Making Changes To The Plans
I can’t find quite the right plans for the trailer I want to build. Can I make changes to the plans at Mechanical Elements to fit my needs?
Answer: A qualified yes. It really depends on what changes you have in mind. We encourage customizing the plans. Because — Hey, making the exact trailer to meet your needs is the best reason for DIY anyway! And, that goes for other projects like a Gantry Crane, or a Can Storage Unit, too. On the other hand, there are some things you probably should not change.
Let’s look at some real examples of what is OK to change, and what is better not. Also, we definitely recommend the article When Is It Safe To Customize The Plans. It gives general guidelines about where it’s safe to make changes to the plans. Yet, for this post, let’s look at some specific examples — which come from your questions.
Example 1: Change A Utility Trailer To Off-Road
The reader question: “I see you have plans for a small off-road trailer, but do you have plans for a 5×10 0ff-road?” Of course, trailer size varies when this question comes up, but context is basically the same. We say YEAH BABY!! Get out there in the woods and take your best DIY with you.
Answer for this Customer Question:
We do have plans for a great 5 x 10 utility trailer. Changes to the plans can certainly include greater ground clearance with larger and more aggressive tires. If that’s what you mean by ‘off-road’, then YES, you can do that! Here’s how.
Start with oversized tires for increased ground clearance as well as for some lift. Big tires will look great with your off-road vehicle! Use matching wheels and tires for an even cooler look.
Next, use a straight axle, not a drop axle. That makes a big difference in under trailer clearance.
If that’s not enough lift, use an Overslung Axle configuration (instead of the underslung version in the plans), which will raise the trailer frame about 5 inches. This will increase your approach and departure angles. If you want even more lift, add a section of steel between the springs mounting and the trailer frame.
Let me make 2 cautions. First, if the trailer will have wide tires, order a longer axle for clearance of the wide tires to the frame. Order a wider Hub Face Distance, but leave the Axle Spring Mount Distance the same. (Example: Our 3500# trailers are designed for 8″ – 9ish” wide tires — 225’s or so. If you plan to have 12″ wide tires, add 3″ to the Hub Face Distance. [12 minus 9, then half of that on each side.]) Second, if you lift the trailer way up, it changes the center of gravity. Make sure you know the tipping point when you’re off-roading.
Example 2: Deck-Over Changes To The Plans
Can I make one of your trailers into a deck-over design?
Answer for this Specific Question:
Let’s look at definitions. I’m not sure what to call a typical trailer where the wheels are outboard of the main bed. That’s the design of most of our trailers (like the image in example 1). Does anyone know if that style has a name??
On the other hand, a deck-over design is where the trailer deck is above the wheels, extending flat over the wheels. See the photo. This style allows more space on the deck, but it’s a higher deck, and the load then has a higher center of gravity. Both types of trailers are very useful for their purposes.
For a trailer designed with outboard wheels, the main frame beams are typically at the outer edges of the deck. That is where the axle mounts and those main beams carry the axle loads. For a deck-over style trailer, the main beams are under the deck, still above the axle mounts, but the deck extends out beyond the main beams — over the wheels. That is a very different design, so converting one style to the other is more than just lifting the bed. It’s the opposite of what many people ask: How Can I Lower A Trailer Deck?
Other considerations are the height of the tongue, how the tongue attaches, details around axle mounting, and choices for crossmembers. Though you could add spacers and change a lot of other things, it’s probably best to start with plans designed specifically for a deck-over. Check out these deck-over style trailer plans.
Example 3: Change To A Torsion Axle
Answer for this Customer Question:
This is not a simple answer. If I just say No, then that leaves more questions. If I just say Yes, then that could lead to disaster. So, please come along as I explain how it’s possible.
First we must understand the differences in various types of suspension. The article Trailer Axles 101 is a good start. Second, please read this article showing the effect on the frame for Torsion Axles versus Leaf Springs. They interact and pass stresses to the frame quite differently. To make these changes to the plans, we must accommodate the force differences.
If we don’t compensate properly for the added stresses of a Torsion Axle, then we might have frame problems. That’s where the disaster comes in. On the other hand, if we do modify for the torsion stresses, then yes, the axles can substitute. Here is what we recommend: First, in our plans, the axles have a separate mounting member to avoid weakening the main frame beams by welding at the points of highest stress. Change that member up one size. For instance, change from 3/16″ to 1/4″ thickness. Change the member height. For instance, if a 2×2 Angle is specified, change to 2×2.5 Angle with the longer leg vertical. Other changes to the plans which strengthen the area of axle attachment will also work. (Sistering beams, etc.)
Second, mount the axle so the spindles are in the axle position. That will place the cross beam of the torsion axle forward from there, but the cross beam position is not the important part. The spindle position is.
That’s it. Not too complicated.
For other suspension types, like this low profile trailer suspension, just note the different forces, and make the frame to handle them.
Our twin torsion axle walking beam suspension is made to mount on any of our trailers (note the capacity) since it includes it own stress spreading members.
Example 4: Aluminum Trailer Frame Instead?
Can I build with Aluminum instead of Steel?
Answer for this Frequent Question:
This is a pretty frequent question, and the answer is pretty simple. There is a big difference in the material properties of Aluminum vs. Steel. While Aluminum is a pretty cool material that has a lot of benefits, plans drawn for Steel are not for Aluminum. Please read this article about trailer frames in aluminum.
Some of our Gantry Crane Plans include options for Aluminum, with the respective load and deflection curves to show the choices. In this case, the plans show options for Aluminum, so Yes.
Yes, there are a lot of good Aluminum trailers out there. Yes, plans for aluminum trailers exist. Just don’t confuse the two because there are accommodations required for aluminum that are different from steel. Please read more about the engineering differences in this Article about Aluminum vs. Steel.
As A Side Note: At Mechanical Elements we choose to design for steel partly because steel is more forgiving in both durability and in welding, but also because it is more accessible for DIY projects. I don’t mean easier to get, I mean the whole picture. Steel is less expensive, easier to get, and more likely for a good result without being an expert. Tools for the project are also more common (like welding). We are focused on DIY, and our goal is to help with your success. Perhaps we’ll have aluminum trailer plans in the future at some point.
Example 5: Changing Size
Can I change the size of the trailer?
Answer for this Question:
Yes, but there are limits. We’ve covered this in more detail in this article about customizing the plans, so we’ll leave it at that.
Making Your Changes To The Plans
For other real world examples of how customers have included changes to the plans, please see the Customer Stories Page. There are several examples — especially for the gantry cranes — where modifications improve function for a specific needs.
We encourage customizing. It’s the best reason to build in the first place, and it gets the end product you really want. We wish you the best as you modify the plans to meet your needs. Be smart with the changes, and you’ll end up with a great final product.