The headset cap is the small piece at the top of the fork. It keeps dust and dirt from entering the headset assembly. It is a relatively simple part and be easily customized. There are many websites and stores were they could be bought but, if you have the ability to print you're own or CNC it then why not. You can put almost any design onto it, or you can even incorporate a Go-Pro mount (However I'm sure thats patented so I'm not going to post how to copy it). I am new to 3D design so feel free to improve on my part and please comment a pic if you do. I currently don't have access to a 3D printer (However if I'm lucky that could change) so I haven't printed this part (yet).
Step 1: Getting Started
To Design this you'll need:
A 3D design program. I used Autodesk 3Ds Max (because I'm a student :), There are free alternatives such as Google sketchup for those who aren't students. I don't know how to use that software but megaduty has posted many sketchup instructables and was nice enough to help me start using the program.
Thats all you need to design it.
Helpful items, A bike, A Ruler.
Step 2: Measurements
Forks come in many shapes and sizes so it's best to get the measurements of you're bike. Or the bike that you plan to be putting it onto. After measuring our three X/C/All Mountain bikes my measurements were: 3cm, 3.5cm, 3.3cm. So that should provide a baseline if you don't have access to a bike. To be even more precise you can completely remove the cap from the headset using an allen key. If you do this be careful getting crude inside you're headset can damage the bike.
Step 3: Creating the Beveled Cylinder
Most headset caps are beveled/chamfered. so I decided mine should be too. However the shape is completely up to you, as long as it is circular and keeps the dust out. Start by making a cylinder that is 3 cm wide and 0.5 cm thick I gave mine 42 increments so that it was more circular and less octagonal.. Next right click it and convert it to an editable polly. Then select the top edge (while in edge mode) and apply a chamfer. I applied a second for a smoother look.
Step 4: Cut Out Screw Hole
Headset caps have a screw to hold them in place. To make the cutout make another cylinder that is longer than the cap and 1 cm wide. Next place it so that it sticks out both sides of the headcap. Then center it. Next select the "screw" and go to compound objects --> Boolean in the drop down menu. Select "subtract B-A" then "select operand B" and click the Cap. Then ( I did this out of order) select the Cap and convert it back into a editable mesh and take the bottom of the screw hole (selected faces all the way around) and Scale them Smaller. This will give the screw something to rest on.
Step 5: Make the Letters
Select the splines section of the objects panel and from that select text. Type the text into the white box at the bottom. Then set it's font and size. One click on the screen and boom the 2d text has been created. Select the text and convert it to an editable poly and select an extrude modifier from the modifiers list. Set the height of the text to 0.5 cm or so. Next decide if you want to have engraved text or raised text. I selected raised because this is going on a bike and it will be easier to keep clean if it is raised. Move the text so that it sticks up a bit from the Cap and position the letters around the circle. Use element mode for this, and watch out ! marks and ? marks are two different pieces. Then group everything together. Unless you want engraved print, in that case follow the same steps as cutting out the screw hole (boolean).
Step 6: Export
Export the file as an .stl (or whatever you're 3d printer uses). Click the Max icon and the export and change the file type to stereolitho .stl and save it. Now all you need is a 3D printer or credit card, shapeways can be used as an online service to print you're new custom Headset Cap and ship it to you. Thanks for reading (if you enjoyed please vote for this Ible in the 3D desighn contest, cuz a shopbot would be amazing).