James had a licensing deal with Iona (Fantom Technologies). While the Fantom Lightning used many of the DC02's designs, the two machines were very different inside. Once the DC02 had been designed and on the European market, James was eager to have Iona make their own version for the US market, because quite simply, it meant more money in his pocket. Every Fantom dual cyclone vacuum ever made put money in James' pocket.
The DC02 was designed for efficiency. While James did make money selling filters, and they were not 'washable' at that time, the DC02 made a serious attempt at keeping fine dust out of the motor. He used an pleated electrostatic pre-motor and post motor filter (a HEPA post motor filter was optional). He used two large entrances to his high efficiency cyclone, allowing for excellent airflow. He used a cross beam in the vortex finder to make the high efficiency cyclone even better.
Fantom was in the business of selling VERY expensive Hepa filters for their vacuums. At $75 a piece, a Fantom filter was very profitable for the company. The Fantom Lightning was designed to fill the Hepa filter within one to two years, causing the need for a replacement. Fantom did this in three ways:
Fantom Lightning's entrance to the high efficiency cyclone was, by contrast to the large double entrances on the DC02, a small opening one inch long, one inch wide. The high efficiency cyclone was far more tapered than the DC02's. The Lightning's clear bin did not have baffles in the bottom to aid the low efficiency cyclone, another difference from DC02. Also, the Fantom did not have the cross beam in the vortex finder.
Yet the biggest difference was the steel mesh pre-motor filter. Large, open stainless steel holes let virtually all the fine dust into the motor. Stopping only the lint and hair, Fantom's entire dual cyclonic range always did nothing to stop the fine dust - to sell more Hepa exhaust filters. You must remember that James had invented the MEMA filters (washable lifetime filters) by the time the Lightning was launched, and Fantom COULD have used them. They chose not to, due simply to the desire for profit from Hepa filter sales. That shortsightedness is what ultimately led to their failure.
Some would argue that build quality was the problem with Fantom. While it was a factor in a far higher than average warranty repair cost to the company, the motor failure caused by the fine dust going through it on the Fury models is what really cost them consumer confidence. The Fury had, in reality, an Electrolux Discovery II motor in it. Made by Ametek, if you stood it next to an Electrolux DII motor, it would look identical. The fans in both motors were smaller than 'normal'. I would give a fair estimate that at least half of all Fury vacuums died of motor failure within four to six years.
Lightning's had their share of motor failure too, as did the Cyclone XT. But nothing like the Fury, as both the Lightning and Cyclone XT had some sort of pre-motor filter. The Fury's wire 'lint guard' kept virtually nothing out of the motor.
Since the Fury was about $100 less expensive, they sold significantly more of them than they did the Thunder.