Hello All,
Here is a BB Flat Kit Box that is easy to make and fits like a glove in the space above the BB.
The space is small if you maintain the width of the downtube and seat tube and provides only a few cubic inches of storage but adequate for a flat kit and puts it a low center of gravity on the bike. About the size of a paper back book.
You need some 1/16 inch thick polycarbonate sheet (Lexan) … usually easy to find at a plastics supply or on the net. It doesn’t shatter (same material as most sunglasses) and is easy to work.
You need some ‘spacers’ or standoffs available in nylon from Home Depot … I used 1 inch long by 3/16" outside diameter and drilled out the hole a bit to fit the aluminum post screws. Cut or sand spacers as necessary to custom fit the sides of the box to match the down tube … seat tube … and top of the BB.
4 aluminum post screws … 2 each 1 inch long and 1 each1/2 inch and 1 each 3/4 inch long … you will have to hunt … but hanging with other screws at Home Depot.
Make a cardboard pattern of the sides of the box to overlap the seat tube to its thickest point and over lap or fit to the down tube.
Locate 4 holes on the pattern that fit close to the bottom of box over the BB and close to the seat tube and down tube.
Cut the Lexan to match the cardboard pattern … you can do this with good quality heavy duty scissors or sheet metal shears. Sand the edges to smooth. Drill the 4 holes … the aluminum post screw take a bigger hole on the main post side (drill for a force fit) and the smaller threaded screws need a smaller hole on the other side.
I generally put all fasteners so they can be adjusted or removed from the bicycle drive side … since if I have to lay my bike on its side I want the derailleur facing up. On this box it doesn’t matter since the screws are covered with wrap and cannot move … and I put a some Locktite on them for good measure.
Insert the screws and spacers and tighten … the box will now be solid … no top … no bottom … no sides … looks like two clear circuit boards fastened together.
Slip it into position … tape the edges with Gorilla Repair tape … use a plastic baggie that fits nicely inside the box when in place … carefully drop in your flat fix parts … wrench if you do not have quick release … Co2 cart and fill valve … patches … glue … vinyl tape … etc. (I put spare inner tube … spare Co2 … etc. in the top tube storage area)
After you have a system for neatly loading … cover sides with vinyl wrap … cover top with black vinyl tape with one corner folded under for quick peel when you need it.
To use the flat kit … peel the top tape … pull out the baggie with all your gear …and fix the flat. Put your gear back in the baggie and put the baggie in your jersey pocket.
I am hoping it will improve the aerodynamics of my bicycle. However the Cervelo white paper seems to indicate that a box in this position may cause some additional drag … this box is very streamlined … however it may cause some pressure resistance as your feet come above the BB since that area is now closed …
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Note round Lexan tube for smooth line on top and for storing small objects in tube.
This box should work for any of Cervélo P series … and other bikes with space for a box.