The magic gear calculator lets you find possible chainring and cog combinations for a single speed bike with vertical dropouts without the need for a chain tensioner.
- Enter chainstay length (in mm)
- Pick an allowable slack percentage (% of one link)
- Pick chainring and cog size ranges
- The list bellow shows all possible options sorted by ratio
I designed a 16 tooth fixed gear cog to attach to a 6 bolt disc brake hub. I used Autodesk Fusion 360 for CAD and CAM, and machined on my Dyna 2400 CNC mill. Machined from 6061 aluminum in four operations.
To install a new fork with a 1.125″ steer tube in a Giant TCX OverDrive frame (headset is designed for a 1.25″ steertube) I made a custom crown race. The crown race needed an ID of 30mm and an OD of 43mm with a 45° chamfer for the bearing to rest on. First I designed the crown race, top of the fork and the bearing in Autodesk Fusion 360. I created an assembly to ensure the crown race would fit both the bearing and the fork. I then 3D printed it in ABS for a test fit. Finally I turned the crown race out of 6061 aluminum on my CNC converted 9×20 lathe.
I have created a Windows program to let you customize the gear profiles on a Magellan Cyclo.
It is simple to use:
- Click backup and choose where you would like to save the backup
- Click Connect
- Select the profile you would like to edit from the drop down list
- Click Read, this will populate the fields below with what is currently set on the device for that profile
- Adjust the gears as you would like
- Click write to save the settings to the device
- If you like it, Donate!
*Note, “Front 1” is the big chainring and “Rear 1” is the smallest cog on the cassette. Also, it lists “Rear 12” even though that does not exist, it is there for future firmware compatibility
**In the Di2 Settings on your Magellan, it will still list the original settings, although the device will show you your customized profile in the dashboard as well as in the GPX it saves.
I highly recommend using the tool to create a backup of the settings before editing them. If you have any issues with it or any suggestions, please let me know.
On my commuter bike I am currently running a 700c wheel on a 26″ fork, since the wheel is bigger than the fork is designed for, I cannot use a standard v-brake. I have designed a v-brake with a slot so the brake will fit almost any wheel and fork combination.
I designed the brake using SolidWorks, which let me do stress analysis to ensure it is strong enough. I have accounted for a max force from the cable (average grip strength of a male) to be 450 N. I calculated the force necessary to stop a 200 lbs rider from 50kph to a complete stop in 10 seconds to be 260 N. Given those forces I have calculated a minimum factor of safety of 2.0 using 7075 aluminum.
After FEA was done, I 3D printed the brake arms to test fit everything. I wound my own springs using music wire and installed all the hardware. The brake works as expected for plastic, the next step is to machine it out of 7075 aluminum.
Most recently, since it is cyclocross season, I decided to make a set of shoe spikes, I used some 6061 aluminum I had and machined four matching spikes. They have 7mm long M5x0.8 threads on one end and a chamfered point at the other. I used my lathe as a 2-axis mill to cut 10mm wrench flats onto them.
Below is the front hub I made from a round bar of 6061 aluminum. pressed cartridge bearings into the shell and made threaded end caps to fit on a M10x1 axle. I drilled 32 holes with a drill press using a drawing from my 3D model of the spoke holes.