Prototype Mk 3 Tailbox

Tailbox

     I want to get into some randonneuring, so I need to add some storage for some of the mandatory items that I would need to carry as well as extra clothing.  Some extra storage would also come in handy for trips to the store and hopefully be al ittle more encouragement for my wife to use the trikes for that reason.  I decided to design a simple frame for the Mk 3 to accomplish this.  I plan on 1/4" 6061 aluminum round stock and some Coroplast for the sides, bottom, etc. I also wanted to add extra tabs for top and bottom mounting of a trailer of some type, as well as top tabs to fasten a rear fender.  As it stands so far, the design I came up with uses less than 50 ft of AL rod, and that would cost under $15 Cdn.  A 4' x 8' sheet of Coroplast runs about $20 Cdn and I have some 1/2" foam laying around.  The 1/2" foam is going to be contact cemented to the inside of the Coroplast to hopefully reduce the drumming effect (if any) and also to server as padding to stop things from rattling around.  I'll TIG it together and leave it unpainted as corrosion is not an issue.  Still pretty flexible on fastening schemes, but as there is no real reason for me to remove the tailbox, as yet, I'll likely use bolts.  If security looks like it might become an issue, I'll just make a more robust fairing that can be locked and/or quick-released.  Not a priority ATM though.

     As it will be my first try, I will likely have mods in mind by the time I'm done, such as more volume, inner compartments, etc.  I also want to make one for the Mk 4 and will apply any lessons learned to that one.  I'm not sure if the 1/4" AL rod will be strong enough but I'm not planning to carry massive weight in it either.  I'll have to wait and see I guess.

     Bare frame view with the tailbox nose on the right side of the picture.  An AL plate is at the top rear for a trailer hitch and lights, with two more trailer hitch tabs at the bottom rear.  2 more tabs in the middle at the top for fastening things to the top and/or fender mounts.  At the bottom middle and front are the tabs that mount the box to the trike's frame.

     Tailbox with Coroplast panels installed.  Not sure if I'm going to use blue or not.  Might use white or black too.  I'll model it in 3D Max and see which one I like the best :)  The panels will be held to the frame using small clear zip ties, which are the same ones I used to hold the wheel disks to the spokes.  The white diagonal lines at the front corners are because the outside panels are a little too small and the frame can be seen.  A few glitches to be ironed out in using the 3D app :)

     Here the top is opened.  I hinged it at the front, but it can easily be changed to hinge from the inside edge at the top as well.  Haven't decided on what I'll use to keep it closed yet.  If the contact cement holds well enough, maybe I'll just use velcro, although I have a couple other simple ideas that might work as well.

Mockup of frame on the trike.

     The flag's pole looks like it's clipped, but in reality, the flag pole would flex about 1/8" to the side and ride alongside the lip.  The top is open to for future improvements.

     Sort of boxy perhaps, but then my whole trike is boxy. :)  For the Mk 4's tailbox I might consider tapering the rear of it mainly for aesthetics, and secondly for aero.  In doing some reading though, a sharp edge allows the boundary layer of air to flow cleanly off the edge, and the air tends to create it's own cone shape as it comes together in the object's wake.  Like I'd be going fast enough to worry about that anyway . . . :)

     I was thinking I might also add a small tab to the bottom left corner to mount one or more tail lights, which are requirements for randonneuring, not to mention being an obvious safety and visibility feature.  I might also consider adding a secondary flag mount to move the flag from the frame to the tailbox.

     As I have about the longest X-seam that would be riding my trikes (~47 1/2") I'll slightly adjust the angle and length of the front of the box to get as close as possible to the seat while I'm riding it.

     I need the box built no later than the end of Feb, so final pictures when it's built.

Sept 24 2005

     In the couple years since building the MK 3, I've ended up riding this Python clone.  To be able to commute on it, I took the tailbox idea and built one for this to act as storage, fender and to possibly give a little aero advantage.  Access to the tailbox is by lifting the seat and it has storage under the seat as well as behind it on either side of the rear wheel.  Fabrication details are here.

14 July 2006

     For storage commuting, to act as a fender and lastly for a little aero improvement, I made a tailbox for the Speed as well.  I'm pretty happy with the amount of stoarage space, it's just that the items can't be over a certain size to fit easily in it