Athlon (Hand Powered Tricycle)

Group Members

Andrew Coats
Kevin Cunningham
Stephen Hamilton
Andrew Lykins
Joseph Sumners

Mission Statement

Our team mission is to build a hand-powered tricycle for ages 10 - 16+. This main goal of this device is to inspire physical activity and recreation for a growing child who has no use of their lower extremities.

Introduction

For the fall of 2010, our team has chosen to design a whole new tri-wheeled device. This device is meant to inspire physical activity and recreation for children ages ten and up who have either lost, or never had the use of their lower extremities.

The name we have chosen for our device is the Athlon, which is Greek for the verb meaning “to compete.” Because we do not have a specific child in mind for our design, we have decided that one of the initial requirements for the Athlon is that certain sections should be adjustable in length. We believe that this will not only allow the Athlon to be used by a variety of middle-school aged children, but that it will also be capable of simple extension to provide use for the child as they reach adulthood.

Our second requirement is that the Athlon should be powered by both pushing and pulling forces generated by the arms. Additional specifications involve safety, lightness of weight, easy transitions for mounting and dismounting, steering, breaking, and gear shifting. We hope to implement a continuously variable transmission for the Athlon; however, the addition of CVT’s would dramatically increase the production cost.

Design Specifications

General Design Requirements
1. Hand Powered only (acceleration, brakes, steering, gear shift)
2. Fully Size-Adjustable (for a growing child, including growing arm lengths)
3. Adjustable Strength (a geared bike should allow a stronger rider to change gears for a faster ride(and more exercise))
4. Ease of use (can the person easily move from their wheelchair to the trike?)
5. Safety of the child
6. Desirability (Is it fun, does the child think it looks cool? Will he/she ride it?)
7. Cost (Will the design meet our budget requirements)

Design Concepts

Our team is currently considering 3 designs. The first concept uses rotational motion to power the trike. It has two wheels in the front and one wheel in the back. With this design, each of the front wheels is independent of one another. Each has it own braking and acceleration. This design offers a high level of maneuverability.

Our 2nd design is a row-action powered trike. It is the only design with one wheel in the front and two wheels in back. The power drive is 2-wheeled, meaning the back two wheels will be locked together, and the steering is left to the front single wheel.

Our 3rd deign is the most complex. It encompasses a mix between the last two designs. This design would be row-action like the first, but have its two wheels in the front. Like the 2nd design, each of the front wheels will be independent of one another, giving the driver steering ability in pumping and braking. This last design is expected to be the most unique, but most expensive to manufacture.

Concept Design Part Color Specification

Part Color
Framing Green
Tires Yellow
Mechanical Drive Red
Revolutes Blue
Suspension Orange
Steering Bearing Purple
Kinematic Motion White

Design Concepts (1-3)

A reverse trike utilizing the rear swingarms, wheels, and drivetrain from existing mountain bikes. The driver will be able to independently turn or brake either side, allowing for “Zero-degree” turns. Also this design allows the driver to push the handles in a complete circle to power the trike, or to use a ratcheting technique of pushing through part of a circle and pulling back to the original position to push again.

flickr:5069399965

Seating, breaking, handles, and gear-shifting has not yet been incorporated into design.

Pro's:

  • Reverse trike design is stable and allows a tight turning radius.
  • Many parts come from bicycles already in production.
  • Capability of having multiple gear ratios.
  • Suspensions from mountain bikes allows navigation through rough terrain.
  • Room for storage behind seat.
flickr:5070026152

Con's:

  • Rear caster wheel could be unstable at high speeds.
  • Requires two separate drive trains to be serviced and adjusted.
  • Gear ratio would need to be changed simultaneously on both sides to keep trike stable.
  • Longer design may be difficult to maneuver.

Concept Evaluation

Meeting with a team of three engineers, the project received some clarification. The biggest change would be the order of importance we ranked our different objectives. We were advised not to focus on adjust-ability. Issues like functionality, efficiency, and safety will be our core focus.

The engineer group commented on several specific ideas. One concern was a child's ability to learn to drive on a bike that requires two seperate inputs. Would a child that has never rode a bike before struggle steering? Here our second design stands out in the simplicity of controls. Another concern is an overcomplicated design. We were advised that time and cost constraints should narrow the scope of our project to the points that matter. Again, the second design was chosen as the best choice.

With a unanimous decision among the engineering group, Design 2 will now be the focus of our project.

