The Euro 6 non-hybrid double-decker market is set to be a competitive one, with four chassis announced so far. Volvo’s B5TL was first to break cover, and the Wrightbus Gemini 3-bodied demonstrator on loan to Lothian Buses has been driven by Tim Deakin. .
When Volvo announced its intention to use the four-cylinder, 5.1-litre D5K engine for both its Euro 6 double-decker chassis â€“ conventional and hybrid â€“ there was a collective intake of breath from the industry.
The similar Euro 5 version of the engine had proved itself a capable and reliable performer in the hybrid B5LH, but would it have sufficient power and torque in a setting where there is no electric motor to help out at times of high demand?
Volvo said it would, backing that up by taking a B5TL along with its Euro 5 predecessor, a B9TL with a 9.3-litre engine, to Millbrook test circuit.
Identically loaded on a hilly course, the B5TL returned a faster lap time than the B9TL. A smaller engine working harder also helps meet the higher exhaust temperature necessary at Euro 6.
Volvo has so far announced MCV and Wrightbus as bodybuilding partners for the B5TL. In February Wrightbus completed a Gemini 3-bodied B5TL for long-term demonstration with Lothian Buses, and Lothian Engineering Director Bill Devlin kindly made it available for a routeone Test Drive.
Evidently it has proved its worth, for the operator recently confirmed an order for 25 long wheelbase, 11.4m examples. The vehicle tested is a short wheelbase, 10.5m bus.
Volvo and Wrightbus have worked to remove as much weight as possible from the Euro 6 ‘decker, which has an ULW of 10,725kg.
The body’s most noticeable difference compared to earlier Geminis is considerably narrower upper-deck windows, saving a small amount of weight and resulting in less solar gain.
Equally noticeable on the test bus is something previously unheard of in the double-decker market. The whole staircase is glazed, creating a head-turning appearance. This isn’t standard on the Gemini 3, but may be specified optionally.
It provides a great deal of natural light inside the bus, but operators who rely on advertising revenue should remember the consequences for placement of T-shaped adverts. The effect is created by adding three pieces of glass to the conventional glazing layout.
At the rear, the D5K engine is mounted transversely to the nearside and is coupled to a six-speed ZF Ecolife gearbox with neutral bus stop function. It’s the first ZF-equipped vehicle to carry Lothian colours for some years. Thanks to the D5K’s small size, engine access is very good.
In common with the B5TL’s predecessors, a large radiator is mounted at the extreme rear offside.
A widely-slatted grille should allow good airflow and a mesh is also present, preventing all but the smallest particles from reaching the radiator and affecting its cooling performance. The combustion air intake is at head height on the nearside.
Destination equipment is from Mobitec. Lothian’s standard front display is made up of two full-colour units, set individually through a single control unit and are exceptionally clear, even from close up. Nearside and rear repeaters are also full colour; the rear unit shows route number only.
Diesel is added at head height behind the signalling window and the AdBlue filler is much lower down, immediately behind the offside front wheel. Volvo has included a small drip tray beneath the AdBlue cap, which should prevent any being spilled onto the ground.
[tab title=”Passenger Access”]
The Gemini 3’s two-piece door is wide at 121cm and its single entry step is 30cm above the floor, which can be lowered to 26cm.
An electric two-piece wheelchair ramp is rapid in operation, which is accompanied by a loud warning noise.
On the lower deck, 14 of the 27 seats are accessible without encountering a step, and the floor is flat until immediately behind the rear axle.
Seats at the rear are slightly closer to the centre of the bus than those towards the front, meaning the aisle there a little narrower.
The upper deck is reached by a nine-step straight staircase. One striking aspect of this, apart from glass having replaced the external panelling, is the amount of room it offers users at the bottom.
Even passengers over 6ft tall can easily negotiate the bottom few steps without having to duck to avoid banging their head, with room available being such that Wrightbus has fitted neither a warning notice nor any padding to the edging. It is an example of design that will be appreciated by passengers.
Headroom downstairs is very good, but predictably the upper deck is not as roomy.
Handrails are numerous and finished in orange.
One curious aspect of the provision of bell pushes is the different between decks; downstairs there are five, located on stanchions both sides of the aisle.
Upstairs they are less numerous, with only three present despite there being 18 more seats. Gemini 2 bodies typically have five bell pushes on the upper deck.
Those upstairs on the Gemini 3 are all located on stanchions to the offside of the aisle, and neither this nor the paltry number is ideal. It needs to be attended to by Wrightbus in production models.
A notable improvement over earlier Geminis is increased legroom for passengers sitting in the coveted front upper-deck seats. Seat pitch throughout the bus is good, with none less than 70cm; passengers over 6ft can sit in any row without their knees touching the back of the seat in front.
A single wheelchair space is to the nearside immediately behind the front axle. It is of a typical size and accessed easily.
On its production buses, Lothian has specified two spaces; that on the nearside will be for wheelchair users only, and the area to the offside is to be reserved for buggies.
[tab title=”Passenger Comfort”]
Ride quality of the B5TL is good, as one would expect from a Volvo, although Edinburgh’s cobbled streets and potholed roads prove more than a match for any chassis, coach or bus. Nevertheless the air suspension absorbs all but the worst of shocks.
Heating is entirely by blown air and no convection radiators are fitted. A fine day meant the bus was warm in any case, but Wrightbus has traditionally made a very good job of heating and it’s unlikely that will have changed with the Gemini 3.
