4 Comments

  1. leo
    February 6, 2019 @ 6:39 PM

    Thank you so much for sharing your information!

    Reply

  2. Ryan D
    March 14, 2019 @ 3:23 PM

    I am a big fan of this website. The knowledge you share here is very valuable to me. Thank you!

    I have a question that is more rooted in academic curiosity than practical application. Everyone discusses “tongue weight”. However, in a physics sense, is actual weight on the tongue the objective, in order to achieve stability? Or is the objective more about locating the trailer’s centre of mass (including the load) relative to the major pivot points (axle & coupler)? (If the latter, I understand that it would be translated to tongue weight rules of thumb, given average tongue lengths, so the layman can easily approximate the centre of mass and achieve a stable condition.)

    If it’s more about centre of mass location, is the primary factor the distance from the axle, or distance from both primary pivot points (axle & coupler)?

    As a thought experiment to illustrate my question, let’s imagine an 8′ utility trailer with an axle set a little back from the centre of the bed, with a tongue length of 4′, loaded evenly, with a result of 15% of the weight being on the tongue at the coupler. Now, ignoring the weight of the tongue material itself, let’s imagine we extended that tongue to be 12′ long. If I remember my math correctly, the weight on the coupler would be cut roughly in half; probably around 8% now. However, the centre of mass would still be the same amount forward of the axle. Would the second case be likely to tow stably, despite being outside the normal rule of thumb? (Let’s also ignore the other inherent stability benefits offered by the longer tongue, for the sake of this thought experiment.)

    Reply

    • The Mechanic
      March 14, 2019 @ 6:01 PM

      Oops, now you’re thinking. We can’t have that! — But these are great questions. How much do you want to know?

      Let’s play with your experiment. Let’s take your trailer and and move the load back so there is Zero tongue load. Now, as you drive your car goes over a bump. That pushes the tongue up fast, which throws the load back, which makes the trailer want to tip back (because the load is now behind the axle). As your car comes down from the bump, the process goes the other way. That back and forth switching causes some weird dynamics for the driver and he feels like it is “bucking”.

      So making the tongue (your 12′ experiment) long does work like you say, and actually it makes the bump feel (to the trailer load) like it’s half as high. A long tongue has other nifty advantages too — within reason — though your 12′ tongue will create other issues. That’s part of why we avoid trailers with really short tongues.

      That’s the straight line dynamic. There’s much more to it, so maybe I’ll write an article about this whole thing sometime.

      Reply

      • Ryan D
        March 20, 2019 @ 10:06 PM

        Leading me further down that thought experiment was helpful. By continuing to follow that though, I think I got some clarity: it’s more about the centre of mass and its location relative to the trailer axle, at least for straight-line dynamics. Brilliant, thanks!

        I relish the idea of an article that delves deeper. I’ll keep my eye out!

        Reply

Leave a Reply

Your email address will not be published. Required fields are marked *