Sometimes looking for the right trailer plans is like a needle in a haystack. Every site has something, but not exactly what you want. So, what is next when you really need a particular trailer that others don’t offer? Custom trailer design is one option.
No doubt, if you can dream it, there is probably a way to build it. And, if that is what you need – Yes, we do Custom Trailer Design. However, before making the big full-custom dive, please consider the balance for resources. When you need something very specific, the best way to get it, is to design it, then build it, the way you want it. That is how the world progresses. And yet, sometimes time, money, or other resources say that is not happening. Well, that is a pickle we know well.
We get this kind of question often: “You don’t have the trailer plans I need. Now what?”
Things We Recommend Before Custom Trailer Design
Custom trailer design is perfect for some, but not for everyone. The cost is much higher (in comparison to buying plans that exist), and there are other barriers too. Before diving into a custom project, here are a few things we recommend considering. Maybe this helps? Maybe not. If you have not already, try this list.
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What are the things of your ideal trailer that you can’t find?
Is it the size? The desired capacity? The shape? Or some special feature? If you can find plans for most of what you need, then maybe you only need to customize the details. Try this article on When It is Safe To Customize Our Plans.
You may also find help in browsing through our conversion plans, for things like a Torsion Axle Conversion or maybe a Tilt Top Conversion. -
Can you buy a finished trailer already made?
Sometimes people send a photo of an existing trailer and ask if we can make plans for them. Sure, but is it worth it? Sometimes it is better to just buy what you need rather than reinventing again. Here is an article on the topic that is worth reading. – When to Buy, When to Build.
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What can you retro-fit?
Can you modify an existing trailer with the special features you need? In other words, can you buy most of what you want, then add or change things to include the needed unique features?
If these items don’t help, then it might be time to seriously look at custom trailer design.
The obvious benefit in finding solutions in the list above are saving time, money, or both. Engineering is an investment, an NRE (Non-Recoverable Expense). Sure, it gives you what nothing else can, but it can also be expensive.
There are times when custom trailer design is exactly the best solution. We can help with that, for sure. However, if you can get what you need while minimizing cost, then you are farther ahead. By suggesting other options, we are not trying to talk you out of it, just wanting to make sure you get the best for you.

Benefits of Custom Design
There are a lot of really great things that come with custom trailer design. Some of the benefits include:
- First, you get exactly what you want (within reason).
- Second, you have something you know will do the job. There is no guessing about “Is it strong enough?” or “Will it really work?” We establish all of that in the engineering.
- Third, you will have something truly unique. It is yours, and you don’t have to worry about licensing, patent, or copyright issues.
Finally, you will get the best in quality when you build from blueprints by Synthesis Engineering Services. Synthesis is the parent company of Mechanical Elements. We have been designing custom products for many years and have a lot of experience with trailers of many sizes and crazy configurations.
To see examples of our thinking, please read this Case Study of A Specialty Trailer Design as well as this Case Study on Tiny House Trailers. Our list of custom design for trailers includes many areas. Expanding mobile batting cages. Mobile kitchen trailers. Fishing pond on wheels. Custom hog haulers. Special mining support operations. And, so many more.
The Costs In Design
Without a doubt, Cost is the big down-side of custom trailer design. As in our Article about Free Trailer Plans, the time and effort for creating plans is not trivial. If we have made it look simple and easy, that is awesome. It means we did the hard work so well that you can’t tell. That is a great compliment.
Cost in engineering boils down to 2 big factors: Complexity and Constraints.
Complexity can be a lot of parts, or a lot of things going on, or a bunch of conditions to meet. As a design gets more Complex, then it takes more time and effort. For example, a simple rigid frame utility trailer that only hauls dirt on roads is much less complex than a full hydraulic dump trailer that hauls dirt and/or tractors and takes a beating in off-road use.
Engineering is the balance of trade-offs. Design Constraints are the limitations that force the trade-offs. The classic example is “I want a 20′ trailer, but it must only weigh 1000 lbs.” That is easy if it does not carry much, but it gets really interesting when it needs to carry 10,000 lbs.
Factors in Complexity and Constraints
There is a ton of work in every set of plans. We start with concepts, and not a few. We work through customer needs while evaluating how things go together, to make it easy to build. There are a lot of convoluted trailers out there, because they skip or short-cut these steps.
Next is material choice – driven partly by available stock, and by engineering analysis. It is a balance of constraints. We analyze using a variety of tools like FEA, fatigue charts, and more – like proper safety factors. Choices, especially for beam shape, depend on the complexities of loading. While it seems simple, we must analyze the model many ways to be sure it is good for all the ways you will use it. Design iterations of analysis, choices, tweaking and back to analysis and sanity checks take time to get right.
