Bike Trailer Classification Scheme

Our group was able to create a classification scheme and choose three main outcomes of the many possible variations.

 

Classification Scheme Evaluation

            Using our classification scheme we were able to come up with 3 different configurations that each could be a successful product however we selected the enclosed configuration as the one that we want to move forward with and continue to develop.

 1.    The first function to be evaluated is the method to attach the trailer, for this function we needed to evaluate the cost effectiveness, ease of use, and user safety.

(a)    The most cost effective option is the rear axle spring bolt, it is an existing product that is easy to acquire and cheap to manufacture. This option is a less user friendly, however it is much safer as it keeps the center of load close to the ground.

(b)   The best option for ease of use would be the seat post clamp, it is the simplest to attach and remove from the bike, and it is the most intuitive, however this option creates a higher center of gravity and is less safe for the user.

(c)    Locking nuts and Rod and Tube are both derivations of these other designs

(d)   We selected the rear axle spring bolt as the best option

 2.    The next function is the shape of the load carrying area.

(a)    The first option is the flatbed design, this option is the simplest and the most versatile however it is not the easiest to produce and it requires extra parts to attach the load to the trailer

(b)   Pannier bags are the easiest produce as we could simply use an existing market product, however they are the most limiting in terms of carrying capacity

(c)    Enclosed soft shell is easy to produce and it limits the carrying capacity

(d)   Enclosed hard shell is also easy to produce and it limits the carrying capacity, however with a rigid shell it allows us to easily add other features and we do not require other attachment devices

(e)    We selected the Enclosed hard shell

 3.    For the position of the load our primary concern was the safety of the user

(a)    Positioning the load on the sides of the wheel keeps the center of gravity low, however it also tends to unbalance the trailer

(b)   Above the wheel raises the center of gravity to high for it to be safe

(c)    In front of the wheel keeps the center of gravity low but makes the trailer to long and limits the turning radius

(d)   About the wheel keeps the center of gravity low while maintaining the turning radius and is the best option

 4.    For the method of transport, we needed to consider the safety of the user and the cost

(a)    For a single wheel design, it keeps the trailer narrow and in line with the bike which benefits the user, however it can be unbalanced if poorly loaded

(b)   For double wheel design, it is wider and doesn't turn as well, however it is harder to unbalance, but it is more expensive

(c)    We selected the Single wheel design as the best option

 5.    Storage of potential energy of the load

(a)    Because we selected the enclosed hard shell design, the shape of the trailer itself will keep the load in place and we do not need any extra methods to attach the load

 6.    Storage of potential energy of the suspension

(a)    The most basic option is a simple spring suspension, this option is the simplest, cheapest, easiest to manufacture, and it requires almost no maintenance. However it is not as effective as a pneumatic suspension

(b)   Pneumatic suspension is more effective, and it is adjustable based on the load. However it is significantly more expensive that the simple spring

(c)    We selected the simple spring as the best option

 7.    Storage of electrical energy – for this category we had to consider if we wanted to store the energy or simple convert it

(a)    The simplest option is no storage, this would mean that only devices that are plugged in at the time of most would be charged, this is also the cheapest option

(b)   Our other option was a form of battery to store the charge for later use. This option is more expensive however it is much more user friendly

(c)    We selected a battery storage as the best option

 8.    Energy conversion is our method of producing electrical energy, user cost is our primary concern

(a)    Rotational converts the energy of the wheel into electrical energy, this is the cheapest option, however it only produces energy while the trailer is in motion and it puts additional load on the user by being the heaviest option and using friction

(b)   Solar power is more expensive however it can produce energy as long as there is daylight, and it is the lightest option

(c)    We were forced at this time to select rotational mainly because of the large cost of solar, however if solar becomes more cost effective we will switch

 9.    Power output

(a)    Our first option is a USA standard power outlet, this is a very cost effective option however it is very large and would require more wiring to convert to 110v AC power

(b)   Our second option is a Standard USB outlet, this option is also very cost effective it is also the simplest system to manufacture, however it does limit the charging ability of the system to devices with a USB cord

(c)    We selected a standard USB outlet

Function Strucure Diagram

After reviewing our requirements list we have progressed into designing our function structure diagram. We submitted our first draft and received constructive comments on how to improve the design.

