Rotol SG Series Accessory Gearboxes

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Does anybody know what aircraft this gearbox is from? Refer to attached photos.

I'm not sure what the part number is or if there is an AM ref number.

The gearbox is very similar to the SG.3/1 that was fitted to the Australian single-seat Vampires. These were fitted with the Rolls Royce Nene. I have attached a schedule of spares marked-up image to show this gearbox. SG stood for Special Gearbox. Thanks to Alan Allen, I do have the manual for the SG.3/1.

There are two of the 'mystery' gearboxes shown; one has a Dowty Mk.28 hydraulic pump fitted.

I'm guessing that the gearbox was bolted to the firewall like with the Mk.30 and Mk.31 Vampires.

The visible drive shaft from the engine then points forward or aft. I guess there are other possibilities.

Presumably it is from a UK design aircraft. It is a type that would have served in Australia. Is it necessarily military? Is it necessarily a jet as the Vampire is? I've been told it is not from the Firefly or Sea Fury.

Gannett? Canberra? Viscount?

Original post

The term Special Gearbox was used by Rotol Auxiliaries to refer to a series of gearboxes designed for aircraft that had limited space above and below the gearbox location. Types and designation are - Lightweight Four-drive Gearbox "B.G." , Two-drive Generator Gearbox "G.G.", and the High-speed Three-drive Gearbox "S.G.".  In the latter case the "S.G." is simply a coincidental to it being a 'special gearbox'. Confusingly, the "B.G." designation was also used by the Universal Gear series, although the Light-weight Four-drive seems to have been restricted to just B.G. 3/ and B.G. 4/ types.

The High-speed Three-drive gearbox came after Rolls-Royce and Power Jets asked Rotol to design a gearbox capable of operating at 5500 rpm. Apart from the special high-speed input gearing and the outer casing it used standard components fitted to other Rotol gearboxes.

The S.G. 1/ series were fitted to the many variants of the Meteor jet. Port and starboard boxes had different numbers eg S.G. 1/27 and S.G. 1/28 fitted to the Meteor NF Mk II. The number used after the forward slash was used to indicate the equipment fitted to the available faces - three in the case of this type of box.

The S.G. 2/1 was fitted to the Supermarine Attacker.

Although my collection of AP 2240 Rotol publications extend into the late 1960 editions, they don't mention the S.G. 3/ types... which is a pity because I have a couple of them amongst my collection of Rotol / Dowty Gearboxes.

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Welcome Oracal.

Is there a Blake's 7 reference in your moniker?

Thanks for the useful information; so I will investigate the Meteor. I have had a bit of a look on line and can see how the gearbox is attached to the auxiliary spar that runs in front of the engine, and I can see how the Heywood compressor pokes up. I also saw an extract from a manual for sale that seems to show the four studs sticking out of the aux spar. Will check Meteor/manuals to see if that is indeed where the two come from.

I have uploaded the SG.3/1 manual here: http://vhjet.com/home/publications/ - it is down the bottom under the Mk.30/31 heading.

I had taken the statement in the extract attached that ties Special Gearbox and SG as a definition for the abbreviation.

Cheers.

Attachments

Subvariants of all Rotol gearboxes on a specific type is down to what is fitted to the driving faces. This does not only include a particular kind of pump, be it a vacuum or hydraulic, or a generator etc., but also items such as Twice-speed and Half-speed reduction rear. The multitude of possible combinations makes knowing the Type/Number/Subvariant number of relevance to establishing what it was once fitted to. The other (more difficult) option, is to understand what was mounted to each face and then work through AP 2240A (Rotol) Vol 1 appendices until you find a match.

Regarding Special Gearbox. The High-speed three-drive gearbox was the last of the three different types to be designed during WW 2. My point about “S.G.” was that it would be wrong to label the gearbox as being the only special gearbox from Rotol. Strictly speaking, it is a High-speed three-drive gearbox.

I have attached an image that gives an idea of what it was possible to attach to gearboxes.

Rotol Accessory Options

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Hi Oracal.

Are you able to tell me the full titles of these pubs?

A.P.2240A, Vol. 2, Part 2

A.P.2240A, Vol. 6, Part 2, Rotol Auxiliary Gearbox and Drive

These entries come from the AAP for the Vampire Mk.30/31. Maybe the second one is Descriptive & Servicing for SG.3/1?

Cheers.

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FYI, here are some gearbox IDs from my Nene notes (Nene 3 to 7 entries from a RR TSD):

 

Nene 3 - SG.2/1

Nene 4 - TG.4/1

Nene 5 - PCG.3

Nene 6 - PCG.3

Nene 7 - SG.2/1

Nene 2-VH - SG.3/1, N37L/2512

Nicko, yes of course, but it is perhaps worth me expanding the answer to include a little extra detail.

Bristol and Rolls-Royce had their own Accessory Gear Boxes and Drives, details of which are contained in AP 2240. The Rotol Accessory Gear Boxes and Drives are included in AP 2240A. Although Rotol Auxiliaries was established as a joint venture by Bristol and Rolls-Royce, there is no commonality of parts between the companies gearboxes.  

There are also AP 2240B - Self-Changing Gears Ltd accessory drives, and AP 2240C - Turbine driven accessory drives (other than Rotol).

Both AP 2240 and AP 2240A initially conformed to the three-volume scheme introduced in January 1943 by AP 2462A, the Rotol edition would later change to a hybrid system that also used a separate 2-book volume 6 that contains repair and reconditioning information, as well as fits, clearances and repair tolerances. However, to complicate matters, some aircraft types had the Rotol Volume 1 and 6 combined in a single volume. You should always be able to find the details for associated publications in AP 2240A and the air publication set for the aircraft in question. Additionally, AP 113 (as amended) contains a complete list of APs. 

The RAF Museum at Hendon holds dozens of the various volumes of AP 2240, AP 2240A, AP2240B and AP 2240C.

Regarding your specific questions:
A.P.2240A, Vol. 2, Part 2 - Fits and Clearances. 
A.P.2240A, Vol. 6, Part 2 - Repair and reconditioning instructions. 

I am unaware of ‘TG’ and ‘PCG’ type abbreviations. Perhaps they can to be found in AP2240C?

The 3-volume tree for AP 2240 and AP 2240A are attached.
 

 

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Turns out one of the gearboxes does have a data plate. So this one is an SG.1/18. I have looked at two manuals, so it could be Meteor T.7 or F.8, for the starboard location. The other is missing its data plate. The main casing casting has the same part-number, and generally the arrangement is the same. However, the lubrication lines are different, there being an extra spur on one and a couple of other differences. I suspect this is a difference of mod status as one of the features on the unit missing the data plate appears in the parts book illustration for the /18, but does not appear on the unit with the data plate. Anyway, not planning on digging through mods right now to figure this out.

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The SG basic body is adaptable, that is the gearbox in general found its way onto many different aircraft types.. There was at least 41 different variants of the SG 1, but all used the same basic body. 

The SG 1/18 was used on the Meteor 4,7,8,9,and 10 starboard engine. Those same Meteor variants used various versions of the SG 1 on the port engine - too many to list, so I will use 'X'.

On those particular Meteor variants, only the SG 1/18 had a hydraulic pump (a Dowty type 5700 RH/1800, whereas the SG1/'X' always had an electrical generator (a Type KK in some cases). BOTH the port and starboard SG1/18 and SG1/'X' had a Pesco vacuum pump type B3X Mk 2. 

To sum up, probably not a modification to the 'basic casing of the 'SG1, but simply a different installation. Have a read of AP 2240, Vol 1, Part 1, Chap 5 to get a better idea as to the adaptability of the SG and plumbing option available.