End Cap for Bicycle Handlebars & Bar End Extenders - Expansion Fit

I use bar end extenders on my bicycle's straight handlebars. I wrap the extenders with padded tape (for cushioning). Recently on a ride, the compression fit end plugs that were provided with the extenders came loose and the tape started to unravel. I concluded that I needed expansion end caps that would grip the tape really well, while staying tight in place. However, my extenders have a smaller inside diameter than most handlebars. This design is what I came up with. It works well. 

There are various inside diameters of handle bars and extenders, so I decided to make 5 different sizes of inserts, ranging from 17.6 mm to 21.6 mm, increasing in diameter by 1 mm. This measurement is taken from edge to opposite edge on the rounded area of the fins on the Insert expansion tabs. 

• FYI: the varying diameters were achieved by widening the fins, while keeping the main body dimensions the same. This makes it so that all of one type of Insert (Regular or Heavy Duty) will work with the corresponding Regular or Heavy Duty End Cap.

As referred to above, I made a Regular version (my first attempt), and a Heavy Duty version (stronger fit), which has more expansion, more area of contact, and more material in the body of the Inserts. Regular and Heavy Duty parts ARE NOT INTERCHANGEABLE. The Regular End Cap goes with the regular Inserts; and the Heavy Duty End Cap goes with the Heavy Duty Inserts.

This design requires one round, pan head 5x25mm (or longer) screw for a REGULAR End Cap/Insert assembly, or one 5x30mm (or longer) screw for a HEAVY DUTY assembly. See the attached photos for the assembly diagram. One 5mm hexagonal nut is also needed for each assembly.

FACTORS FOR DETERMINING WHICH INSERT SIZE TO PRINT:

• What is the inside diameter of the handlebar or extender? and 
• How much of the inside diameter will be filled with bar tape (the end or beginning of a wrap)?

As a general rule, you want to print the insert that is closest to, but less than, the inside diameter of the handlebar, keeping in mind any allowance for handlebar tape. The goal is to have the insert fairly snug inside the handlebar tube BEFORE you start tightening the expansion screw. To a degree, this is trial and error – you might need to print an additional insert that is the next size smaller or larger.

When you have found the best fitting insert size, assemble the four pieces (Insert, End Cap, Screw & Nut) as pictured in the attached assembly diagram.

• NOTE: the slots in the Insert should begin to engage the splines on End Cap; this keeps the Insert from spinning inside the handlebar while tightening the expansion screw.

Using a flat screwdriver or similar tool/object, push on the tips of the Insert expansion tabs, in the direction of the handle bar opening, so that the whole assembly begins to be inserted into the handlebar. When the INSERT is fully inserted into the handlebar, or slightly deeper, push the End Cap against the end of the handlebar, while tucking in and holding in place the handlebar tape. Hold the End Cap tight in place while tightening the expansion screw.  As the Insert expands, and as you hold the End Cap in place, the assembly should tighten up in place, with the handlebar tape secured, and the visible portion of the End Cap tight against the handlebar/tape.

PRINTING:

• The Inserts are printed on their side to provide greater layer strength on the expansion tabs. The End Caps are printed on their face. As such, supports are needed. 
• 100% Infill is recommended.
• I used Black PLA, and it worked fine.