If you have trailer plans, and are interested in building a teardrop trailer, or a utility trailer, this page might be of interest. This particular chassis was built specifically for a teardrop trailer, although it could very well be utilized for utilitarian purposes, or perhaps some other special use trailer.
The page title is "Trailer Chassis Build". However, I will begin this page with the Torflex Axle. If you are not at all familiar with this type of axle, it is suggested that you read all you can about Torflex axles at Dexter Axle's web site (link below). The chassis shown in the picture above, is bolted to a Dexter #9, 10 degree up trailing arm Torflex axle, and is easy to install if done correctly. It is also easy to remove if necessary. The maximum load for the Torflex #9 is about 2200 lbs. This particular axle was de-rated to 1800 lbs. It was ordered directly from Dexter Axle . They are very pleasant to work with, and will provide you with the correct axle for your chassis.
The axle was received completely assembled. It was also ordered with a hangar kit (AP-161-00), which includes four 1/2" bolts and washers, as well as the axle hangars, and lug nuts. This particular side mount hangar kit was designed for installation upon rectangular frame rails The Dexter axle installation guide states that the axle bracket which is factory welded to the axle tube (shown in the picture), is to be bolted to the axle hangars, at a torque of 70 to 90 foot pounds (shown at left forefront of picture). 80 foot pounds sounds like a good number. This should be done prior to welding the axle hangars to the chassis frame rails. This procedure will make axle alignment to the frame rails accurate and easy.
Note: Prior to mating these parts together, I use a very light coat of axle grease placed on the inside mating surface of the axle hangar. I will explain the reason for this later. The Axle hangar is then placed upon the axle bracket, and in position for receiving the 1/2" bolts and washers.
Bolts are inserted from the outside of hangar, with washer and nut secured to the inside of the axle bracket surface (when mounted to frame rail, hangar will be facing inside of frame rail). Since the axle hangar and axle bracket are not exactly a perfect mate, you may have to use a clamp to completely seat the bracket to the hangar. It is important that there are no gaps between the brackets and hangars.
The reason for lubricating the inside surface of the axle hangar is that I will be disassembling the axle brackets from the axle hangars after I tack weld the axle hangars to the frame rails, and removal is much easier with lubricated surfaces....ask me how I know!
The removal is for two reasons. First, because in addition to welding both ends of the hangars to the frame rail, it is also necessary to weld three 1/4" x 2 1/2" fillets on the inside and outside of each hangar to the frame rail. I find it difficult positioning a mig torch with the axle bracket and trailing arm in such close proximity. A much easier and better weld can be made when there is room for the torch. If this is not a problem for you the hangars may be welded to the frame rails with the axle attached. The heat from welding will not harm the rubber chords in the axle assembly. Stick welding might be another solution if you don't want to disassemble the brackets and hangars, although Dexter axle's specification for the welding description is Metal Inert Gas.
The second reason is that I still have to prime and paint the completed chassis and it's easier to mobilize the chassis without the extra bulk and weight of a 70lb. axle.
Three axle hangar bracket fillet welds to frame rail. These welds are also made on the opposite side of each hangar.
If you don't want to get involved with arithmetic's, and are ordering your axle from Dexter via telephone, then you will be happy to know that they will do most of the work for you. You will be asked for the Hub Face to Hub Face dimension, desired axle weight capacity, brakes or no brakes, type of frame rails (for the hangars), desired height from bottom of frame to ground, or perhaps you already know the angle of the trailing arm setting that you want)., How about EZ lube, or de rating the axle weight capacity.
After speaking to a sales representative, upon request or suggestion, you may be directed to their engineering department. You will be asked a few more questions and they will provide you with an e-mail containing a .pdf file your axle specifications. They utilize a proprietary engineering software to determine as to whether or not your axle will work with the information you have provided. If there is a problem, they will let you know while you are speaking with them. If you aren't replacing an existing axle, then you might want to determine your Hub Face dimensions. The following is the method that I use and I'm sure most fabricators use a similar if not the same method for this calculation. The axle on the above trailer dimensioned based on the following. The method is slightly different from that used for a straight axle because of the trailing arm.
The following method is used for determining the hub face to hub face measurement, using a short spindle Dexter #9 Torflex axle.
