college of engineering white

Project 13: Bike Redesign for Steering

Abstract

The Fall 2023 team will be making three main modifications to the bike. These modifications include incorporating lower body motion when rowing, adding steering, and upgrading the rear lifting mechanism. Other ideas include allowing the bike to roll backwards and replacing the “running boards” on the side of the bike.

Mac O’Connor, Jakob Coats, J.W. Beasley, Josiah Reese, & Ishak Lamei

Problem Statement

We were introduced to students that struggle with riding pedal bikes but desperately need an exciting and rewarding form of exercise. We encountered a challenge that included modifying a bike that is stimulating, fun and that accommodates to specific needs of Putnam County School System students, while also applying design details that are considerate of the academic care takers helping students use the vehicle. The challenge was to add steering and rowing pedals to the existing bike.

Design Specifications

Generic Specifications:

  • Safety – Priority number 1. Student must ride the bike without experiencing injury
  • Reliability & durability – Bike must sustain potential contact with surroundings
  • Rewarding experience for rowing efforts¬†– Ride must be enjoyable while putting in physical work
  • Adjustability – Student riders’ height range from 4’5″ to 5’5″
  • Caretaker control – Caretaker must be able to gain control steering of bike if student veers into obstacle(s)
  • Steering function¬†– Bike can turn left and right

Technical Specifications:

  • Bike geometry – Bike must fit in school hallways, door frames and can be a portable size
  • Weight – Bike must not weigh so heavy that it is difficult to transport. Portability is key.
  • Turning radius – Ideally, student can have ability to turn around in hallway environment at school.
  • Sturdy support structure¬†– Weight of students must be securely supported
  • Reverse gear – The ability to reverse the bike would assist the caretaker in moving the bike around
  • Efficient propulsion drive – Minimal opportunity for stalling when rowing

Background Research

Our team first met with Spencer Meeks and his team from the spring of 2023 to get an idea of what they thought needed to be upgraded along with the steering. We then met with Melissa Draper at Upperman High to see her point of view as she actually uses the bike. Her biggest request aside from the steering was to incorporate foot motion along with the rowing motion. We then did research online to figure out how to effectively add steering onto the bike. The best option that we found was a company that has a bike that has a similar design to our bike. We used sites like McMaster-Carr to source the parts to assemble the steering.

Concept Design 1

Foot rests/pedals redesign, with optional foot pegs

Concept Design 2

Steering implementation and handle redesign. We also plan to adjust the angle of the front fork and wheel

Concept Design 3

Rear lift mechanism and caster wheel improvement and possible platform in the rear

Selected Concept Design

Our overall design will incorporate a hybrid between concepts one and two. We have chosen to implement steering into the bike along with foot pedals that move back and forth as the bike is rowed.

Overview of Selected Design

The selected designs will allow for a better experience for the child, and keep them engaged and active for longer periods of time. Some of the features were suggested by the children’s caretaker and some were our team’s idea. We will also conduct some minor maintenance.

The following features will be added:

  • Mechanical steering system using two shafts and U-joints
  • Foot pedals (remove rests)
  • Wider rear caster system

Describe Design Details

  • Steering Assembly

The steering design we have chosen will allow the child or driver to turn the bike around, making it unnecessary for their chaperone to get them off the bike in order to turn around. This is made possible by removing the existing rowing arm, and replacing it with a dual-action double shaft that allows for both forwards/backwards and rotational motion. The outer shaft will be mounted at the same rowing point low on the bike so we can keep the existing gearing system. The outer shaft is what drives the bike’s sprocket. The inner, rotating, shaft is for the steering. It will sit in 2 bearings pressed into the outer shaft, and have a U-joint welded to the very bottom. The U-joint will have to be lined up perfectly with the horizontal drive shaft in order to steer properly. At the top of the inner shaft we will attach a handle.

  • Pedals

The new pedal design will allow the child to move their lower body in sync with the rowing motion, similar to a row machine at the gym. It will be a welded assembly attached to the bike frame, with rotating pedals at the bottom. The upper portion will be attached to the rowing arm with a multi-directional bearing, which will allow for smooth motion in tandem with the rowing arm.

Engineering Analysis 1

For our first engineering analysis, we used the 3D file available from McMaster Carr and used that in Solidworks to analyze the motion of the U-joint.

Engineering Analysis 2

Our next step was to 3D print a model of a joint to understand the physical limitations and differences between a single universal joint and two joints. We then got two U joints and welded them together to fully analyze the motion of the steering and rowing put together.

Engineering Analysis 3

CAD Drawings

Document Fabrication Process

The fabrication process involved both making new parts and retrofitting old parts for our new design. We began by disassembling the old bike so we had room to work, removing the old foot rests, rowing arm, seat, front wheel, sprocket, and chain. We made the rowing shafts out of welded round steel stock. The bearings had to be pressed in. The underplate with its bearing (which keeps the U-joint rotation lined up) was cut out of aluminum and mounted on to the bike with scrap angle brackets. The new front fork, which is smaller than the original, was sandblasted and the new wheel was attached. The pedal assembly was welded together and pinned onto the frame rails. Everything was painted a fresh black and yellow. Finally, we re-welded the caster attachment plate on, bolted the big handle, and then the casters.

Semester

2023 Fall