Dear Josh and all involved with the AEC forum; especially the other-marques bit,

This is, in effect, a re-post of something lost when the old forum crashed, although I have re-compiled it. It’s probably a bit incomplete around the edges so I’d avidly welcome comments on it.

List of Bedford Bus Chassis 1931-87 with approximate dates of production and brief description.

1931-40

WHB 1931-5 6-cyl 26hp (RAC-rating) OHV petrol engine, normal control, purpose-designed bus for 14-seat bodywork. Derived from British-assembled Chevrolet LQ.

WLB 1931-6 6-cyl 26hp (RAC-rating) OHV petrol engine, normal control, purpose-designed bus for 20-seat bodywork. Long-wheelbase equivalent of WHB.

WTL 1935-6 Engine as WLB, but semi-forward control layout, up to 26 seats, modified goods chassis.

WTB 1936-9 Purpose built semi-forward control passenger chassis, longer wheelbase and wider springs than

WTL, larger 28bhp (RAC) engine from 1938, bull-nose front (concealing radiator) at same time, resembling the 1934 Opel Kadett car.

OB 1939-40 Longer wheelbase with components as the O-series lorry, engine, springs and bull-nose front and bonnet similar to later WTB, cancelled in wartime, generally 26 seat coach.
1943-71

OWB 1943-6 Utility version of the OB built to Ministry of Supply orders, only wartime single-deck chassis. Initially 32-seat utility bus bodies to Duple design built by Duple, Mulliner, Roe and Scottish Motor Traction. Many rebodied, some (especially for SMT and Highland Omnibuses) converted to forward control at the same time.

OB 1946-50 Renewed production for peacetime market. Still with 28hp petrol engine as standard, some of these and OWB modified to (mostly Perkins P6) diesel, generally 29 coach seats, but Plaxton, Trans-United and Willenhall Coachworks (the latter two in limited numbers) produced forward control conversions, as H .V. Burlingham did later (from 1952) on rebodies of OB and OWB, these sat up to 31.

SB 1950-4 Full forward control for the first time on a standard Bedford passenger chassis, nominal bodied Length 27ft 6in generally 33 seats, 5 speed synchromesh gearbox and 300 cu in 6-cylinder OHV petrol engine. Some later examples had extended rear overhang and up to 36 seats. The entire SB/SBn/NxM production run was over 45 thousand, making it the most successful bus/coach of all time in sales terms.

OLAZ 1950-4 Modified goods chassis/scuttle, engine as OB, appearance like the OB but higher-set, shorter and narrower, mainly bodied by Duple, maximum seating 25, major customer Macbraynes.

SBO 1954-8 Full forward control, longer wheelbase from 1955, giving 30ft bodied length. Perkins R6 indirect-injection 6-cylinder OHV diesel engine (excepting 24 for Eastern Counties Omnibus Company in 1954 which had Gardner 4LK units from new).

SBG 1954-8 As SBO but with petrol engine from SB. SBG and SBO initially 37, then 41 seats, More than 1000 units of SBG/SBO per annum sold in most of the 1950s with Duple coach bodies alone.

A4LZG 1954-9 Replacement for OLAZ goods chassis; normal control, modified to normal control coach including bonnet and scuttle by Duple (26 seats) and forward control coach (up to 29) by Plaxton.

A4LZO 1954-9 As A4LZG but Perkins diesel engine.

SB1 1958-61 As later SBO but with Bedford 300 cu in diesel engine. First Bedford–built CI engine.

SB3 (later NFM) 1958-87 As later SBG. Last examples for the Channel Islands.

C4Z1 1958-61 Modified forward-control goods chassis, Bedford 300 cu in diesel engine.

C4L2 1958-61 As C4Z1 but Bedford 215cu in petrol engine.

C5Z1 1958-61 As C4Z1 but 5 ton rather than 4 ton payload + body.

C5Z2 1958-61 As C4Z2 but 5 ton rather than 4 ton payload + body.

