Hello one and all, long time no see...

(Those of you of a delicate disposition might like to look away before this post goes much further)

We all know of the Cremina's legendary longevity and robustness I think - well I'm here to warn you that even the strong can be broken at the hands of a 17 stone half wit (c. 105kg/240lbs-ish numskull, for the imperially impaired). Below you will see what can happen when, over quite some time, you fail to notice that your lever group takes more and more pressure to generate a shot. This kind of micro incremental resistance creep will one day produce the wonderful experience my 33 year old Cremina and I had a couple of months ago...



and for comparison


Yep... that's a lever broken just inside the lever yoke. You can see how much of the threaded head is left by comparison with the other OEM lever next to it in the second photo. Now I want to make it clear that I don't feel this should in any way damage Olympia Express' or the Cremina's reputations. It may indeed be that there was a fault in the metal of the lever but even then it's taken 30 odd years to show and I was putting it under considerable duress, so to be honest, I think this is my own stupid fault.

Thus I say to you all - love your lever this Holiday Season, give the piston the lubing it deserves and get those gaskets checked or replaced before you too hurt the one you love.
with apologies for the rather poor photography -
YOU HAVE BEEN WARNED

Sneaky

Ooops. Good to see you posting again. It is really nice to get a heads up like the info you posted!
Respectfully
~Richard

Beware the incipient specter of subcritical crack growth!

Well Sneaky, that looks like a bother, but not insurmountable. I'm sure it will come out right in the end. I have been wondering myself about a refurb on the 3000-shot Ponte Vecchio, so maybe this will prompt me. And since it got you to post again, well, it's good to hear from you.

PC

I agree with kmills.

Most likely a crack developed at the weakest point - I suspect the undercut on at the base of the lever's thread and propagated during use. With "the last pull breaking the camels back" so to speak. This could be caused by either the undercut or some other machined feature being "out of spec" weakening the structure or a metallurgical issue or both. Also if the seals were sticking then this would exacerbate the problem by causing additional stress on the lever.

The good news is the lever failed before any serious or irreparable damage occurred to the machine or the operator and the lever is easily replaceable.

Consequently I think our British friend should not berate himself too much.

Cheers
Geoffrey

Actually, I've always thought lubing piston seals was overrated, since the water does most of it. I suppose Ken and Geoffrey are on to something here, and that it wasn't to be avoided. I suppose it's a rare occurrence, since we've never heard of it here on HB before.

Interestingly, when I had a Pavoni on loan a while ago I noted that the lever arm was considerably thinner than is that on the Ponte Vecchio. This is the opposite of what one would expect, since the Pavoni takes more stress, being a manual lever. I suppose the Pavoni is properly speced, since we don't hear of them breaking often either. This suggests that the PV is over-speced.

PC

peacecup wrote:since the Pavoni takes more stress, being a manual lever. I suppose the Pavoni is properly speced, since we don't hear of them breaking often either.
PC

Having skateboarded for over 20 years, the only thing that we broke more than the board, was the kingpin. The more the threads got closer to the baseplate, the weaker the bolt. Where the Pav's threads only hold the handle, the Cremina's threads take the brunt of everything being up so close to the fulcrum, where most of the pressure lies.

Looking at the threads on my Cremina, I am of the opinion that the threaded portion is in tension during use. If the lever is loose in the yoke, it would place the threads in a bending mode, causing crystallization over time. The lever screwed tightly into the yoke places the larger diameter of the rod as a fulcrum against the yoke.
Who knows????
Respectfully
~Richard

Very interesting comments and alternate theories. KnowGood I think is giving an example of a stress concentration problem. And espressme a metal fatigue issue. He also brings up an important point that when the handle is tightly screwed into the yoke most of the load is taken by the handle. A good argument for making certain the handle is tightly screwed into the yoke. Especially on a direct piston machine where I suspect the handle forces are higher than on spring piston machines.

Speaking of handle loads. If Sneaky intends to use the handle on the left of his photo I would suggest that he be even more careful than before because it is longer than the original and consequently has greater leverage. The ideal solution would be to make it the same length as the original.

As for lubricating the seals. This can get really complicated and confusing because seal chemistry and mechanics are so end use specific. For example some of the seals in the fuel lines of older automobiles will fail when exposed to ethanol. A good rule of thumb is if the manufacture says to lube then lube, and then only with an approved lubricant.

Here is a link to the Parker Company's O-Ring Handbook for anyone who is really curious about seals:

http://www.parker.com/literature/ORD%20...ndbook.pdf

Cheers
Geoffrey

Imperially impaired...I love it! I am glad it is a simple fix.