Lancaster bulged bomb bay question

[belcherbits]

OK, I thought I had all the information I needed, but of course, I don't.

The Lancaster II (and most Lanc Xs as well) had a bulged bomb bay, commonly called the '8000 lb doors' because it was big enough to enclose an 8,000 lb HC bomb which was 38" in diameter. I found a cross-section drawing of these doors which actually raised more questions than it answered. The cross section confirms that the central bulge of these doors does indeed go around a 38" bomb . However, these bombs were suspended from the bomb bay 'roof' by conventional suspension lugs.

The Tallboy bomb was also 38" in diameter, but it was held in position by a jointed chain around the mid-section, since these bombs did not have suspension lugs for aerodynamic reasons. Take a 38" Tallboy, wrap a 2" linked belt around it and it no longer is 38" in diameter, more like 42" or even more. 

My question is: did the bomb bay doors completely close around the Tallboy, or were they sort of cracked open a bit when they were loaded? If they closed, how?

I have looked at all the photos I could find and could not see anything which helps answer this question.

 

 

Edited April 11, 2018 by belcherbits

[Jure Miljevic]

Hello belcherbits

Lancaster B Mk.II bomb bay doors were not designed to cover Tallboy bomb as they bulged further aft and not right from the doors' leading edge, as was the case with Tallboy carrying B Mk.I and Mk.III. I believe Lancaster B Mk.II was not designed to carry Tallboy anyway. A year or so ago Tallboy bulged bomb bay doors had been debated at some length.

I hope it helps. Cheers

Jure

Edited April 11, 2018 by Jure Miljevic
link added

[belcherbits]

Yes, I saw the previous posts, but they spent a lot of time talking about what doors fit what kits, and most people didn't seem to know about the rear of the bulged doors changing shape to fair into the fairing for the underside turret. That turret was quickly dropped from use, but the 'pinched' rear shape for the bulged doors remained.

Nobody seemed to know how a set of doors designed to closely fit around a 38" 8,000 lb bomb worked when they inserted a 38' diameter Tallboy with a clunky type chain around its mid-section. I'm still hoping someone has this info stashed away somewhere.

[Atom.uk]

I read somewhere (no idea where,sorry) that the Tallboy bomb doors worked on bungee cords, that opened from the weight of the bomb then were pulled closed afterwards. 

[Troy Smith]

 

On 7/3/2017 at 19:10, Finn said:

To further clarify, the 4000lb Cookie had a dia of 30" while the 8000lb, 12,000lb Cookies and Tall Boy had a dia of 38", of course the Tall Boy had the tail fins to worry about.

 

Tall Boys have no lifting lug I read correctly,   and do not go on a hanger?

 

the following is just supposition/suggestion from looking at the information presented  

 

Tallyboy in bay

Quote

Frank Hawkins looks up at a
tallboy in position in a Lancaster's bomb bay.
The aircraft's bomb doors were modified
so that they could close around
the weapon's 38" (95 cm) diameter.

 

from

http://www.bombercommandmuseum.ca/s,tallboy.html

 

I presume this is a lifting platform, as the youtube link (below) shows the 12,000 lb cookie being winched up on a lug, perhaps the lack of lug and hanger mean the Tallboy sits that bit higher in the bomb bay  which would allow for the clunky chain?  

 

                                                                                                                                                     

 

from

http://www.lancaster-archive.com/lanc_bomb_bay.htm

 

 

4000lb cookie mount

 

grandslam chain

                                                                                                                                                               

 

 

youtube of cookies being loaded

 

[janneman36]

Linky to a page with a tallboy hanging in the bombbay..

http://www.bombercommandmuseum.ca/s,tallboy.html

This one is a tallboy lanc..

http://www.lancaster-archive.com/lanc_photos_dispersal.htm

http://www.bomber-command.info/JohnnyWalker.htm

Also one with tallboy doors..

https://awritersden.files.wordpress.com/2014/08/lancaster1.jpg

 

Cheers, jan

[stevehnz]

I'm with Troy on this. The depth of the chain beneath the Tallboy is compensated by the lack of bomb support frame & lugs above it to my mind. Not sure how that equates to the width though, maybe a bit more leeway in that dimension.

Steve.

Edited April 12, 2018 by stevehnz

[Selwyn]

15 hours ago, belcherbits said:

Yes, I saw the previous posts, but they spent a lot of time talking about what doors fit what kits, and most people didn't seem to know about the rear of the bulged doors changing shape to fair into the fairing for the underside turret. That turret was quickly dropped from use, but the 'pinched' rear shape for the bulged doors remained.

Nobody seemed to know how a set of doors designed to closely fit around a 38" 8,000 lb bomb worked when they inserted a 38' diameter Tallboy with a clunky type chain around its mid-section. I'm still hoping someone has this info stashed away somewhere.

The bulged doors would have been designed to not fit "Tightly" around the 8000lb bomb,   there would be an appreciable gap between the store and the door inner surface  to allow for any inflight movement of the store.  Probably the tallboy securing chain was designed in a profile that fitted in the gap between the  store and the door, which would have been a much quicker and cheaper option than redesigning the doors yet again. I also suspect on tallboy  there must have been some method of either  retracting the chain after release so that the  chain did not get stuck in the closing doors, or  maybe the chain links were spring loaded  to lift it back upwards after release? I cant see it being left dangling in the airstream especially when used with grand slam.

