As a freelancer design draughtsperson, I have received widespread experience for my contributions in both mechanical and electrical engineering draughting being involved in product development, presentation, and design reviews. My work involves a combination of technical expertise and creativity. I also brings together technologies from different environments and works inventively. In so doing I am able to translate ideas into working products that meet the needs. As a blogger, I strive to inspire my readers by bringing you content through this value added service. I endeavour to help designers and other professionals improve their creativity and productivity. My primary function is to identify the specific needs of professionals sector within the desgn industry and then to meet these requirements in a professional, time sensitive and cost-effective manner. I also offer services as complex as Concept Design, Project Planning and Compiling Design Applications or Presentations. My team of skilled and experienced freelance professionals of professionals are dedicated to providing reliable and professional service that is on time every time.In my Design and Drawing office, I use the latest Synchronous 3D modelling software. On site, I use laser and infrared reflector-less surveying equipment. I also provide layout drawing, design, shop detailing and mechanical surveying depending on the clients requirements. This is my design journey.....

Thursday, August 18, 2016

Cycling ReDesigned | Engineering

Drift trikes are like three wheeled go karts with smooth rear wheels that allow the trike to slide sideways around corners. I tried drift triking out recently with some friends and one of them said “When you get it right you get up and go yeah physics!” So this made me decide to build my project while exploring the physics of drift triking and how to use it in drift trike design. I first discovered the world of drift trikes about 9 months ago and became instantly hooked and decided that I had to design and build one of these tricycles to have some fun on the tracks in the area where I live. I used to ride mountain bikes on these tracks but past injuries have left me unable to grind some of the tracks I used to, this is something I have missed over the last few years but now that I am working on my trike design I can once more enjoy the numerous tracks in my area.

The project is planed to start in September and it is was going to have a motorhead theme but finishing the project on schedule will be an added bonus. I have to procure all material and get ready for this project in a couple of months, I had planned this to be an over summer project and hopefully with no surprises. The trike will not see much action until next spring during testing were the days are longer, warmer and drier and I get the road safety side of things organized......This is only a general guide as to how i built my trike, I will not be responsible for anyone who decides to build a trike of their own, anyone building or riding a drift trike should take personal accountability for their own actions. Therefore anyone planning on building or riding a drift trike should be aware of the numerous dangers involved.

If you build a drift trike build it strong to minimize the risk of failures that result in injury. Drift trikes fall into the same category as bicycles and therefore require brakes and reflectors and also lights if you intend to ride at night. Personal safety equipment should also be worn by all riders,  most drift trike riders wear full face motorcycle helmets. In addition to a helmet knee and elbow pads are recommended along with gloves and wrist guard if you have them.
For the trikes most people start out with an off the shelf trike but it’s quite common for people to build their own or modify off the shelf ones. The following sections provide basic guidelines on what dimensions I will be using.

The front wheels are generally 20” (508mm) BMX wheels. The rear wheels are much smaller, around 200-220mm, and are either plastic wheels or go kart wheels with PVC pipe on the outside. The dimensions of the trike are important to get right to allow for the trike to slide and also be stable enough to not flip over constantly. Wheelbase Length = 970-1150mm  Track Width = < 1m  - Note: If the track is too wide it’s hard to drift however narrow ones are more unstable. Seat Position = 250-350mm forwards of the rear axle
Note: If the seat is too far back it’s easier to tip backwards and if it’s too far forward it’s harder to put the trike into a slide. One of the factors at play when going around a corner is inertia. Newton’s first law of motion, aka ‘Law of Inertia’, is:

An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

a = acceleration
t = track width
w = wheel base
l = longitudinal centre of gravity position
h = height of centre of gravity

Using the average recommended dimensions (t = 1m, w = 1106mm) and assuming a centre of gravity at height at 0.4m and longitudinal position 0.3m gives a roll over acceleration of 0.9g. The effect of inertia in cornering is that a vehicle and your body will keep trying to go forwards, to the outside of the turn. The frictional force on the wheels also acts at a distance from the centre of gravity so this creates a torque on the vehicle trying to tip it in the outwards direction. This results in more weight being transferred to the outside of the turn. This tipping force is balanced by the outer wheel normal force but there is a limit to the normal force. At high acceleration and friction force the inner wheel will stop supporting any weight and the outer wheel normal force can’t increase any more. If the frictional torque increases the normal force cannot provide enough resistance and at some point the trike will tip over. One of the ways that this is countered is by leaning inwards towards the turn. This shifts the centre of gravity so there is a greater moment arm acting from the outer wheel normal force to stop the trike from tipping.

Friction Force: F = μ N
N = Normal Force
μ = Coefficient of Friction

It’s also possible to calculate the minimum cornering acceleration that would cause the trike to tip. This can be found by doing static analysis of the forces and assuming that the inner rear wheel gives no support. Friction is another important part of vehicle dynamics. Friction force depends on the normal force (from the weight) and the coefficient of friction. When wheels are rolling smoothly, not slipping, the contact point on the wheel is stationary relative to the ground. This means that the friction force depends on the static friction coefficient. When the wheels start sliding the point of contact is in motion and the friction depends on the dynamic friction coefficient. The dynamic friction coefficient is generally less than the static friction coefficient so when the wheels are sliding the friction force is reduced. The rear wheels on drift trikes are designed to have reduced grip, either by being made of plastic or having PVC pipe covering the wheels. This allows the back wheels to slide easier.

Turning the front wheel creates a sideways frictional force that causes the vehicle to change direction. The frictional force from the front wheel is much higher than the rear so if you keep pointing the wheel in the direction of the corner this will resulting in the trike continuing to spin around, often tipping over in the process. Unless you’re trying to do a spin, the way you need to get around the corner is by pointing the front wheel in the opposite direction, e.g. turn left while you’re going right, also referred to as counter steering. This balances out the movement of the rear wheels and keeps the trike heading in the right direction......Drift triking is great fun and it’s interesting to find out more about the physics behind it as well.

Mamphake Mabule
c. 2016, Mabule Business Holdings
Post a Comment