SB5 (later NJM) 1961-87 As SB1 but Bedford 330cu in diesel engine, lightly turbocharged from 1983.

SB8 1960-63 As SB1 but Leyland O:350 engine.

SB13 1962-67 As SB8 but Leyland O:370 engine.

VAS1 1961-67 Purpose built small bus or coach, 16 in wheel/tyre equipment. Nominal 25ft length for 29 seat coachwork, Bedford 300cu in diesel

VAS2 1961-67 As VAS1 but 215 cu in petrol.

VAL14 1962-67 6x2 forward-control chassis for 36ft nominal bodied length with engine and driving position on extended front overhang, 16 in wheel/tyre equipment with power-assisted steering to the twin front axles. Up to 52 seats as a coach and 56 as a bus. Leyland O:400 engine.

J2Z9 1964-77 TJ goods chassis modified to forward control. Up to 21 seats, bodies by Duple (Midland), Plaxton or Salvador Caetano. 214 cu in 4-cyl diesel

J2Z2 1964-66 As J2Z9 but 215 cu in 6-cylinder petrol.

J3LZ1 1964 Normal control 25 seat modification of longer-wheelbase TJ goods chassis, 300 cu in engine by REALL of London, diesel. One demonstrator built, later became a mobile shop.

J3LZ2 1964 As J3LZ1 but petrol engine as VAS2. Catalogued but not believed built.

VAM14 1965-67 Forward-control chassis with engine and driving position on extended front overhang, for nominal 32ft bodied length, up to 45 coach seats. 20 inch wheels/tyres to conventional four wheeled layout, engine and transmission as VAL14.

VAM3 (Later TFP) 1965-70 As VAM14 but 300 cu in petrol, main customer Salopia.

J2Z10 1966-77 as J2Z2 but Bedford 214 cu in 4-cylinder petrol,

VAS3 (later PFK) 1967-87, as VAS2 but 300 cu in petrol.

VAS5 (later PJK) 1967-87 as VAS1 but 330 cu in diesel, lightly turbocharged from 1983.

VAM70(later TRP) 1967-71 As VAM14 but Bedford 466 cu in engine.

VAL70 1967-72 As VAL14 but Bedford 466 engine. Body length relaxed to 11.3m (37ft) from 1968, so 53-seat coaches allowed.

1971-87

YRQ 1971-6 replaced VAM70 for 10m nominal bodied length, 466 engine mounted vertically in mid chassis, Turner-Clark 5 Speed synchromesh gearbox, Allison automatic optional.

YRT 1972-6 replaced VAL70 for 11m nominal bodied length, 466 engine mounted vertically in mid chassis, Turner-Clark 5 Speed synchromesh gearbox, reversion to 4x2 layout with full size wheels and tyres. Allison automatic optional.

PJK 1976-80 Pre-production urban midibus underframe, six constructed with GM-styled Marshall 24 seat bus bodies, transverse Bedford 330 driving through Morse ‘Hi-Vo’ multiplex chains to Allison automatic transmission with Telma retarder.

YLQ 1976-82 As YRQ but low-rated (140bhp) 500 cu in Bedford engine.

YMT 1976-87 As YRT but higher rated (160bhp) 500 cu in Bedford engine lightly turbocharged from 1983.

YLQ/S 1977-82 As YLQ but shortened wheelbase (by Tricentrol Chassis Developments) for 8.5m nominal bodied length, up to 35 coach seats.

YMT/L 1977-82 As YMT but lengthened wheelbase (by Tricentrol Chassis Developments) for 12m nominal bodied length, up to 57 coach seats.

YNT 1980-87 Uprated YMT, with 201bhp turbocharged 500 engine. Initially 6-speed Turner-Clark gearbox with Teleflex-Morse cable operation, from 1982 rod-operated ZF 6:180 gearbox.

