Lancaster nose longeron kink

Yes, JT442. The 2nd photo illustrates it very well. Super photos by the way.

But in your photo it seems more of a curve rather than a kink with the apex of the curve well in front of frame F, almost at frame G.

Your photo is square on. So there is no distortion. It looks to me that your photo proves the kink/curve in the longeron. Agreed?

Many thanks
Mike

Vertical Channel Supports

Geoff, I’ll do my very best.
Which is it you want?
This

or this

If it’s the first, then more photos would help. I will have to calculate the dimensions using what I know of the turret bowl and the frames H & J
Mike

Reinforcing skin plates

“The hip bone is connected to the leg bone” etc etc

The turret ring rests on the turret deck. The turret deck is supported by the main longeron which, in turn, at the side s by frames J and H. The deck is supported at the rear by a channel bar stretching across frame G. But what about at the front?

Here’s frame K with the turret support bracket indicated (it’s called this in the Avro drawing). It looks as though it is intended to support the longeron at the front.

Unfortunately, the longeron, turret deck and ring are angled up at the front which leaves a most uncomfortable gap between this bracket and the longeron/turret ring and deck.

There must be some support to avoid instability. But what is it? I’m thinking it may be external reinforcing skin plates of the form I suggest in my drawing. You can just see something like this in my photo if you blow it up.
Mike

Let’s get the show on the road: Coordinate tables

Geoff, I can let you have tables for all the nose frames in a couple of days or so if you still want them after reading this.

That units in a Cad system are arbitrary is key. I could be working with something that is miles across in dimension or nanometres across. It makes no difference within the Cad system. It’s when the data has to come out of the Cad system into the real world that the problem starts. In the real world units matter and they cannot be arbitrary.

I can work happily within the Cad system drawing a Lancaster nose section frame, say J, to a precision of 1/10 of a mm (That’s more or less the standard Avro precision). But how do I get the info out into the world? The frames are symmetrical about the fuselage centre line. So I need only get out a half frame.

But frame J is one of the smallest frames. A full scale half J frame is still approx 632 x 1202 mm. It’s big and, for example, frame 1 is much bigger. Are there many printer/plotters accessible that can handle these sizes?

So I thought of a system of coordinate tables. For this, I take the raw data from the Cad system and work on it using MS Excel. I’ve sorted out the techniques necessary with the help of some good software. So I can proceed quite rapidly now.

A coordinate table is a set of X-Y coordinates which give the shape of one of the curves involved in one of the Lancaster frames/formers to full scale. The object is to plot these coordinates onto paper or wood to give a pattern for cutting the Alclad sheet to create a real frame.

For frame J, there are around 60 points to be plotted and I have tried to make it a bit easier by interpolating clean X values which are multiples of 20 mm. So X values range …,-40,-20,0,20,40,… about the fuselage centre line. The Y values are more complex, given to 1 decimal place.

Once the coordinates are plotted, the dots have to be joined by eye drawing the best curve possible through the plotted points.

OK, so what’s wrong. It’s not easy to plot the coordinates to such a large scale. Basically you have to draw first a very big piece of graph paper with, say, 5 cm squares. All the lines of the graph have to be parallel or perpendicular to a high degree of accuracy. That’s not easy. In fact, pretty difficult for most people. Once you have the graph paper arranged, it’s a lot easier. But arranging the graph paper is a major problem.

Neither printing on a printer/plotter nor the coordinate tables are a good solution. So how do I get my stuff out into the real world where it can be used by you guys?

I have attached an image of an Excel plot of frame J showing the curves which give the face of the frame and also the outer edges of the flanges which have to be bent down (4 curves). Also an image of the frame cross-section showing how the flanges should be bent downwards and a text coordinate table for the outer edge of the face for frame J.

Can anyone suggest a better method?
Mike

Thanks, Tony. That was quick. I thought I could assume a simplification where the vibrations were not propagated. That they are propagated suggests that the simulator deserves respect.

My immediate objective is to get to good Kf and Df values. But there is another problem looming. Some one has mentioned the dreaded words ‘tensor analysis’ in the parametrisation of the inertia values. Know anything about that? I’m clueless.
Mike

Plan B

I’ve got to accept that it is now unlikely that the data I need still exists.

I believe it would be reasonably easy to calculate the volumes of the various structure components. Then if only I had a value of the individual structure density of these, I would have a reasonable approximation – I think?

Now if I assume that the individual structure component density across the major constructors of that time was more or less the same. I can apply those to the Lancaster to obtain an approximation to the individual weights – valid assumption?

So how do I get this information for aircraft like the B24 and the HP Halifax? Or has this gone with the wind as well?

Comments, criticism, help and brickbats – all gratefully received.
Mike