hbuchtel wrote:Cool. Where did you find that image?

I have to say I prefer the elegance of the original design over this one . . . the cup warmer would come in handy tho!

Henry

hbuchtel wrote:It isn't that the boiler temp is unstable, it's that the brewing temp is unstable. Doesn't necessarily mean the espresso isn't good, but rather it is a challenge to get the water to a good brewing temperature.

Inside a boiler at steam pressure the water temp is far above the range of acceptable brewing temperatures. Lever machines with this design rely on the exposed metal group head to absorb heat from the couple ounces of water you will introduce to the coffee.

After a certain amount of time or certain number of shots the group head gets too hot to perform it's heat-absorbing function, and you get unpleasant shots.

With the gravity-lever or open (unpressurized)-boiler machines in this topic the whole shebang (boiler, group head) is kept at brewing temperature, so getting a good shot should be much easier.

Another interesting thing about comparing pressurized-boiler and open-boiler designs is that they will have different temperature profiles during the extraction. Pressurized-boiler designs should start out hotter and cool a bit, while open-boiler designs should have a flatter profile. I don't know how these two profiles would effect the taste.

Henry

timo888 wrote:Where did I find the image of the Caravel Little?

Elsewhere on H-B. I will say no more at this time.

'Little' is a Lilliputian moniker--small compared to some, true, but rather large compared to others. The cup-heating tray is a convenience until it's time to fill the boiler, I'd imagine.

If only there were a ready source of malleable 110V calrods!

Regards
Timo

timo888 wrote:Where did I find the image of the Caravel Little?

Elsewhere on H-B. I will say no more at this time.

'Little' is a Lilliputian moniker--small compared to some, true, but rather large compared to others. The cup-heating tray is a convenience until it's time to fill the boiler, I'd imagine.

If only there were a ready source of malleable 110V calrods!

Regards
Timo

Staffan wrote:That doesn't explain why the Achille's heel of the Achille would be the pressurized boiler, since it is a basic HX.


Ps. It's probably fed by the suction of the piston, not gravity.
ds.

hbuchtel wrote:Honestly I cannot see any weakness in the Achille design, only that it would take a lot of experience to know when the brew water was at a good temperature...

timo888 wrote:I guess it depends on how one defines 'design weakness'. To produce good espresso requires control, perhaps first and foremost, over temperature. I'm puzzled that anyone would consider an espresso machine well-designed if achieving and maintaining proper brew temperature is not simply to be taken for granted.

Regards
Timo