 

Selwyn 

[belcherbits]

Selwyn

I scaled the two drawings to a common scale, and overlaid the doors on the Tallboy. Even with the Tallboy tight up against the roof of the bomb bay, there appears to be interference between the chains and the doors.

My guess is the fit was extremely tight, and with a Tallboy installed, the doors probably gapped open a bit. No such gapping needed with a 8000 or 12000 lb HC, which were suspended from their tops and need no chains. However, you can see the fit would have been quite tight. These bombs were held in place and braced at the top so there wouldn't have been very much inflight movement ... you don't want 12000 lb loads wobbling as you fly along. Maybe an ex-armourer could chime in here?

As for the chains after the drop, there is an indication on the one drawing of a retraction cable which I am assuming does exactly what you suggest, pull back the chains so they didn't flop around until the doors were closed.

[Troy Smith]

1 hour ago, belcherbits said:

Maybe an ex-armourer could chime in here?

He did, @Selwyn I believe is an ex-armourer, certainly ex RAF ground crew.  

note comments here

http://www.britmodeller.com/forums/index.php?/topic/234917818-raf-bomb-colours/

 

Not trying to be rude or smart, just adding some perspective to Selwyn's comments,  which are based on experience, rather than my suggestion above, which were supposition.

[Selwyn]

1 hour ago, Troy Smith said:

He did, @Selwyn I believe is an ex-armourer, certainly ex RAF ground crew.  

note comments here

http://www.britmodeller.com/forums/index.php?/topic/234917818-raf-bomb-colours/

 

Not trying to be rude or smart, just adding some perspective to Selwyn's comments,  which are based on experience, rather than my suggestion above, which were supposition.

Not strictly "EX" if you please! Have a different  job title but still  involved with woosh bangy things!

 

Selwyn

[brewerjerry]

Hi

   Maybe an enquiry to the RAFM, to see if they have the parts AP,

( is it Vol III ? )

    this might give part numbers or drawings 

   cheers

     jerry

   

[belcherbits]

Selwyn

No intention to disparage any comments you made, just wanted to differentiate between 12,000 lb HC and 12,000 lb MC (i.e.Tallboy) suspension methods. 

From my look at the drawings, it appears the 8,000 lb /12,000 lb HC bombs were a tight fit in the bulged bomb bay doors. Maybe the drawings are wrong.

Mike

[Selwyn]

47 minutes ago, belcherbits said:

Selwyn

No intention to disparage any comments you made, just wanted to differentiate between 12,000 lb HC and 12,000 lb MC (i.e.Tallboy) suspension methods. 

From my look at the drawings, it appears the 8,000 lb /12,000 lb HC bombs were a tight fit in the bulged bomb bay doors. Maybe the drawings are wrong.

Mike

Mike no offence taken at all! I just wonder if the doors were modified for tallboy, but on the inside surface which may not be apparent on external images?

 

Selwyn

[mick b]

All of this is covered in some detail in the Haynes manual Dam Busters which also shows a photo of the bomb bay roof mods particular for the Tallboy.

 

It doesn’t mention the doors not closing fully but the chain did hang initially causing damage to the doors edges when closed so rope was attached to it and it was responsibility of the crew to pull up the chain prior to the door closing.

 

Mick

[belcherbits]

Darn. I was in my local hobby shop today and I'm pretty sure they had that on the shelf! I'll look that up.

Mike

[sloegin57]

14 hours ago, Selwyn said:

The bulged doors would have been designed to not fit "Tightly" around the 8000lb bomb,   there would be an appreciable gap between the store and the door inner surface  to allow for any inflight movement of the store.  Probably the tallboy securing chain was designed in a profile that fitted in the gap between the  store and the door, which would have been a much quicker and cheaper option than redesigning the doors yet again. I also suspect on tallboy  there must have been some method of either  retracting the chain after release so that the  chain did not get stuck in the closing doors, or  maybe the chain links were spring loaded  to lift it back upwards after release? I cant see it being left dangling in the airstream especially when used with grand slam.

 

Selwyn 

Spot on as near as dammit.  Not spring loaded but cables attached to each end of the chain halves and probably retracted by means of winches mounted on the bomb bay roof inside the main cabin :-

 

Still from a film made during the raid on the Bielefeld viaduct :-

Note the stbd chain being drawn up into the bay.  There also appears to be some sort of support "pad" in the bay roof

Loading a Grand Slam:-

Final attachment of the support chain.  Note the electrical cable top right and the "hoist" cable in front of the SNCO's face

 

I would imagine that the Tallboy chains were retracted enough for the bay doors to be closed on them but that the Grand Slam chains would form two neat but secure "loops" when pulled in.  The bulged area at the back of the Tallboy bomb doors look as if they were incorporated to clear the fins of the weapon, it being mounted in the bay with the fins in an 'X' position.

 

HTH

Dennis

(Rigger/Sootie)

 

 

 

Edited April 13, 2018 by sloegin57