Bouncing Pack Eases Those Tired Shoulders

If you are a hillwalker, wherever your preferred stomping ground may be you’ll know the importance of a pack with a good strap system. A comfortable pack will make the difference between tiredness and agony, and can easily add a considerable difference to your daily range.

At Arizona State University’s Human Integration Laboratory, they were approached by the US Army to investigate means by which the effect of carrying a heavy backpack could be mitigated. A soldier’s full kit is extremely heavy, and while the best available webbing systems will make a contribution to the comfort of carrying it, they can only go so far. There is still the jarring effect of the impulse force of such a significant load bearing down on the soldier’s shoulders as it comes down after every step, and this when taken over a lengthy march makes a significant difference to overall endurance.

The ASU lab’s solution was to mount the load on a spring-loaded vertical actuator attached to the pack harness and frame. The on-board microcontroller judges the moment of maximum downward impulse force as the wearer comes down from a step, and applies a corresponding upward force to the actuator. Power comes from a lithium-ion battery pack. The effect is to make the load oscillate up and down, and to lessen the wear and tear on the shoulders. It does not reduce the weight you are carrying, but it does lift it off your shoulders for an instant just when you need it.

There is a video of it being tested in the sun-drenched Arizona mountains, that we’ve placed below the break.

This is the first oscillating weight-saver backpack we’ve seen here at Hackaday. We have brought you a propeller backpack though.

Thanks [Rich] for the tip.

41 thoughts on “Bouncing Pack Eases Those Tired Shoulders

  1. …… so it reduces the impact by accelerating the pack upwards? Your smart pack is pushing off something, I don’t see how this reduces the impulse. If anything it increases it.

    Far better to use a good hip belt and secure the load better, IMO. Better still to buy lighter gear or pack less. I imagine this is aimed at soldiers who don’t habe that option, but again. Proper pack sizing and belt usage mitigates the impulse, walking sticks help in hilly terrain but again soldiers have their hands full.

    1. I can say that his pack was not sufficiently weighted to say it would work for soldiers. Also too many moving parts and power requirements. That said interesting concept and maybe someone will be interested in the civilian market.

      1. If this worked, and Leithoa’s point wasn’t strong (even hip shift will only be disastrous for your hips, a sensitive place really), then for a military backpack you’d need a very powerful actuator and batterypack which would increase the load enough to offset any gains.

        This needs a passive solution – or a Boston Dynamics (now owned by Softbank) carrying robot.

    2. Other way around. When you need to push up, it pushes the bag down, essentially lifting *you* against the inertia of the pack. Then once you’re up, it spreads the load of raising the bag up across a longer time period, so the peak load is smoothed out and pushing against your bones when your knees are straight and locked instead of when they’re bent and your thigh muscles are carrying the load.

  2. A steadycam for your back pack? Cary the weight on your hips. It takes three days for shoulder strap trapezius pain to ease in teenagers and longer in adults if you hang packs on the shoulders. It is a cool idea though. Looks like it lifts the pack a little just before the human used legs for lifting and lets it down as the person goes up. So, there must be real work done by batteries, which is bound to make it easier. It seems it should work some for level walking by lifting when the leg is vertical, etc. In fact, we can all wear them and they can be adjusted for difficulty to make everyone equal.

    1. ” It takes three days for shoulder strap trapezius pain to ease in teenagers and longer in adults if you hang packs on the shoulders.”

      Learned this the hard way in college. Ouch.

  3. Looks like effort to carry, yet, more weight.

    With the correct bag and straps to support it, I’ve carried a steel cage of 1.2mm-thick sheet steel containing 8x 6Ah 12v lead-acid batteries to test out an electric bike build over 10 miles (20 total as I return the pack to work).
    Apart from being stupid and trying to lean to the side to sign-in causing a back ache for over three weeks, I’d say proper usage gives the better results usually.

    Battery pack described was an APC SMT2200RM2U battery of the 24v type and from the older era, the era that such UPS growls, or in this case the UPS was scrapped for tripping mains and plain making scary sounds.

  4. “There is still the jarring effect of the impulse force of such a significant load bearing down on the soldier’s shoulders as it comes down after every step”

    This is why they make hip belts for packs, dude. Shifts most of the weight to the hips, and off of the shoulders.

