Biomechanics: Kayak Exercise Stefan Cautino, Geoffrey Cohen, Jason Colella, Alex Wilson, & David Zankowsky

Biomechanics 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 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… 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 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

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.

Market 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 Product

Final Design Solution Major Components: Framing Paddle and Resistance Mechanism Seat Rotation

Design 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 Matrix Criteria Cost x1 Weight x1 Size x1 Availability x2 Maintenance x2 Complexity x2 Totals Fan Generator Cam/spring Flywheel The fan was the winning design

Paddle Resistance Mechanism Rotational 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 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 View Isometric View

Frame 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 Calculations 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 Calculations

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 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 $1400 For mass production, we expect this cost to drop due to using extruded beams and welding Initial goals were met with respect to cost and footprint, as shown by table below OursDansprintKayakpro Cost ($) Footprint (ft 2 )247555

Future 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?