When we say the plans are fully engineered, this is what we mean. This is a step we don’t skimp on.
Finally, all the details. They say the devil is in the details – and if that means time, then that is certainly the details. And, the more complex the design, the more time it consumes. All the views on the drawings, the notes of instruction, the steps and dimensions so you know how to build it. End documents must show the design, sure, and communicate how to build it. Yet, that is what we do, because it is part of doing the job right.
So What Does It Cost?
Custom design makes your trailer unique, so the cost is unique too. Without knowing details, it is impossible to guess about cost. However, here is some direction based on previous work.
There are 3 categories of custom trailer design.
- Minor modifications to an existing design. If your ideal trailer is an easy change to current plans we have, for instance a change in width, then the cost is less. We have made these kinds of design changes ranging from $500 to $1500+. Obviously the more complex the changes, the more the cost.
- Significant modifications to an existing design. This is the middle ground. For instance, if we have a trailer that is close, but you need more capacity, another axle, or extensive size changes, then that fits this middle category. Prices range from $1000 to $4000+. Again depending on the changes.
- Full Custom Trailer Design. This is the hardest to estimate as everything depends on the need. Large complicated trailers (one previous example: 5th-wheel, tandem dually, wide load, trailer) is in the $5000 to $12,000+ range. On the simpler side, we have done several trailers in the $2500 to $5000 range. It really depends on the amount of work (Complexity and Constraints). One custom trailer design was over $18,000!
The best way to know cost for your project is a discussion with us. If the above numbers fit, then please give us shout. We are happy to help if we can, but please understand we can’t work for free.
TIP 1:
Settle on the design specification before we start the work. We can help with that. When the design constraints (requirements) change in the middle of the project, it can mean a lot of re-work and unnecessary cost.
Rule of Thumb:
We often joke about engineering cost by saying – the trailer plans in our store are the best deal around! They are all at 99% discount.
Yes, it is joking, but there is a strong element of truth. To get a perspective on the cost to fully engineer them, simply multiply the price in the store by 100. That is not exact, but it does give perspective. We have to sell 100 or so copies of each plan just to break even on the cost to do all the engineering and detail.
When Does Custom Trailer Design Make Sense ?
The above discussion may feel a little negative. Well, that is not the intent, but if the costs of custom trailer design are scary, then maybe this is not the right path for your project.
We typically see these reasons as most appropriate for Custom Trailer Design:
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The trailer has a unique purpose which supports the NRE.
For example, a custom trailer that hauls a unique product – perhaps one that has special loading / unloading requirements. It justifies the NRE because it is part of the delivery process. If you make and deliver $300,000 machines, the NRE of engineering so they arrive safe is easy to justify.
For example, one trailer we did was for mining operations to move special equipment. Another example is livestock transport to expedite and destress the loading and unloading of animals. A third example is a Park Home delivery system.
Another situation is where the trailer makes the money. We have done a few trailers that facilitate business for their owners – like a mobile fishing pond, and traveling amusements. One trailer we did carries the machine a contractor uses for their special operations.
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Trailer Manufacturer / Builder
If you are a trailer manufacturing shop that wants a design to build and sell, then custom trailer design can certainly benefit you. We have helped several custom trailer builders with their own designs. They want certain features, and they want to know the engineering is right. The cost is worth it for peace of mind. The unique plans are also worth it because they don’t pay royalties, or worry about competing with duplicate trailers.
In a nutshell, if you will make many, the custom cost can easily amortize out. (Sometimes this does not require custom trailer design, you can build from our existing designs with a royalty agreement.)
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Unique Design justified by time and use.
Some custom trailer uses justify unique design. We have done custom design for businesses to use in shows or for marketing. We have done custom tiny home trailer designs for individuals needing something special. For them, the cost of engineering is worth it because they will live in it for a long time. The same for custom food trailers we have helped with – like putting a full brick pizza oven on a trailer – because it gives them an edge in their market.
This list is not exclusive. You may have your own reasons too. If cost or timing are not an issue for you, the there may be many reasons to justify custom trailer engineering and design. The sky is the limit, and we are here to help if custom trailer design is what you need.
If You Are Ready?
If the options for filling your needs are not readily available, custom trailer design is one more possibility. As mentioned above, we know it is not cheap, and it is not for everyone. We always recommend that you look at other options first. Perhaps modifying existing plans, or purchasing an existing trailer to modify? Only you know the answer to that.
Custom design is the top rung in the ladder. It is the way to get exactly what you need. So, when there is no getting around the needs, then you have found the right place. Through Synthesis (our parent company) we do Custom Trailer Design and Engineering. Please give us a call.
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