chappcc wrote:How will you change the set point for brew and steam with a "brew - off - steam" switch.

I modded a Salvatore E61 Lever machine using a double pole, double throw switch with an off position. In the brew position, I used a PID controller to control boiler temperature and in the steam position, I use the p-stat to control boiler pressure. With a boiler, cycling back to brew took a few minutes for the group to shed the excess heat from steaming. With a TB, cycling should be much faster.

The switch will go between two thermoblocks. This is to avoid needing a 20A circuit, but I may go that route later. I don't steam much, so the steam setup I will do last.

Set point will be changed with other switches not shown that are integrated into the LCD shield. Have a look here: https://www.adafruit.com/products/714

The drawings aren't 100% complete, just a starting point to get an idea for now.

You might need to experiment with the location of the thermocouple that's being used to control the thermoblock. On the thermoblock would probably best for controlling the group head heat but would less effectively control the flowing water output temperature. In the water outlet would probably be best for controlling the temp of flowing water but less so for the group head. There is a lag in heat transfer from the block to the water that impacts the switching from no flow to flowing water then back to no flow. That can cause overshoot or slow response. With an arduino you may be able to switch between sensors at various points in the shout routine.

Yeah, I have been thinking about how to take advantage of the inline water temp sensor. If nothing else I may just display it for a while, but like you say, it's really only meaningful when you lower the lever and there is actual flow.

I could install a flow sensor to at least see when there's flow. But overall, I don't know how quickly I could control temp on the fly based on the relatively quick flow of filling the cylinder.

For actual temp profiling, I think 2 separate heating elements and points are needed. For example if the TB and group plate were disconnected, you could get a rising profile by setting the TB temp lower, and plate temp higher. For a falling profile, TB higher and plate lower. The curve would then depend on the difference between the two (with some obvious tuning as all that matters is water output temp not the temp of the TB).

I'm hoping just initially that enough temp gathering points will give me the data to change the design. One or the other may seem good on paper, but I'm kind of a trial and error type person, sometimes on paper there's a factor left out or forgotten, whereas in practice I can gather data and examine the results and adjust.

More or less, I think the TB location is fixed as there is already tapped holes for the stock thermostats (3) and I plan to use one as a TC, and one as a thermal cutoff as used in the original design. But temp gathered there I can just apply an offset to make the system numbers make sense in relation to one another.

I'll also be comparing the whole system to the Scace output curve.

Another plan that someone suggested to me by PM was to wrap tubing around the TB to pre-heat the incoming water. I've been thinking about this since seeing it on the Australium. Not sure if the TB will need that since it already does that inside the TB, but I plan to try without and add it later if it looks like it's needed (shot cools too much towards end). I'll also add insulation at a later time and see it's effect. I plan to make one change at a time and gather data, hopefully will tell me if anything changes the final output or capabilities of the machine...or if insulation will just help with efficiency.

EspressoForge wrote:The switch will go between two thermoblocks. This is to avoid needing a 20A circuit, but I may go that route later. I don't steam much, so the steam setup I will do last.

Set point will be changed with other switches not shown that are integrated into the LCD shield. Have a look here: https://www.adafruit.com/products/714

The drawings aren't 100% complete, just a starting point to get an idea for now.

I've been thinking about the 3 position switch for brew and steam. Instead I was thinking to handle the switching in software. This would let me heat up the steam TB after the brew TB is at a less than a 100% duty cycle.

I could then just have a couple switches (or setup menu in the controller, but I like switches!) to select between keeping the steam totally off, brew priority, or steam priority.

To me this seems more flexible, and other than a little more programming work, I don't see much for a downside.

This should also work fine with a TB for brew and a larger boiler for steam for those that make more milk drinks and will go that route with their build.

EspressoForge wrote:This should also work fine with a TB for brew and a larger boiler for steam for those that make more milk drinks and will go that route with their build.

Seems like the controller would be focused on brew temp management since it is the most critical and needs the most flexibility to respond to the dynamics of water flowing through the TB to the group. A steam boiler could just get by with a simple p-stat control.

Thinking about this a little more, there seems to be a couple of control objectives being addressed by the controller. One is steady-state (idle) temperature control of the group and the second is dynamic (brew) temperature control of the water being sent to the group. The controller would need to know when to switch between control objectives. If you add control of steaming, then you add another control objective.

That's true if you use a 3 position switch, 20a 120v circuit or a 220v circuit. I don't think PID control of the steam system is so critical, but it would allow them to be heating at relatively the same time (though obviously the controller quickly switches).

Dynamic brew temp I can't see working with such large amounts of metal. I think you can change the metal temp, which affects the water temp...but without a low mass group and a mixing valve, I think true temp profiling on the fly isn't possible. This isn't to say that the profile couldn't be changed in the method I mentioned previously, but just because I can record a temp at a specific place doesn't mean I can control the water temp at that location with the controller without the required hardware.

OldNuc wrote:Silver solder the SS together as the cost of SS bolts-nuts-washers adds up real fast and drilling holes in 1/8" thick SS angle and channel is a very difficult task.

Looking more into frame metal prices, this seems to be a pretty good suggestion. 56% silver solder joint seems pretty easy to make and quite strong. I see some videos of SSF-6 on youtube, but that looks to be a bit expensive. Has anyone used Harris 56% silver solder on stainless and know it's strength? It looks like it can be done with just a propane torch, which I would consider to be relatively easy, though may be a little time consuming.

Alternative would be to weld or bolt together mild steel and then paint it, but costs seem about the same if you use a good rust proof paint or powder coat.

I used some 56FC on copper tubing and it held up just fine. I also used it to fix a milk pitcher when the factory made spot welding dots failed that held the handle to the pitcher. It seemed to flow very, very nicely and the weld has held up to lots of abuse since then. I'm not sure why but the areas around the silver came out discolored. The silver solder itself has a halo of black which doesn't seem to come off with a buffing wheel. I also used MAP gas instead of propane. That could be my problem.

There are different formulations of silver braise(solder) and some will leave a deposit and some do not flow well. The tighter the joint is mechanically the stronger the bond.

I have used silver solder in many different percentages and formulations for years. The metal mass that is being dealt with dictates Oxy-propane or oxy-acetelene so as to keep the heat input controlled and not burn the surrounding metal. MAP gas will work if you can find it but the flame is a bit on the large side.

This type of frame construction usually require outside fabrication/assembly of the basic frame as few people have the tools and expertise to do this type of work. The tools are expensive so if an individual wants to pick up a new skill and can afford the learning curve this would be a good project.

The cadmium alloy silver solder goes from a solid to a liquid and flows like water and has a absolute minimum plastic state.

Finding a small shop to build frames in batches may be the cost effective approach.

OldNuc wrote:Finding a small shop to build frames in batches may be the cost effective approach.

Yeah, was trying to figure out a cost effective approach for the prototype. I'm thinking maybe I'll just go with galvanized struts and plan to replace it at some point or maybe send it to be powder coated. I can't imagine the zinc plating lasting that long, but at least it would let me get the shape right. One thing I haven't figured out is exactly how long the legs need to be to avoid needing a weight at the back.

The tipping video in the Arin thread shows just how dangerous it can be if stability wasn't thought about in the design. Of course, wall-mount is an option, but I don't have any great places to wall-mount right now and lots of counter space.