82045 The way ahead?

Our October update is now posted http://www.82045.org.uk/news/82045_news-oct15xx.html

 

82045's FB page shows the arrival of the bolier barrel at Bridgnorth.

 

Our new update is here http://www.82045.org.uk/news/82045_news-nov15.html

 

A tech. question if I may please.

The firebox, are Llangollen building the outer steel box and Bridgnorth the inner copper, or vice-versa or neither of those!

Thanks

46118

 

The October news item states South Devon Rly - Firebox ? Barnshaws - Barrel, SVR ordering Copper, if that helps.

 

I don't understand the geometry here. How does one fit a circular tube into an elliptical one satisfactorily?

 

Help.
so does the vacuum ejector exahust ring sit inside the chimney and exit through the slots in the 'Flare' ?

 

The ejector exhaust ring is bolted to the bottom of the chimney. The exhaust steam exits from the ring into the chimney itself, via 28 1/2" dia holes drilled at an angle, between the inside diameter of the ring and the outer chamber.

 

I think the wrong word has been used here. I would say that elliptical should read unequal.

 

Nope,
If you truncate a cone at an angle ( albeit a slight one ) the resulting aperture is an ellipse ( albeit a slight one), and a Variable Degree of flanging would be required to mate that with a circular section...

 

I thought you got a parabola or egg-shape..

 

I think you have to truncate a cylinder to get an ellipse..

 

As the November news update attempts to say, one of the first jobs will be to make the ends of the taper barrel truly circular for a length of 5 3/8" in order to mate up with the circular barrel section at the smokebox end and the firebox at the other end. Advice has been sought from those who have done it before.

 

If it's been rolled with the correct tapered rollers, it should be okay..

 

Maths note: there are a family of curves you can get by truncating a cone at different angles, and because of that the family are called "conic sections".

The conic sections are: circle, ellipse, parabola, hyperbola.

If you cut the cone with a plane that is normal to the cone's axis, you get a circle. If the plane is at an angle, but still cuts the cone in such a way as to create a closed loop, you get an ellipse.

 

So now we know!

 

Interesting. So, how come, when the barrel is drawn up on CAD, the horizontal and vertical axis are the same dimension?

 

Only if the taper is concentric about the centre line. In this case the bottom of the barrel is horizontal, the ends are vertical and so perpendicular to the bottom, and all the taper is concentrated along the top. The top of the barrel is therefore angled to the ends, the angle increasing with the degree of taper. So the vertical dimension is slightly greater than the horizontal one.

 

The two roled rings were submerged welded. Is the joint top or bottom?

 

Interesting, I'd always assumed that the sections of a tapered boiler would all be circular in the vertical plane, and thus the tapered section wouldn't be part of a right cone, but an oblique cone, with the vertex in line with the base of the boiler (or top if its a Bulleid).