Stiffness and Damping vs. Hanging Weight

It is generally accepted knowledge in the photographic community that hanging weight from the bottom hook on a tripod increases the stability of the system.  I have even seen claims that a cheap tripod can exhibit the performance of one several times its price when weight is hung underneath it.  Here we are going to examine exactly what effect hanging weight has on a number of tripods.

I am going to be using the standard torsion spring oscillation method used on this site to determine stiffness and damping.  In short, I set a large amount of rotational inertia oscillating on a tripod and then measure the frequency and decay rate of those oscillations.  In this post, I am only going to be looking at the yaw oscillations, or those that correspond to left and right camera motions.  Tripods are by far the weakest in this direction and so performance changes will have the greatest effect here.

For these tests I simply hung weights directly off of the tripod bottom hook using a short piece of paracord.  This is not necessarily the optimal way to hang weight from a tripod, but it is the most straightforward way to measure the effect.  It is more ideal to let the weight lie on the ground and attach it to the bottom of the tripod via a bungee cord.  This prevents the weight from swaying and inducing motion in the tripod.  I was working under ideal indoor conditions and so this wasn’t a problem.

I tested seven different tripods.  For each, I would start with zero weight and add 2.5 lbs at a time up to 20 lbs.  At each point I recorded the stiffness and damping.  I would only take a single data point for each weight, so the data is somewhat noisy.  Some tripods could not adequately handle 20 lbs, and so were stopped early.   Below is the data for the stiffness versus the amount of weight hung:

Clearly the results are underwhelming.  I don’t see any effect at all here on the axial rotation stiffness.  Any of the small fluctuations seen in the plot above can easily be explained by noise in the data collection process.

Now lets look at the damping vs weight hung:

There is clearly more structure here, but that isn’t saying much.  The noisiness of the measurement process is clear.  Some of the tripods exhibit what is clearly a small increase in the damping as more wight is hung underneath.  But I must emphasize how small the effect is.  The best tripods exhibit damping around 1.0 Js/rad.  You can achieve much better damping by simply resting your hand on the tripod.

While I didn’t find any effect on the axial stiffness and very little on the damping, that doesn’t mean there are no benefits to hanging weight.  It dramatically lowers the center of gravity of the system, making it much less prone to tipping over.  If you are working in gusty conditions, around children, bears, or are just clumsy, a lower center of gravity can be the difference between an upright tripod and a broken camera.  There could be application in which a slight increase in stiffness about the pitch axis (vertical camera motions) due to hanging weight is valuable despite the lack of an effect on horizontal motions.  I struggle to imagine it though.  Testing for changes in stiffness about the pitch axis will be the subject of a future post.

7 thoughts on “Stiffness and Damping vs. Hanging Weight

  1. Hanging weight swings when there is wind, with the sandbag I’ve been using tangible picture wobble starts to
    occur when wind speed exceeds 4mph. A better way to do it would be tying the tripod to something sitting on
    the ground(backpack, rock..etc) with a elastic strap. It really helps to reduce the wobble area.

    1. Yes, having a bungee to the ground is absolutely the correct method in practice. I am hanging weight in the lab simply because it is easier to get consistency and without wind, should give similar results.

  2. Would you already know or consider testing putting weight that was firmly attached to the apex of the tripod (say
    screwed underneath or connected somehow so that it is solidly part of the tripod) rather than hanging or resting
    on the ground attached via a cord how it would affect stiffness and damping? My thinking is, in terms of
    stabilizing a camera, having more mass near the camera and firmly attached essentially adds more inertia thus
    reducing vibration, correct? It would be interesting to know how this affects stiffness and damping in the
    yaw/axial direction. I feel like part of the reason your results are a bit underwhelming is due to the paracord not
    taking advantage of the weight properly and its effectiveness to what we’re testing (Although this article was
    great insight!). Certainly having a hanging weight on the ground helps with preventing the tripod from tipping
    over, but I would imagine vibrations are more important for most cases and we should therefore use the weight
    to solidly attach it underneath and use its moment of inertia to our advantage (whereas a hanging weight via a
    bungee cord wouldn’t benefit from this due to the weight not rotating). I could be totally wrong or missing
    something but just thought I’d ask if you knew or would consider looking into it! Thank you for testing these
    kinds of things for us! – Austin

    1. I haven’t but probably will at some point. Its hard to imagine how it would help the stiffness of the tripod in any way, but its reasonable to expect more of an effect on damping with the straps rubbing on the legs.

  3. I think adding weight is mostly
    helpful when on soft ground, as the
    added weight will compress the
    ground, thus make it stiffer.

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