It may be necessary to attach the bamboo to Aluminum like the head
tube or bottom bracket shell. As little "engineering type information"
on these parts are available for working with composts as they relate
bicycles the information has to be , well extrapolated. First off
bonding to ferrous metal with fiberglass, carbon fiber or similar material
requires that the metal surface be properly aggravated. This may entail
the use of sandpaper like 60 or 80 grit emery, bead blasting and the
most extreme of all knurling the metal.
However When it comes to aluminum you have the additional problem of the aluminum oxide, the protective layer that forms over all aluminum as it oxidizes. Add into the mix the little issue that aluminum has high coefficient of thermal expansion and you have a material that requires some thinking when using.
So here are the steps as they were taught to me in several classes at MSU.
Step #1 controlling or balancing thermal expansion of the aluminum head tube, bottom bracket and dropouts outs. Materials tend to expand in the direction of greatest materiel dimension. in the case of the tubs that would be the length of the tube. Drilling the holes at evenly spaced intervals helps to balance the expansion so that the amount of movement is held to a minimum thus reducing the effect and negative effects.
Wikipedia has an excellent write up on the coefficient of thermal expansion. Most interesting is the example of rails bent due to heat. http://en.wikipedia.org/wiki/Thermal_expansion Notice that the railes expanded in length and that is most noticeable but most inportrnt to remember is how much heeti is actuyaly requered and how long the part must be.
Step #2 aggravation of the surface with drilling and emery to improve the ability of the Epoxy to adhere to the aluminum takes several steps to assure a reliable bond. Once the holes are drilled the surface needs to be scuffed with emery paper 40 to 60 grit. This step increases the surface area and provides a bite for the epoxy and more surface equals more hold
Step #3 Etching., aluminum oxide is the protective surface that forms on aluminum based on time and exposure to oxygen. One way to remove the aluminum oxide is 60 or 80 grit emery, however this only last about three hours so acid etching is the way i make sure i have the best bond possible. Phosphoric Acid i one but for cost and simplicity Permatex Rust Dissolver Gel a pink gel product actually has several acids int including Phosphoric and its stick nature is great. Use the product with gloves on and then rinse with water and rey just before use .
However When it comes to aluminum you have the additional problem of the aluminum oxide, the protective layer that forms over all aluminum as it oxidizes. Add into the mix the little issue that aluminum has high coefficient of thermal expansion and you have a material that requires some thinking when using.
So here are the steps as they were taught to me in several classes at MSU.
Step #1 controlling or balancing thermal expansion of the aluminum head tube, bottom bracket and dropouts outs. Materials tend to expand in the direction of greatest materiel dimension. in the case of the tubs that would be the length of the tube. Drilling the holes at evenly spaced intervals helps to balance the expansion so that the amount of movement is held to a minimum thus reducing the effect and negative effects.
Wikipedia has an excellent write up on the coefficient of thermal expansion. Most interesting is the example of rails bent due to heat. http://en.wikipedia.org/wiki/Thermal_expansion Notice that the railes expanded in length and that is most noticeable but most inportrnt to remember is how much heeti is actuyaly requered and how long the part must be.
Step #2 aggravation of the surface with drilling and emery to improve the ability of the Epoxy to adhere to the aluminum takes several steps to assure a reliable bond. Once the holes are drilled the surface needs to be scuffed with emery paper 40 to 60 grit. This step increases the surface area and provides a bite for the epoxy and more surface equals more hold
Step #3 Etching., aluminum oxide is the protective surface that forms on aluminum based on time and exposure to oxygen. One way to remove the aluminum oxide is 60 or 80 grit emery, however this only last about three hours so acid etching is the way i make sure i have the best bond possible. Phosphoric Acid i one but for cost and simplicity Permatex Rust Dissolver Gel a pink gel product actually has several acids int including Phosphoric and its stick nature is great. Use the product with gloves on and then rinse with water and rey just before use .
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