AEC Reliance Export ModelsThe AEC Reliance bus chassis has had extensive treatment in the literature, with reasonable mention of the export versions. What I have endeavoured to do in this posting, which will be in two parts, is to extract from available sources the chronology of the export models, which I haven’t seen done elsewhere in a standalone fashion. Some references to the domestic models have been necessary for context and clarity. I have used “Commercial Motor” (CM) magazine articles and items as chronological markers. The CM archive is available at:
http://archive.commercialmotor.com/.
The AEC Reliance was announced in CM 1953 October 30. In its original form, it was a 16’4” wheelbase chassis with 5’13/8” front overhang, suitable for carrying 30 ft bodies with a gvw of 9½ tons. It was offered with a choice of the then-new AH410 and AH470 engines, and with a choice of 5-speed synchromesh or 4-speed air-operated epicyclic gearboxes. Vacuum brakes were standard for the domestic version with synchromesh transmission. Air brakes were standard with the epicyclic transmission , and optional with synchromesh. Its model number was MU.
From the start, an export version was offered, dimensionally similar, but with a thicker section frame. This no doubt had a higher gvw. I have not seen a number for it, but 11 tons, as for the later 2MU export model seems likely. It had air brakes as standard equipment. The same model number MU was used, but with an E suffix for the right-hand drive versions. The left-hand drive versions were export-only, and so did not require this suffix.
During 1956 the export version of the Reliance MU was replaced by a dedicated export model, the HMU. The chassis was flitched between the axles, rather than using a heavier section as had been the case with the MU-E. The HMU was available in two wheelbases, namely 16’0” and 17’6”, suitable for respective nominal body lengths of 30 ft and 32 to 33 ft. Both had a front overhang of 5’9¾”. The longer variant was new in the Reliance range, and used the same 17’6” wheelbase as had earlier been chosen for the core model in the Regal IV series, which was also intended for 32 to 33 ft bodies. It looks as if the shorter HMU variant was obtained simply by subtracting 18 inches from the wheelbase. That gave it a longer front overhang than the MU model, making it more suitable for urban applications where reasonably wide front doors were desirable. Gvw was 11½ tons. Details were provided in a sales brochure dated 1956 July:
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AEC Reliance Overseas #545 195607 p.06.jpg [ 840.64 KiB | Viewed 1125 times ]
Only the AH470 engine was available, whereas the domestic model still offered the choice of the AH410 and AH470, as recorded in a 1956 May brochure. The gearbox options remained the same as previously, namely 5-speed synchromesh and 4-speed Monocontrol.
Mentioned in CM 1958 September 26 in a report on that year’s Earl’s Court show was a chassis change for the Reliance, namely the adoption of mechanical rather than belt drive for the auxiliaries. With this the MU and HMU models became the 2MU and 2HMU respectively. A road test of the 2HMU in 17’6” wheelbase form was published in CM 1959 May 30. Curiously, a 1959 September sales brochure featured the new auxiliary drive, but still referred to the series as HMU, not 2MU. I suspect that this was an editing error.
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Also recorded in that same CM item was the availability of an air suspension option for the Reliance. Chassis so equipped were known as the 3MU and 3HMU, although not many were built.
There was an extra-short version of the Reliance produced for export, with a 13’7” wheelbase, in both the MU and 2MU eras. But whether this was derived from the domestic (2)MU or the export (2)MU is unknown.
In mid-1961, two longer Reliance chassis, suitable for 36 ft bodies, were introduced, as announced in CM 1961 August 11. These were a response to the change in the UK C&U regulations that allowed a 36 ft maximum length for buses in place of the previous 30 ft.
Both models had an 18’7” wheelbase with a 6’6½” front overhang. One was the Reliance 470, model number 4MU, with the same running units (and options) as in the 2MU. Initially the gvw was 11 tons. Evidently AEC thought that there was enough change as compared with the 2MU to warrant a new model number, and 4MU was the next available in the MU series. The 4MU chassis was similar to the 2HMU chassis in that it included a between-the-axles flitch.
From about the time that the 4MU was introduced, the Reliance 470 name was also used for the 2MU (and presumably the 2HMU models), which continued unchanged. It appears to have been applied retroactively to earlier-built (2)MU and (2)HMU models, although whether that was done officially by AEC or informally by common usage is unknown.