1. Measure width of trailer...in this example it equals 56" inches.
2. Width of tire = 8" mounted on a zero offset wheel which will be
bolted to the hub face, and is then divided by two =.....4" inches
3. Trailing arm distance from frame rail =......................1 1/2" inches.
4. Trailing arm distance to inside of tire =.....................1 1/2" inch.
5. Add figures from steps 2 - 4 = ..................................7 inches.
6. Since there are two sides to the trailer, multiply total
of 7 inches x two sides with a yield of ........................14 inches
7. Don't forget the width of the trailer .........................56 inches
8. Hub Face to Hub Face for this example =............ 70 inches
There are variables to the above calculations. The axle may be ordered with the inside trailing arm distance moved to within 1/2" of the frame rail if desired. As a fixed variable, the distance from the inside of the trailing arm to the inside of the tire should be 1 1/2 inches. I chose to dimension the trailing arm to frame rail at 1 1/2" to allow for the trailer sides. which covers the frame rails and added an additional 1/2" on each side. I could have chosen 1/2" for the trailing arm to frame rail giving me a 1/2 clearance to the side wall. This change, then would have made the Hub face dimension 68".
The remainder of this page will be dedicated to planning, fabricating, and welding the trailer chassis. Some of the ideas for this build are my own, some are gleaned from reading and discussion. Just a reminder again about safety. I cannot say enough about safety while building a trailer chassis. To be more specific, I am referring to power tools and electricity. I am also referring to the end product and it's safe use on the highway.
Prior to taking advantage of CAD, most of my planning for a project was done with a few notes, paper sketching, and mostly intuitive construction. I have become very dependent upon the computer to enable me to fabricate most of my construction projects. If you haven't already utilized the power of CAD then I urge you to give it a trial.
The power tools used for the fabrication and welding of this Teardrop trailer chassis are more than adequate for this project, and tools of a more modest stature will certainly complete the task at hand. I am assuming that if you are contemplating this type of fabrication that you own some type of saw capable of cutting metal, as well as some form of clamping devices and basic hand tools. You will also need a welder, as well as the skills needed to utilize it. If you don't have the welding skills, then I suggest contracting someone that knows how to weld, a weldor. Purchasing a bolt together trailer chassis would be another option.
Most of my welding experience is self taught, but also includes two certificates of completion in welding fabrication, taught at a local community college. These classes can be a lot of fun, and most of all, provide you with the confidence to fabricate projects that you can be proud of and share with others.
After obtaining and cutting the required materials, 2" x 2" frame rails, are laid side by side and clamped together. The placement for cross members, axle location, axle hangar locations, and all other optional accessories are transferred from the CAD drawing to the frame rails.
A horizontal metal band saw was used to make 45 degree angle cuts for joining all frame rails. A cheap chop saw with cutoff wheel is much faster and will work just fine, provided you can handle the noise, and sparks. Also, butt joints are faster and easier to create, but I prefer closing the rails at the four corners, by using the angle cuts, and think it looks more professional. As always, the choice is yours.
Accuracy in measurement and cutting is most important if you want a finished square trailer chassis. I can't stress enough, the importance of precise measurement. Inaccurate cuts will make alignment and squaring increasingly difficult, and bring about slowed progress.
There is more than one way to layout and square chassis framework. I use these homemade adjustable stands for lightweight projects, which are adjusted too high , making the platform unstable, and will have to be lowered. Each stand is continuously adjustable, and allows for very easy and accurate leveling, front to back and side to side. Great for any welding project requiring two or more supports for light weight projects.
The framework was leveled side to side, and then checked front to back. All is well. If the frame is not level, make it so. If it is not square you will experience tire problems and possibly premature blowouts, or a trailer that dog tracks while going down the road.
Using the diagonal measurement from the CAD drawing, the frame was squared, measuring corner to corner, then tack welded Two cross members were tacked to the frame rails. Again measuring, and cross checking the diagonal measurements is important after any movement or welds. As the welding proceeds, the affects of warp will diminish. To prevent warping, I tack side to side, to reduce warping and do the same when welding corners, and cross members. I frequently check the diagonal measurements for out of square condition as the welding progresses.
Corner gussets are also employed for reinforcing the corners, support for the trailer floor, and the hole is for passing some wire. The heat affected zone is visible from the short stitch welds on the opposite side. If it doesn't turn red, it's not hot enough.
Frame rail joint tacked and welded on top and bottom. If the material thickness were 1/4" or greater, the edges would need to be beveled prior to welding. These frame rails are 11ga. or .125 inch, and are two thin for beveling.
The frame rails will be covered with 1/2" ply so it was necessary to grind the welds flush. I would do the same if it were exposed just for aesthetics. The top of the rails will also be ground flush to enable a good fit to the trailer floor.
