belcherbits Posted April 11, 2018 Share Posted April 11, 2018 (edited) 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 1 Link to comment Share on other sites More sharing options...
Jure Miljevic Posted April 11, 2018 Share Posted April 11, 2018 (edited) 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 Link to comment Share on other sites More sharing options...
belcherbits Posted April 11, 2018 Author Share Posted April 11, 2018 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. Link to comment Share on other sites More sharing options...
Atom.uk Posted April 11, 2018 Share Posted April 11, 2018 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. Link to comment Share on other sites More sharing options...
Troy Smith Posted April 11, 2018 Share Posted April 11, 2018 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 1 Link to comment Share on other sites More sharing options...
janneman36 Posted April 11, 2018 Share Posted April 11, 2018 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 Link to comment Share on other sites More sharing options...
stevehnz Posted April 12, 2018 Share Posted April 12, 2018 (edited) 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 Link to comment Share on other sites More sharing options...
Selwyn Posted April 12, 2018 Share Posted April 12, 2018 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 Link to comment Share on other sites More sharing options...
belcherbits Posted April 12, 2018 Author Share Posted April 12, 2018 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. Link to comment Share on other sites More sharing options...
Troy Smith Posted April 12, 2018 Share Posted April 12, 2018 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. Link to comment Share on other sites More sharing options...
Selwyn Posted April 12, 2018 Share Posted April 12, 2018 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 1 Link to comment Share on other sites More sharing options...
brewerjerry Posted April 12, 2018 Share Posted April 12, 2018 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 Link to comment Share on other sites More sharing options...
belcherbits Posted April 12, 2018 Author Share Posted April 12, 2018 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 Link to comment Share on other sites More sharing options...
Selwyn Posted April 12, 2018 Share Posted April 12, 2018 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 Link to comment Share on other sites More sharing options...
mick b Posted April 12, 2018 Share Posted April 12, 2018 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 2 Link to comment Share on other sites More sharing options...
belcherbits Posted April 13, 2018 Author Share Posted April 13, 2018 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 1 Link to comment Share on other sites More sharing options...
sloegin57 Posted April 13, 2018 Share Posted April 13, 2018 (edited) 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 1 Link to comment Share on other sites More sharing options...
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