So I've been working on a project that I hope will be exciting to the community. Here's my simple take at a manual espresso machine.
Basically it's a manual pour-over press, capable of generating lever to pump pressures required for real espresso. So far I've designed, had built by a local machinist, and tested the device, but I'd like to release the design (not that it's all that complex) as a concept to the community. Since many of us are engineers, I'm looking for any kind of feedback to help with the design.
I'm limiting project scope to the following (mostly for cost reasons):
- A manual pour-over press capable of reaching at least 8 bar pressure (~116 psi), with a reasonable downward force
- As cheap as reasonably possible, without major manufacturing or overseas production, or major quality or longevity problems
- 304 stainless in production (current prototype is Aluminum)
- No heater or other electrical items requiring UL or FCC certifications
- Cheap and simple to maintain
Current features as I see them:
- Capable of real espresso, not just strong coffee
- Inexpensive (planned to cost approximately $200-250 each for the first run in aluminum)
- Portable (ideal for camping or single person office use IMO)
- Simple Robust Design (low amount of maintenance or parts to break, only 2 rubber seals required currently)
- Capable of pressure profiling if a gauge is attached as with prototype
- 58mm baskets (bottomless ring, so any 58mm basket should fit...may try to make a 51mm size or adapter ring later on)
- Device Dimensions are approx: 14"h x 3.5"w (at base) ... tripod 6" tall
Planned changes from prototype you see:
- New handle for piston that's more ergonomic and cheaper
- Some tape/sleeve/coating to help with both grip and heat on the pipe and lower ring
- Top threads of pipe are unnecessary and will be trimmed or not applied (this pipe was purchased off the shelf because I was only buying one)
- Teflon tape will be replaced with a food-grade loctite sealant...I only used teflon because it was easier for me to find right now as a proof of concept
- Shower screen and tripod (as noted below) may not be part of the project...they add to cost, and can be optionally purchased in aftermarket. I'm not looking to start selling parts that are already for sale easily by other vendors.
- Possibly other suggestions!
Depending on the interest of the community depends on if this stays squarely as a fun project where I can make a few of these for other HB members, or if I can launch it beyond. Hopefully we can make the design better as a community without sacrificing the primary project goals. I have a local committed machinist who is able to do some small scale production in the range of 10-50 parts within a reasonable amount of time. The current parts were built on his CNC machine, and we are both hobbyists charging hobbyist prices. Still I have to get final numbers from him to be able to calculate a reasonable price for the first run to cost in total.
Also as a note, the tripod stand I got this on Amazon for about $11, there's lots of models, but basically they are used as a stand for heating flasks in lab equipment. Cheap, easy and seems to fit this project perfectly! Just in line with project goals. You can also press right on top of a mug, I have a couple that fit great...but I like to use my espresso cups, and mostly I've had close-calls with an Aeropress that made me not want to try it with this press.
Videos I'm planning to upload tomorrow when I can caffeine up a bit more. I've taken a few, but video is so much harder than pictures to get to come out even decently...I'm no videographer, so go easy on me.
For now, here's some additional photos to give you an idea:
Extraction video, 60 psi pre-infusion for about the first 10s, then up to 120 psi and trailing off slightly from there:
And here's the first video with larger cylinder (harder to press than currently):
Current excerpt from post #87 about pressure required to press:
60 psi - 21.4 lb (4.1 bar - 9.7 kg)
100 psi - 35.1 lb (6.9 bar - 15.95 kg)
120 psi - 41.0 lb (8.2 bar - 18.6 kg)
140 psi - 47.7 lb (9.6 bar - 21.68 kg)
160 psi - 53.5 lb (11 bar - 24.3 kg)