Paraplegic Prototype

Whilst it is possible to modify a whole range of different motorcycles with the design, a Honda CBR250RR was selected.

This was primarily because I already owned one and I couldn't afford to purchase another motorcycle for the project.

Energy Source

Early in the project it was decided to use compressed air as the main energy source.

A temporary system was set up so that initial testing could be conducted.

This setup included fitting a compressor and air tank into the rear section of the motorcycle (see left image). This space is normally reserved as a storage compartment.

Mechanical air control equipment was mounted onto an aluminium plate which was then strapped to the top of the fuel tank.

With this equipment in place, I had a compressed air supply ready to use so I started designing a pneumatic (compressed air) gear changer.

Gear Shifting

The original gear changer (top picture) consisted of a set of linkages connected to the gear box.

When this lever is clicked up or down by the riders toes, a higher or lower gear is selected.

To overcome the fact that a paraplegic cannot use his toes for this function a pneumatic ram was implemented.

A custom plate was deigned, manufactured and bolted to the motorcycle. This allowed a pneumatic ram to be mounted in place of the toe lever (middle picture).

A pneumatic ram has two air lines going into it. When compressed air from the compressor is passed through the right line, the ram shifts to the left changing to a lower gear.

Similarly, when compressed air is passed into the left line, the ram shifts to the right, selecting a higher gear.

Initially this air flow was controlled by manual valve (bottom picture) however it did not allow very precise control over the gear shifting.

Electronic Control

To increase the level of control and flexibility, the mechanical control equipment was upgraded to an electronic control system.

This electronic control system consists of a programmable microcontroller with signal conditioning.

This system was also much smaller allowing all the equipment to be mounted in the rear storage section (right picture).

Gear Shifting

Once the electronic control system was in place, a click of the thumb lever on the left handle bar (left picture) could be used to shift down gears and a thumb lever on the right (right picture) to shift up gears.

The advantage of this system is that as soon as the click of a button is detected, the electronics takes over. This allows the gear shifting parameters such as the air flow duration and pressure to be optimised giving a smoother gear change.

Another option this system allows is for an automatic gear shift function should the rider so desire. All that is required to monitor the engine's RPM and to program the microcontroller to shift gears up and down when a predetermined RPM is reached.

Braking System

The original braking system contains two levers. The front brakes are operated by a hand lever whilst the rear brake is operated by a foot lever. This foot lever needed to be somehow exchanged with a hand operated system.

The first method experimented with was a thumb brake however there was not really enough room with two thumb operated gear shifting levers already in place.

The second method trialled was a second hand lever mounted parallel to the existing one (left picture). This system worked but it felt uncomfortable to use and was difficult to actuate both the front and rear brake evenly.

The third system utilised was to link both the front and rear brake into the normal single lever system. To do this a master cylinder with a larger bore was required. To allow the rider to pre-set the front to rear brake weighting, a brake proportioning valve (right picture) was mounted under the seat.

To overcome the safety hazard of only having one braking system, a second independent emergency park brake will be added to the motorcycle.

Ergonomic Supports

A rider normally holds their legs in place on the foot pegs, using their leg muscles. A paraplegic without leg muscle control is not able to do this.

The level of ergonomic support required depends on the individual's disability.

The first system developed was for someone with a relatively high spinal injury (eg T8 paraplegia). This system would lean the rider forward similar to a kneeling chair (top right picture).

Foot plates, moulded knee supports and a moulded lumbar support (all shown in red) would be included to keep them in this position.

A laser scanning system was utilised to design supports that are perfectly moulded to the rider's body. This minimises the possibility of pressure sores which are common with a paraplegic's decreased blood flow.

For a rider with an even higher spinal injury (such as T5 paralysis) an additional torso support may be needed to hold the rider's upper body in place. Some sort of steering damper would also be essential (left picture) to ensure the rider has maximum control over the motorcycle.

For a rider with a fairly low spinal injury such as L3 paralysis or an incomplete fracture, the need for ergonomic supports are reduced. It is possible they may only need some Velcro and foot cups.

One side of the Velcro is glued on the fuel tank (middle picture) and the other side stitched into their riding pants. This holds the rider's upper legs in place. The foot cups mounted to the regular foot pegs (right picture) are similar to that found on a bicycle. They hold the rider's lower legs in place.

Stabilising Outriggers

The stabilising outriggers are a cross between training wheels on a child's pushbike and the landing gear on an aeroplane. As the rider slows down, a sensor picks up the change in velocity and the stabilisers deploy into position via two pneumatic rams. As the rider speeds up, the stabilisers retract out of the way.

To get the shape right, a prototype was made from PVC tubing (left photo) as it becomes very flexible when heated. Once the design was finalised, the real version was hand crafted from steel (right photo).

Once the stabilisers where manufactured they had to undergo three major testing procedures to ensure they would be strong enough to perform their task without putting the rider at risk.

Once the stabilisers pass safety testing, the next step is to mount the sensors and other electronic components. With this complete, the microcontroller is programmed to operate the stabilisers.

The stabilisers are then mounted on the motorcycle and under go one last workshop test making sure they go up and down at the correct speeds. The motorcycle's velocity is simulated with a frequency generator (top picture).

One last safety feature is now added - a chain driven manual override which acts as an emergency system in case of a failure such as air pressure loss. A number of key components are monitored by a variety of sensors located around the motorcycle. If a failure is detected, the rider is alerted via a Heads-Up display to use the emergency system.

The stabilisers are now complete and the motorcycle is ready for a road test (bottom picture).