At Mechanical Elements, we encourage customers to modify and customize our plans. That is one way to help you build the perfect project. So, what things can you customize? And what things should not change?
This article explains what changes are safe when modifying trailer plans, and which changes require caution or engineering review. We will use examples of customizing both trailer plans and gantry crane plans. Also, the guidance is for reasonable modifications, not for a complete redesign.
Searching For The Perfect Plans
You have been thinking about this new project for a long time. You want a specific trailer, and you also have some great ideas for customizing that will make it perfect. So, you search the web and find some good trailer plans that are similar, but not exactly what you are thinking. At this point you realize the best way to get what you want is to build it. That is cool too, because DIY is awesome.
You then turn your attention to finding plans, good plans. And again, you don’t find the perfect ones. So, Which plans should you buy? You could just settle for something available, but instead, what if you customize the plans? What if you buy plans that are close, then modify things to be exactly what you want?
Well, that could be a lot more work, and what if you make a mistake? What if you modify something that should not change?
These are valid concerns when you customize the plans, so let’s talk about what matters. The important things first, versus the areas where you are free to modify.
When To Customize The Plans
Do-It-Yourself is the name of the game here at Mechanical Elements. We know that every customer has a little bit different idea about what is perfect, so we encourage you to customize the plans to fit your needs. However, we always want you safe, so this article is a guide to customizing safely.
Of course, all of our plans are fully engineered to meet and exceed the limits stated in the descriptions. And, we know modifications to the plans can change the engineering, so it is important to understand what areas can change, and what cannot. Here are some guidelines to help you make the right decisions – and to help you avoid potential issues.
In general, plan changes that affect load paths and structure require caution. Changes that affect features and accessories are usually safe. Let’s look now at some specific examples of how to apply these ideas.
Adapting the Plans For Metric Materials – Is It Safe?
We get frequent questions about customizing the plans to use metric dimensions, and specifically metric materials. The good news – in most cases, this is a safe modification, but certain rules apply. It depends on how the conversion is done.
Yes, you can customize the plans for metric dimensions – both for overall size, as well as for the material selections. Please read the article about Plans in Metric, then apply it by following the guidance in this article regarding size choices.
Plans that use special beam shapes, like various I-Beam shapes, may require a little more research for beam substitutions. Not all beams are available in every area. It may take some time in research for a proper conversion, but you can certainly do it.
In your conversions, choose beams that are the same size or slightly larger. Choose material thicknesses that match, or are slightly thicker. That will make the conversion safe.
Converting to metric dimensions is actually a significant way to customize the plans. It is a way to get what you want from our plans that do not already offer it as an option. That is all in the spirit of DIY.
Areas Requiring Strength
In some plans, like the Speakers, there is not much to require strength. Modifications to those plans will not likely affect strength. Yes, some changes can affect the sound performance – like if the internal angles or volume changes – but they won’t change strength or make it unsafe.
However, when we consider structural projects like a gantry crane, or trailer, strength is super important. For a crane, beam and leg strength are critically important. Changes to these parts can drastically affect load capacity and safety, so be careful if you wish to customize the plans in areas of strength. Calculate Safety Factors for the modification, and make sure it is good for what you are trying to do. Often the right material size change can make a modification work.
These are two examples of changes – one that does not affect safety, and one that might. In general, it is fine to modify the plans in areas that do not affect strength.
In areas where strength is important, like a gantry crane, it is almost always OK to shorten the overall dimensions. For example, if the crane design has a 10 foot length I-Beam, you can safely shorten it to 9 feet if that is what fits in your garage.
Shortening Beams, Legs, or Trailer Frame Members, Is OK If:
- The beam type does not change. (If it calls for a steel 3″x 3″ square tube with 3/16″ wall, please use it.)
- Beam overlap and support members do not change. Please don’t change overlap of beams (like how much of the upper leg goes into the lower leg on the crane). Please don’t change supporting members like gussets or axle mounting bars.
The same principles apply to all structural members.
Some Plans Anticipate Changes
In some cases, we know there are areas where you might want to customize the plans. In our Upsized Gantry Crane we have included this graph to help understand the practical limits for changes in length, height and beam type. You can choose the beam size, load, and length that meets your needs.
Another example is our Car Hauler and Deck-Over trailers. These plans include ramps, for driving a vehicle up onto the trailer. We know each owner will have different needs, so the plans include a chart showing ramp strength as a function of length and material type. You can easily choose what ramps to make based on how you plan to use them.