Here is the bike trailer's revised function structure diagram:

Overview of Requirements

Geometry

The geometry of our trailer involved a long group discussion. We looked at similar products and considered the opinions of people who have used bike trailers in the past. We found that the shorter and thinner we make the design, the safer and more agile it will be. 

When considering clearance from the ground, we used the standardized sizes of bike tires. The higher the load is kept, the higher the center of gravity which is not good for stability. We chose smaller tires similar to other trailers which would range from 6" minimum to 12" maximum. a good amount of clearance is necessary while off the road as small obstacles on the ground would otherwise create problems.

Kinematics

Many competing products have an option for suspension at an elevated cost. We believe suspension is a definite requirement to provide a safe and comfortable ride for our consumers.

Forces

The forces acting on our trailer is a big topic and can be discussed for days. To provide a brief overview we will only consider the main forces acting on our trailer. The trailer's load should not exceed 100lbs. While the material making up the structure can support more weight, we want to provide a significant factor of safety for our consumers. It is also important to note that the consumer will have to tow this trailer via their own power and probably cannot travel long distances with a load exceeding 100lbs.

Later this month we should have optimization results from a project we are doing in our CAD/CAM class. This project involves stress analysis of a 3D model of an existing trailer. We will post those results soon!

Energy

We would like our bike trailer to address some of the concerns of our prospective consumers. One of the main issues for people traveling long distances or in off-road camping type locations is the fact that they cannot charge their small electronic devices. We would like to include a means of converting energy from the trailer in motion into electrical energy that is either immediately used and/or stored and used later. The minimum requirement is the ability to charge a small electronic device such as a cell phone or GPS unit at least once over the coarse of riding for one day.

Material

There are many options for materials used in this design. Because of the volatile nature of the outdoors everything must be corrosion resistant. We require that the items stored on/within the trailer are also protected from the surrounding environment and weather. Also, all electronics including the container surrounding the energy generating element and consumer devices must be waterproof.

The materials used in the trailer's structure should be weldable and machinable otherwise production and cost would be too high.

Safety & Ergonomics

There are many aspects of our design that incorporate safety and ergonomics. Our group briefly mentioned brake lights, turn signals, torsion control (single wheel), and a quick release mechanism as wishes that are not necessary. Many of the above items can be purchased and installed later and would only increase our overall cost.

Some other aspects we deemed as demands which include a maximum speed rating of 50mph, a narrow body for agility and safe street use, an easy mechanism for connecting the trailer to a bike's rear axle, and finally an environmentally friendly final product design.

Production

We will eventually come to the point where we decide if we actually want to market our design as a real product. If and when that happens we will need to organize our design in a way that allows for mass production in a cost effective way. Not only that but we must also perform many tests like load bearing tests and fatigue and usage tests. There is also the possibility of needing permits and certifications for our product since it will more than likely be used on public roadways and other government regulated property.

Assembly

As of now we have not progressed far enough to finalize our trailer's structure. We can only speculate that we will either manufacture our trailer to be one piece, multiple connectable parts, or something that needs to be fully assembled. It seems like a reasonable  assumption that one piece will provide a more structurally sound product while something that needs to be assembled provides a method for portability and convenient storage but also more maintenance.

Operation

We already know most of our consumer demographic and we know that we want our trailer to fit their traveling needs including the option for rugged and off-road terrain. The demographics that match our expectations are as follows: Environmentalist,  Conservationist,  Active Lifestyle, and Travel demographic.

Maintenance

We agreed that while maintenance is an important factor of design, we must progress further before knowing what will and should be required for maintenance. The only aspects of maintenance we have come up with to date is rust, wear and tear, and if we include other parts they would have their own respective maintenance responsibilities.