Rated 1-5; worst to best
Consideration Design 1 Design 2 Design 3
Ease of Use: 3 5 4
Cost: 2 4 1
Learning Curve: 2 5 3
Motion/Manuv. 4 3 4
Ease of Construction: 3 5 1
Total 14 22 13

Design Overview

Engineering Analysis (1-4)

Our Analysis focus on the kinematic movements of our Bike. First we've chosen to look at a Gear Ratio Analysis, which looks mostly at gear teeth relations. Second, we've examined the Ratio of Rotations per Full Stroke and the Distance per Full Stroke, which take into account the CVT we will be using to gear the bike. Next the steering Ratio was examined. Here we look at input vs. turn angle to make sure the bike will turn properly. Lastly, we look at the drive system, measurements, and expected lengths of the drive system.

Gear Ratio Analysis

Part teeth circ (in)
CW 28
CVP hub 20
CVP CW 44
Rear hub 20
Tire 62.83185307

(CW=Chain wheel)

Ratio of Rotations per Full Stroke

Gear Ratio Chain wheel CVP hub CVP CW Rear Hub
0.5 1 1.4 0.7 1.54
0.6 1 1.4 0.84 1.848
0.7 1 1.4 0.98 2.156
0.8 1 1.4 1.12 2.464
0.9 1 1.4 1.26 2.772
1 1 1.4 1.4 3.08
1.1 1 1.4 1.54 3.388
1.2 1 1.4 1.68 3.696
1.3 1 1.4 1.82 4.004
1.4 1 1.4 1.96 4.312
1.5 1 1.4 2.1 4.62
1.6 1 1.4 2.24 4.928
1.7 1 1.4 2.38 5.236
1.8 1 1.4 2.52 5.544

Distance per Full Stroke

Gear Ratio Inches Feet
0.5 96.76128 8.06344
0.6 116.113536 9.676128
0.7 135.465792 11.288816
0.8 154.818048 12.901504
0.9 174.170304 14.514192
1 193.52256 16.12688
1.1 212.874816 17.739568
1.2 232.227072 19.352256
1.3 251.579328 20.964944
1.4 270.931584 22.577632
1.5 290.28384 24.19032
1.6 309.636096 25.803008
1.7 328.988352 27.415696
1.8 348.340608 29.028384

Bill of Materials

Part Part # Quantity ID OD Length Width Cost/Part Cost
Tricycle - Traditional 20" N/A 1 449.99 449.99
Seat 2680T58 1 132.13 132.13
Bearings 6384K61 3 .5" 1.125" .375" 6.90 20.70
Tubing (steel) 7767T43 1 1.26" 1.5" 6' 29.98 29.98
Tubing (steel) 9220K92 1 .402" .5 36" 7.15 7.15
Tubing (steel) 89955K86 1 .75" .875" 6' 27.85 27.85
Square Tubing (steel) 6527K31 1 .75" 1" 6' 1" 24.14 24.14
Rod (steel) 8924K35 1 .5" 6' 9.53 9.53
Rod (steel) 8924K33 1 .375" 6' 6.03 6.03
Rod Ends 1064K741 2 .375" 1" .5" 6.13 12.26
Elbow 4891T14 1 1.278" 1.66" 2.701" 16.40 16.40
Shaft Collar 9414T11 4 .5" 1" .4375" 0.79 2.37
Shaft Collar 9414T8 3 .375" .75" .375" 0.65 1.95
Connecting Rod 6516K22 1 .375" 12" 8.72 8.72
Pulley 3091T521 2 .5" 2" Guide: 1.625" .625" 12.45 24.90
Steel Flat Stock 8910K554 1 .25" 36" 1.5" 18.36 18.36
Steel Flat Stock 8910K941 1 .5" 12" 1.5" 12.48 12.48
Aluminum Sheet 8975K923 1 .125" 36" 5" 23.63 23.63
Aluminum Flat 8975K429 1 .5" 12" 4" 16.81 16.81
Aluminum Flat 8975K86 1 .25" 12" 4" 10.39 10.39
SS Cntersunk Screws 91771A539 1 .25" - 20 .625" 5.84 5.84
SS Cntersunk Screws 91771A537 1 .25" - 20 .5" 7.55 7.55
Total not including taxes or S&H 869.16

Part Drawings

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Assembly

Images

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Videos

The video below demonstrates the trike's Grashof Mechanism, which has 2 toggle points when the two bars are in parallel. To get around this we will attempt to use a magnetic assist to push/pull the bars through.

Implemented Design

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Summary and Conclusions