Bicycle frame project – some help in planning/overview

Bicycle frame project – some help in planning/overview

I'm starting a pet project that will test and stretch my skills as an engineer: an electric bicycle/moped.

The purpose is two-fold: first to delve into mechanical engineering (which I had little to no contact so far, my field being CS/automation with a bit of electronics background) and second to understand what development of a proper product is like (hardware AND software).

I'll design the frame myself (steel alloy tubing) and either have it manufactured from sketch to final product, or at least have the cuts made professionally and I'll weld the pieces.

In order to make things a bit easier, I will not be imposing any cost constraints (within reasonable limits, say 3-5k euro) nor any strict weight constraints (I'm targeting a maximum of 40kg for the machine, which should be sufficiently lax).

What I lack is an overview over the stages of design process, so I'll just write down my thoughts and anyone is welcome to correct or contribute more. Please note that many of the below topics are not familiar to me and each will include some research on my part. Anyone is welcome to provide reading material.

I'll be using Solidworks for the design (in which I'm still self training at the moment with good progress).

  1. The first step I thought would be to do a small study in ergonomics, since with pedal assist and e-throttle I can design the frame lower and the position more upright, without worrying too much about optimal power delivery to the crankset.

  2. Second would be to identify and maybe source the important bits: motor and battery cells. Motor will define the rear hub width (and thus swingarm size and sprocket geometry).

  3. Then I would tackle the issue of suspension – first geometry (rake and travel), then dynamics (optimal preload and damping), then identifying readily avaliable parts (rear shock, front stanchions/lowers, I'm split on desigining a crown or just using one off the shelf), then modeling the parts.

  4. Multiple cycles of design and analysis on the frame – design should be straightforward, for analysis I'm not so sure what kind of scenarios I should be simulating – I'm thinking static tests for the following: suspension (big bumps or even jumps), braking and front impact tests.

  5. After reaching a successful model, have it manufactured. Assemble some of the bits and pieces, simulate battery with some weights and test the behavior of the bike in real life scenarios.

  6. Manufacture battery case for current model, mount battery, motor and electronics. Final tests and adjustments.

What do you guys think?

Submitted July 31, 2017 at 05:31AM by Rimio
via reddit

Bicycle frame project – some help in planning/overview

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