Recycling

As we want our trailer to be environmentally friendly we would like to incorporate materials that can easily be recycled and/or reused. From a production standpoint we would like to be able to reuse material that is extra and/or defective. From the consumer's point of view we want them to be able to easily dispose of the product after its life and demonstrate the environmentally friendly nature of our product.

Costs

The cost of similar competing products is around $380. This price point only includes features like the trailer frame, a waterproof bag for storing the load, and  a suspension. The maximum load is only around 70lbs.

We would like to design a competitive product that is either cheaper with the same or better functionality or more expensive but with added features that justify the additional cost.

Schedule

We plan to have our bike trailer fully designed and have a working prototype by April of 2014 which is near the end of our last semester - Spring 2014.

Requirements List Created!

After discussing many ideas we have put together a list of requirements for our bike trailer including both demands and wishes. The list of requirements below is a vital part of organizing and progressing our design.

Group A		Bike Trailer Requirements List	Page : 1 of 1
Changes	D/W		Responsible
		Geometry
	D	Length - 63"
	D	Width - 18"
	D	Height - 16"
	D	Clearance from Ground - 6"min to 12" max
		Kinematics
	D	Suspension
	D	3" Travel
	W	Air Shock Suspension
		Forces
	D	Linear Axial
	D	Angular Axial
	D	Weight < 20lbs
	D	Load - 100lbs max
	D	Elasticity
		Energy
	D	Power Output
	W	USB 3.0
		Material
	D	Corrosion Resistant
	D	Weather Resistant
	D	Elastic
	W	Weldable
	D	Machinable
		Waterproof Container for Battery
		Safety & Ergonomics
	W	Brake Lights
	W	Turn Signals
	D	Environmentally-Friendly
	D	Narrow Body
	D	Easily Connectible to Bicycle - Rear Axle
	D	Max speed - 50 mph
	W	Torsion Control
	W	Quick Release
		Production
	W	Potential for constant production
	D	Produced as one-off
	D	Load Bearing Tests
	D	Fatigue Tests
		Assembly
	W	End-user Assembly
	D	No-assembly required
		Operation
	D	Rugged Outdoors
	D	Environmentalist Demographic
	D	Conservationist Demographic
	D	Active Lifestyle Demographic
	D	Travel Demographic
		Maintenance
		Rust
		Parts Wear
		DC Motor
		Recycling
	D	Metal - Aluminum
	W	Plastic - Carbon Fiber
		Costs
		Schedule
		Constructed by April 2014

Within the next few weeks we will post a short overview of the many discussions we had in order to create this list. 

Off-Road Bike Trailer Ideas

Now that we all have agreed on an off road bike trailer for our senior design project we can expand on the idea.

Knowing that there are similar products in the market we first analyzed the pros and cons of many designs. We also researched our target consumers and asked a few simple questions:

1. What activity did you do to warrant using a bike trailer?
2. What trailer did you use?
3.  What did you like and not like about your current bike trailer?
4. Are there any features that would have made your activity easier or more enjoyable?

After discussing our findings with each other we concluded many things:

• There are many people who participate in long distance bike trips and/or activities (such as camping, etc...) that would require a bike trailer.
• Almost every trailer in the market today is a two wheel design.
• There are a few one wheel design trailers out in the market but they are very expensive.
• Many people complained about the lack of agility in two wheel designs.
• There is a need to charge electrical components such as phones and GPS devices.
• Safety is a big concern to everybody and features such as trailer size and stability were found to be a problem in some cases.
• While a trailer has one real main use, many people requested a design that helps them in their off-bike routines while on the road (cooking, storage, shelter, etc...)

As of now we have an outline of what we want to create.

We would like to design a bike trailer capable of traversing rugged off-road terrain while still being able to tow the equivalent of what is necessary to accompany a long distance trip up to a maximum of 100lbs. We also want to incorporate a power generating device capable of charging up small electrical devices either on the go or later through means of stored energy. This design must be safe, comfortable, and easy to use.

Soon we will be putting together a requirements list featuring the various demands and wishes of our design.