Lancaster UC support beam

The web here is a specific reference to the upper & lower wing spar beams and the sheet between them as here:

Sorry, Greg, but I don’t think a single machining instruction could identify this piece, whereas a design stressing value could do so.

Mike

Hi Mike,
Another interesting thread into the intricacies of the Lancaster.

Reading the 7G, my assumption would that it would be information relevant to a machinist etc; so something like 7 gauge /thickness or some material property, like hardness?
They wouldn’t know (I expect) that the part is stressed to 7G.

Thanks again for these threads.

Greg

Paul, yes you could be right But both O.2516(Lancaster) and O.2923(Lincoln) show the trim of the apex on both sides of both outer & inner beams.

Both these drawings are complex and very, very crowded. What I’m trying to do is to confirm my understanding of the drawings by finding matching photos if I can.

Something else which seems very interesting is a comment on drawing O.2362. This drawing shows how the beams are attached to the front wing spar web. Here is the comment for the shim, drawing 13/E.4560, “Not Required when 7G Web is used”:

I interpret this comment to confirm that for some Lancasters at some point in time the wing spar webs were stressed to 7G. Think stresses caused by the ‘corkscrew’ combat evasion. That 7G value is pretty high.

The last amendment date of O.2362 is 23rd Feb 1945. So I cannot say when the 7G wing was introduced other than on or before this date.

I’d be very keen to see some comments on this finding i.e. What was the stressing value for earlier wings?, Is this a good indication of the stresses caused by a violent corkscrew? etc.

Mike

Just a guess here Mike, in the photo you are using above it appears the left and right hand beams have angled mounting points at the top, could the right hand beam have the apex of the triangular cutout extended on the inner face? You will need to find a photo of the other side of either the left or right hand beams to compare them.
Paul

To illustrate the subtleties that are causing me problems, here is a relatively unimportant issue. It might, of course, illustrate my inability to read engineering drawings.

Here is a section from your photo, Rob, for which many thanks.

Looking at the beam on the left, the outer face of the port inner beam, the apex of the triangular cutout has been extended or eased. The righthand beam, the port outer beam has no such extension of the apex.

Now look at a part of the Avro 5/O.2510 drawing.

I believe the two areas circled the drawing are where the casting (aluminium magnesium alloy DTD 900) has to be trimmed to prevent the slinging cable from chaffing.

The Avro drawing is itself confusing, particularly if you don’t read the bit about chaffing. But the dotted curves in the upper circle do suggest that the apex of the triangular cutout should rounded and extended on both sides of the beam. How to resolve this with the appearance in Rob’s photo, that is the question.

All four beams are either identical or mirrored copies except that the outer faces of the outer beams have a small further machining slot right at the top to give space for a big outer wing joining bolt.

Mike

Front view of Centre Section showing inner Undercarriage Support Beams

Starboard inner beam_________________________________Port inner beam

The locations of the outer beams are indicated by the red rectangles
Mike

Great photos Robbo.
That is an impressive bit of hardware for sure.

Andy

…which is this coming weekend I believe

Mike, the u/c beams are easily inspected on NX664 at Le Bourget when Ailes Anciennes have an open day. http://eternal.flight.pagesperso-orange.fr/wu21/lancastercr.html

Lancaster NX664 WU-21_4764 by Rob Leigh, on Flickr

Avro Lancaster WU-21 NX664 Le Bourget_4765 by Rob Leigh, on Flickr

We have two new ones in store at Coventry, they’re the same part on Lincoln and Shackleton, though some Yorks seem to have the fabricated item you mention.

Regards,
Rich

I have Avro drawings for two very different variants of the beam. One was probably used for Manchesters and only very early Lancasters.
The early one was constructed with sheet and standard channels. The later one as above, the one that interests me, is a one piece casting.

As I said, I have the drawings but they have some very fine subtleties and it would be a great help to have photos to confirm these. There are plenty of photos showing the beams installed in the aircraft but unfortunately very little can be seen. I think it must be a beam out of the aircraft on the bench with photos taken at various angles in close-up. Perhaps I’ll get lucky with Canadian Warplanes Heritage as you suggested, Andy.

All the best and thanks
Mike

There are a few pics online

I do believe that Canadian Warplane Heritage had to replace one of these during the rebuild of their Lanc. It was cracked. The damage was quite possibly done during a ground loop, much earlier in the aeroplanes history.
I would be surprised if such an item would have been disposed of.

Andy Scott