YNT/L 1980-84 As YNT but lengthened wheelbase (by Tricentrol Chassis Developments, from 1982 Tricentrol renamed Comtech) for 12m nominal bodied length, up to 57 coach seats.

YMQ 1980-87 As YLQ but with YMT engine.

YMP 1982-87 As YMQ but lower-profile tyres and lower GVW.

YMQ/S 1980-87 YMQ shortened as YLQ/S (from 1982 Tricentrol renamed Comtech).

YMP/S 1982-87 YMP shortened as YMQ/S by Comtech.

YNV Venturer 1984-87 Engine and gearbox as later YNT but full air suspension with ferry lift, up to 14 tonne GVW, 12m nominal body length, up to 57 coach seats. The only named Bedford passenger chassis.

BMV 1984 Designed for ‘dirt road’ export markets, heavy-duty TM goods-vehicle derived frame with engine and driving position on extended front overhang featuring TM dash panel, 16 tonne GVW up to 12m bodied length, engine and gearbox as later YMT, prototype bodied by Wright Brothers (believed 11m B62F) for Kenya.

Production dates are the dates the chassis was offered as a PSV in the British Isles (excepting the export-only BMV, I’m going by its date of announcement in Buses) notably the VAM70 (TRP) was exported into the later 1970s and there was also a 500-powered TMP, marketed in Australasia as the VAM75. The General Motors computer-compliant all-letter coding was applied to Bedford passenger vehicles from 1971, and thus must have applied to the VAL70, but I have no reference of its code, a guess would be QRT as it was next after the VAS and that got P as the chassis, whilst subsequently the VAM got T. the 466 engine was coded R and T would have been the weight-class (qv: YRT).

In some publications I have read it’s suggested the Luton works in later years produced such un-catalogued variants as NLM (140bhp 500 in SB) and YNQ (201bhp turbo 500 in YxQ). The after-market modifications to Bedford PSVs are myriad and deserve a book rather than an article.

The list of modified goods chassis is solely those known in the UK and approved by Vauxhall Motors or GM(Europe) for the purpose, various other countries, notably Malta and Cyprus, had large numbers of buses built on Bedford goods chassis.

Also around six Bedford QL (a wartime 4x4 goods chassis ) were converted for Southport Corporation by local Bedford dealer Rimmer Brothers with a passenger compartment behind the cab and used to take passengers on tours of Ainsdale beach, the last of these were withdrawn in the late 1960s.

Note also that from 1960-4 W. S. Yeates, the coachbuilders and coach dealers of Loughborough Leicestershire, modified (with Vauxhall Motors’ approval) a total of 56 SB1 and SB5 chassis with extended front overhang to allow an entrance forward of the front axle, they bodied all of these themselves with Europa and Fiesta bodies, 32 as buses and 28 as coaches. The last of these, registered ACT101B, was completed by Duple after it had taken over Yeates’ coachworks and was supplied to The Delaine of Bourne Lincolnshire in June 1964, they ran it for five years before selling it to Suffolk operator Chambers of Bures.

When General Motors announced the end of Bedford production a large number of chassis was stockpiled, some Bedford coaches not entering service for a few years afterwards.

Errors and omissions excepted.

Best Wishes

Stephen Allcroft

Cardross

Scotland

Whoops, on re-reading some sources a number of mistakes have been posted, I shall come up with a revision in due course.

Best Wishes

Stephen

A very belated "thanks".

Hi Stephen, that is certainly an impressive list.

To flesh out here and there with some additional detail:

The 195508 SB wheelbase lengthening, from 206 to 216 inches, was accompanied by significant changes in the chassis, including a flat profile and a new front axle. In hindsight, it is surprising that the model numbers, SBG and SBO, remained unchanged.

The 330 diesel engine option for the SB, as the SB5, was announced 196111, I think at the same time as the braking system changes were made (basically the application of the TK system, as used on the VAS from the start.) But the 300 diesel option (SB1) did not disappear right away. It is still shown in a Bedford brochure dated 196302, but not in one dated 196409.

