The Concept

Overview: 

The Revbox Erg supersedes existing stationary trainers by providing athletes with a high performance training tool that has an unlimited resistance range in a compact transportable layout. Design requirements were to create a device that would allow extremely high power output training, from very low to very high cadences, suitable for even the most powerful elite athletes. 

Just replicating general road conditions was too broad an objective. Our real goal with the Revbox Erg was a training unit that would stimulate specific muscular, aerobic, and anaerobic adaptations to improve key areas of a cyclist’s performance. The Revbox Erg uses the chain of the bicycle to transfer power to the fan for immediate, non-slip resistance. 

Designed and engineered in Christchurch, New Zealand, unparalleled targeted performance gains are possible that cannot be achieved with tire-roller based stationary trainers. For cyclists serious about achieving their goals and seeking precise time managed training benefits, the Revbox Erg is the ultimate high performance training unit. 

Resistance:

If required the large 580mm diameter fan produces air drag that allows training at power outputs in excess of 2000 watts. In a 53/11 gear ratio, just 50 pedal revolutions per minute, requires an output of 500 watts, making the Revbox Erg an ideal training unit for low cadence strength training. At the top end, 90 RPM in a 53/11 ratio requires 1800 watts and at the low end peddaling with 90 RPM in a 39/28 ratio requires less than 130 watts, which demonstrates the versatility, and resistance range of the Revbox Erg design.  

The format of a low friction mechanical connection to the bike via the chain, and the high revolutions of the fan, creates an inertia rate unlike that of any stationary device, and perfect for the specific high power output training demands of the ambitious athlete. 

Standard trainer designs have a usable resistance range defined by the mechanical limits of the small diameter units, and exhibit linear resistance increases. An extremely large diameter fan, however, displaces a huge air volume and provides exponential resistance for training across a broad range of parameters. This is a significant part of what makes the Revbox Erg such a brilliant training tool

The resistance scale provided by the Revbox Erg is suitable for amateur riders through to Tour de France athletes and Olympic track sprinters. 

Fan Inertia:

Next to monitoring, and training to, specific power outputs, understanding inertia rates are a critical aspect to improving performance on the bike. A stationary trainer with high inertia only replicates riding on the flat on a smooth road with calm conditions or a tail wind. The Revbox Erg with its deliberately tuned low inertia lightweight air-braked fan encourages increased muscle and motor-skill development at high cadences, as well as providing a very effective means of constant resistance for strength training at low cadences. Developing neuromuscular efficiency, essentially brain to muscle coordination, at high intensities, is crucial to a rider improving the efficiency of oxygen utilization by the working body. 

Inertia rates of a stationary trainer have a significant impact on a rider’s pedaling dynamics. Training at carefully chosen pedal speeds and power outputs, certain muscle recruitment is targeted, and results in effective coordination and physiological efficiency gains. The Revbox Erg’s low friction chain connection to the bicycle, enhance the specific inertia characteristics, which make for very stable dynamics at high intensity pedaling loads. This means the resistance unit will not gather momentum at high cadences, nor will it stall at low cadences. This is an ideal environment for the athlete to target exact physiological responses. 

Development:

Years of research, design, and prototypes have led us to create the most versatile high performance stationary trainer in the world. No other unit can claim to have such a wide resistance range, such specific training benefits, and be so easily transportable. The first priority was the resistance, which had to be suitable for the most powerful riders. To have no compromises we concluded the Revbox Erg must be made with a large diameter air-braked fan unit. 

Next, our designers considered the biomechanics of cycling at various power outputs and cadences. A stationary trainer that would be designed for specific high intensity training at pedal speeds from 50 - 250 RPM and power outputs up to 2000 watts would only work effectively within a narrow band of resistance inertia. 

A unit that could provide high resistance with a specially tuned low inertia rate had far reaching performance enhancing implications, especially for improving the neuromuscular efficiency of a cyclist. Creating a low friction mechanical interface with the bicycle and eliminating the traditional tire-roller connection was a key step in building such an effective training machine. The Revbox Erg is the final result of our work, an advanced training tool for cyclists seeking an edge over the competition. 

Construction: 

Once the Revbox Erg design had met the resistance requirements we looked at optimising the size and weight. It has been made to be compact, easily packaged, and made of the highest quality materials. The side panels are the main structural component of the device and result in a very low side profile to minimise the overall volume. These rigid side panels along with the aluminium plate cover around the outer circumference make for a durable unit that will withstand even rough travel conditions. The stabiliser legs are removable without tools, in seconds, and the whole unit packs quickly in an optional reinforced, padded travel bag. 

The fan unit is made of a specially machined hub that holds nine aluminium fan blades. The dimensions of the blades have been carefully designed to promote a resistance range that allows incredibly high power output training at even very low pedal speeds. A cadence 45 RPM in a 53/11 gear ratio requires a huge 500 watts. 

Materials used for the Revbox Erg are injected moulded ABS for the side panels, aluminium along with stainless steel for all other parts. No paint or coatings are required. Every single part is available as a replacement in case damage should occur. Compatibility is for road bikes for 130/131mm rear wheel spacing and 10 and 11 speed cassettes provide a further adjustable means of resistance increments. Indexing compatibility for 10 or 11 speed drivetrains from Shimano, Sram and Campagnolo is possible. 

Transport: 

The Revbox Erg is a valuable asset when a rider cannot train where they intend to perform. For example when preparing for London Track events it would be most beneficial to train on that track, or when focused on the Giro d'Italia, to ride the Passo del Gavia. If financial reasons, logistics, or the need to race where the competition currently is, makes this not possible, the athlete can use the Revbox Erg to prepare for the fitness requirements of the goal events. 

In a situation where the race environment is not ideal, like in Beijing 2008 preparing for the Olympic road race where smog was an issue, the Revbox Erg can be easily and cost effectively transported to inside venues and used to train at specific power outputs targeted for the event. For track cycling competitions where often equipment needs packing up on a daily basis, the Revbox Erg is easily disassembled with two quick release levers. With the optional reinforced travel bag the unit can be carried away conveniently by hand. 

The travel bag has dimensions 60cm x 750cm x 20cm for a transport volume of just 0.09m3 and a total packaged weight of approx 12.5kg. The unit on its own is just under 9.0kg, lighter than many other trainers, but with a considerably higher resistance range. The Revbox Erg has the best ratio of unit resistance to size and weight of any stationary trainer in the world, making it especially practical and economical for international air transport. 

How To Use: 

By simply removing the rear wheel, a road bike can be fitted to the Revbox Erg. The quick release skewer on the drive hub is tightened on the bikes dropouts just like a skewer on a wheel. Stabiliser legs are fitted to the unit with attached quick release skewers. No parts need to be removed or adjusted. The Revbox Erg works without a front wheel block as it has been designed to be the same height as a 700c x 23mm road wheel. 

Every 10 or 11 speed cassette with Shimano spline can be fitted to the freehub body and the Revbox Erg can take ratios up to 11/29 to allow also beginners to train with very low power put with less than 130 watts if required.

If a rider does not have a power measuring device such as an InfoCrank, P2M or any other power meter, power can get messured with our Revbox Power App, which is available for free from the Google Play store. To use the app a special sensor kit is required.

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