Research Papers: Design Automation

Design of Compliant Bamboo Poles for Carrying Loads

[+] Author and Article Information
Karna Potwar

Purdue University,
585 Purdue Mall,
West Lafayette, IN 47906
e-mail: kpotwar@purdue.edu

Jeffrey Ackerman

Purdue University,
585 Purdue Mall,
West Lafayette, IN 47906
e-mail: ackermaj@purdue.edu

Justin Seipel

Purdue University,
585 Purdue Mall,
West Lafayette, IN 47906
e-mail: jseipel@purdue.edu

Contributed by the Design Automation Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received March 14, 2014; final manuscript received October 1, 2014; published online November 14, 2014. Assoc. Editor: Matthew B. Parkinson.

J. Mech. Des 137(1), 011404 (Jan 01, 2015) (14 pages) Paper No: MD-14-1167; doi: 10.1115/1.4028757 History: Received March 14, 2014; Revised October 01, 2014; Online November 14, 2014

Carriage of heavy loads is common in developing countries and can impart large repetitive forces on the body that could lead to musculoskeletal fatigue and injury. Compliant bamboo poles have been used to carry heavy loads in Asia for generations and could be a low-cost, sustainable, and culturally acceptable way to minimize the forces acting on the body during load carriage. Experimental evidence of running with a 15 kg load suspended from a pair of compliant poly(vinyl chloride), or PVC, poles shows that the poles act as a vibration-isolating suspension, which can reduce the peak forces on the body during locomotion. However, it is currently not well-understood how to design and optimize poles for load carrying such that the peak forces on the body are minimized during carrying. Further, current users of bamboo poles do not have a reliable way to measure forces on the body and so cannot empirically optimize their poles for force reduction. Our objective is to determine the geometric and material design parameters that optimize bamboo poles for load carriage and to develop recommendations that could make it easier for load carriers to fabricate well-suited poles. Our approach is to synthesize a predictive model of walking and running from the field of biomechanics, which can predict the peak forces on the body as a function of pole stiffness, with a bending beam model of the bamboo pole that relates pole geometry and material to the effective pole stiffness. We first check our model's ability to predict the experimental results from a well-established study with PVC poles. We then extend the predictive design study to include a wider range of stiffness values and pole geometries that may be more effective and realistic for practical load carrying situations. Based on stiffness, deflection, strength, and pole mass design constraints, we specify an appropriate range of dimensions for selecting bamboo poles to carry a 15 kg load. The design methodology presented could simplify the selection and design of bamboo carrying poles in order to reduce the likelihood of musculoskeletal injury.

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Fig. 1

People have been known to carry heavy loads with bamboo poles in parts of Asia for centuries. Large, bulky loads are often carried in large baskets tied with a long rope to each end of the pole. Carry loads with compliant bamboo poles may reduce the peak forces of carrying a given load. Further, compliant poles free the arms, which may then be used to help stabilize the baskets from swaying during locomotion. (a) “Yoke China” by unknown author is licensed under CC-BY-SA-3.0, via Wikimedia Commons. (b) “Chinese Women are Carrying Basket” by Stougard is licensed under CC-BY-SA-3.0, via Wikimedia Commons.

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Fig. 2

Possible configurations of a bamboo pole for carrying a load. The load is assumed to be evenly split on each end of the pole for balance.

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Fig. 3

Diagram showing our overall approach

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Fig. 4

The hip-actuated SLIP model of walking and running with a vertically constrained load suspension and representative trajectories. During running, the leg touches down when θ = β. During walking, there are two independent legs, with θ and Ψ describing the angle of each leg in stance. Each leg touches down independently when θ = β or Ψ = β. In both models, the leg lifts off of the ground when the vertical component of the leg's ground reaction force is 0 N.

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Fig. 9

Model predictions of the peak shoulder forces over a range of effective pole stiffness values while running with a 15 kg load at 3 m/s, walking with a 15 kg load at 1 m/s and 1.34 m/s, and walking with a 30 kg load at 1 m/s and 1.34 m/s

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Fig. 5

The bamboo pole supported on the shoulder with a symmetrically distributed load P could be treated as an equivalent linear beam bending system with simplified boundary conditions

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Fig. 6

The area moment of inertia about the centroid for a split bamboo pole with a hollow semicircular cross section (HSC) can be calculated using the parallel axis theorem by subtracting the moment of inertia about the HSC centroid (XHSC) of the smaller semicircle (SSC) from the larger semicircle (SC)

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Fig. 7

The model trajectories of the load and the body (left) approximate the experimental results (right, reproduced from Ref. [1]). The results for the hip-SLIP model show the dynamics of the system at steady state, which differs from the more complex behavior shown in the actual experimental data.

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Fig. 8

The peak force predictions of the model for a compliant pole and a rigid backpack as compared to the experimental results reported by Kram

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Fig. 10

Recommended bamboo pole design region for running with a 15 kg load at 3 m/s

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Fig. 11

Recommended bamboo pole design region for walking with a 15 kg load at 1 m/s and 1.34 m/s

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Fig. 12

Recommended bamboo pole design region for walking with a 30 kg load at 1 m/s and 1.34 m/s

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Fig. 13

Other possible designs of carrying yokes which are strong and sufficiently compliant. The top two images the side profile and the top profile of a yoke that could be carved from wood which would have a high second moment of inertia and a relatively low distance to the neutral axis, increasing strength. The bottom image shows a stacked arrangement of flattened wood or bamboo.




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