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):

1. A manual pour-over press capable of reaching at least 8 bar pressure (~116 psi), with a reasonable downward force
2. As cheap as reasonably possible, without major manufacturing or overseas production, or major quality or longevity problems
3. 304 stainless in production (current prototype is Aluminum)
4. No heater or other electrical items requiring UL or FCC certifications
5. Cheap and simple to maintain

Current features as I see them:

1. Capable of real espresso, not just strong coffee
2. Inexpensive (planned to cost approximately $200-250 each for the first run in aluminum)
3. Portable (ideal for camping or single person office use IMO)
4. Simple Robust Design (low amount of maintenance or parts to break, only 2 rubber seals required currently)
5. Capable of pressure profiling if a gauge is attached as with prototype
6. 58mm baskets (bottomless ring, so any 58mm basket should fit...may try to make a 51mm size or adapter ring later on)
7. Device Dimensions are approx: 14"h x 3.5"w (at base) ... tripod 6" tall

Planned changes from prototype you see:

1. New handle for piston that's more ergonomic and cheaper
2. Some tape/sleeve/coating to help with both grip and heat on the pipe and lower ring
3. 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)
4. 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
5. 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.
6. 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)

How is it used; it looks to me like you pump it similar to a bicycle pump?

Its basically an rok right? Only instead of the handle mechanism you put it on the floor and pump?

Also, have you checked the temp at the group? 100 in might easily be in the 80s or lower from the coffee and metal

It's a piston and cylinder design (no pump, you can change pressure near instantly). You just press on the top (a rod of aluminum, it goes inside the pipe), I'll try to show the whole process in a video tomorrow. It stays on my countertop during pressing.

I haven't yet measured internal temp... Without preheating I notice a little sourness, but you can preheat the device with a bowl to eliminate that.

For pressure, I've also plans to video it on a bathroom scale, so you can see how much pressure downward gives how much inside.

Updated original post with a video. It is a little bit awkward to shoot a clear video and press at the same time, usually if I'm not shooting a video I'll press with my head further down so I can see the pour and the pressure gauge at the same time. In this way, it's easier to keep a higher and constant pressure. I haven't yet measured the downward force, but my guess is for around ~100 PSI it takes about 40lbs of downward force.

I'll try to get a full video explaining the process and showing my full routine including preheating and locking in the basket.

Shot look pretty good, good use of a tripod stand for this, I saw someone using one of these with a Mypressi Twist a while ago. I see a pretty good espresso machine in the background, this manual press looks like it might travel well.

PVC pipe is a decent insulator, at least over the short term. I ran some hot water thru my faucet today until it came out at nearly 140F, and the PVC pipe remained fairly cool to the touch. So a PVC pipe might make a nice "sleeve" for your aluminum cylinder if you can find a size that fits and can be glued in place. Or, you can use a slightly larger PVC pipe to create an air space between cylinder and sleeve for extra insulation, then create some bushings on the ends. This will keep the aluminum cylinder hot after preheating and keep hands cool when handling.

Looks pretty workable and it produced a nice looking shot. I am guessing the ID of the cylinder is roughly 0.70 inches, since you estimated 40 lbs of force to generate 100 psi pressure. Smaller diameter will require less force, but of course, it will make the piston and cylinder even longer.

Lou

yakster wrote:Shot look pretty good, good use of a tripod stand for this, I saw someone using one of these with a Mypressi Twist a while ago. I see a pretty good espresso machine in the background, this manual press looks like it might travel well.

I think the tripod worked out pretty well...a sturdy mug works too, but I feel like the tripod is a bit safer. Maybe I'm wrong. Surprisingly, I found that while the press takes some manual effort, because it's direct, it seems a bit easier to get a good shot than my Strega at times, especially from my PeDe box hand-grinder. Mostly because you can adjust pre-infusion pressure and on the fly for a poor grind or distribution...might not get as high of a pressure shot, but it's usually still good.

lbdina wrote:PVC pipe is a decent insulator, at least over the short term. I ran some hot water thru my faucet today until it came out at nearly 140F, and the PVC pipe remained fairly cool to the touch. So a PVC pipe might make a nice "sleeve" for your aluminum cylinder if you can find a size that fits and can be glued in place. Or, you can use a slightly larger PVC pipe to create an air space between cylinder and sleeve for extra insulation, then create some bushings on the ends. This will keep the aluminum cylinder hot after preheating and keep hands cool when handling.

Looks pretty workable and it produced a nice looking shot. I am guessing the ID of the cylinder is roughly 0.70 inches, since you estimated 40 lbs of force to generate 100 psi pressure. Smaller diameter will require less force, but of course, it will make the piston and cylinder even longer.

Lou

Good idea of the PVC, for now I used some rubber electrical splicing tape, the kind that stretches a lot. It seems to make a nice feeling grip and lowers the heat conduction enough...but it does get warm after pre-heating. I like the idea of PVC since it would be faster to slide over the pipe and screw in the fitting to be done...as long as it was pretty solid I think it would be great. Going to see if there's anything I can find locally that fits well.

ID I think is 0.8 inches, and I have thought about reducing it to require a bit less force (60 psi is extremely easy and can be done with half-strength on one hand, over 100psi requires 2 hands but is pretty easy for me if I'm leaning my shoulder into it). But reducing pipe size means the amount of water that 12" of pipe gives would go down...currently seems to be ideal. There's extra for most doubles I've been pulling (17-18g), but on overfilled baskets even more, or triples, or lungos...it would just give the flexibility that most levers don't seem to have. Maybe reducing pipe size would be better for a smaller basket diameter which wouldn't fit as much coffee as a 58mm? I always did like the tiny Caravel basket, but a 51mm standard lever size might be a good choice for seals and aftermarket baskets.

Played more with the PeDe grinder today and the machine. I haven't used it for espresso in a long time, but seems to be fairly bean dependant. Darker roasts seem easier to pull, but lighter ones were a challenge to grind as fine with it. Looks like I'll be looking into other travel grinder setups to use with this machine...maybe HG-One has just spoiled me.

So far, my testing plans are:

1. Shorten piston and cylinder by 3" - even with a larger shot, there seems to be at least 3" of travel always left, so I think this height is just unnecessary. Pressing currently is significantly easier on a lower surface than my counter, such as my kitchen table, so I think reducing the height will help.
2. Try out a smaller diameter cylinder/piston - current one is working, but over 100 PSI takes significant effort...similar to grinding a Pharos. It can be done, but ideally it would be a little easier if possible.
3. Try a PVC shroud for heat as suggested above
4. Record more numerical data - downward force it takes to press for a given pressure for each pipe size, as well as temp of water as it hits the coffee with and without pre-heating.

I've also been thinking of a redesign of the handle on the current piston. Something like the below sketch:

Basically trying to lower the handle which should make it easier to get more leverage while on the higher tripod. Of course, shortening the tripod would help as well as shortening piston/cylinder.

I also have a source for machining the first run, around 10 pieces, which could be done in either aluminum or stainless. They've agreed to do them at a much reduced cost, as close to material cost as possible as a favor to me. My plan is once the initial prototype is to a stage I feel ready for this run, that I can take 10 pre-orders on the initial run at a reduced cost from a final production retail price. Hopefully this development process, including this thread will get everyone interested a better designed device at a lower price point than would be otherwise possible with a sizable up-front investment needed on my part.

Please keep the ideas and improvements coming, I believe the press already makes good espresso, but if it's easier and more ergonomic to use, all the better.

if it is awkward to see the gauge as you press, I am sure you could just use a 90* fitting to face the gauge upward so you could see it from above.