The SB8 (Leyland O.350) to SB13 (Leyland O.370) transition might have been a simple changeover occasioned by the runout of O.350 production. The 196302 brochure shows the SB8, whereas the 196409 issue shows the SB13, so the transition took place somewhere in that date range. Leyland announced the O.370 in 196108, and as best I can determine, Bedford offered it as an option in the KG truck, replacing the O.350, from 196209, at the same time as the O.400-engined KH was released.

The VAL14 was fitted with a special version of the Leyland O.400 engine, modified by having a reverse flow cylinder head in place of the standard crossflow type. But Bedford used the crossflow variant in the KH truck and VAM14 bus. Leyland and Albion later used the reverse-flow variant in Ergo-cabbed trucks.

The (much needed) end-to-end cylinder head coolant flow change for the 330 diesel engine was announced 196409, and applied to the SB5. The same change was also applied to the 300 diesel and 300 gasoline engines, but possibly somewhat later.

Abandonment of the Leyland O.400 in favour of Bedford’s own and very noisy 466 in the VAM and VAL happened around 196709, about a year after the KH and KG trucks went over to the Bedford 466 and 381 engines respectively. I suspect that the SB13 quietly exited at the same time.

I am not sure when the 5-speed gearbox option was first offered on the SB, but it was available by late 1960 at least. Rather oddly, the SB 5-speed option remained constant-mesh through to the late 1960s at least, even though the VAM and VAL had synchromesh 5-speed gearboxes.

Notwithstanding that the Bedford SB was the most significant bus chassis produced by the British motor industry, it is odd that the British publishing industry has not seen fit to produce a decent monograph on it (“decent” meaning good coverage of the engineering aspects). The same omission applies to the chassis in #2 position, the Leyland Worldmaster.

Cheers,

Has everyone forgotten the lowly NJM? I still own the only "bus" ever to be allowed to take driving tests for both "truck" and "bus" licences by DVLA. It is an ex-army vehicle and even converts to a 12 stretcher ambulance with seats removed and frames substituted. A very versatile vehicle with a long and interesting history.

I believe these were also used as black marias for the police, with alternative bodies.

As a mechanic, underneath, it looks like a truck!

The NJM was the later model designation for the Bedford SB5, which Stephen has included in his list.

The appeal of the Bedford SB in many world markets was that it was a truck-derived bus chassis, and so shared parts and maintenance commonality with a broader fleet. The same was true of several other export-oriented bus chassis, including the Leyland Comet, Albion Victor, Albion Clydesdale, Ford Thames Trader 570E and AEC Ranger to name a few.

Cheers,

I am certainly no expert on Bedfords but have just noticed one missing from the list: VAM5, with 330 engine and Turner-Clarke 5-speed synchro box.
SB originally had a Bedford 4-speed synchro box which had been introduced that year with the last of the O, M and K goods chassis and possibly the last OB coaches. It was a wide-ratio unit but a close ratio set was later used for those with Leyland O.350 engines. In the equivalent S-type lorries, this engine often overloaded the gearbox; some operators subsequently fitted Albion 5-speed boxes, which then overloaded the back axles.
I think the 5-speed constant-mesh box introduced c.1960 in the SB was an ENV unit. As far as I know, all VAMs and VALs had 5-speed synchro boxes. When 466 engines replaced the Leylands, gearsets were changed to wider ratios - I believe 3rd speed on VAL70 was something like 1.9 to 1; with direct-drive 4th, 5th was something like 0.82 to 1. I have never understood why these lightweight motors (including Bristol LH) had such uneven ratios, whereas AEC and Albion had perfect spacing; slightly convergent going up the box, then a half-step to overdrive.

