Crank Arm Assembly With Threaded Removal for Friction-Fit Disassembly
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Solution Overview
Problem
Conventional exercise machines face difficulties in efficiently disassembling crank arms from crankshafts due to strong frictional engagement, even after the fastener is removed.
Innovation Solution
A crankshaft assembly design featuring a threaded crank arm bore and a removal tool with a larger diameter than the fastener, allowing the removal tool to disengage the crank arm mounting surface from the crankshaft mounting surface by pushing it off, facilitated by a tapered engagement mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a fastener is used to secure the crank arm to the crankshaft, then the crank arm is firmly attached, but the crank arm becomes difficult to remove after the fastener is removed due to strong frictional engagement
Solution Approach 1:
A removal tool with a tapered outer surface acts as an intermediary between the crank arm and the user's applying force. The tapered surface engages the crank arm's corresponding tapered cavity and converts rotational motion into axial extraction force, overcoming the frictional engagement between the crank arm mounting surface and crankshaft mounting surface.
Solution Approach 2:
The removal tool utilizes dynamic rotational motion to generate the force needed to overcome static friction. By rotating the removal tool within the threaded crank arm bore, the user dynamically applies increasing axial force that eventually overcomes the frictional engagement, allowing the crank arm to be extracted from the crankshaft.
2Stability of the object's composition
If the crank arm mounting surface is frictionally engaged with the crankshaft mounting surface, then the crank arm remains stable during operation, but significant manual effort is required to disassemble the crank arm
Solution Approach 1:
The removal tool serves as a mechanical intermediary that amplifies the user's input force. The tapered outer surface of the removal tool engages with the tapered cavity in the crank arm, creating a mechanical advantage that reduces the manual effort required to overcome the frictional engagement between the mounting surfaces.
Solution Approach 2:
The removal tool changes the application parameters of the disassembly process by converting rotational torque into axial extraction force. This parameter transformation allows a user-friendly rotational motion to generate the high linear force needed to overcome the frictional engagement that ensures operational stability.
3Reliability
If continuous frictional engagement is used to secure the crank arm, then the connection is reliable, but wear on the mounting surfaces increases over time
Solution Approach 1:
The removal tool enables clean extraction of the crank arm from the crankshaft by overcoming the frictional engagement without requiring excessive force that would damage the mounting surfaces. This controlled extraction process minimizes wear and potential damage to the crank arm mounting surface and crankshaft mounting surface during disassembly and reassembly operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates easy and efficient disassembly of crank arms from crankshafts by overcoming frictional engagement, reducing manual effort and wear on components.
Implementation Method 1
a crank arm having a threaded crank arm bore and a crank arm mounting surface that is frictionally engaged with the crankshaft mounting surface
Implementation Method 2
a fastener that axially extends through the threaded crank arm bore and into engagement with the crankshaft bore to fasten the crank arm to the crankshaft
Implementation Method 3
rotation of the removal tool in the threaded crank arm bore causes the removal tool to disengage the crank arm mounting surface from the crankshaft mounting surface
Implementation Method 4
rotation of the removal tool in the threaded crank arm bore causes the removal tool to force the crank arm apart from the landing surface which forces the crank arm mounting surface off of the crankshaft mounting surface
Data Source
AI summary
An exercise machine has a crankshaft having a crankshaft mounting surface, a landing surface, and a crankshaft bore, a crank arm having a threaded crank arm bore and a crank arm mounting surface that is frictionally engaged with the crankshaft mounting surface, and a fastener that axially extends through the threaded crank arm bore and into engagement with the crankshaft bore to fasten the crank arm to the crankshaft. The threaded crank arm bore is configured for threaded engagement by a removal tool such that removal of the fastener and insertion and rotation of the removal tool in the threaded crank arm bore causes the removal tool to disengage the crank arm mounting surface from the crankshaft mounting surface and thus facilitates removal of the crank arm from the crankshaft. Methods of disassembling an exercise machine having a crank arm are also provided.