Alex, if you can find a photo from one of the earlier threads and post it here that might help. I'm not sure which part you mean.

My Caravel shots on Friday were quite good. A new O-ring for the piston center hole, and some Dow 111 from Greg seems to have helped to increase brew pressure a little.

In my experience so far I find that the shots blond towards the end of the pull no matter how I grind/dose/tamp. The flow usually slows to a fast drip and begins to blond towards the end. Anyone had any experience with this, and found a solution?

Also, what temperature are you Caravel users pulling shots at? Full rolling boil, pre-boil, post boil? I have yet to even put a thermometer it the boiler or brew water, but plan to do so soon.

I've found that the Caravel PF is just 1-2 mm smaller diameter than that of the Ponte Vecchio. In fact, the OD of the baskets are the same, the ID diameters are what varies. This got me thinking that a new Ponte Vecchio group head gasket might fit the Caravel, and I'm anxious to try this. DUring very hard pulls on the Caravel I get a few drops of water escaping over the PF, which suggests a new gasket is in order.

PC

peacecup wrote:Alex, if you can find a photo from one of the earlier threads and post it here that might help. I'm not sure which part you mean.

Right. I'll borrow one of Walter's photo since my model appears identical :

I'm missing the metal cover at the top of the pic. The machine works fine, but knowing that the part exists, I'm a bit wary of pulling too hard on the lever.

peacecup wrote:My Caravel shots on Friday were quite good. A new O-ring for the piston center hole, and some Dow 111 from Greg seems to have helped to increase brew pressure a little.

In my experience so far I find that the shots blond towards the end of the pull no matter how I grind/dose/tamp. The flow usually slows to a fast drip and begins to blond towards the end. Anyone had any experience with this, and found a solution?

Also, what temperature are you Caravel users pulling shots at? Full rolling boil, pre-boil, post boil? I have yet to even put a thermometer it the boiler or brew water, but plan to do so soon.

I've found that the Caravel PF is just 1-2 mm smaller diameter than that of the Ponte Vecchio. In fact, the OD of the baskets are the same, the ID diameters are what varies. This got me thinking that a new Ponte Vecchio group head gasket might fit the Caravel, and I'm anxious to try this. DUring very hard pulls on the Caravel I get a few drops of water escaping over the PF, which suggests a new gasket is in order.

PC

The piston is very narrow, as is the basket. So you don't need to pull very hard on the lever to get good brew pressure. Pressure, as you know, is force divided by area; the smaller the area, the greater the pressure.

Given the blown gasket, and the blonding, and your statement that you use "hard pulls", I would guess that you're pulling too hard, and that this is the main reason you have blonding. You could be pulling at 11 bar or so. Again, the smaller piston translates the force into greater brew pressure.

Try a gentle semi-pull to preinfuse and then lift lever to get more water, and then press down firmly but not "hard".

I have tasty shots with the kettle water temp at 205F, after several warming flushes.
Regards
Timo

Thanks timo, I'll try the 205 temp. One problem I've had is if I grind coarse enough for just a "firm" pull I don't seem to get enough pressure to produce much crema. Conversly, if I grind finer and try "no tamp" I find that the pull compresses the puck over the course of the extraction, and that it becomes too firm at the end. I need to kepp working on these things.

Here's a photo of a fine little two-group lever setup:



PC

peacecup wrote:... if I grind coarse enough for just a "firm" pull I don't seem to get enough pressure to produce much crema .... if I grind finer and try "no tamp"... the pull ... becomes too firm at the end. I need to kepp working on these things.

When the overmuch resistance does not present itself until well along in the shot, I would conclude that the basket had been overdosed and had swelled mid-pull. A smaller dose, allowed to swell early during preinfusion, ought to rectify that. So, you could try a grind at the finer end, a light tamp (finger on the tamper), a dosed reduced by 1g or 2g, and a Fellini preinfusion.
Regards
Timo

P.S. Also, too much pressure causes the flow to stall.

With an all metal chassis, I'm thinking that the caravel could benefit from a ground wire. Has anyone replaced the original power cord with a 3 wire cable ?

The power plug on my machine is a two-pin italian model with a short length of cable extending out of the plug and wrapped around the main cable. I'm not sure what this little white wire is for since it doesn't extend all the way to the machine. It also looks like a ground pin can be screwed in the center of the plug.

Any thoughts ?

alex f wrote:With an all metal chassis, I'm thinking that the caravel could benefit from a ground wire. Has anyone replaced the original power cord with a 3 wire cable ?

I ordered these rubber gloves in "Caravel orange":

alex f wrote: I'm missing the metal cover at the top of the pic. The machine works fine, but knowing that the part exists, I'm a bit wary of pulling too hard on the lever.

Hi Alex, sorry I didn't see this message earlier- I left that little metal cover out the last time I took the piston out (about half a year ago) 'cause I couldn't figure out which way to put it in... it seems to be purely for aesthetics and does not effect the functioning of the piston in any way.

By the way, if anybody can tell me the right way to put it in, I'd much appreciate it!

About the ground cable, mine came with a grounded plug. I'll take a look later this evening to see where it was grounded in the machine.

Henry

Of course, its wise to match those gloves with proper insulating footwear