But that is hence the question about there being any flush-rivetted tenders of that sort, if there is a historical fig-leaf, I'd advise grabbing it with both hands
I think this one is one I particularly question as you are adding hundreds of extra operations that are at best purely cosmetic, at worst potential failure points (corrosion traps and potential heat stresses)
Here is the proposed method for Dummy rivets.
don't forget the threadlock!
(Imagine if the vibration was at just the wrong frequency and vibrated all of one side loose... then you run back and all the ones on the other side undo... )
Not what I'd do, but it looks a sensible way of doing it. What will you fix them to? the inner or the outer face?
And I don't think M4 is very historically appropriate - some piece of imperial arcana like 14/64ths Whitworth would surely be right...
Looking forward to seeing this project flourish.
Yes, Epoxy to attach the Head to the tank side - thread just holds it in place whilst the epoxy gois off. A quick clean off, followed by 2 coats of hi build primer, several coats of undercoat - then the debate as to the colour of the 3 top coats, lining, then a couple of coats of varnish - that shouls all stick them in place
Epoxy has to hold them for the duration of the livery debate...?
but it only lasts about 20 years...
Thx. Presumably on the original the rivets secured angle irons for the coal plate, surge plates, front bulkhead etc. Are these still fitted with angles in your design or are the plates butt welded? What thickness is the tender platework?
Thanks Barry - I assume the studs are electrically butt welded to the flat steel plate? I would like to see how the rivet heads are made. I again assume in some sort of capstan lathe which centres, drills and taps then the parting off gives most of the hemisphere?
Its CNC today (Computer Numerical Control), with a bar feeder, you write your program, load up and set the tools on the carousel, put in the number you want and leave it to get on with the job. If you have a real flash machine with laser scanning and robotic control it will also replace tips on the tools when they are worn out and adjust the tools to ensure all parts are made within spec, not necessary on something as mundane as a dummy rivet head.
Thanks Avonside....CNC was just coming in when I did my engineering training (1970's!). I was interested in how the parting off was achieved to give that profile, but I expect it is done in several passes using the same tipped tool but cutting in a 2 axis manner?
You are spot on Phil. My own CNC experience was with a machine not much further on than a Capstan, in terms of processes. So yes the parting or grooving tool would be used to create the dome and just a thin pip left to part off. Removal of remains of the pip would be a secondary op to us, done in the old fashioned way with a manual machine or left to the customer to finish off with an off hand grinder and soft pad. I dare say with much cleverer machining centres, it could be done in one op. Creating the shape would be a series of steps getting deeper on each offset and then a finishing cut to the profile using the corner of the tip. Tricky bit is calculating how small a diameter you can make the pip without the part breaking off before parting.
Indeed there were angle irons to attach the baffle plates to the sides, now the ends of the baffles are butt welded to the side plates. Only the main longitudinal waist height angle remains to stiffen the side - and that is welded in place.
On the MS&LR drawing, the side plates are 9/32" (7.14375mm) thick - we are proposing to use 8mm thick.
The main concern is that there may be weld derived 'witness pull' that could mar the superb polished finish!
We will see what the vendor has to say - the drawing is a guide for them to work with...unfortunately price is a big constraint as we found with the riveted version. If it lasts 10 years it won't be my problem to sort it......
I like the comment about vibration - its a while since I experienced 'Roaring Rails'. Strangely, I worked for a company that made and installed vibration monitoring instrumentation so I really like the idea of one side being affected in one direction, and the other on the return journey!
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