Mat underframed Prisma
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by Noel Millier • Mercedes-Benz and Leeds coachbuilder Optare have jointly launched the Prisma, a 12m city bus based on the proven Mercedes-Benz 0405 underframe. The Prima matches the Optare Alusuisse body system (used on the Daf based Delta and Dennis based Sigma) with the box-section steel spaceframe-type 0405 underframe. This will be engineered at Mannheim and supplied to Optare with front-end and wheelarches adapted for the Prisma.
The bus meets 1997 DPTAC recommendations and has a low first entry step of 320mm which can be reduced to 240mm by kneeling the front air suspension. Two further 200mm steps lead into the saloon with a further step of 190min forward of the rear suspension. Alternatively a ramped floor can eliminate the need for the saloon step.
Prismas are offered with a choice of layouts for up to 54 seated passengers. The first demonstrator has 49 seats with room for 23 standing.
As with other Optare products, the electrical system is centralised inside the vehicle. Lower body panels are easy to remove for repair; front corner panels hinge out for easy bulb replacement and gasket-glazed tinted side windows are standard.
Power comes from the Mercedes-Benz Euro.1 naturally aspirated 12-litre in-line six producing 210hp (157kW) at 2,200rpm with 5331bft (750Nm) of torque at 1,400rpm. A Euro-2 model is available. Drive is transmitted from the rearmounted engine via a Voith three-speed or ZF four-speed automatic gearbox.
Other details include air suspension all round and a Mercedes-Benz hub-reduction drive axle. Options include ABS and ASR (anti-wheelspin control), tachograph activated autolube and adaptation for guided bus use.