EMPATHY & DEFINE
OBSERVATIONS
At times, elite mountain bikers aren't able to ride their bikes to their destinations and so they transport them in a car or on a rack on the roof racks or on a tow bar rack. The first two options, inside the car and roof rack, are at most times not practical; this is because the car needs to hold other things or the bike is dirty or roof racks are not trusted to hold the expensive bikes secure in a high wind/ low clearance scenario. So the best and most common place is on a rack on the back of the car.
The problem observed many times with bikes being transported on racks is that the car boot cannot be opened while the rack is attached to the tow bar. In this circumstance, the bikes are taken off the rack and then the rack is taken off the car so that the boot can be opened. This is observed to be an intense and laborious process, resulting in wasted time. It is also observed regularly that people attempt to remove the rack with the bikes still attached, but the person struggles to lift the rack (with bikes). Then the bike frames experience unnatural stress resting on the ground attached to the rack and this damages the bikes. It is also worth noting that these bikes are extremely expensive, ranging between $2000 and $15000, and there should be no circumstance where these bikes are damaged.
The problem observed many times with bikes being transported on racks is that the car boot cannot be opened while the rack is attached to the tow bar. In this circumstance, the bikes are taken off the rack and then the rack is taken off the car so that the boot can be opened. This is observed to be an intense and laborious process, resulting in wasted time. It is also observed regularly that people attempt to remove the rack with the bikes still attached, but the person struggles to lift the rack (with bikes). Then the bike frames experience unnatural stress resting on the ground attached to the rack and this damages the bikes. It is also worth noting that these bikes are extremely expensive, ranging between $2000 and $15000, and there should be no circumstance where these bikes are damaged.
BIKE WEIGHT
The weight of the bikes of elite mountain bikers varies depending on their mountain biking discipline. For example, mountain biking can be split into XC (cross country) and DH (downhill), each with vastly different weights. Although the weight of the bike is affected by the money spent on top of the range parts, the general weights can be split into four categories of bikes:
It is important to note here that riders in these four general categories can all be classified as 'elite' as there are competitions and races where a bike in each of the four categories would be highly appropriate. Therefore a solution to carrying the bikes of elite riders must be strong enough to carry the heaviest bike which is a Downhill bike.
- Carbon Hardtail with 3-4" suspension
- Carbon Dual with 3-4" suspension front and back
- Dual with 5-6" suspension front and back
- Downhill with 8+" suspension
It is important to note here that riders in these four general categories can all be classified as 'elite' as there are competitions and races where a bike in each of the four categories would be highly appropriate. Therefore a solution to carrying the bikes of elite riders must be strong enough to carry the heaviest bike which is a Downhill bike.
ERGONOMICS
By looking at the swing of a car boot, it can be observed that a certain arc is followed each time. For the user to interact properly with not only the solution, but the boot, the ergonomics should allow room for that arc. Observations show that an arc from an SUV car boot would be too wide for a tow bar rack to shape around it. Instead, a rack that could hinge down from the tow bar would be an ideal solution to the particular car boot problem; as shown by the company Thule who have made a hinging tow bar rack.
Thule have made a bike carrier that mounts to the tow bar and folds down to allow the swing of the boot. It holds the bikes by supporting them from the bottom and only folds part way, not letting the bikes hit the ground. Its only negatives are that it has a limited carrying capacity based on the tyre slots in the base plate. This is an effective solution to the car boot problem. A similar technique of a hinging rack could be adapted.
HINGING
The ideal way to hinge a tow bar rack can vary; it depends on the stress exerted on the hinge, the shape of the hinge and the way in which the hinge is moved. There are hinges such as the one employed on the Thule racks discussed above or a simple box steel lengths hinged by a pin.
A hollow ball bearing style hinge has been influenced by the Shimano Hollowtech bottom bracket which is used in high level mountain bikes. It's hollow center gives it a very classy and professional look whilst keeping weight down. The aesthetics are second to none and it would work well as an adaptation to a hinge for a curved bike rack.
ANTHROPOMETRICS: ARM HEIGHT & REACH OF A PERSON
It is important to get the ideal height for the rack once mounted on the bar. There are two options for this: a stationary height based on averages or an adjustable height.
The average arm height from the ground when arms are held parallel to the ground is:
The average arm reach from shoulder to fingers is:
Average height of a tow bar from the ground:
It is important to note that an elite mountain biker can be anyone; their are no specific height or reach traits to mountain bikers so it will be effective to base the measurements of the rack on averages within genders and between genders. The fact that specific anthropometric values are irrelevant to being a successful mountain biker has been tested by a group of four sports scientists. They concluded that athletes needed experience and high training volume rather than specific anthropometry values. (Journals.lww.com, 2014) This supports my observations that elite riders are diverse, and so supports the need for the rack to accommodate all sizes of person.
- Men. 140 (cm)
- Women. 133 (cm)
The average arm reach from shoulder to fingers is:
- Men. 61 (cm)
- Women. 55 (cm)
Average height of a tow bar from the ground:
- 45 (cm)
It is important to note that an elite mountain biker can be anyone; their are no specific height or reach traits to mountain bikers so it will be effective to base the measurements of the rack on averages within genders and between genders. The fact that specific anthropometric values are irrelevant to being a successful mountain biker has been tested by a group of four sports scientists. They concluded that athletes needed experience and high training volume rather than specific anthropometry values. (Journals.lww.com, 2014) This supports my observations that elite riders are diverse, and so supports the need for the rack to accommodate all sizes of person.
"successful athletes in a mountain bike ultramarathon, in a special environment and using sophisticated equipment, need prerace experience coupled with high training volume, rather than any special anthropometry." Knechtle B, Knechtle P, Rosemann T, Senn O
MATERIAL PROPERTIES
There are a few options of materials to build a bike rack from, the most common being steel and aluminium. However if a component needs to be reduced weight so the user can easily fold it down for boot access, a material such as aluminium would work perfectly but it would not be as strong as steel. The carry weight of the rack would also be crucial; a maximum of 50 -75 kilograms (lets say) would put the count at roughly two downhill bikes and up to four of the other three types, which would be sufficient.
However with bumps and jolts in the road, the aluminium may not be the best choice structurally. Or the structure may be composed of the two metals together at different parts. With either metal, welding and machining will be a key point in forming the rack and will be limited to processes available in the workshop, which may rule out CNC machining and aluminium welding.
However with bumps and jolts in the road, the aluminium may not be the best choice structurally. Or the structure may be composed of the two metals together at different parts. With either metal, welding and machining will be a key point in forming the rack and will be limited to processes available in the workshop, which may rule out CNC machining and aluminium welding.