Friday, June 1, 2012

Designing a Better Bike Polo Mallet

My big pastime is bike polo, so naturally I find myself thinking about the sport a lot. It is still a developing sport, so there are constantly innovations in gameplay, tactics, and equipment. In a materials science class we were talking about plastics, and it got me thinking about polo mallets... there is a lot to be desired about their design. ABS tubing has been used in bike polo mallets for years now. It is cheap, easy to find, and light, but it wears quickly and shatters into jagged edges. This means that we have to make new mallets all the time, which is a pain. In addition, the jagged edges make for inconsistent shots, so people started using solid caps on the ends of the mallets to try and even things up.

Wanting to use some of the engineering principals that I've been learning about, I decided to design a better mallet head. The main design goals were: light weight, durability, and performance.

I started out just testing materials for their wear characteristics, from HDPE, to Bakelite, to molybdenum phenolic. Finally I settled on UHMWPE (Ultra High Molecular Weight Polyethylene) as it had the best wear-resistance to weight ratio.

After settling on a material, I made some prototype mallets out of tube stock with an attachable cap, but the added weight of the cap and the machining time proved prohibitive. To try and save on weight, I tried drilling out the sides of the mallet head, but that weakened it too much and introduced lateral flex.

To get around this, solid stock was machined out and internal butting was introduced to find a balance between weight and stiffness. By drilling a blind hole, we automatically had an integrated cap, which provided both a good striking surface and added strength. With this design, I took the mallet to the club and after group testing, several rounds of improvements, and a host of manufacturing problems due to the blind hole, I went into production with the Portland Bike Polo Mallet Head. The mallet heads have now been shipped world-wide and have a 5th place finish at the World Championships under their belt.