G3 0-4-4T 'Project' based

jamiepage

Western Thunderer
Thank you very much, David, I appreciate that. Personally, I'm delighted when it wanders off in different directions- Les Proper's engines are difficult to resist. In fact, I haven't resisted.
Anyway, next step is to finish the cylinder/ steamchest assembly. Crosshead, tube guide, valve rod knuckle, and steam and exhaust unions.
 

jamiepage

Western Thunderer
The crosshead was turned up from bronze, cross drilled and tapped 5ba for a gudgeon pin. Fitted to the end of a carefully measured piston rod, it was again drilled through to pin one to the other.

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A trunk guide was fettled from brass tube and the end counterbored to pressfit onto the rear cylinder cover's register.

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It is not a terribly elegant type of assembly, but the trunk guide is self supporting and removes a need for slidebars, motion plate etc.
The piston rod gland was packed with twisted PTFE tape; it will be a fiddle to replace but with luck will last a long time.
 
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jamiepage

Western Thunderer
Work on the steamchest has temporarily stopped, awaiting some brass and bronze hex rod, so I thought the smokebox handrail might be a quick job for today.
Well, it wasn't. The knobs were a pain, with only one being 'normal', so could be turned, cross drilled and finished. Its opposite number doubled as a blower elbow, while the front one doubled as a lamp socket. Some fiddly silver soldering got them made up, and tails tapped 8ba allowed them to be screwed in place.
The handrail itself was bent up from 16swg nickel silver, a statement which rather quickly draws a veil over hours, really, hours, of bending and checking. It could have gone well and fitted first time, but it didn't. Each check required the rail to be fed through all three knobs and the whole smokebox assembly slotted into position to check where the ends would fall, relative to a couple of locating holes on the tank ends. It didn't go well, and was frankly not a pleasant way to spend so much time.
Sort of got there in the end, with the rail sitting parallel where it should, and fairly symmetrical around the front, but it definitely isn't perfect.
here's a shot showing the handrail and a semblance of the blower feed temporarily slotted onto it's elbow on the RHS.
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A shot showing bits that will become invisible.
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And I've just noticed I forgot to make and fit an elliptical mounting flange for the blower elbow, so the job is not finished after all.
At least the elbow can be unscrewed from smokebox and a shaped flange slotted on.. but not today.
 

David Taylor

Western Thunderer
I hope you get some consolation when I say I looked at the handrail before I read your comments about it and thought "He did a nice job on that, looks nice and smooth". So you can see the imbalance but I'm guessing most others will go "wow!" if you don't mention anything ;)
 

jamiepage

Western Thunderer
Thanks David, appreciated.
Mind you, it's all bent again now having wrestled the blower elbow out, in preparation for fitting the f..f..flipping forgotten flange.
Still, the hex brass has arrived so back to the simple pleasures of the lathe soon.
 

jamiepage

Western Thunderer
Still awaiting some hex brass, the right size this time (!), so a couple of jobs have been completed.
First, the pesky blower elbow was completed with its flange.
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Unfortunately, that photo rather shows up the simplified smokebox saddle. The other side is pretty well camouflaged by sandbox rodding but this side is not so endowed. I'll live with it, but lesson learnt.

Another job was a spirit tank.

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Soldered up from nickel silver with brass and stainless turnings for vent pipe, filler and fuel tap. The vent pipe will be cut back and the end chamfered once a sump is bolted to the bunker underside. That can be done after the platework is removed from the chassis again.

It slides into place thanks to a removable cab.

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The cab has a rear 'shelf' on which will be built up a former with coal load. The former will include a couple of metal gussets to add strength to the 'shelf'/ cab butt joints.

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I've decided now that the cab roof needs to be made and soldered in place before the loco is disassembled again, to make sure it will still sit well on tanks and bunker, and to guard against an unwanted twist.
After that, I think, it really can be taken apart for valve gear etc.
 
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jamiepage

Western Thunderer
Thank you, Giles. Praise indeed!

The tanks, bunker etc have all now been removed and put aside until final assembly. Next target will be to get the chassis running on air, and so with the correct hex brass to hand, the various unions can be turned up for the steamchest.
However, the connecting rod and valve gear also need to be made, so today saw the crank axle take shape. Steel webs, sliding fits, loctite and cross pins did the job.