The other new model in 1961 was the Reliance 590, model number 2U, which had a very similar chassis to the 4MU. This had the AH590 engine, which was effectively a smaller bore version of the AH690, the engine used in the Regal VI export chassis that had been announced in CM 1960 August 26. It was successor to the Regal IV, and was very similar to the Reliance in its layout. Its model number was U, which explains why the closely following Reliance 590 was the 2U. That was the beginning of an interleaved U series, with the Regal VI having the odd prefix numbers and the large-engined Reliance the even numbers.
The 36 ft version of the Regal VI had a 19’6” wheelbase, inherited from the long version of the Regal IV, to suit overseas requirements. To meet the UK requirements for 36 ft buses, particularly the turning circle, a somewhat shorter wheelbase was needed, and as noted above, AEC chose 18’7”, already in its inventory as the wheelbase of its longer version of its Regent V front vertical-engined chassis.
The Reliance 2U gearbox options were 4-speed synchromesh, 6-speed overdrive synchromesh and 4-speed Monocontrol. Gvw was 12½ tons. Details of the domestic Reliance 470 and 590 models were provided in a 1962 July sales brochure. By this time the gvw of the 4MU had moved up to 12 tons.
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AEC Reliance #711 196207 p.07.jpg [ 536.35 KiB | Viewed 1125 times ]
The 4MU was essentially a domestic chassis, and although some were exported, these appear to have been to the domestic specification, there being no evidence that there was an E-suffix export version. On the other hand, the 2U was also intended for export. To that end, a 17’6” wheelbase variant was also offered. This had the same 6’6½” front overhang as the 18’7” wheelbase variant, so in that respect it differed from the 17’6” wheelbase variant of the 2HMU. Both wheelbase options were shown in this 1962 August export sales brochure, #724, and gvw was the same as for the domestic model, namely 12½ tons:
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AEC Reliance Export #724 196208 p.07.jpg [ 992.29 KiB | Viewed 1125 times ]
The only Reliance 470 variant listed in that brochure was the 2MU export version, with 16’4” wheelbase, 5’13/8” front overhang, and 11 tons gvw. From that one may infer that AEC may have abandoned the 2HMU, and returned to an updated version of the original MU export version. Only the 2U was described as having a flitched chassis., which indicates that the 2MU was not flitched.
However, an undated French language brochure for the Reliance presented a somewhat different picture. This had number 724B, so it was probably somewhat later than #724:
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AEC Reliance 590, 470 France #724B p.07.jpg [ 123.02 KiB | Viewed 1125 times ]
No model numbers were given, but the Reliance 590 was shown in both 17’6” and 18’7” wheelbase variants, albeit with a gvw of 14 tonnes (13.8 tons). The Reliance 470 was shown in both 16’4” and 17’6” wheelbase forms, both with a 12.5 tonne (12.3 ton) gvw. The short version was dimensionally identical to the 2MU export. The longer version was dimensionally identical to the 17’6” wheelbase variant of the 2U. That gave it a 6’6½” front overhang instead of the previous 5’9¾”. Presumably that was done for standardization.
On paper at least it would appear that at the time or soon after the 2U was introduced, AEC modified the 17’6” wheelbase version of the 2HMU to align with the same wheelbase version of the 2U. Then rather than leave the 16’0” wheelbase 2HMU as an “orphan” model in front end terms, it opted instead for an export version of the 2MU. Also, it appears that AEC offered different mixes of Reliance variants in different overseas markets.
An updated version of the AEC air suspension system was announced in CM 1962 July 13. This used four rather than two air bellows per axle. The 3U model number was applied to the air suspension version of the Regal VI, with 4U applied to the Reliance 590. The air suspension versions of the 2MU and 2HMU continued to be known as the 3MU and 3HMU respectively, with 5MU used for the air suspension version of the 4MU. The last-mentioned was probably quite rare, although 2 are known to have come to New Zealand.
During the currency of the Reliance 470, an additional gearbox option was added, namely 6-speed overdrive constant mesh. This had happened by the time home market specification #711 was issued in 1964 January. It is reasonable to assume that the same option was offered on export models.
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To be continued.
Cheers,