Now a National
Page 17
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quiet bus by Martin Hayes
• A development of the Leyland National city bus. said to be quieter than any of its foreign competitors, was unveiled this week. The bus — which features insulation material over the top of the engine but does not use undertrays — is said to be 25 per cent quieter at the rear of the saloon than its competitors.
The bus was shown at the first press visit to the Cumberland factory (described on page 40). It has a 200bhp engine, which is not derated, and automatic transmission. The bus had just returned from Oslo where city transport authorities had compared it with other -Quiet" buses. The results of their tests — which were not to British Standard conditions — are listed below.
Interior noise levels Leyland National: front 65DbA, middle 68, rear 70; Scania CR111 (the Swedish equivalent of the Metro-Scania Quiet Bus): 65, 70, 75; BUssine, BS110V Prafekt (to VOV specification): 74, 75, 80.
Exterior, accelerating up hill: at 40kph: Leyland National 62; Scania, 67; Rtissing 72. At 50kph: Leyland National 63; Scania 64; Bussing 67.
When CM tested the Metro-Scania Quiet Bus under BSI conditions (accelerating from 31 mph) it achieved 76DbA. It seems likely that under the same conditions the National may achieve at least 10DbA better.
The conversion work on the National — which consists of inserting sound-deadening material under the floor along the whole ength of the vehicle and around the sides Ind top of the engine compartment — was Jndertaken by the Danish DAB concern. ks it had only just returned from them,
Leyland engineers did not know what additional weight penalty was involved. However, Mr Ron Ellis, managing director of British Leyland's truck and bus division, told me that in production the additional cost of the package might be around £500-E600. It would probably be offered as an option at first.
Leyland engineers told me that their Quiet Bus was Phase 2 of a noise-beating programme for the National, Phase 1 is already incorporated on production models. Phase 3 may entail complete encapsulation and, possibly, engine de-rating.
Brief rides in the rear of the Quiet Bus and a standard vehicle confirmed that noise during idling and heavy acceleration has been appreciably reduced by the insulation work. However, there did not seem, subjectively, to be a great deal of difference under a trailing throttle.
Lord Stokes. chairman of BLMC, said at an inaugural lunch that the Leyland National factory would shortly be producing 22 vehicles a week (the projected maximum is 40). He revealed that British Leyland now has a record bus order book worth £57m.
He and other Leyland personnel were reticent about future derivatives of the National. But it seems likely that faster and more luxurious versions are on the stocks. Although the factory could obviously accommodate a double-deck design, indications are that Leyland's integral B15 design — still only on the drawing board — may be built elsewhere because its production would be too small for the automated Leyland National plant.