I wanted to install receivers to accommodate slide in dining table, and a bumper that is planned for a later date. Two sets of bracket assemblies were also fabricated to support a platform or step runner for storing shoes outside the trailer, and elevation while washing the top of the trailer. If you have ever slept in a teardrop, you will understand the desire of removing and storing shoes outdoors. The step runners look like running boards, but are narrower and shorter than a running board.
Receiver for rear bumper re-enforced by joining to table support receiver. The hole drilled in the receiver is for a 5/8" receiver hitch pin to prevent the bumper from ejecting from the receiver. The same set of receivers exist on both sides of the chassis. The homemade wing bolts are not available at the hardware. These are used for tightening the male insert, to prevent vibration and noise.
Checking the step runner support frame for fit after inverting the chassis. The step runner is also adjustable by way of matching index holes. By removing two 3/8" bolts with nuts and washers, the step runner may be re-located on it's support channel, and stored out of site under the chassis. When extended, the step runners are secured 4" outboard of the frame rails.
Trailers generally have a tongue with A frame supports or a single straight tongue. This chassis is equipped with a single 2" x 3" x .125" straight tongue. It's overall length is 88" and is attached to the first, second, and third cross members. It is gusseted at all three cross members. and welded on all sides except the bottom. It extends 51" beyond the front of the chassis. Before any attachment of the tongue to chassis is made, it is paramount that the tongue be aligned to the chassis. Again, measuring diagonally from the end of the tongue to the front corners of the trailer should yield the same measurement. If not, stop and find out why. A diagonal check from the front of the tongue to the rear corners should yield the same results. Another check can be made from the rear center of the tongue to the front corners, and rear corners.
If all your diagonal measurements are equal, or within 1/16 inch. then you can continue on. You can probably live with 1/8". If you start seeing a 1/4", the problem is getting out of hand. How well your axle will be aligned to the frame, prior to installation, will depend heavily upon tongue placement .
Once the tongue alignment procedure is complete, and the chassis bottom is facing up, the tongue is tack welded on both sides. to each cross member. I start from the most rearward cross member and work forward, alternating the tack welds left to right as I go along. When finished, I then go back and finish a complete weld using the same orientation. Then the chassis is inverted, and welds are completed on the topside in the same manner.
Align the axle to the chassis. Again I use the diagonal method, measuring from the tongue font center to the center of the axle spindle. I also check for equal distances to the axle mounting hangar locations. If you know everything is square and have marked the placement for the axle hangars, the hangars can be tacked to the frame rails, and the axle can be unbolted from the hangars.
Before prime and paint, the chassis will need a set of chains for safety while towing and a tongue jack.
I use quick links, welded to each side of the tongue. These are 5/16" rated at 2200 lbs each, and the chains are the same size in a grade 8. The other end of the chains are also equipped with the same size quick link. It may seem and probably is overkill, but I don't think so, and that's all that matters to me. These links are mounted 12" from the end of the coupler. In the event of a separation of coupler and hitch ball, the crossed chains will easily cradle the tongue.
This is or was an Atwood tongue jack. A simple device made from acme screw, some washers and two pieces of thin tubing. I spent more time modifying this contraption than time put forth fabricating half of the chassis. The tongue clearance to ground is approx. 10" and the jack would not retract far enough to pivot after dropping the trailer on the hitch. The supplied mounting bracket and hardware was discarded, and the jack tube support bracket was cut and relocated down the tube 5". The center tube was also cut back 1". The new mounting bracket is made of 2 1/2 inch DOM over 2" DOM. which is welded to a 7" x 3/16" backing plate also welded to the tongue. The assembly is can be rotated 360 deg. or locked in the horizontal travel position. It can also be removed easily by pulling the 5/8" hitch pin which will decouple the Jack assy. from the mount.
The methodology in fabricating these frameworks vary from individual to individual. This web page follows my own particular style, and in no way was it intended to infer that it is a preferred method. It is preferred by me alone, hopefully you as a reader will glean something from the information contained within this page.
If you work alone 99 to 100 percent of the time, and without the assistance of an extra set of hands, you might find this project somewhat bulky and heavy to work with. I estimate by my published metal tables that this chassis weighs approx. 350 lbs. Without the axle, wheels and tires it becomes much lighter, but still bulky, and difficult to mobilize. The one assistant that I do employ is a 1 ton chain fall, which can be purchased for about $40.00. It is really the answer to silent and cheap labor.
Step Runner installed to support brackets
That's all for now. If you have questions, e-mail :
Page last updated on 01/18/2011
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