NEW WATER TANK DESIGN

We're currently experimenting with a design that moves the water tank under the machine, instead of being on the right hand side. I want to tell you guys about it, and get your thoughts.

The side tank that we have in the current design has been really, really hard to find a manufacturer for, because we want it to be made out of glass, and not plastic. We could make it out of soda lime glass, but then it would weigh 2kg (5lbs), and be brittle. Out of borosilicate (pyrex), it's at the far-edge of the comfort level for all the glass manufacturers we've talked to, and so a risky proposition. By putting the water tank underneath (like the GS/3) the tank becomes very easy to manufacture, and we reduce the width footprint of the DE1 by a third.

In our current design of this new water tank, the uptake tubes are in the middle of the tank, so you can fill the tank one of two ways:

• 1) from behind, you slide the water tank along rails up to about 4", and fill it directly there.
  2) from the front, by taking out the drip tray, and sliding the water tank along the rails 4" forward, and fill it there.

There is a latch on the back of the machine, which lifts the uptake tubes completely out of the tank, so that you can remove the water tank and put it in the dishwasher.

The new water tank looks similar to a baking dish, as it can be made from pyrex (borosilicate) and the side handles sit on rails under the DE1 that travel the entire depth of the DE1. The tank has no lid, because it fits snugly in the flat undercarriage of the DE1, which then acts as a lid. The capacity of the tank with this design is about 2 liters.

Here is a photo of the idea, with a baking dish (not the final tray).

How's the sloshing? Would baffles be helpful?

Yes, sloshing is absolutely a concern we have with this approach, and we're designing this water tank to have side baffles to mitigate that.

Seems like a good solution. Two things come to mind.

- How does the user monitor water level? Can one see into the tank?

- Front fill: the actual convenience of operation (i e just exactly how easily each step is done) of front fill access really makes a difference. Rear fill I would think is unnecessary if there is front fill.

I had a BDB that was good in those respects, as a point of reference.

cpreston wrote:- How does the user monitor water level? Can one see into the tank?

The software tells you (on the tablet) how much water you have left, and lets you know when it's getting low (at 20%) and when it's empty. We've installed a metal tube, connected to the water uptake tube, which is connected to a water level detector. You can't easily see into the tank.

cpreston wrote:- Front fill: the actual convenience of operation (i e just exactly how easily each step is done) of front fill access really makes a difference. Rear fill I would think is unnecessary if there is front fill. I had a BDB that was good in those respects, as a point of reference.

I agree. I bought my lead mechanical engineer Brad a BDB when he started working for me. There is lots to admire in the design of the BDB. Their engineers really sweated the details.

All this talk about the Baratza Sette suggested that I should post an update on our Decent Espresso Grinder Prototype which I've done in a separate HB thread.

If it is an open tray that would slide in, I suspect it would be hard to avoid things like coffee fines etc from finding their way into the reservoir. All it would take is some fines etc to be on the side of the seal and be disturbed as the tray is inserted.

Not sure about the internal design but potentially they could be 'sucked' into the machine or just rest on the bottom of the tray.

Well, I highly doubt I will think of anything that you guys haven't so I say all this realizing someone may have already used my 2 cents. I will no doubt end up thinking on it more, too, and may have to come back and revise. Ultimately, if it works well, is convenient etc then I am sure it doesn't matter. But, as a consumer I guess things that are coming to my mind are:

1. How does this affect minimum water volume? I am imagining that the tube needs to have a certain water column height in order to function, and that the wider base means more volume to achieve that height. So, how low can you safely keep the water line to maintain a viable heating cycle and what percentage of total volume is that?


2. How sensitive would it be to leveling? Assuming there are some leveling feet on the machine it's probably fine, I assume that if the tank is wide enough then even subtle off-leveling could throw a lot more water off to one side of the tank or the other, possibly making more spill problems or reducing overall operating volume further?

3. How would heat affect the countertop surface. It might be a non issue I suppose, but I imagine leaving a container of constantly heated and occasionally boiled water directly on or just above my cheapo laminate top might eventually cause problems?

4. Finally, at least from my initial response, I think something would need to be done to make the consumers feel comfortable about hygiene. While it probably is the EXACT same as any other tank, the bottom of the machine is often perceived as being pretty dirty, open to contamination due to the size of the opening particularly lubricating moving parts, cleaning solution, coffee drip and run off, etc. At least those are my first thoughts. Maybe a dedicated lid with a fill port and fittings running through it would help alleviate those perceptions? Or, maybe I am alone, and its more of just an obsessive HB regular paranoia.


5. By the time you add in the tank, leveling feet, and a tablet will it fit under residential countertops?

Sloshing was my main concern as well. I think if there is a way to fill the reservoir without sliding it front to back, that would improve things. Perhaps take some of the savings of width you are getting to incorporate a fill tube from the top. Or, have a portion of the reservoir extend into the drip tray area to act as a fill area. I am thinking of the BDB design where the drip tray extends into the body of the machine to catch the purge from the 3-way, as an example, but in this case the reservoir extending into the drip tray area. Also, I think with the body of the machine acting as the "top", it would be good to have some sort of gasket to seal reservoir to "top" primarily for any sloshing issues.

I do like the idea of the machine without the reservoir on the side. I think it will look cleaner.

If you make a shot 2 minutes after turning it on, we're currently about 3°C under temperature,

Should be an issue that you can largely account for in software. Ie, if there is insufficient warm-up time, add more heat to compensate. Should be the same for incoming water temperature. Ie, measure it and compensate for it (instead of pre-heating it).

I'd also consider high temperature plastic or stainless steel.