Biomechanics: Kayak Exercise

Biomechanics: Kayak Exercise

Stefan Cautino, Geoffrey Cohen, Jason Colella, Alex Wilson, &

David Zankowsky

Stefan Cautino, Geoffrey Cohen, Jason Colella, Alex Wilson, &

David Zankowsky

Biomechanics of KayakingBiomechanics of Kayaking

•Differences between Kayaking and Rowing:

•Rotation of torso, alternating side of force application•Legs not involved in motion of kayak, used for balancing

•Motions involved in kayaking:•Twisting of torso to generate power, results in yawing of kayak•Pitching and rolling of kayak due to buoyant forces•Pushing and pulling of paddle by user

Statement of ProblemStatement of Problem

There are very few kayak exercise devices Existing machines:

Lack accurate recreation of motion of kayak Are grossly oversized Are costly and require other items to function Do not seem to be designed for high volume

use, such as in a gym environment

There are very few kayak exercise devices Existing machines:

Lack accurate recreation of motion of kayak Are grossly oversized Are costly and require other items to function Do not seem to be designed for high volume

use, such as in a gym environment

Statement of Problem cont…Statement of Problem cont…

Our goal is to create a machine with… Small footprint Compact, accurate paddling motion Movement more reflective of a kayak High use tolerance Affordability for home or gym use

Our goal is to create a machine with… Small footprint Compact, accurate paddling motion Movement more reflective of a kayak High use tolerance Affordability for home or gym use

Patent ResearchPatent Research

While looking for similar designs, there were several existing patents found

These devices simulated the kayaking arm motions

They didn’t account for the motion of the kayak itself, they don’t rotate or give any sense of being in a moveable craft

While looking for similar designs, there were several existing patents found

These devices simulated the kayaking arm motions

They didn’t account for the motion of the kayak itself, they don’t rotate or give any sense of being in a moveable craft

These are two of the designs which provide a kayaking arm motion, without the movement associated with a kayak

These are two of the designs which provide a kayaking arm motion, without the movement associated with a kayak

This is the closest match to the machine we’re designing. The user is free to rotate, engaging the core muscles essential to kayaking. However, the machine does not simulate the motion of a kayak, which is a key part of our goal

This is the closest match to the machine we’re designing. The user is free to rotate, engaging the core muscles essential to kayaking. However, the machine does not simulate the motion of a kayak, which is a key part of our goal

These designs also incorporate the same basic motions as the Dansprint design. They all are fixed machines, which allow the user to rotate, but the machine is fixed in place.

These designs also incorporate the same basic motions as the Dansprint design. They all are fixed machines, which allow the user to rotate, but the machine is fixed in place.

Market ResearchMarket Research

Our primarily market is franchise gyms as well as college gyms, so we focused our requirements on the Marino Center

We met with Sue Ekezian who purchases equipment for the Northeastern gym and we asked these questions…

Size constraints 3ft safety zone around machine If heavy must fit on elevator Or breakdown for carrying up stairs Cannot obstruct 44” fire path Location of powercord Low power usage/generation

Our primarily market is franchise gyms as well as college gyms, so we focused our requirements on the Marino Center

We met with Sue Ekezian who purchases equipment for the Northeastern gym and we asked these questions…

Size constraints 3ft safety zone around machine If heavy must fit on elevator Or breakdown for carrying up stairs Cannot obstruct 44” fire path Location of powercord Low power usage/generation

Cost Higher budget for longevity

3yr lifespan for treadmills which cost around 8k 6-7yr lifespan for weight machines

Our target lifespan will be between these two spans Maintenance

Simple is preferred Student maintained after warranty Availability of parts is key Preventative maintenance is not a problem

Cost Higher budget for longevity

3yr lifespan for treadmills which cost around 8k 6-7yr lifespan for weight machines

Our target lifespan will be between these two spans Maintenance

Simple is preferred Student maintained after warranty Availability of parts is key Preventative maintenance is not a problem

Final ProductFinal Product

Final Design SolutionFinal Design Solution

Major Components:

