This is a great question we get in many variations. Are Your Trailer Plans Certified? Are they DOT Approved? Do the plans have an engineering Stamp?
These are important questions. We think you should know, so asking about certified trailer plans is great.
Part of the confusion is with terms like “DOT Certified,” “Engineer Approved” and “Stamped”. Sometimes, they don’t mean what we think. So, let’s dissect some vocabulary and connect it to what actually matters for a safe and legal trailer build.
In this article we will explain the terms and differences, so you know what to ask, what to check, and what Mechanical Elements plans provide.
Here are the details. Hopefully, we will touch on your version of these important questions.
What Are Certified Plans?
“Certified” means review and approval by an authority for adherence to specific rules or requirements.
Two familiar examples are UL and CE for electric devices. The markings, UL or CE, mean the product meets certain levels of electrical safety. Certification comes after a review of the design AND testing the product.
Something similar happens with trailers. In most jurisdictions, inspection to be “Certified For Highway Use” comes after construction. They inspect the trailer for roadworthiness and adherence to local laws (axles, tires, lights, wiring, chains, etc.). They also look at construction (welds, bolts, and components). The inspector looks at the finished trailer, rarely, if ever, the plans.
Unfortunately, there is not a regulatory body, or even a defined set of rules, for certifying trailer plans. The Department of Transportation (DOT) does not provide that service. They leave it to the engineers, which is smart, because there are so many variations. That means there is no such thing as DOT certified, or DOT approved trailer plans.
Yet, the plans still matter, even without an outside validation. This emphasizes the importance of getting quality plans from an authoritative engineering source – then building the trailer with integrity.
So, What Are Certified Trailer Plans?
The concept of “Certified Trailer Plans” is kind of a misnomer: First, there is not a way to get DIY trailer plans certified. Second, getting “Approved For Highway Use” is through inspection of the finished trailer. The trailer inspection is the certification, and it is required in most jurisdictions.
Is The Process Silly?
Some say it is ridiculous, because plans should be part of certification. After all, you should know what the trailer is designed for, right? I agree. Yet, plans don’t control choices. You can put 5000 lbs on a 2000 lb trailer if you want. It might break, but plans can’t stop you. The same is true if someone switches to weaker, cheaper material.
Inspection can check legal requirements, but cannot prove strength, or test the material alloy. They can look at the build, but cannot verify weld integrity, or towing stability. Inspection promotes safety, and helps keep rattletraps off the road. Yes, it is limited, but within that sphere, there is some value.
Are Your Plans DOT Approved?
When asking for certified plans, some people are really asking about a DOT approval. As mentioned above, there is not a DOT approval for DIY trailer plans. While that would be nice, it unfortunately does not exist.
Approval to use the trailer on the road comes through an inspection process. Laws differ, but usually the trailer inspection is done by a local authority – perhaps at a police station, highway patrol office, or the DMV (Department of Motor Vehicles). Most places require an inspection, then they give you a VIN (Vehicle Identification Number) or a report. The DMV then uses the inspection report or VIN so you can license, title, or register the trailer.
I think an inspection is good, because it looks at the actual trailer. However, I also understand the missing piece – before building, which is the trailer plans.
An inspection will look at materials, welds, and verify component ratings (axles, tires, coupler, chains, etc.). They will look for adherence to local laws (lighting, wiring, brakes, chains, etc.). An inspector may ask to see plans, but usually not. They inspect the trailer, not the plans. That said, feel free to show them the plans!
In my experience, most inspections are not super thorough. If the trailer looks nice, the welds look good, bolts are tight with lock nuts, and it appears well built, they may focus on the lights, brakes and other legal requirements. In all the trailers I have built, only one had a thorough inspection – and it passed fine.
So, Are These Plans DOT Approved?
Actually, the right question: Will your work pass inspection? Do a good job building the trailer, meet local requirements, then inspection should go well. The plans matter a lot for building a strong trailer to perform, but they are not part of getting approval to use the trailer on the road.
Do Your Plans Have An Engineering Stamp?
When considering certified trailer plans, some people are really asking about a “stamp” from an engineer. Yes, Professional Engineers have a stamp, which has meaning. But for DIY, the practical value is limited.
Certainly, the source of the plans – and the engineering behind them – is important. It is nice to know the plans were reviewed by an engineer. That is one benefit of the stamp, but there is a lot more behind the purpose and meaning of a Professional Engineer stamp.
Side Note: The idea of “Stamped” plans sounds reassuring, but what does the stamp really represent? A stamp assumes exactness in the specifications AND in following the plan. In a formal context, this includes paying more for material with certs, employing only certified welders, documenting procedures, and even doing weld test samples. That is not practical for DIY, which makes a stamp less relevant.
If plans lack the specification implied by a stamp, or if the customer does not follow exactly, then the stamp loses meaning. For DIY, it is misleading, especially if you wish to customize the trailer.
