The New Bike
This is the next platform of the Cornell Autonomous Bicycle Team. It is intended to be a more stable, reliable, and versatile platform than The Old Bike. The bike is still largely in the design phase, so wiki sections are limited to the current state of the bike.
- LAST UPDATE FALL 2021
Contents
Design Overview
The main objectives for the new bicycle was to prevent the need for welding and other permanent structures compared with the Old Bike. To do this, we've adopted a modular design approach with all the added components of the bicycle to allow for re-design opportunities of different parts and fixtures present on the bike. This approach will extend the usefulness of the platform for years to come.
The final design for the bike can essentially be split up into two major regions: the Brain and Body. This split is defined by the connection between different components. The “Brain” sits around the diamond of the bike frame while the “Body” is situated around and extending outward from the head tube. This distinction, though somewhat ironic considering the relative locations of the regions, is useful because it lends itself to let us think and design more locally.
The “Brain” is defined by its contents: the electronics. It is composed of 4 clamp-like components, 2 sheets of acrylic, and 2 panels for the electronics to sit. The clamp-like components connect to the edges of the bike diamond in order to give the acrylic sheets points to connect to in order to enclose the frame. The electronics, once situated onto their corresponding panels, will be attached with velcro to the acrylic sheets.
Similar to the brain, the “Body” is defined by its function, in this case the handling of actuation and vision on the bike. The body is composed of 2 main intertwining assemblies. One centered around the motor and the other around the camera. The motor will be attached to the stem of the bicycle with the use of a custom shaft collar.
- Add Render**
Mechanical Components
Frame Joints
Top Frame Bracket
As stated in the intro, the frame joint acts to suspend the clear panes that will encase the electronics in the center of the bike. The top frame joint specifically is made for the rounded surface at the top of the bike. It is made up of 4 major components: a machined piece of aluminum or other light metal, a piece of rubber that sits between the bike and the machined component, two hex head screws, and two nuts to match.
Near the bottom edge of the aluminum there are four threaded holes (two on either side) that indicate where the aluminum will attach to the clear panes. The rubber sits directly on top of the curved edge of the aluminum. It is meant to provide grip strength so that the component does not slip out of place. There are two 9/16" holes on top that propagate through the entire design and the bike frame itself that make space for the bolts and nuts to compress all the components to the bike frame.
- Someone add about machining issues?*
Bottom Frame Bracket
The bottom frame joint has an identical function as the top frame joint. However, the bottom frame joint's geometry differs from it because the cross section of the bottom tube is elliptical. This presented a unique design challenge that we had to work around. We ended up on settling on an idea that combines 4 different parts together: 2 flat plates, a hemispherical piece, and rubber.
In order to match the elliptical shape of the bottom tube these parts are screwed together as seen in the image. There exist larger holes on the surface of the hemispherical piece to make room for screw heads, and there exist threaded holes that cut through half of the flat pieces. Near the top edge of the flat plates there are threaded screw holes for attachment to the clear planes. The rubber again acts as a way to grip the components to the frame and prevent slip. Just like the top frame joint, there are two 9/16" holes made in both the frame, rubber, and hemispherical piece to make room for the bolts and nuts to compress the system to the bike frame. 2 Bottom frame joints will be used to hold the clear plane.
- Someone add about machining issues?*
Front Motor Assembly
Camera Assembly
The final design of the camera seat consists of 6 parts: 4 connecting bars and 2 small machined blocks of aluminum. The first rectangle of aluminum is used as an anchor for the camera itself. It has a ¼” hole near its center to make room for a bolt to attach the piece to the camera’s threaded bottom. The second rectangle of aluminum serves to connect the clamping components (connecting bars) to the system. Similar length bars are paired together and clamped, by way of nut and bolt, to the top of the upright piece. In addition, the upright piece also has a squared hole in order to make room for the USB of the camera. This piece is then connected to the first piece of aluminum by 4 screws. The final design is shown in Figure 8.
The camera seat acts as a point of securement for the camera on the new bike and as such needs to fulfill the goals of interfacing with the variable angle and variable height components within the body assembly. This requires the camera seat to fit onto the assembly bar, this is shown below in Figure 9, in full context in Figure 5. The design allows the camera seat to fulfill these goals by clamping directly to the connections at the end of the connecting bars to which the assembly bar would be placed in between. These bars are specifically designed to uphold the design requirements of the camera: needing to have 20% of its field of view above the horizon in the default position and enabling variable height. First, we must understand how variable angles are achieved.
The assembly bar is secured by one of the motor attachments as mentioned earlier. A clamp is attached to the top of the head tube. This clamp has on it an extruded piece of aluminum with its own slot. Sliding the assembly bar’s slot up or down relative to the extrusion allows for different angles to be achieved. This angle is able to be changed up and down 10 degrees from its origin.
The head tube clamp was made from 2 machined pieces of aluminum. Both have a large curvature on one of their faces in order to interface with the bike. Similar to the frame brackets, the inner curved surface of the grips have a piece of rubber to ensure that the clamps do not slip. The two pieces are compressed together through the use of four 20mm screws.
With a field of view of 56 degrees, 20% field of view equates to the camera sitting at an angle of 26.8 degrees below the horizontal. In the full assembly this results in a range of 16.8 to 36.8 degrees for the positioning of the camera. The second requirement is satisfied through the use of adding multiple points that the connecting bars can connect to on the assembly bar. This allows the camera to be moved up and down along these holes and thus change the height of it. The assembly bar itself is positioned at a 15 degree angle from vertical in its default state and thus the computation for the length of the connecting bars reflects this.
Fixtures To The Plexiglass
Everything Camera
Bike Details
The frame is a ***cm KTM Trento with serial number ******.
The wheels are 27 inches in diameter. The planned tires will be 27 inch road bike tires. General dimensions for the bike can found in the image to the right.
