Pump it!
98.75% of a cup of coffee is water. That makes me think that this TipsyBrew thing should know about moving some water around or something.
So obviously a coffee maker needs to move water and essentially the complicated and tedious process of mastering pour overs is all about moving water. So, the pour over machine should be able to do it well, like REALLY well*.
I haven't discussed pour over patterns yet because that is something that I feel like people are going to want to customize. Not every user may have the same showering feature. It will depend on a number of factors. One user may use nothing but a 2 cup brewer, another user nothing but 8 cups at a time, and others may mix it up depending on how little sleep they got the night before.
Another factor is how much time and effort someone really wants to put into the machine. If you always use the same brewer at a relatively similar amount of coffee, a quality shower head may be sufficient. However if you mix things up often or just really want the flexibility to dial in every detail of your cup, then you will want a moving spout that more accurately mimics a human pour.
Bah! I told myself I wasn't going to get into all of that today and two paragraphs later I haven't even said 'pump' yet! Pumps are the real topic of discussion today. A pump may not be as exciting as the pre-cone water dispersal device, but it is arguably more important. With out a pump (and/or gravity) how are you going to get the water to the coffee grounds!?
Gravity
I wanted to discuss gravity or siphoning even though it would be a fantastic solution, I have ruled it out. Using gravity would be great because when the system needed to disperse hot water it could just open a valve and gravity would push it out. It is simple and I love simple.
However, it poses a few problems. First, it would require the hot water to be above the brewing cone. Although I have joked elsewhere that the TipsyBrew should be dangerous to operate for idiots, I don't want to elevate the level of hot water any more than necessary. Another problem is that I am trying to design this using off the shelf parts. This means I do not want people to build their own boiler, especially if they already own one that may work. Other than those large 40+ cup coffee urns, there aren't many kettles on the shelf that drain from the bottom. With gravity it is either open or closed and the flow on open may vary based on the kettle each person uses. If anyone begs to differ, please do contact me with details, because I really do like gravity.
Peristaltic pump
Ok, full admission here. I have a weird bias for peristaltic pumps and have wanted to make one for a while now. The plan all along has been to make one for this project. Despite my complete bias, there has been an alternative suggested and I will get to that.
If you are not familiar with peristaltic pumps, they work by pinching the tube that you want to pump a substance through and then moving that pinch along the tube in the direction you want the substance to move. This causes a suction that will move things along. That is the general concept and although it is not required peristaltic pumps are usually found in a circular form factor as below.
This is common because it makes for a direct drive by a motor and rapid pinch circulation easy. For this project the main benefits are the water never touches any pump parts other than the food safe hose, the pump flow rate is directly related to the speed the motor turns, and it is self priming, which means we don't have to worry about the pump not getting water movement started on its own.
There are some risks with this pump though. The first one is pretty obvious, if you repeated pinch, squeeze, and/or roll a hose enough, it is going to get mad and give up. Luckily the hose should be easily replaced, but if that happens often it won't be fun or practical. After all we are making this machine to make great coffee more convenient, not to replace coffee making time with hose replacing time.
The other disadvantage has to do with max flow. Any pump is going to be limited by the size of the tubing attached to it, but if we use the same hose through the pump (which I plan to stick with) then the only other ways to increase flow is increasing the circumference of the roller path (AKA pump head) or increase the speed of the motor powering the pump (AKA more RPMs). I'm no pump engineer, but I look forward to playing around with this and all of you will be able to see any progress here.
Diaphragm pump
I'm not as knowledgeable about diaphragm pumps as peristaltic pumps but looking at the animation above, especially if you only consider one half of it, it is quite simple. The diaphragm pump came to my attention by a discord user that I was discussing the pour over machine with. Look for a discord channel dedicated to TipsyBrew to open up soon.
Anyways, diaphragm pumps are commonly used in food safe applications and have robust lifespans. I have seen many listed with flow rates up to 6 liters per minute and the flow rate can be adjusted by adjusting the speed of the motor. Similar to the peristaltic, diaphragm pumps are self priming as well.
At the moment I am having some trouble locating a cheap (less than $20 US) diaphragm pump that is food safe and can handle temps of at least 93°C. I am hoping that isn't a real issue, because I am looking forward to a pump throwdown!
* stupid water joke