A couple of pages back bmcricket asked about versatility of the lever for pressure profiling if you're only able to retard it. If you have a strong enough spring that's all you need.

A manual lever has preinfusion baked into the design. The spring lever requires a strong spring for effective preinfusion. That is going to require a front leg length somewhat greater than the horizontal lever length measured from the pivot point to the end. The measurement from the pivot point to the center of gravity will work as the basic counterbalance. The idea will be to have the rotational force about the end of the front legs counterbalanced by the down force at the center of gravity. Going to take some info on the internal components to come up with a good value here for this ideal length.

All commercial levers that I know of (except for the initial Gaggia) operate with a cam, so once the lever is in the downward position it will stay there (imparting line or boiler pressure preinfusion) until the lever is lifted manually. The spring normally takes effect after the preinfusion stage and as part of the full infusion, funny lever manipulation techniques aside.

OldNuc wrote:A manual lever has preinfusion baked into the design. The spring lever requires a strong spring for effective preinfusion.

dominico wrote:All commercial levers that I know of (except for the initial Gaggia) operate with a cam, so once the lever is in the downward position it will stay there (imparting line or boiler pressure preinfusion) until the lever is lifted manually. The spring normally takes effect after the preinfusion stage and as part of the full infusion, funny lever manipulation techniques aside.

From my understanding, I would say the same that pre-infusion is more a boiler/hydraulic design than a function of the group. The options I can think of:

• Dipper - boiler pressure
• Pump (Strega)
• Line Pressure (whether HX or other design) ideally with a regulator

As mentioned, you can do Fellini move on pretty much any lever, and even pump machines if you really want to.

drgary wrote:A couple of pages back bmcricket asked about versatility of the lever for pressure profiling if you're only able to retard it. If you have a strong enough spring that's all you need.

Although you can't necessarily produce any profile like you can with a Vesuvius for example: 2-6-12-4 bar profile. Since with a spring the highest pressure must be at the beginning of the shot as opposed to middle or end. Also, I feel based on my experience on the Strega attempting this, that it's near like flying blind without a pressure gauge to guide you.

One alternative that I feel is viable is to flow profile on a lever, looking for constant flow, and if the flow speeds up you can hold back the lever. This worked decently on the Strega, and I think produces good results, but it only seemed necessary on occasion since the natural spring profile seems to do nearly that anyway.

OldNuc wrote:That is going to require a front leg length somewhat greater than the horizontal lever length measured from the pivot point to the end. The measurement from the pivot point to the center of gravity will work as the basic counterbalance. The idea will be to have the rotational force about the end of the front legs counterbalanced by the down force at the center of gravity. Going to take some info on the internal components to come up with a good value here for this ideal length.

This is what I'm thinking about, and while I think I have a good starting place, I also feel like the flexibility of moving supports around on a strut would be a nice confirmation of exactly how long is needed to guarantee no tipping. I could weld or bolt something, then start cutting length off the legs, but I think this would be too easy to overshoot.

Mass at the back of my design is planned to be negligible, so I would prefer to have length of legs at the front counteract the lever force. Of course if they need to be way too long, I'll have to think of something else. I know Curtis ended up stacking a bunch of gym weights at the rear of his machine. Maybe just a place to clamp/bolt to the counter, or stack weights is a fine solution.

Obviously not much of a concern if you wall-mount.

The biggest problem in coming up with a "standard frame" is that every kitchen is different, and often different countries tend to do things differently. Where I have no wall space near my sink, another might have a great spot. And where I may have a ton of counter depth, others may have half.

Though a bit pricey, the perfect material (if you don't have any fabrication skills/tools) may be this strut:
https://www.grainger.com/product/GRAING ... nnel-2HAL3

304 stainless, already drilled on one side, and can use strut hardware. Just need it cut to length, or you can even order it in 1, 1.5, 2, 3, 4, 5 or 10 ft lengths. I'm not sure how easy it would be to get anywhere in the world, but I know regular galvanized steel struts should be easy to find locally most anywhere.

Or for even 3x the price, fiberglass strut is available...no idea the strength capacity. Rough price comparisons for 10 ft lengths look to be: $20 galvanized steel, $110 stainless, $300 fiberglass.

For pressure profiling like a Vesuvius you can buy a Vesuvius. Another approach is the Strega hybrid where a vibratory pump can boost pressure. Then it's a matter of figuring out how to measure this so you're not flying blind and can get repeatable results. But my larger point was this. A strong enough spring is sufficient to allow you to profile by holding it back. After getting used to my Conti lever, I've relied on spring pressure for the stronger part of the pull. If the machine chokes I've ground too fine and dosed too much. I hold it back if flow rate is too rapid. Otherwise I'm perfectly happy with results in the cup with a declining spring profile and don't feel the urge to profile more than that. YMMV.

Regarding pre-infusion, since you can lock a commercial lever in the down position, you get preinfusion because boiler water flows into the puck and saturates it. I would think this is independent of design otherwise, isn't it, or am I missing something? Boiler water is under higher pressure than the external atmospheric pressure. By watching droplets hit the bottom of the cup you can decide when to release the lever.

drgary wrote:For pressure profiling like a Vesuvius you can buy a Vesuvius. Another approach is the Strega hybrid where a vibratory pump can boost pressure. Then it's a matter of figuring out how to measure this so you're not flying blind and can get repeatable results. But my larger point was this. A strong enough spring is sufficient to allow you to profile by holding it back. After getting used to my Conti lever, I've relied on spring pressure for the stronger part of the pull. If the machine chokes I've ground too fine and dosed too much. I hold it back if flow rate is too rapid. Otherwise I'm perfectly happy with results in the cup with a declining spring profile and don't feel the urge to profile more than that. YMMV.