Ventilation may prove to be a different matter.
Both decks have only four opening hoppers each, and they are shallow.
The upper deck will benefit from less heat intrusion than earlier models thanks to its smaller windows, but the glazed staircase on this bus and a large expanse of lower deck glass may lead to uncomfortable temperatures in warm weather.
Seats are reasonably padded, but not overly so, and the 25 production Gemini 3-bodied B5TLs ordered by Lothian will include additional cushioning. Lighting comes from two concealed strips integrated into the ceiling on each deck, and is more than adequate.
Noise levels are on a par with most buses, but on poor roads rattles are generated at the front of the lower deck by the anti-assault screen and cash vault specified by Lothian.
At tickover the D5K engine has a harsh, slightly metallic note, similar to that generated by the outgoing B9TL’s D9B unit, but it is much more refined when under load.
[tab title=”Driver Comfort”]
The driver is well looked after in this bus, although the choice of a basic Chapman seat lacking air adjustment and suspension is puzzling.
In its favour it is leather, but winding handles to raise and lower the base are a throwback almost two decades. Operator preference will no doubt see air suspended seats specified universally on production Gemini 3s.
Cab air-conditioning is fitted and a two-piece signalling window is within easy reach. The Volvo standard steering wheel adjusts via a third pedal, and is attached to the instrument binnacle, with both moving as one unit. This has long been a Volvo bus fitment and prevents the wheel from obscuring any dials.
The dash unit is that fitted to Volvo’s coach range, and is slight overkill for bus work. It would benefit from having a more obvious speedometer, although a digital reading can also be displayed via the on-board computer.
The pedals are large and bottom-hinged, affording a good feel. Room around the pedals is excellent, although that surrounding the seat is less so and space is tight for the driver’s bag. The cab door, which is lockable from the inside, is wide enough, and a very deep manual sunblind is fitted.
External visibility from the cab is good, helped by the Gemini’s trademark deep windscreen and the new model’s altered glazing arrangement to the offside. This gives a good view combined with narrow A pillars, along with mirrors which are quite small but well located.
The glass assault screen slightly restricts the view into the saloon through the internal mirror. The upper deck is monitored through a colour LCD screen above the windscreen coupled to one of 10 on-board CCTV cameras. The screen has buttons to scroll through other cameras, but a secure Perspex cover prevents the driver from doing so.
The 5.1-litre D5K is a four-cylinder version of the Nissan-derived D8K engine which powers the B8R and B8RLE chassis.
Its rated power is 20bhp lower than that of the B9TL’s 9.3-litre unit, and torque output is likewise reduced by 200Nm.
What is noticeable is that the Ecolife gearbox adopts broadly the same shift strategy with both engines, although at time of high power demand when climbing hills it understandably takes the D5K’s speed higher to mitigate against its smaller displacement.
Peak torque is developed across a plateau from 1,200-1,600rpm. On flat terrain the Ecolife makes full use of that band, and when travelling at a constant pace keeps engine speed at around the 1,100rpm mark.
Remarkably for its size, the D5K doesn’t ‘bog down’ when this happens and is perfectly capable of digging in from such a speed.
Never did it give the feeling of struggling for power, even when climbing hills; while the bus weighs in below 11 tonnes, it is still a heavy vehicle propelled by a small engine.
Equally impressive was the bus’ behaviour when accelerating uphill from rest.
It showed a keenness which belied its engine’s small displacement and had no problems reaching 30mph quickly despite the gradient.
Loading the bus to its theoretical total capacity of 102 passengers would provide a much sterner test, although Lothian has been running the B5TL on one of its hilliest routes and reports no problems.
Stopping power is as impressive as the bus’ get-up-and-go. As with all Volvos the brakes are a delight to use and coupled to the Ecolife’s hydraulic retarder allow very smooth stops to be made. Pedal feel is excellent; Volvo brakes take some beating.
The Ecolife works well with the D5K and together they create a pleasing package. Manoeuvrability is excellent, aided by a superb steering lock, and drivers unaccustomed to the bus will rapidly become at home with it. It handles very well.
The B5TL is electronically limited to 50mph, although this can be varied depending on customer requirements.
[tab title=”Verdict & Specs”]
Euro 6 needs high exhaust temperatures regardless of duty cycle, meaning that small engines are here to stay in buses, whether the industry likes it or not.
Despite initial scepticism, that may be no bad thing; they offer potential fuel and weight savings, and with huge expenditure on research and development it’s likely that durability will be at or around the levels of previous larger units.
What is less clear is its affect on pricing. Volvo has refused to give a retail price for the bus, but says Euro 6 attracts a premium of around 8,500. We were also unable to obtain fuel consumption figures.
The D5K’s performance comprehensively scotches any suspicions that the new generation of small power units may lack get-up-and-go. Its performance, albeit in an empty bus, was no different to that of a larger engine’s, and it seems easily man enough for the job.
This bus is a development of a tried, tested and very popular combination. As a very early example of the Gemini 3, the body would benefit from a small number of improvements, but apart from those it is difficult to pick fault.
If the D5K proves to be as durable as Volvo promises, then coupled with an ULW almost 1,500kg less than some earlier Wrightbus-bodied Volvo double-deckers this combination may offer a natural progression for buyers loyal to both brands.