Plans are now available for the Twin Torsion Axle Walking Beam Trailer Suspension. This was introduced on a build early in 2018, with posts about the trailer including a video of the suspension in action.
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. They’ve been re-invented many times and are 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 torsion axles. They work well as singles, and best in light duty applications. The hiccup with torsions is they don’t work effectively in tandem or triple. That begs the question: Can you combine the benefits of a Walking Beam Trailer Suspension to overcome the load sharing inadequacies of typical 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 load capacity of 2000# 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 also work.
- The beefier 8K version of the walking beam trailer suspension is similar, but with options of 5000# up to 8000# total. Again, this system uses two matching torsion axles each of half the capacity desired for the total.
Both suspension systems include complete plans and parts detail. They even have the CAD files needed for the special CNC parts (laser or waterjet cut).
Note: You can find laser cutting and/or water jet 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. Big Blue Saw cut the parts for us.
Please see the images, comments, and walking beam trailer suspension support videos below. Check out Trailer Axles 101 for more on torsion axle specifications.
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 shown — more than just what is explained — for ideas in getting the fabrication perfect.
Matching and aligning the parts left and right is 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. It’s not long, but it gives tips for precision, the technique, and why.
Certainly, setup is important with suspension so trailer tracking is consistent and stable. Please take your time while building 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.
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. Just stick a 1/4″ diameter piece of rod through those holes and the holes in the beams and shims for alignment.
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 required.
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). Unfortunately, because of the clamps and because of the way they are held together, you must tack things on the inside first, then unclamp, and weld the outsides. Weld the insides last. That will cause weld pull, so watch the next video about 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.
Note 2: This next video mentions, but does not explain so well — the washers in place prior to welding. They make the gap extra wide with anticipation of the welds pulling the plates in. They did pull in, as expected, but more than wanted. This video shows how 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 in the first place, the videos are here to help.
Here are the final walking beam welded parts set together. They all fit, including the pivot bolt. The next step is to attach everything to the axles and the frame, 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.