One company claims they are the only one with engineered plans. Not true, but their plans do include a stamp, from a long time ago. I think the engineer did a good job structurally, but if you read his plans, they can be a bit confusing, and incomplete. The point: A stamp does not ensure the plans are clear, complete, or easy to build from. A stamp does not inherently make the plans good.
Limitations Of An Engineering Stamp
While we absolutely support the idea of licensed professionals with a way of signifying it, as the systems are now, especially for DIY, this does not happen well. We wish it did.
A silly example: A stamp from an engineer of one state may, or may not be valid in another state. An engineering stamp from the USA is no good in Canada, and the opposite is also true. Yet, you can legally tow a trailer into another jurisdiction where the stamp is not recognized. Hmmm. Maybe gravity is different? Maybe the laws of physics change across borders? It sounds ridiculous only because it is.
With regard to things like trailers, the system is broken, but not only for location. A professional engineer may or may not have expertise in trailers, yet the stamp is the same. It is certainly good to have standards, but as we consider things like stamped trailer plans, we must also acknowledge the limitations in what we are saying.
So, Are Mechanical Elements Plans Stamped?
At Mechanical Elements, our plans do not carry a stamp – it is not really pertinent. Selling “Stamped” plans for DIY is misrepresenting what a stamp implies. We do not wish to mislead or misrepresent or overstep jurisdictional borders, so we don’t do that.
All our plans have full engineering (see below).
We also do trailer engineering and plan design for other companies – not just for Mechanical Elements. Check out Johnson Trailer Parts for one. We design and engineer their plans too, like this Dump Trailer.
Fully Engineered Plans
In asking about Certified Plans or DOT Approved plans, some people are really asking about the engineering. Do the plans include proper and complete engineering? Or are they just a pretty picture?
Those are fair questions, because there are plans that seem suspect. It does not mean their plans are bad. However, it may mean the design was not fully analyzed. It may mean the trailer works for the builder, so now plans are for sale.
The reason to ask about engineering is final project success. Customers want to know if the finished trailer will perform as claimed. We think that is perfectly reasonable, and frankly, expected. You should know the skill and experience behind the plans so you can build with confidence.
Full engineering for a trailer includes evaluating the structure in the ways it will function. For instance, it is not enough to check a car hauler for driving on smooth roads. We must also evaluate the process of driving a vehicle onto the trailer, and conditions where it is too far forward. We must look at road conditions, like bumps, and pot-holes. Of course, these are items of use, not abuse – that is different.
Especially in DIY, long lasting performance requires care and common sense – both in the build and in how the finished trailer is used.
So, Are Your Plans Engineered?
Yes. We sell Fully Engineered Plans from our parent company Synthesis Engineering. The design process includes engineering analysis with tools like FEA (Finite Element Analysis) in combination with decades of trailer-specific experience in design, consulting, fabrication, and testing. Trailers are a focus area.
Trailers built from these plans will perform as stated – when built as defined, with proper materials, skill, and care in construction. We do the engineering, and we control the details so we can make sure it is right. With our plans, if you build it well, it will perform as stated.
One warning, however, about abuse and misuse. If you overload it, hit a tree, etc. – that is different. No certification will help that. Of course, our designs are robust enough to handle the inevitable minor oops that surely happen.
This is true of all our plans, like Shop Tools Plans for cranes, presses, and everything else. Full engineering is how we roll.
If You Must Have Certified Trailer Plans . . .
I will argue that very few people actually need trailer plans with a stamp or other type of certification. Before spending money on it, take time to verify. As explained above, there are myths and misunderstandings around certified trailer plans, DOT approval, an engineering stamp, and the purpose of inspection.
In the rare case where your company requires certified plans for some reason – even if the reasons are artificial – you are welcome to take our plans to an engineer in your area. The plans sold at Mechanical Elements are well designed, and I am not concerned about having an outside review. It can be costly, but you have our permission.
Certified Plans Summary
Questions about the validity of plans are important. We understand the need to feel comfortable with the source.
People often come with a preconception of what is needed, but the assumptions often come from misleading information. Hopefully this article has busted some of the myths around certified trailer plans, DOT approval, stamps, and inspection.
In summary, Mechanical Elements plans do not have a DOT Approval, DMV licensing guarantee, or other government certification. Really, such approvals do not exist for DIY. In most jurisdictions, inspection is the point of certification, so it is the build quality of your trailer that matters. Build it well, then inspection should go well.
In comparing our plans to others, certified or approved is not really the point. I do not know of any plans out there that are fundamentally weak. From what I see, the weakest trailers are not from plans, but those purchased from big retailers. (See the article about a Bent Tongue on a Weak Trailer.)
That said, I believe the quality of our plans is superior because we provide more options, better detail, and good explanations in the instructions. They are fully engineered plans, because that matters.
For your trailer, I personally recommend starting with the plans that suit your needs best, even if you buy from a competitor. Yes, we have many trailer plans, but not everything, so look around. When you are ready to buy trailer plans, if we have one you want, we are confident it will give a great road map for building your awesome trailer.
Next article to read: Advice For The Inspection After You Build.
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