Case Study: Custom Trailer Design

What does it take to create a custom trailer design?  And what does it cost?  These are some great questions, so let’s look at a case study as an example.  This is a trailer design for a Synthesis customer with several special features to meet their system and delivery requirements.  We won’t go into the proprietary nature of the trailer and what it does, but we will talk about the process involved in custom trailer design.

Step 1:  Start With The Requirements.

The process for a custom trailer design is much like a retail product, or a military devise, or a special machine.  Of course there are significant differences in the knowledge needed for different types of products, but from a high level perspective, it’s product development.  As such, we start with a requirements document as outlined in our well known article, The Product Development Process > Requirements.

We look at how the trailer will function.  Look at how it will be used, and ways it will be abused.  What does it carry?  In what environment?  Are there special needs for loading, or unloading, or supporting the cargo?  What about legal requirements and limitations?

A complete document of requirements is not necessary to begin a conversation.  In fact, many aspects will come once we know the right questions to ask.  In this example, the customer came with simple sketches, and a list of things the trailer must do.  That is a perfect launch point.  From there, through questions and collaboration, the requirements list grows into a specification.

A specification for a new trailer will include things like length, width, capacity, required duties, environment, use cases, and much more.  These all become part of shaping the final design.  Even when there are conflicting requirements, the engineering process will find the trade-offs for good decisions.

Step 2:  Create Design Concepts.

The old saying “There’s more than one way to skin a cat” is rather morbid when thinking literally, but is certainly a great metaphor when it comes to custom design.  The concept stage of design is where ideas flow freely with lots of ways to accomplish the tasks.

This is an exploratory stage where we think about the requirements, and especially about the customer use cases.  Decisions made in this step will define the product — and whether customers love it or hate it.  It’s super important to think about all the variables and possibilities.

For a one-off product (like a custom trailer), the iteration shown with the circular arrows in the above image happen more on paper and in the computer than in real life.  For instance, the prototype & testing phases are done in the model with testing being the FEA (engineering analysis).

In this example, there were several concepts for loading and unloading.  While the overall concept of loading did not change, the methods for settling the load were many.  Each idea requires different structure in the trailer frame, so careful thinking is key — with a lot of analysis repeats.  The final design did not include the most innovative approach, but it did include combining some clever ideas.  At Synthesis innovation is a means to solutions, not an objective, and that’s where it is for this design.

This step is complete when everyone nods their head in agreement.  The design concept will fill the needs.

Step 3:  Custom Trailer Design & Engineering.

Steps 3 and 4 are mix together.  It doesn’t make sense to complete a design without thinking about how to make it.  Working on details to accomplish the concept of Step 2 requires all the engineering of material selection, fabrication methods and analysis rolling into one.

This process is often one of iteration, as above, particularly when there is some design optimization.  In this case, the cargo and trailer must clear under 13′ vertical, which leaves precious little for ground clearance.  That means the custom trailer design must optimize beam load distribution within the physical constraints.

Another design parameter is the total load.  When set for travel, the load requirements are not so difficult because of load sharing with the tow vehicle.  However, the loading process has other equipment and extreme loads in a few locations, so those conditions become most important.  Potential impact while loading is also a big factor.

Finally, the design intent is for significant time on washboard dirt roads.  The trailer strength must withstand these extremes for a lifetime, so careful analysis and treatment of each condition is key.  Engineering to a final design brings all of these things into focus with analysis for all the challenging conditions.

For more detail information about engineering for custom trailer design, please see the Case Study for a Tiny House Foundation.  Or this similar Article.

Step 4:  Design Refinement For Manufacturing.

A hallmark of a good design is the ability to make it.  As mentioned above, this involves both Steps 3 & 4.  We list the manufacturing here separate because of its importance.  There is always a balance in cool design versus a design that is easy to make.  For this example, a custom beam to carry the loads in a compact manner is the cool approach, but price and availability of standard beams wins in this design.

Quantity makes a big difference in design for manufacturing.  If the customer will make many, then the focus is more on streamlining construction because special tooling costs are justified.  On the other had, like in this example, if the customer will make just a few, then the focus is on ease of construction with available material.

Steps 3 and 4 culminate with a complete design that is practical, feasible, and manufacturable.

Step 5:  Custom Design Details.

Design is a function of bringing all the requirements together including the trade-offs and often some innovation.  For this trailer, innovation appears in some custom ways of connecting the axles and distributing the loads.  While most components are off the shelf (for ease of manufacturing and price reduction), there are a few custom pieces.  We don’t show some of those, and won’t go into detail for proprietary reasons.

Finishing a design is always in the details.  In most cases, the final output is shop drawings ready for build.  In a case like this, the shop drawings include the trailer, of course, with each beam and piece defined.  It also includes details and drawings for assembly and for special parts.  Where appropriate, instruction is there to convey ideas and processes.  Finally, there is a List of Materials — the stock and cutting lengths, and a list of things to purchase.

What Does It Cost?

This question is super important.  What does custom trailer design cost?  Unfortunately, the answer is nebulous — it depends — because cost is a function of many things.

First, Design Complexity.  If a trailer is straightforward like this example, then cost is less than one with a lot of moving parts.  We did a design a few years ago for a trailer that expanded — both length and width once parked.  All the mechanisms and support for such action requires more effort, so greater cost.

Second, the Intricacy of Analysis.  While many trailers have just a few simple use cases, others have many.  Think about a trailer that is loaded and unloaded with a crane.  The cargo goes on the trailer in the right position and that’s it.  Now think of a trailer where a bulldozer drives on to it.  The analysis includes the bulldozer on the trailer for travel, as well as the loading process for getting it there.  Still other designs have mechanisms or unique features with even more thinking.

Third, Deliverables.  Usually a project concludes with shop drawings to build from.  If the custom trailer design includes complexity, then there is more detail in the drawings.  If the trailer has special machine parts, then deliverables include more.

Each custom trailer design has its own unique features — or there would not be a need for the custom design.  Call us.  It’s the best way to get answers about the cost of your project.

Do You Need Custom Trailer Design?

This is an example of a Business Solution through Engineering Design — one that could fit in your industry.  Though this illustrated as a case study for a custom trailer design, it applies in a variety of industries.  Innovation is definitely a Best Business Strategy.

The above description is an outline of the Synthesis process in design.  The process is not hard, yet, knowing how to best fit details and make the trade-offs, is another story.  That’s where the engineering experience comes in.  That’s where it’s good for you that the Engineer here is also a welder and a fabricator.  We know what it takes, so we design trailers in a way that makes sense to build them.

If you need a custom trailer design, we can help.  We have designed a lot of trailers over the years.  Start the Conversation Here.

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