1. David Avard
    August 25, 2019 @ 12:29 AM

    One other factor you didn’t mention is the sensitivity of tandem torsion axles to hitch height (and the axles being level).

    My club has a custom 28′ trailer that the builder unfortunately put the axles in the center of, and some people had no problems towing it and for others it was a nightmare. Someone who works on trailers (for semis) suggested that it was related to the height of the hitch changing the effective length of the tongue (ie: when the trailer was tongue low, the front axle carried more weight and when tongue high, the rear axle carried more weight. This changed the load center of the trailer and made it unstable when tongue low or less unstable when the tongue high.)
    We confirmed some of this by measuring the weight on the hitch at various hitch heights. With a 10,000# trailer, the tongue weight varied by 500# (800#-1300#) over a 6″ variation in hitch heights (3″ +/- from level), with it weighing around 1050# when level.

    I’m sure I didn’t phrase that in correct engineer-speak, but you should understand the idea.


    • The Mechanic
      August 28, 2019 @ 4:28 PM

      You communicated the situation, and that’s more important than the “engineer-speak”! You bring up a great point, and you’re exactly right. Thanks.


  2. Travis, KC Slider LLC
    September 27, 2019 @ 4:24 PM

    Love everything in this articular. We specialize in building a product to load and unload cars in the trailer. I also tow a lot of miles each year myself. I have seen and experienced the damage to many different manufactures trailers that use tandem and triple torsion axles. What are your thoughts about putting an air bag on each end of the of the walking beam? My thought is to help spread the load better across the beam rather than concentrate that load at the pivot.


    • The Mechanic
      September 27, 2019 @ 4:36 PM

      Thanks for the endorsement. Yes, you can use air bags with the walking beam suspension, but make sure they are linked — as the front one compresses, it puts the air to the back one — so they both stay the same pressure. Yes, that would spread the load. Incidentally, that center pivot is high load, but it’s big & fat — designed to take it. Load is then spread with the underpinning beam between the trailer frame and the pivot.


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