One Big Area Of Concern
People ask a lot about changing the axle type – from a leaf spring type to a torsion axle – for instance. This has some dangers as pointed out in this post. The forces from these 2 axle types are different, so the design must accommodate the differences. Not that one is good or bad, they are just different, so we must handle the forces differently. (For this situation, we have Torsion Axle Conversion Plans which solves the problem without guessing.)
Other options like changes from a straight axle to a drop axle for lower trailer deck height (or vise-versa) really are no problem since the loading to the trailer frame is the same. (Note that some accommodations may require an axle length change to fit properly.)
Customize Trailer Plans Length Or Width?
Another common question is about trailer frame changes for width or length. For example, you want a 4.5′ wide x 8′ long trailer. You see our 4′ x 8′ trailer plans, but is it safe to add 6″? For this we recommend the 5′ x 8′, then customize the plans by narrowing. This will give a safe design. (Just remember to shorten all the parts – decking, axle, cross members, etc., so it all comes together right.)
How about a Jeep example? If you want a 4.5′ wide x 6′ long trailer, you might find our 4′ x 6′ Off-Road Trailer Plans and think: “Hummm, that is close, but I want it wider. Perhaps I could customize the plans?”
We don’t have a 5′ wide similar trailer, so the above technique of narrowing will not work. For this, think about how the width is used. If the loads are not near the limit, just make the trailer wider. If you are not sure, then up-size the cross beams. Some added info on How to Make A Trailer Wider might also help.
In this situation, the cross members are angle iron (1.5″ x 2.0″, the 2″ leg vertical), so increasing the angle iron from 2″ to 2.5″ will make the beam stronger for the increased width. Alternatively, you could add more cross members of the original size to increase strength.
General Rules Of Guidance To Customize The Plans
This method works for small changes, but is NOT good for big changes. In general, changes going narrower and/or shorter are almost always OK. Changes up to 6″ wider and/or 6″ longer are also almost always OK. If it is bigger, like a foot, don’t do it. Start with a different set of plans.
Read more examples in the article Making Changes to the Plans. It is easy to read with examples from customer questions.
Loading / Axle Position
Another common customization is building the trailer for the way you will load it. In most cases, this simply means moving the axle to a position for stable towing with your specific load. Please read this post about axle position for details.
We also wrote an introduction to trailer loading and the engineering. That is worth thinking about if you wish to change the trailer loading.
It is not complicated, but it does require careful thinking. Also, this method is NOT good for big changes. For small changes like 6″, it works great. If the changes are bigger, then please don’t do it. Contact us and we will help you figure it out. Or, it might be time to consider custom trailer design.
Customize The Plans For Function
Functional changes are much easier. Functional things include details like how tall the sides are, where the spare tire is located, or the type of crane trolley to use. Almost always, you are free to make changes in these areas without constraint. Use your head, of course. The kinds of trailer lights you choose and where you select to install them, for example, will affect visibility, hence safety when towing at night.
Many of our plans include options that are, of course, ways to customize the plans. Adding certain equipment or using options that fit your needs are a way of creating the perfect and unique project. A lot of these options are listed in the product descriptions, or are shown in the product images. Many are highlighted in the animations. Incorporate them as you see fit — or modify the ideas to make options of your own.
Another popular change is that for an adjustable hitch. That is certainly an acceptable change, but do be careful with implications of ingress angles, even if your trailer is not particularly low.
What About Conversion To Off-Road?
At Mechanical Elements, we do offer a few specific Off-Road trailers – Jeep trailers really. But that is not exclusive. Other trailer plans can also be converted for off-road use. If that is what you want, we have a full article about making the conversion to off-road. This is a great way to customize the plans.
This applies only to trailer plans from Mechanical Elements. I cannot speak for other designers and what will work with their trailers. We know the engineering in our plans is for tough trailers, but many others are not. Please read the article to know what we recommend as you customize our plans.
The Perfect Project
When you finish building, and when you are satisfied with the work, then the project is perfect. Whether you customize the plans or just build it as designed, it does not matter. What does matter is how you feel about it, and how it works for you.
So go ahead, customize away. Use this quick reference as a guide for Safe vs Risky Changes
- Usually Safe To:
- Shorten length
- Narrow width
- Add features
- Convert to metric (when following the rules above.)
- Requires Caution when:
- Increasing width or span
- Changing axle type
- Changing structural members
This is your project, so make it right for you! If you have questions, let us know, and we will be happy to offer suggestions.
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