P12031: Motion Assisted Seating Device for Sailing

Detailed Design

Table of Contents

User Dimensions

The design of the system was heavily driven by the user’s dimensions. The prospective user, Richard Ramos, has been extremely accommodating in providing these dimensions so we can appropriately place the crank system and seat relative to the user.

Richards Body Dimensions was assessed through sharing multiple emails and documents. Richard was also very helpful in providing us with data from a previous fitting he had at the Physical Therapist: Ramos measurement.

The first fitting session helped to accurately identify the exact orientation of the crank system that Richard would prefer.

Custom Seat Dimension

The custom seat dimensions have not yet been provided by Aspen Seating of Colorado since the User has not been sized and measure for the seat yet. The company has been able to provide the dimensions of the generic seat pan that they intend to use for the Custom Seat. The Seat Pan dimension provided by Colleen Wolstenholm of Aspen Seating was that the ASO seat pan will be 19 wide x 18 long and about 4" tall.
Generic Custom Seat

Generic Custom Seat

While consulting with Joe Bieganek of Aspen Seating, he has described that the seat pan will have a t-nut fastener heated and sunk into the seat on the inside plastic, then a 1/4-20 stainless knob screwing from the outside of the aluminum tabs to the seat. His recommendation is that to wait until the team has access to the custom seat before attempting to weld the aluminum tabs to the Aluminum seat plate. There is no exact measurement for where the bolt and fastener is located since the user has not yet been measured for his seat. Aluminum tabs can be welded on to the seat plate once the team has access to the Custom Seat so to align with the location of the bolt.

Generic Custom Seat

Generic Custom Seat

Sonar Constraints

It must be noted that we are constrained by dimension of our vehicle of choice: Sonar Boat.

Sonar Dimensions thanks to Keith Burhans

Sonar Dimensions thanks to Keith Burhans

For the safety of the user and the appropriate functionality of the system, the design must be heavily driven by the constraints of the Sonar boat. Such constraints as the contours of the boat, clearances against moving parts such as the boom, and location of mounting points were measured and considered during the detailed design process.

Greater detail of the System Constraints are explained in the linked document.

Enhanced Product Benchmarking

Easy to Release Grip

More benchmarking is completed as per the customers request. The C5 grip and crank came under the spotlight as a great benchmark to design against. the C5 grip and crank allows the user to disengage quickly from the system as desired.

C5 Grip

C5 Grip

The C5 grips must mount into the C5 Cranks that are specially designed for hand cyclists.

C5 Crank

C5 Crank

Richard Ramos has demonstrated the functionality if this system through the following video:C-5 Glove & Crank

Richard Ramos has also provided a personal video to show the C5 Grips in greater detail: C5 Gloves

Commercial Seat and Harness

Benchmarking is also completed to assess the best commercial seat and harness to use for the new system. Please read document discussing the comparison between the stock Seat and Harness that will eventually be purchased for the system.

Crank System Orientation

The Crank System is oriented to fit the needs of the current user Richard Ramos. The Crank System is oriented so to have the Crank Axis 14” across from the user’s chest and 18” up from the top of the seat. The crank system crank length has to be 6” long. The distance between hand attachment points has to be shoulder width which is specified as 18”. Inevitably the cushion thickness of the bottom of the chair, and overall thickness of the back of the chair will be key design parameters, which will be needed if the crank is to be built in the right position, to get a design down on paper we will be assuming thicknesses until the real numbers are available. The tilt function of the seat must be accounted for when orienting the crank system to match the user’s preferences.

Points of Adjustability for Alternate Users

Points of adjustability for alternate users are heavily dependent on the orientation of the crank assembly and partially dependent on the placement of the seat. Factors that can be adjusted include:

Feasibility / Engineering Analysis

The analysis begins with calculations of the different States of Loading. These escalating States of Loading will account for normal operations, rough sailing operations, and critical worst case scenario operations. From these States of Loading we can design for the worst case and be perfectly fine during normal operations.

The analysis continues by deciding on a Material Choice for application in marine environment would include high corrosion resistance, relatively high strength properties, versatility in terms of mounting and welding, and common enough to replace easily.

Analysis is conducted on the Mechanical Advantage in the system to calculate whether the team has amplified the user's strength atleast 30%.

Easy to Release Grips have also been designed to provide the user a versatile and quick method of releasing their hands.

Analysis then continues into the independent subsystems:

Subsystem Subsystem analysis
Pedestal Base The Pedestal Base is assumed to remain the same as the previous design except for a slight increase in the pedestal height.
Track Platform The new Track Platform design was analyzed.
Passenger Interface The new Seat Plate design and the new Crank System design was analyzed with worst case loading.
Tiller Strut The Tiller Strut was analyzed with worst case loading and was redesigned to have a higher Factor of Safety (FOS).
Tiller The Tiller is assumed to remain the same as the previous design.

Detailed Design Review

DDR Information Packet is sent out ahead of the meeting to give the prospective attendees a sense of the structure of the meeting as well as the guts of the design that was completed during the course of detailed design.

Detailed Design Review presentation that is presented at the meeting is also available for review.

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