("The Whisper^®, efficient, quiet and clean")

"The Whisper^®" during one of many test runs in Heerenveen (January 2004)

A groundbreaking cooperation by which brand new Ambassador 200 type bus manufactured by coachbuilder VDL Berkhof (Heerenveen), purchased by Connexxion (bus operator) for use in the Town of Apeldoorn in the Netherlands, (project grantor), with financial assistance of the Province of Gelderland (subsidy provider) was converted by e-Traction Europe B.V. (inventor, manufacturer and lead contractor for the conversion) and NUON (local energy company) joined efforts to test a revolutionary dual electric direct drive traction concept that was believed to hold much ecologic and economic promise.

Historical Perspective

The ambitious production schedule with a for fully functioning vehicle was set for early October 2003 to coincide with the town of Apeldoorn being the host to the finals of the Nations in Bloom competition.

Delivery of a brand new bus straight from the production line occurred on June 2nd, 2003.

Pending final review of the overall project by the Province of Gelderland, a temporary and limited approval to commence work was granted on on June 11th, 2003. 

The interior of the section being converted was removed and stored on the roof of the "the Whisper^®". Redundant parts were weighed and shipped to a Connexxion storage facility for use as replacements for the conventional siblings of this Ambassador 200 bus.  The weight of the parts removed was eventually compared with the parts that have replaced them. With the later deemed oversized traction unit and its tires and the fairly heavy Nickel-Zinc batteries the reconfigured bus weight roughly 500 kg more than it originally did.

Final assembly of two prototype TheWheel™ SM700/3 units took place in Apeldoorn in late September. 

The engine bay was adapted to contain a track-mounted marine grade 50 kW diesel powered generator housed in a sound proofed container.

28 Ni-Zi Batteries are stored in drawers on the rear left which also contained the AC chargers on top. These chargers were being fed by either the generator or the power grid.

The specially manufactured Continental tires with a diameter of 136 cm were mounted on the rims surrounding TheWheel™ SM700/3. These oversized low pressure tires turned out later to have a major impact on the rolling resistance and thereby fuel consumption. At some point in the not to distant we hope to entice a manufacturer to built a tire that better meets our specifications for this particular traction system.

With the removal of the traction diesel motor it became necessary to install a 24 VDC electrically powered compressor air suspension and brake systems and electrically powered hydraulic pump for the power-steering.

On October 3rd, "the Whisper^®", a name conceived by Marko van Beckhoven - son of wethouder (alderman) Jan van Beckhoven, was introduced to the press.  Unfortunately shortly before the event, while bringing the tires to proper pressure, the left rear wheel rim failed.  As a spare wheel rim was not immediately available the invitees had to satisfy themselves with a static display in which the motors were running and the generator was cycled on and off to simulate the noise, or better yet the lack there of, could be experienced.

On Sunday October 5th  "the Whisper^®" was put on display at the central square in front of Town Hall of Apeldoorn for the delegates to the Nations in Bloom event and the citizens.

Former Wethouder Jan van Beckhoven in front of "The Whisper^®"

Initial test prove viability of the concept but fuel savings disappoint

The possibility of a four wheel drive version equipped with TheWheel™ SM500/1FE had been rejected for practical reasons. At the time the project was started only one other traction system had been developed that, based on the advice of those deemed knowledgeable, was considered powerful enough to propel a bus of this weight, with two TheWheel™ SM700/3AL units. This decision turned out to be less than optimal because these motors proved to be both too powerful and much too big. Furthermore, no suitable tires could be located for use in passenger operations. Thus it was decided to first verify the concept, while e-Traction® would develop a more manageable size traction system, TheWheel™ SM500/2FE.

Once installed, and after some initial mechanical and electronic glitches, the combined system ultimately performed as expected. The air pollution was lower and additional improvements were considered very likely with increased fuel savings. Most notable was that the noise level was substantially reduced from 78 decibels to only 58 (see: noise pollution for further details).

The fuel savings, compared to the ultra efficient Ambassador 200 diesel bus of VDL Berkhof, were disappointing. In a simulated city operation comparison test the hybrid version of the Ambassador bus demonstrated only a 7.4% improvement in fuel mileage. One should bear in mind that this was the first use of this truly novel traction system, and it that was being compared against a propulsion system that had been perfected in many different ways and is being used for more than 100 years in massive quantities, but one that probably is currently about as efficient as it will ever get. TheWheel™ is merely at the threshold of its technological development and should no doubt see many advancements in efficiency of production and use.

In depth analysis attribute the disappointing fuel savings of the "the Whisper^®" in large part to the high rolling resistance of the low pressure tractor tires that were specially converted for this application by the Continental Tire Company with road worthy thread (see also: Fuel Savings Calculator). Whereas a conventional Ambassador bus has a rolling resistance of 13 kilograms per ton, "the Whisper^®" had one of 19 kg/ton. The rolling resistance of the recently completed e-Traction® Bus with its high pressure Michelin super-single tire, model XDU 455/45 R22.5 tire has been established at only 11 kg/ton.

In addition, due to the disappointing performance of the batteries, the generator wound up doing extra duty further negatively impacting fuel consumption.

The oversized traction system was never taxed for more than 8% of its potential. This excess capability resulted in unnecessary weight and resistance of the oversized units. Furthermore, these oversized units, and particularly their tires, also resulted in a loss of 8 seats in the bus.

Impact of the smaller TheWheel™ SM500/2FE wheel hub motor clearly illustrated

Complicating the decision to commence the planned second development phase, however, were both a lack of funding and the loss of project partner Connexxion of the concession in Apeldoorn and surroundings. To resolve this problem e-Traction® has now assumed full ownership of The Whisper^®, and become solely responsibility for the conversion from "the Whisper^®" configuration to that of the Whisper^® utilizing its own financial and human resources.

To view the next phase of development click on the link to the Whisper^®. 

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Last modified: April 28, 2009