Plans are now available for the Twin Torsion Axle Walking Beam Trailer Suspension. Please see the early build in 2018, with a couple articles (links below) about the trailer including a video of the suspension in action. Plans are now in the store, in the Trailer Accessories section.
For a long time we’ve admired the action and ride control of walking beam style suspensions. They are mostly on large and very expensive equipment like high-end semi-truck trailers and massive machinery, like mining equipment. It is a concept that has been re-invented many times over, and is found with all sorts of variations.
This image shows one heavy truck example.
At the same time, we also like the natural damping of rubber and the ride quality found with it. Torsion axles (which use rubber) work well as singles, and best in light duty applications. The hiccup with torsions is they don’t work effectively in tandem or triple.
The above ideas raise the question: Can we combine the functional benefits of a Walking Beam Trailer Suspension to overcome the load sharing inadequacies of Torsion Axles?
The Walking Beam Trailer Suspension
To the question of combining benefits, the answer is YES. We built it. We may not be the first, but we engineered this DIY system and built it. Now many of you have requested blueprints, so we added instructions, and have them in the plans store as a trailer accessory.
Plans are available right now for 2 versions of a twin torsion axle suspension:
Our 4K suspension system gives options for a total trailer load capacity of 2000# (lbs) up to 4200# by using two matching torsion axles. Use matching axles of 1000# each (for 2000# total); up to 2,100# each (for 4200# total). Options between, like twin 1500# axles (for 3000# total) also work.- The beefier 8K version of the walking beam trailer suspension is similar, but with options of 5000# up to 8000# total capacity. Again, this system uses two matching torsion axles – each axle for half of the total desired trailer load capacity.
Both suspension systems include complete plans, illustrations, and parts detail. The plans even have the CAD files needed for the special CNC parts (laser or waterjet cut).
Note: You can find laser cutting and/or waterjet cutting for steel online or locally. The technology is very common, so most cities have folks that do it. Do a search and you’ll likely find several possibilities. If you need an online source, we tried Big Blue Saw to cut the parts for us, and they did a good job.
Also, please see the images, comments, and walking beam trailer suspension support videos below. Check out Trailer Axles 101 for more on torsion axle specifications. These plans specifically use the Dexter Torflex #9 (4K walking beam version), and Torflex #10 (8K version). Other brands can adapt with some modifications.
Images & Videos Of Construction Technique
For many experienced DIY builders, fabricating with some precision is not a problem. However, for those that are not as confident, here are some images, comments, and a couple videos to assist. Look at the things they show – more than just the explanation – for ideas in getting the fabrication perfect.
Matching and aligning the parts left-side and right-side is really important, so we build everything in matching pairs.
Walking Beam Setup
First up is a video showing the clamping and setup for the main rocker beams. The video is not long, but it gives several tips for achieving precision, the technique, and why.
Certainly, setup is important with suspension so that the trailer tracking is consistent and stable. Please take your time while building these systems so the final product will serve you well.
See the blueprints and compare with the images below for the complete product assembly. That will also show more about the welding intent. Plans include several notes that help with the processes of bringing it all together.
Suspension Pivot Setup
Moving to the frame mounting brackets that support the suspension pivot, these two images show the setup. The CAD parts show a 1/4″ hole to use for alignment. That’s it’s only purpose. We recommend running a 1/4″ drill through the holes to make sure they are all to size. Then, just stick a 1/4″ diameter piece of rod through the holes and the holes in the beams and shims for alignment.
This image shows the two – left side and right side – supporting bracket assemblies stacked side by side. With the pins passing all the way through both, and the axle pivot bolts through both bracket sets, even if things are not perfect, both the left and right brackets assemblies will be the same. Same is more important than perfect.
Clamp all the pieces as shown. Oh, and make sure you don’t forget the shim stock between the beam and the laser cut parts. Those thin spacers are very important.
After clamping everything as shown in the above images, remove the 2 big bolts, and clamp that area as shown in the video below. Add an extra washer or two so there is pressure outward – which will compensate for some of the weld pull. Get it ready, then weld it all up carefully. (But don’t weld that pin – it must come out).
Please note that because of the clamps and because of the way all the pieces are held together, you must tack weld things on the inside first, then unclamp, in order to weld the outside. Full weld on the inside last. That will cause weld pull, so watch the next video for tricks in solving that problem.
Suspension Pivot Adjustment
This second video shows how to adjust the pivot braces on the frame mount after welding so the walking beam does not pinch while in action on the trailer. Welding is a ton of fun, but when precision matters, we must compensate for weld pull.
Note 1: Setup for the frame mount beam is very similar to the rocker beams above. We suggest aligning all the holes and clamping the two assemblies so everything aligns. Again, it is important that the left and right sides are the same.
Note 2: This next video mentions, but does not explain so well about the washers there in place prior to welding. They make the gap extra wide with anticipation of the welds pulling the plates in. As you will see in the video, they did pull in, as expected, but more than wanted. This video shows one way to correct the spacing and make it perfect.
I’m not sure if accuracy with the walking beam trailer suspension is more or less important than for other suspension types, but I know for sure that getting it right makes excellent towing. It’s also pretty easy to achieve by aligning everything in advance of welding, then tweaking things carefully for assembly. Since the towing experience is the reason for building this suspension in the first place, the videos are here to help.
Test It !!
Here are the final walking beam welded assemblies all together. They all fit, including the pivot bolt. Note that the pivot bolt is longer than perhaps usual, so that the pivot is all on the shank of the bolt, rather than on the threads. The bolt is the bushing surface for walking beam pivot, so more surface area is better, and we definitely don’t want to pivot against threads. While this may not be the best solution for longevity, we find that is enough. It is certainly strong, so use a really robust grease, and it will be fine.
The next step is to attach everything to the axles, then to the trailer frame. With everything else prepared, we can then make a test run.
Share Your Experience / Share Your Skill
I’m sure many of you are more skilled in fabrication, so please share if you have added insight. We’d love to know about better ways. Please leave comments below, or on the Contact Us page. Thank you.
For a lot more information about the design and about building the walking beam trailer suspension, please see the post about building the suspension and the Engineering Case Study about the suspension design.
Also, after you complete your build, please share here! Other readers would love to see your project. Follow the link to share your story.
Finally, for some more reading, see this other unique trailer suspension. Or, read about some of the Independent Trailer Suspension Fallacies that make us want to create this walking beam trailer suspension for smaller trailers.
We wish you the best of luck building your new walking beam trailer suspension.
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