BiKinematics

Application to analyse mtb suspension kinematics.

Written as a project to learn Python :)

Uses the following main packages:

• Kivy - GUI
• Numpy/Scipy - Linkage Simulation
• Matplotlib - Plotting
• bikinematicsolver - A library I made to analyse bike supsensions
• Jupyter - Development/prototyping of solver eqns/maths

Installation

1. Ideally setup a Python 3.10.11 virtual environment - later python versions should work however I haven't tested.

2. Install requirements

pip install -r requirements.txt #Python reqs

python -m pip install https://github.com/kivy-garden/matplotlib/archive/master.zip #https://stackoverflow.com/questions/77910687/kivy-2-3-0-attributeerror-figurecanvaskivyagg-object-has-no-attribute-resiz

Usage

Run app

py BiKinematics.py

Features

Current features

• Background image import
• Simulated motion of following (tested!) suspension systems - can probably handle more, solver is reasonably general (handles any system that is a single-piv or a 4-bar arrangement with slightly different placed pivots (seems like >80% of suspension despite all the different names/trademarks):
  • Horst Link
  • DW Link
  • Split Pivot (Devinci)
  • Single Pivot
• Axle Path
• Leverage ratio calculation
• Anti squat calculation
• Results Plotting

To add

• Other suspension systems (whatever tf yeti is doing, specialised demo/canyon sender with the extra links for shock)
• Idler pulley support (solver side is almost there, not much more work to be done)
• Pedal kickback calculations
• Improved results plotting (axis ranges, data normalising to zero etc..) and graph image saving
• Slicker UI
• Write specific optimised solvers for each layout (4 bar, single piv etc)

Guide/Workflow (Slightly out of date - best to load up an example and see what it contains):

Typical workflow for analysing bike image

1. Add image

2. Add points

• Click add point, then click on screen where you want to place it
• Ground points do not move relative to front triangle (usually attachment to front triangle)
• Linkage points will move relative to front triangle as suspension compresses
• Front and rear wheel should be pretty obvious...
• Note points can be dragged around after placement

3. Add links between points

• Click add link, then click the points to add between in turn
• Add links between any points on the same member (rigidly connected to each other)
• Add shock between shock mountings

4. Add wheelbase in User Parameters

• Allows scaling from px to mm, gives accurate travel distance in simulation
• Either get from datasheet or adjust until shock eye- eye length (mm) is correct

5. Save model if desired

• Will save all geometry and wheelbase values in /SaveFiles/ in json format
• Note - there are some examples of bikes I have been testing with already in SaveFiles

6. Simulate for desired travel

• The results will be saved in /Results/Filename.csv

7. In plotting screen, select data and desired characteristics to be plotted

• Note all simulated results saved can be loaded in, so multiple different bikes can be compared