Dear Bruce,

Yes, thanks for pointing that out, quite a glaring omission on my part as with it's native power it was the volume model supplied to dealer stock, whilst the VAM14 was built to order as were the comparatively tiny numbers of VAM3.

best Wishes

Stephen Allcroft
Cardross
Scotland

I will get round to the promised revision, some time after I have uploaded the Guy Arab Article to Wikipedia. In the mean time I can tell you (thanks to the Nostalgia Road book on the type) the VAL70 was coded WRT under the computerised system which turned the VAM70 into the TRP, the SB5 into the NJM etc...

Best Wishes
Stephen Allcroft
Cardross
Scotland

That prompted some looking for numbers and a few calculations. I have attached a page from the 1965 July brochure for the Bedford VAM. I imagine that this brochure was the initial issue for the VAM. The selected page includes engine and gearbox details.

The Bedford four-speed gearbox available with the 300 gasoline and 330 diesel engines had the following ratios:

1st 7.059:1
2nd 3.332:1
3rd 1.711:1
4th 1.000:1

If we assume that the target for first was 7.0:1, then the corresponding geometric sequence would be: 7.000; 3.659; 1.913; 1.000, with an inter-ratio spacing of 1.91. So there is some gathering or convergence, but that I think is the normal trade-off with four-speed units in order to keep the spacing between 3rd and 4th not unreasonably large.

The direct top 5-speed gearbox (Turner-Clark) optional with the 300 and 330 engines had ratios:

1st 7.080:1
2nd 4.090:1
3rd 2.240:1
4th 1.380:1
5th 1.000:1

The geometric sequence would be 7.000; 4.306; 2.646; 1.627; 1.000, with an inter-ratio spacing of 1.63. So the actuals are well away from this. The spacings are 1.38, 5-to-4, 1.62, 4-to-3, 1.83, 3-to-2 and 1.73, 2-to-1.

Perhaps the reasoning was that as the basic 4-speed gearbox was deemed to be satisfactory, there was some freedom in the placement of the intermediate ratios in the 5-speed case. And that in particular, having 4th quite close to 5th was seen as beneficial, perhaps to enable the maintenance of higher road speeds on undulating routes.

The 1.38 spacing from 5th to 4th was about the same as the spacing between the high and low ratios in an Eaton two-speed axle. So when the latter option was fitted, 4th high and 5th low would be close to identical.

By way of comparison, here are the ratios for the Albion GB241:

1st 6.988:1
2nd 4.308:1
3rd 2.655:1
4th 1.605:1
5th 1.000:1
6th 0.760:1

The spacings from 5th down to 1st are quite close to the geometric sequence, and possibly as close as can be realized with practicable tooth counts. As Bruce said, the overdrive is at half-spacing, the theoretical being 0.784.

The basic 5-speed gearbox GB241 would have been ideal for use with a splitter, either a 1.278 underdrive or 0.784 overdrive. It took quite a while for Leyland to wake up to this possibility, though.

Returning to the Bedford VAM, the 5-speed overdrive gearbox that came with the Leyland O.400 engine had the ratios:

1st 6.06:1
2nd 3.00:1
3rd 1.70:1
4th 1.00:1
5th 0.80:1

Assuming a 1st gear target of 6.0:1, the geometric progression for 1st through 4th would have been: 6.00; 3.30; 1.82; 1.00, with a spacing of 1.82. Against this, it may be seen that there has been some convergence, as per normal 4-speed practice, given that this gearbox was essentially a 4-speed-with-overdrive unit. The 5th overdrive, at 0.80, is spaced at just a bit less than half of the 4th to 3rd spacing, which would have put it at 0.77.

Presumably with a given rear axle ratio, the O.400 engine provided the same hill-start capability with its 6:1 1st gear as did the 300 and 330 engines with their 7:1 1st gears. But again with a given axle ratio, the O.400 would have required the overdrive 5th to reach about the same top speed as did the 330 engine with direct 5th. Although that said, whether the 330-engined VAM could reach its theoretical top speed when fully loaded might be debatable.


Cheers,