  5. One of my teachers was an operative for a 3 letter agency and had a lot of packing to do over his career. Years later when I met the person and he was taking a class full of us kids into the woods for 2 weeks of archaeology I noticed something odd. Everyone had large packs with lots of stuff, he grabbed his pack and it was small. More surprising was the fact that it only weighed a few lb’s (1+ week’s full gear dry weight was under 10lb). After that day I learned a valuable lesson. DON’T PACK ANYTHING you don’t absolutely need and know you will use. He even took the labels off of his tea bags. He told me he could get it to under 5lb for a weekend trip but to get much lighter would cost $1000 per oz of weight removed.

    I mistakenly thought that this meant he didn’t have much in the way of comfort. I could not have been more wrong. He had everything, music, a chair, etc. The trick was just about everything had more than one use.

    As an example of this thought process look over your choice in a water bottle. His choice was to reuse the lightest soda/spring water bottle you can get, about 16oz capacity and had almost no weight. As for a water treatment system, bleach and time. A single eyedropper bottle had many week’s worth of water purification and uses the same chemical your water plant does.

    As for a stove –

    I am rambling about this because this article’s design is the wrong direction. Stop trying to make heavy packs easier to carry the same weight and focus on what is actually heavy. Ammunition is one item. Change that out for Caseless. Now you can carry more at the same weight or reduce total weight for the same number of rounds. Foods most army food has added water. Anything metal look for plastics or titanium options. There are options but they are expensive and that is why the foot soldier has this issue. Its cheaper to have them have to carry more weight than making everything lighter. That teacher’s pack I was talking about costs well over $10,000 for all the gear. He even had if he wanted titanium tools (pry bar, shovel etc) but didn’t need them on most trips.

    Overall adding a active system would be nice but why not use something that extends that down to the ground so that all of the weight is not on the body but on an exoskeleton. A spring on a backpack that has a hard plastic frame and an power requirement just is junk mucking up the works. I doubt the system can be made reliable enough for field use.

    1. You really only need to keep it under 30lbs for your average adult male. Under 20lbs is easily attainable without breaking the bank, under 15lbs starts getting expensive or sacrificing comfort. The knowledge in your head weighs nothing so learning a new skill makes it worth your time if you plan on spending a lot of time in the wilderness.

    2. For military, every bit you save means that much more can be added to expendables like ammo and food/water, and com gear. Similar to airplanes were every structural weight savings means more fuel.

    3. 5lb is attainable on an under 100 budget. Store white gas in small waterbottle, marked with duct tape, for repairs. Stove can be a catfood can with holes punched in the sides, graundpads can function as chairs, etc…

  6. It appears to be smoothing out vertical acceleration over time. Trying for a constant load on you as you make small bounces up and down with each step. As mentioned functioning like a steady cam.

  7. Hook up the system in reverse. Generate power whilst walking and carry that many less batteries needed later. The mil is on to this, that’s approximately 19 pounds per infantry soldier.

    1. I’ve read about testing with the military backpack with the built-in battery chargers. The problem is that much of a soldier’s gear runs on batteries, so the idea was for this backpack to use coils to generate current from the downward motion of the pack. It was a great idea, except the net result is that it worked exactly like the opposite of this “pogo pack.” The charging coils kicked in and sucked energy out of the load just as the bag was about to bounce back up. This resulted in a bag that felt like carrying a sack of wet cement.

      For the weight saved, the soldiers who tested it would rather have carried the extra batteries.

    1. Don’t be silly, it’s just a proof of concept prototype. In a real application it would obviously be kept inside the backpack together with the ammunition and maybe other explosive devices.

  8. I seem to recall there being a ARPA/US Army project like this with the bouncy framed pack in the 70s/80s to replicate the ease with which some Africans were able to carry large loads on their heads.

  9. “We were asked to design systems to make a 45 kg backpack easier to carry for the soldier.”

    The weight is set, and they are asking for novel solutions. Carrying less weight or using an existing backpack tech is inherently outside the scope of what you are being asked to do.

    The speaker is mischaracterizing what is going on though. Saying a “hand lifts the bag” makes it sound like an external force is applied to the bag. A more accurate description is that the pack maintains the pack’s vertical height off the ground while the carrier can bob up and down normally with their gait.

  10. seems like passive push-pull springs with damper system would be as effective. it would have to be adjusted for the actual weight of the loaded pack, but that would be simple, the dial could actually be labelled in pounds.
    concept is cool, though.

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