Alpha7 Velomobile Light Pod

I wanted some extra visibility on my velomobile - particularly when riding at sunrise / sunset, so I designed this to go on the top. With a pair of Exposure's Trace lights set to full brightness and strobing, it's pretty visible now!

This design relies on transparent filament to print the diffuser at the rear of the cap, so was only printed in PLA - not UV resistant, and not particularly heat resistant either. I've a new design that can be printed in ASA to overcome these issues.

Printing:

Print the base with the curved side up, and enable supports - there are some features such as the mounting locations for the lights' clips that need to be reasonably accurate

Print the cap vertically with the pointed end at the top, and if you're not printing exclusively in clear material, you'll want to insert a filament change at the point where the diffuser starts - you can see this in the model where there's a small change in the flange to mate to the base part. You'll want supports enabled so as to print the retaining tabs.

Print the two parts of the front diffuser with the rear face laying down on the print bed. Again, use clear PLA for this.

The clips should be printed laying down with a flat face on the print bed. Print these with 4 perimeter walls for strength.

Other things you'll need:

• M3 heat press-in inserts x 4
• M3 x 12 mm dome head bolts and washers x 2
• M3 x 16mm dome head bolts x 2
• M5 x 25mm cap head bolt, M5 nylock nut, M5 washer, M5 penny washer - all x1
• Superglue
• Epoxy
• Some 2mm thick EVA foam (I got an A4 sheet from Hobbycraft for £0.50)
• Optional but recommended: 20x5x2mm neodymium magnets - these can be glued into the slots in the cap's locking tabs and the equivalent ones in the base to give some extra security. Before I figured this out I did actually lose a cap due to wind! When you glue these in, just take care to get the polarity right.

Assembly:

The clips and lower part of the front diffuser are designed to take M3 brass inserts, so you'll heat press these in. When you assemble the clips to the base, use M3x12 dome cap bolts with a washer, and also add a dab of threadlock. The diffuser uses M3x16 dome cap bolts, but these are really only to located it - I used superglue to fix it to the base.

With the lower diffuser fitted, mount the front light and fit the cap (insert the rear tab, and then press down at the front to connect the locking tabs). With this in place, tack the top part of the front diffuser in place with some superglue, taking care not to glue it to the light or the lower part of the diffuser. Once this is cured, remove the cap and apply a bead of epoxy to the inside lip connecting the diffuser to the cap to make it permanent.

To fit to your velomobile, position the base carefully on the top, making sure it's central. Mark the centre of the base's mounting slot and then drill a 5mm hole in the velomobile's shell. Use a good quality, sharp drill bit with minimal pressure - let the bit cut through the carbon fibre rather than you push it through. 

Position the base again onto the velomobile, but this time with the EVA foam sandwiched between your 3D printed part and the velo'. Draw round the base and mark the location of the mounting slot. Cut out the EVA foam - I've found that a curved No. 10 scalpel blade on a cutting board works better than either scissors or a Stanley knife.

Bolt the base to the top of your velomobile, with the foam cut out in place so you won't scratch the paintwork. The M5 bolt with the standard washer go through from the top, and use the penny washer and nut on the inside. Test fit the cap - if it doesn't latch in place easily, you may want to slacken the base's mounting bolt off by ¼ turn or so. This is the other purpose of the EVA foam, as it allows slight variations of where you mount the pod to be absorbed.