Getting the Blade into the Pitcher

Trial and error has been a huge part of making and refining the blender.  In tackling the blade and pitcher attachment, there has been a lot of trial and a lot of error.  The ideal solution is still waiting to be stumbled upon.  However, even with no end result, there is a lot to say about what has been discovered about how not to attach the blade to the pitcher.   

As mentioned in a previous post, a pitfall of the current blender is the amount of glue used to attach the blade apparatus to the pitcher, and finding an alternative method of attachment proves to be almost equally problematic. 

 

Initially, a small hole was cut in the base of the pitcher and the blade was inserted so the lip of the bottle cap rested on the base of the pitcher.  To secure the blade, the lip of the bottle cap was glued to the inside of the pitcher.  To reduce the contact between glue and blended matter the lip could be simply glued to the outside bottom of the pitcher.  The main problem with this solution is that the blade assembly would have to be finished after the lip had been glued to the pitcher because the diameter of the blade is greater than that of the hole in the pitcher (hole in the pitcher is approximately the diameter of the bottle lip).  It is possible to finish assembling the blade after the lip has been glued, but doing so adds an unnecessary level of complexity.  Although this may be the most straightforward solution, is it is not necessarily the most practical. 

To find the best way to attach the blade, it was necessary to think about completely redesigning the base of our blender.  Looking at the most successful commercial blender designs provided a framework a new design. A two-piece design composed of a pitcher with a threaded base, and a threaded cup that holds the blade and screws into the threaded base of the pitcher was pretty universal.  Unfortunately, the dollar store pitcher currently used for the bike blender does not have a threaded base, so to use the current commercial design there would have to be a major modification.  Regardless, a two-piece design seems plausible and would make blade maintenance much easier.  

  

Being able to insert and remove the blade apparatus from the bottom requires a larger hole in the base of the pitcher, and a larger hole means there is a larger area for liquid to seep through.  An initial idea was to cut the water bottle at a wider part and fit the diameter of the bottle into the bottom of the pitcher, secure it and make a watertight seal.  Conceptually, this seemed like a reasonable, good solution, however, the technicalities of how it would be constructed still had to be worked out.  Another point to consider was that using more bottle cap would mean pushing the blade higher and higher until the diameter of the bottle matches the diameter of the seal, whereas ideally, the blade rests ¼ of an inch or less from the bottom of the pitcher.  

Aware of the potential challenges of the design, it was time to start on a prototype.   Initially, most time was spent looking into ways to secure the extended bottle cap to the pitcher.  Using a paper bowl to simulate a rubber pitcher, a hole with a diameter of two inches was cut from the bottom and four nails were inserted so their heads protruded into the hole.  The idea behind the nails was that they would fit into grooves cut in the water bottle, effectively holding the bottle in place.  There were a few problems encountered during construction; first, a longer bottle makes inserting the ball bearing nearly impossible because the channel is too narrow for a hammer, the next drawback was that the neck of the bottle does not meet the screws at right angles which makes it difficult for the nails to fully support the cap, and the last problem was that connection was not watertight. 

 nails inserted in the paper bowl that is substituting for a plastic pitcher

full water bottle prototype

 

A few other initial prototypes:

 

Tin Foil seal

screw lock mechanism

rubber seal and screw lock mechanism

To revise the blade connection design, a more effective attachment and sealing mechanism was needed.  Going back to brainstorming, a convincing idea was to line the inner edge of the hole with rubber.  A rubber lining could potentially serve both as a sealant and a support.  The logic behind this new design was that the friction between the rubber and the bottle may be enough to hold the blade apparatus to the pitcher, and simply placing the rubber around the hole and jamming the cap into it may be enough to create an adequately watertight seal.  However, thinking jamming a bottle into rubber could be the solution was slightly too optimistic.  There were many leaks in the seal and the blade apparatus did not appear to be secure enough to be able to withstand the force acting on it during blending. 

bottle cap jammed into a rubber seal

Thus, currently no solution has been reached about how to connect the pitcher and blade.  This means it is back to brainstorming!