Reason why the lever of (commercial) lever espresso machines dont remain down - Page 2

A haven dedicated to manual espresso machine aficionados.
JimH

Postby JimH » Jul 10, 2019, 1:29 pm

For the sake of clarity, do you have the post-2001 upper group labeled as part 12 or do you have the pre-2001 upper group that is unnumbered but displayed on the left with part 32?

Lincoln

Postby Lincoln » Jul 10, 2019, 1:31 pm

Ja its an older design, the cam pulls the rod up to compress the spring, so when its not sitting in the bed nicely there is a lot of recoil on the handle, and on the one im working on there was a lot of fine metal shavings and absolutely no grease. I am asking because they are so difficult to dissasemble and reassemble as the spring needs to be compressed to wind the piston rod onto the bed (15) through the main 'cylinder' head

User avatar
drgary
Team HB

Postby drgary » Jul 10, 2019, 1:34 pm

Paul_Pratt wrote:I do not think I have ever seen a commercial lever machine that does not have a rest position at the bottom. They all do. Some small home levers such as the Elektra do not have a rest position.


Off topic for this thread, but worth a note. The only home lever I've ever seen with a lockdown for preinfusion is the Lady Duchessa.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

OldNuc

Postby OldNuc » Jul 10, 2019, 1:54 pm

The Gaggia has a mechanical latch that is clearly observable. The majority of the remaining true commercial groups use an over center latching system. What this means is that when the lever is full down and the spring is also fully compressed the level pivot point that is NOT the link compressing the spring is now behind the piston rod centerline so as spring force is holding the lever down. Each design accomplishes this little mechanical trick in any number of unique ways. The non commercial home machines do not have this feature.

ira
Supporter ♡

Postby ira » Jul 10, 2019, 2:47 pm

In that picture the lever handle has two holes at the bottom for pins or bearings. I believe if you look closely when the lever is fully lowered, the holes cross, i.e., the lower hole is located behind the upper hole which keeps the lever down. If so, it's likely something has worn so that doesn't happen. In an earlier picture there was a notch in a cam that caught the lever at the bottom. Those are the two most likely methods of holding the lever at the bottom. My Rancilio seems to use the overcenter method which I assume will be more common than a cam.

Ira

OldNuc

Postby OldNuc » Jul 10, 2019, 3:43 pm

What you are describing is a reversed toggle lock.