Trailers – How to Design & Build

NOTES

This is at least the second or third major version of this book and hopefully the final version. After 14 years of writing, rearranging, drawing and calculating we have found that it will take three volumes to present this material. The first volume has six chapters which include most of the things people think about when they think about building a trailer. The 2nd and 3rd volumes cover calculations and other technical aspects which are also very much a part of building a trailer and often don’t get included in the process. Frame strengths and towability are covered in Volumes 2 and 3. If you actually do intend to design and build your own trailer, reading and understanding all three volumes will help you understand many of the basics necessary to start and work through your project. The information in this series applies primarily to trailers under 7500-lbs gross capacity. Some may be applicable for larger trailers but an expert should be consulted.

Volume 1 has been divided into six chapters. Chapter 1 and 2 are introductory. Chapters 3, 4 and 5 cover components. Chapter 6 discusses the actual building and assembly, cutting, layout, welding and painting. Major suppliers are listed in the Appendix. If you have no place else to start searching, this is a good beginning. Other beginning ideas can include recreation areas where people use trailers. Find one you like and use it as a starting point. Use the cautions in these books to evaluate and improve upon that existing design. Do be cautious because some trailers aren’t what they seem, as we discuss here.

This book is a record of my experience building trailers and is in no way “the Gospel.” There are certainly other ways of doing it which are just as effective. The advantage of a book is that you have the choice of using the information or not. The disadvantage is that you often have no one to check the manner in which you choose to use the information. As a result it is difficult for us to take any responsibility for what you can create or what you do create. Remember this as you read or use the information contained here. Make sure it makes sense to you and to your situation. If you have any questions about it, be sure to consult with someone who has the necessary knowledge to help you.

ACKNOWLEDGMENTS

As with any book, it takes more than the author to complete it. And with a technical book of this nature, this step is especially important. In the beginning, Rich McCormack of Newport Press helped with the concept and initial formatting. Overall editing and finding of those infamous little errors was done by two trusted friends—Wendy Jo Block, a journalism expert and R. E. Williams, a technical expert in the field of engineering.

Typing the first draft of the manuscript (and a few thereafter) was the tedious doing of Delores McTaggart with an old fashioned typewriter. Finally in 1987 drafts were transferred to the Macintosh computer. From there, the book began to take its present shape. Debbie West and Paulette Kelly tirelessly revised draft after draft on their own computers as the book was transformed into its present configuration. And now thousands of hours later with numerous corrections, additions and changes behind us we have a 100 page book which has grown to two volumes of almost 200 pages each.

Although the majority of drawings in this volume were done from my own knowledge, data for some was gathered from other sources. Especially helpful were the people at Kruse Feed & Supply in South El Monte, California who assisted me with weighing of alfalfa bales when I showed up with a scale. Comments on Chapter 3 were solicited from my friends at Century Wheel & Rim Richard Starks, Gene DiSano and Jerry Milsap. The ade calculations in this same chapter were checked by Ken Foster, a structural engineer and Merle Bolden, a trailer engineer with Century. Wheels and tires for photographs were provided by Al Featherstone at Industrial Tire Company. And Dan Guinn of D & G Welding in Littlerock, California provided his plasma cutter and heliarc welder for photos used in Chapter 6.

And I certainly must thank all the torsion axle manufacturers for their assistance in providing information to make a thorough discussion of torsion axles possible. Norm Reynolds of Torax wrote a 5 page detailed letter about the benefits of torsion axles in general and more specifically the benefits of steel torsion axles. Don Boerger and Vic Rosengarten at Henschen were also extremely helpful in providing useful test data and general technical information in this area. Conversations with Vince Scott of UCF and Mike Platz of AL-KO rounded out the subject of torsion axles. Mike Platz also looked up and sent me a large amount of data and literature on mechanical brakes commonly used in Europe.

Ron Haase at Dutton Lainson provided accurate information on bearing protectors and an engineering drawing, included as an inset in one of the Figures in Chapter 3. John Bechtold of Unique Functional Products also took the time to discuss the benefits of bearing protectors and send photos and drawings.

Tom Kneiss of Hammerblow Corporation referred me to a distributor, AgServ West where John McKeon, Jr packaged and sent several heavy duty trailer jacks for the photographs in Chapter 5. Thom Perry and Julie Dunham from SuperwinchTM sent a chart describing methods of calculating winch strengths for use in Chapter 5. Charles Perry followed with an additional detailed letter providing information which has been added to this newer version.

Photography in general was largely my doing with many photos taken from files of vacations across the Southwest. Most product pictures were chosen from the IRD library of photos, which were also taken by the author. Some product photos were provided by Hammerblow, Unique Functional Products and Dutton Lainson. The Mubea ironworker photo shown in Chapter 6 was the courtesy of Steve Cashion of Meyer Sheet Metal Machinery in Los Angeles. As you can see it takes effort from many people to compile the information necessary to write a complete book. We must all be extremely grateful to these people (and I sure hope I haven’t missed any), because they helped to fill in areas of the book that were weak or non existent. Luckily, my 18 year tour of duty in the trailer manufacturing business was instrumental in providing the foundation .

SAFETY FIRST, LAST & ALWAYS!

This book has been written to improve your safety and the safety of trailers in general—not decrease it. We believe that increased knowledge is a prime key to your building of a successful trailer. Bear in mind though that all the knowledge needed is NOT included here. There are so many aspects to a project like this, we can’t possibly cover them all. This book contains few outright recommendations and is merely a list of specifications for items used to build a trailer. How you combine these parts and pieces is beyond our knowledge and control. Any trailer designs you concoct must be carefully considered and done with the entire system including the tow vehicle as part of your thinking. Due to these facts and the immense number of variables, what you create is your own responsibility.

Remember, changes to improve the trailer’s towability may decrease the tow vehicle’s performance or put extra strain on the trailer’s structure. TRAILERS – How to Buy & Evaluate discusses some of these aspects. Volume 2 and 3 look more closely at concepts and describe calculations one might want to perform to gain insight into these areas while designing a trailer. Any newly built trailer should be checked out and road tested slowly and carefully, preferably in some remote unoccupied area, such as an empty parking lot or test track designed for such maneuvers. An extra wide EMPTY boulevard as one might find at 6am Sunday morning may be more accessible. Freeways, city boulevards and winding mountain roads are least desirable and not recommended. As you venture forth, listen and watch for sounds and sights of trouble. Be sensitive to the movements of the trailer and don’t risk anything. Remember that instability can be initiated by downhill grades, wind gusts or passing trucks (to name a few) and caution is the watchword here. Speeds must increase slowly, and any hints of instability heeded and checked immediately and thoroughly. Please don’t just keep driving in hopes it will just disappear. An inherently unstable trailer may not show its colors until it’s too late. If available, the use of test equipment can improve your perceptions and knowledge.

Because your ability, along with the resulting combinations, modifications, materials and methods used are beyond our control, naturally we cannot assume any responsibility as to the results obtainable. Bear in mind that building a trailer for use on public roads is serious business, as are any vehicle modifications you may attempt. And while few laws exist as restrictions to your design choices, common sense and an accurate assessment of your abilities is imperative to assure your safety.