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The uncluttered cylinder underside reminds me to fit a couple of automatic drain cocks.
 

jamiepage

Western Thunderer
David,
The ones I have experience of are individual units.
They use a ball, loose but captured within a chamber. The chamber has an inlet from the cylinder, and an outlet to atmosphere. This outlet is set horizontal. The idea (and it does work) is that excess water creates turbulence within the chamber and keeps the ball from seating, but once the steam 'dries', the ball settles over and seals the outlet.
The dimensions of chamber length, and diameter, ball dia, and outlet dia, no doubt matter, but there are a few published drawings of ones that have been proven.
Having said that, I just buy them, ready made, from DJB Engineering.

Here are four of their items screwed into the underside of a twin inside cylindered loco. (Two set forward facing, two rearward, primarily to prevent fouling with the bogie).
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jamiepage

Western Thunderer
I assume, but am not entirely certain, that the automatic drain cocks need to sit pretty close to horizontal.
The cylinder sits at 6 deg. in this loco, so I took the precaution of angling their tapped holes.

Sticking a piece of polished stainless through the bore help protect against the bore getting squashed whilst the main block was held in the vice at the correct angle. (And the correct orientation!).

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It was then easy to spot face, centre drill, drill blind holes and tap M4. After removal from the vice, steamways were drilled into the bore with a 1.0mm drill from the bottom of these holes, angled to breakthrough just within each cylinder end cover.

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Jon Nazareth

Western Thunderer
That's an interesting little gadget, Jamie, a clip on angle gauge. But then, the machine will need to be dead level before it can be used, I suppose. I was thinking about something like this when I come to machine the angles on the crane timbers.

Jon
 

David Taylor

Western Thunderer
You can set the zero on the digital gauge. So just set zero when sitting on the table or vice and assuming you are sitting the cylinder block on parallels you'll end up with the block at 6 deg relative to the machine.

I don't think machines need to be dead level. They just need to be free of twist and their spindles orthogonal to the ways. A situation in which none of my machines find themselves :( I'm now pretty sure the headstock on my lathe is not parallel with the ways as even using a 3/4" boring bar my cylinders are coned. But sans-gaskets and everything else my engine still runs on air. We're only making steam engines, the tolerances are pretty forgiving.
 
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jamiepage

Western Thunderer
Jon, as David says, you just set it on a datum (in this case, the machine bed), set zero then angle away. It has a magnetic base (useless on this brass cylinder of course, but handy normally), and is one of those tools that become indispensable.
Jamie
 

jamiepage

Western Thunderer
The connecting rod, as any part of the valve gear, makes no pretence to 'scale', but is purely functional. It was important to get the length right; not just to guard against the cylinder bashing into one cylinder cover or the other, but ideally to equalise the free space at each end of the stroke.
It was easy to calculate what it should be, but with driving axle and cylinder plus piston rod length all fixed in place, it was thought prudent to actually measure it.
Easier said than done in practice though, so a length of plastic strip was drilled at one end for the crosshead pin and cut to an approximate length. Trial and error with bits crudely stuck on or removed in situ eventually found a length which did the job at both extremes of crank throw, with equal gaps between crank and plastic.
The length (plus 2mm for a 4mm crank) was then used to fettle a proper job from steel.
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The crank end is split, and a split bronze bearing was soft soldered into place. Shorter 10ba bolts will be found.
The little end shape is less than attractive in this photo; I wish I had noticed it earlier. Fortunately though, it won't be seen unless and until the bronze bush needs replacing one day.
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Fitted in place.
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jamiepage

Western Thunderer
As a single cylinder, slip eccentric design, the functional valve gear is very straightforward, and a few enjoyable hours finished all the bits ready for assembly.
Although the various items didn't entirely follow the original G1 project design, (nor indeed did the overall lengths of rods and arms, modified to suit the loco), all the important dimensions most certainly did stick to the words and music.
The eccentric strap and rod was a confection in brass with a mild steel eccentric. A thin strip of ptfe sheet was cut and trapped within the eccentric groove to act as the working face.
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Not much more than the eccentric assembly is needed really, just a stop collar (brass), a rocking arm to bring the eccentric movement inboard toward the valve rod (silver soldered brass), and a few specially turned pins and washers.
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This second photo shows all these bits; the only outstanding item is a simple link between rocking arm and valve rod knuckle, which will be measured and cut after everything else has been assembled.

The rocking arm is essentially a brass tube which rotates around a stainless rod; the rod itself sits laterally across the frames, tapped into one frame and with a screw slot cut at the other end. This feature, plus the Walsall removable wheels, will certainly make any future stripping down rather painless.
 
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