Peppina Marries MiniGaggia - Page 52

by **espressme** on Tue Dec 05, 2006 6:13 pm

espressme wrote:Hi Timo,
Now that you've settled the lever head, :?
An idea for the "Beast" group is circulation of water through it but not like the regular HX. It would be similar to the "Achille" in having a pre pull circulate kettle temperature water through and out of the grouphead to make nice nice convection in the kettle and then to fill the piston from the kettle for the shot. One pull two kills! At the exact temperature!
Very simple to accomplish and for the small increase in money a significant advance! :o No electronics here! :!:
And it works spring or direct.8)
:?: Any one else out there? :?:
Best to all
Richard / espressme

Hello Tim,
This thread just came up again, I don't remember seeing it before:
http://www.home-barista.com/levers/clevis-to-lever-further-explorations-in-espresso-space-t1243.html#top
The first few entries say it all!
Regards
espressme

by **timo888** on Tue Dec 05, 2006 9:59 pm

espressme wrote:An idea for the "Beast" group is circulation of water through it but not like the regular HX. It would be similar to the "Achille" in having a pre pull circulate kettle temperature water through and out of the grouphead to make nice nice convection in the kettle and then to fill the piston from the kettle for the shot. One pull two kills! At the exact temperature!

I do see the benefits of various kinds of circulations, Richard, but they apply to designs where you are trying to maintain the ability of the group to sink off excess heat. The Beast will not have that particular issue because its brew water is only a couple of degrees above desired brew temperature as it leaves the unpressurized kettle. Moreover, the Beast doesn't have a massive group that could take such a channel drilled into it; the Beast's group simply holds the PF in place.

Now, the Achille's piston chamber contains cool water, according to the details revealed in the unfolding saga. With its piston upstroke, cool water in a vestibule above the piston flows down through a tube in the piston itself into the now empty piston chamber. Then, with the piston downstroke, that cool water in the chamber is forced into the HX system. The HX system runs through the boiler and back out through the dispersion block to the puck. When cool water is pumped into the HX tube by the piston, hot water already in the HX is pushed out to the puck.

The question on the table is, what is the best way to ensure both inter-shot and intra-shot temperature stability on the Achille? Does it involve a cooling flush? How much? What's the best starting temperature on the extraction? Will a higher starting temperature keep the heating element off for a longer time, preventing temperature overshoot mid-extraction? Does bringing cool water down into the piston chamber and allowing it to linger there for 'n' seconds figure in the equilibrium equation, or are the effects of the cool water on the group's heat-sinking negligible?

Regards
Timo

by **espressme** on Tue Dec 05, 2006 10:28 pm

I do see the benefits of various kinds of circulations, Richard, but they apply to designs where you are trying to maintain the ability of the group to sink off excess heat. The Beast will not have that particular issue because its brew water is only a couple of degrees above desired brew temperature as it leaves the unpressurized kettle. Moreover, the Beast doesn't have a massive group that could take such a channel drilled into it; the Beast's group simply holds the PF in place.

\
Hi Timo,
The thought was to assure the air cooled group would be at the same temp as the liquid in the boiler. Accomplished by a simple (?) hollow "L" channel welded around the group and flushed by the upstroke of the piston drawing water through the channel and expelling it into the kettle, mixing all liquid together - ( and perhaps preventing temperature stratification.)

This happens before the intake fill and down-stroke. ( up-stroke to Peppina fans!) This could be a useful (? no hole in piston !) replacement for the hydraulic lock preventer one way valve in the piston.

The one way valve would then be on an outlet of the channel into the piston cylinder. Then the group channel water would be changed by the first upward movement of the piston.

Complex? maybe! Useful? who knows! Possible? yes.
Regards
richard / espressme

by **timo888** on Wed Dec 06, 2006 10:12 am

espressme wrote:The thought was to assure the air cooled group would be at the same temp as the liquid in the boiler.

The goal is to achieve the design intent through the simplest means possible, using Occam's Razor at every turn
(avoiding multiple entities when one will do). The integral kettle/group achieves this.

The conductive part of the Beast's group is not made of brass but of stainless steel; it consists of the piston cylinder which is situated inside the kettle, where it is bathed in brew water; it extends down and out of the group to become the dispersion screen housing:

That inner cylinder is all one tube.

The bell of the group (not shown) is just a way to lock the portafilter in place, a PF-harness. It has a flange that is bolted to the kettle flange. Sorry if the wire-frame obscures this, but the bottom flange belongs to the PF-harness (not shown) and not to the inner tube.

To prevent too much heat from being conducted to the PF-harness via the flange-to-flange union, there will be an insulating gasket between the two flanges. The thickness of the gasket and its insulating capacity remain to be determined.

Heat will also be conducted down the integrated piston cylinder/dispersion screen tube. But since the piston cylinder is bathed in brew water inside the kettle, I don't think we don't need to worry much about regulating this conduction. It's the heat from the heating element around the outer kettle wall that is the main focus.

Regards
Timo

by **espressme** on Wed Dec 06, 2006 11:24 am

timo888 wrote:
espressme wrote:The thought was to assure the air cooled group would be at the same temp as the liquid in the boiler.

The goal is to achieve the design intent through the simplest means possible, using Occam's Razor at every turn
(avoiding multiple entities when one will do).

He was a sharpy NO?

Heat will also be conducted down the integrated piston cylinder/dispersion screen tube. But since the piston cylinder is bathed in brew water inside the kettle, I don't think we don't need to worry much about regulating this conduction. It's the heat from the heating element around the outer kettle wall that is the main focus.
Regards
Timo

So, you have decided upon a band heater?
Best regards
Richard

by **timo888** on Wed Dec 06, 2006 12:51 pm

Band heater makes most sense given the design, I think. Keeps the inside of the kettle clear of stuff and easy to clean. No need to drill holes in the kettle for the element. Easier to install and replace. No need for a custom design. Bands come ready for a PID upgrade.

Regards
Timo


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