•Framing

•Paddle and Resistance Mechanism

•Seat Rotation

Design ProcessDesign Process

Our design process took into account the needs to simulate kayaking biomechanics

Major design factors: Yawing motion Energy absorption mechanism Framing

Strength Fatigue resistance

Footprint concerns

Our design process took into account the needs to simulate kayaking biomechanics

Major design factors: Yawing motion Energy absorption mechanism Framing

Strength Fatigue resistance

Footprint concerns

Energy Absorption Design MatrixEnergy Absorption Design Matrix

CriteriaCostx1

Weightx1

Sizex1

Availabilityx2

Maintenancex2

Complexityx2

Totals

Fan 5 3 3 4 4 4 35

Generator1 1 4 4 3 1 21

Cam/spring3 2 2 2 3 3 23

Flywheel 3 2 2 2 4 4 27

The fan was the winning design

Paddle Resistance MechanismPaddle Resistance MechanismRotational Parts Exploded

(b)*

(a)

(c)*

(d)

(e)

(f)

(g)

(a): Bike freewheel

(b): Freewheel to rope adaptor

(c): Shaft to freewheel adaptor

(d): Bearing

(e): Flywheel with attached fan

(f) : Flanged shaft collar for flywheel

(g): Steel shaft with two tapped ends

* custom machined parts

Framing OverviewFraming Overview

Calculations have shown all framing components to have a safety factor of 5 or higher.

lower

frame

upper frame

fan support frame

turntable

Side ViewIsometric View

Frame DesignFrame Design Our frame uses Bosch-Rexroth Aluminum

framing. B-R struts are very high strength, cheap and

allow for effortless mounting of accessories, such as our shaft mechanism, seat and footrest.

Turntable to enable yawing motion Analysis of frame members shows that

entire frame has a factor of safety > 5

Our frame uses Bosch-Rexroth Aluminum framing. B-R struts are very high strength, cheap and

allow for effortless mounting of accessories, such as our shaft mechanism, seat and footrest.

Turntable to enable yawing motion Analysis of frame members shows that

entire frame has a factor of safety > 5

Factor of Safety CalculationsFactor of Safety Calculations

€

σ =stressFtotal =1334N

Small :

σ = (1335N • 145mm) /4 • (6.147• 103)

σ = 7.86Pa

Ystength (Bosch −Connectors) =100Pa − each

N =Ystength /σ

N = 200 /7.86 = 25.4

Long :

σ max == (1335N • 546mm) / 4(6.147 • 103)

σ = 29.6 Pa

Ystength (Bosch −Connectors) =100Pa − each

N = 200/29.6

N = 6.75

Our calculations were based on data published by Bosch-Rexroth™.

We assumed a worst-case scenario of a 300lb user working on the machine.

Loading was assumed to be static.

Show a minimum of N=6.75

Our calculations were based on data published by Bosch-Rexroth™.

We assumed a worst-case scenario of a 300lb user working on the machine.

Loading was assumed to be static.

Show a minimum of N=6.75

Fatigue CalculationsFatigue Calculations

Paddle Resistance Mechanism Cont.

Paddle Resistance Mechanism Cont.

The bungee’s take up any slack in the ropes during the return stroke.

The freewheels allow the rope on one side to be retracted while the rope on the other side is in tension.

Seat Rotation

A turntable sits between the upper frame and lower frame.

As the user paddles, the inertia of their moving body causes slight rotation of the upper frame.

A return force is applied to the rotation by attaching elastic cords.

Rotation is limited by placing rubber bumpers 5 degrees in either direction.

Final ConsiderationsFinal Considerations The final cost of the prototype was

approximately $1400 For mass production, we expect this cost to

drop due to using extruded beams and welding

Initial goals were met with respect to cost and footprint, as shown by table below

The final cost of the prototype was approximately $1400

For mass production, we expect this cost to drop due to using extruded beams and welding

Initial goals were met with respect to cost and footprint, as shown by table below

Ours Dansprint Kayakpro

Cost ($) 1400 5000 2000

Footprint (ft2) 24 75 55

Future WorkFuture Work

Replacing some components, ie. Higher quality pulleys

Increasing rotational inertia of the fan Adding an electrical display and sensors for:

Power Output Cadence Distance Time

Replacing some components, ie. Higher quality pulleys

Increasing rotational inertia of the fan Adding an electrical display and sensors for:

Power Output Cadence Distance Time

Questions?Questions?