I agree most people probably don't need or want to do true pressure profiling, but that was my point as well. Spring levers do what most pressure profiles try to emulate most of the time. There is a few exceptions, and I just wanted to highlight that. I think we are saying the same thing, but I wouldn't call it pressure profiling on a spring lever exactly.

drgary wrote: Regarding pre-infusion, since you can lock a commercial lever in the down position, you get preinfusion because boiler water flows into the puck and saturates it. I would think this is independent of design otherwise, isn't it, or am I missing something? Boiler water is under higher pressure than the external atmospheric pressure. By watching droplets hit the bottom of the cup you can decide when to release the lever.

This is how it works for a dipper design, so I don't think it's design independent, but rather group design independent. A pump or line fed system would allow adjusting that pressure with a bit more ease than boiler fed.

drgary wrote:For pressure profiling like a Vesuvius you can buy a Vesuvius. Another approach is the Strega hybrid where a vibratory pump can boost pressure. Then it's a matter of figuring out how to measure this so you're not flying blind and can get repeatable results. But my larger point was this. A strong enough spring is sufficient to allow you to profile by holding it back. After getting used to my Conti lever, I've relied on spring pressure for the stronger part of the pull. If the machine chokes I've ground too fine and dosed too much. I hold it back if flow rate is too rapid. Otherwise I'm perfectly happy with results in the cup with a declining spring profile and don't feel the urge to profile more than that. YMMV.

Regarding pre-infusion, since you can lock a commercial lever in the down position, you get preinfusion because boiler water flows into the puck and saturates it. I would think this is independent of design otherwise, isn't it, or am I missing something? Boiler water is under higher pressure than the external atmospheric pressure. By watching droplets hit the bottom of the cup you can decide when to release the lever.

This is pretty much spot on.

I will add as well that the speed at which you lift the lever will have an effect on the flow rate as well. If you just quickly lift the lever up the shot will run more slowly than if you lift the lever up in a controlled manner of the course of 5 to 10 seconds or so. I have used this "slow ramp" style to get a finer grind out of coffee that I believe needed it and it works well.

I've also been able to increase the body of lever shots by preinfusing at a higher pressure, I do this on my thermosiphon lever by lifting the lever up to a position a little taller than horizontal and then holding it there for about 5 -10 seconds, or until about a gram of liquid drops into the cup, then I lift the lever all the way up and let the spring fully take over. This I have found empirically to increase the body of the shots.

So in short, pressure profiling is totally doable on levers for those that want to nerd out about it, but not necessary for those that just want the standard lever profile.

My point, which has been missed, is you have almost unlimited preinfusion pressure control with a manual lever. The spring lever has a maximum pressure that may be manually reduced. Once you move on to hybrid levers then every design will be different and an attempt to automate what can be done with a manual or straight spring lever.

The manual lever was never routinely, if at all, used in a commercial setting either. The spring lever was an attempt to automate the process with existing technology.

OldNuc wrote:My point, which has been missed, is you have almost unlimited preinfusion pressure control with a manual lever.

dominico wrote:The spring normally takes effect after the preinfusion stage and as part of the full infusion, funny lever manipulation techniques aside.

EspressoForge wrote:As mentioned, you can do Fellini move on pretty much any lever, and even pump machines if you really want to.

I'm not so sure it was exactly missed, as much that I had assumed you meant a Fellini type move. And at least on most levers, I haven't seen any other that have a pressure relief system like a Caravel piston does. To me this means you must pull up on the lever after pressing, risking puck fractures, and then the cylinder will fill with the same pressure water as before (lets say 1.5 bar boiler pressure). This really isn't the same as a 3 bar constant pre-infusion pressure that comes from line pressure.

The only thing that may make it similar is if you had plenty of volume available in the cylinder, and never needed to raise the lever to introduce more water. If you know of a manual lever group like that...or really any manual lever group suitable for this project, what would it be? The only options seem to be Pavoni (49-51mm) sized groups which have quite a limited volume capability, even with a Fellini move. Most lever groups also don't have a pressure gauge to know what pressure you are pre-infusing at as well.

I'm trying not to bring in a major discussion of the Forge (as it is a much different device), but as I'm aware it's the only 58mm manual "lever" available (and does have adequate volume to do as you are describing). Please correct me if I'm wrong, I would be interested to check out a different group.

Someone could certainly design and build a manual group, and I have a friend who is planning on doing that for his own machine for fun...but it's a bit outside my plans for this project. I feel commercial groups available fit in nicely with this project and at a much more reasonable cost than a totally custom designed and built group.

drgary wrote:For pressure profiling like a Vesuvius you can buy a Vesuvius. Another approach is the Strega hybrid where a vibratory pump can boost pressure....

This doesn't give true pressure profiling. At best, it gives blind pressure profiling if you leave the lever down the whole time and just manipulate the pump (via the mod). But even with that you only have about 20 or so seconds before the pump times out.

The only pressure profiling the Strega can do with the pump is the pre-infusion ramp. Once the lever is released from lock, it's off the microswitch and the pump shuts off.