Side channeling solved by accident. - Page 2

#11: Post by **woodchuck** » June 29th, 2006, 7:55 pm

Wow, nutating motion, sounds cool! Look forward to some interesting "nutating" discussions tomorrow at CCC .. Cheers Ian

#12: Post by **s_m_k** » June 29th, 2006, 9:37 pm

woodchuck wrote:Wow, nutating motion, sounds cool!

Warning! Off-topic Geek Talk follows.

I've been doing this off and on for awhile. In other words, when I remember, I do it. Now to the geek talk:

I haven't heard any reference to nutation since I got out of the Air Force in 1982. The APQ-120 Radar System in the F4-E used a nutating feedhorn to track airborne targets. The feedhorn is the reflector/waveguide assembly that is positioned at the focal spot of the parabolic antenna. It was designed to spin with a 5 degree tilt that would cause the RF pulses to be transmitted in a circular pattern around the target. The strongest reflection would indicate the direction the antenna needed to move in order to center on the target. This was likely a common design in analog radar systems. Now it's all phased arrays with multiple target tracking and other stuff that I don't understand.

What's this have to do with espresso? Absolutely nothing. Just all of this nutation talk fired off some long-dormant synapses.

June 30th, 2006, 10:08 am

I had problems also but the tamping method was not at cause.

I was getting side channeling and it was always on the same side: near the handle.

Looking at Perfecting the Naked Extraction, I found out that 1) I was overfilling the basket and 2) the puck was touching the dispersion screen when locking in. Tamping was not the problem; ambitious overfilling was. Even if I tried to tamp as hard as I could, too much coffee in the basket would always touch the screen.

Sometimes, if the dispersion screen gets clogged up, water can come out one side instead of a uniform flow......

Anyways, what would we do without HB?

#14: Post by **cannonfodder** » June 30th, 2006, 1:05 pm

That is a good point to bring up. If you follow a regular cleaning schedule Espresso Machine Cleaning Why, How, and When you should not have an issue with a clogged dispersion screen.

Overdosing is another issue. Different machines have different headspace, the basket you are using also makes a difference. To check that, dose and tamp a shot then lock you portafilter into the group but to not engage the machine. Remove the portafilter and examine your puck. The surface should still be smooth and shiny with no indentation. If the puck is cracked, it looks like the surface has been scraped, or you see an indentation from the dispersion screen, you have too much coffee.

After an extraction, it is normal to have a slight impression of the dispersion screen in the puck. The coffee swells as it absorbs water, my best shots have a light impression on them after the shot.

This puck produced this shot with the above tamp technique.

#15: Post by **popeye** » July 3rd, 2006, 1:02 am

I've got a different take on "nutation." I use two bottomless portafilters (one homemade with a dremel) a La Marzocco triple basket, and a flat reg barber. My primary portafilter has the spring removed. I leave it in my zaffiro while i dose into the (removed) basket and use the WDT. Then i tamp 80-90%, holding the tamper level. I tamp the remaining 10% with a slight tilt, then spin the basket 45 degrees, tamp, spin, tamp spin, etc, until i've got the last 10-20% of the tamp done around the clock. Then i remove my portafilter, drop in the basket (the lack of spring means the grinds don't get jostled) and replace the portafilter.

The downside is my filter basket is cold, although my portafilter is hot. With the temp stability of the zaffiro, i don't think it's a problem. The upside? I think rotating the basket, rather than the tamper, allows for a little more precision and does not break the sidewall adhesion. I noticed i get less side channeling with this method. However, my triple baskets are about 1 mm too big for my tamper, and i'm not sure if this method simply compensates for the tamper-sidewall gap. I've been using some double baskets, which fit better, without this method. No side channeling, but they're overextracted at the bottom edges because they don't have vertical sides. Can anyone recommend a filter basket that works well with the 58mm reg barber (no gap) and has vertical sides?

#16: Post by **cannonfodder** » July 3rd, 2006, 9:38 am

popeye wrote:Can anyone recommend a filter basket that works well with the 58mm reg barber (no gap) and has vertical sides?

My 58 Reg stainless convex tamper fits my two LM ridgeless baskets perfectly. I believe the proper term would be a friction fit, the tamper does not stick but you can feel the basket and tamp base sliding by each other. However, as documented in the LM Basket Woes thread, tamper to base fit can be temperamental and will vary from tamp to tamp and basket to basket.

#17: Post by HB » July 4th, 2006, 8:02 pm

Espresso Distribution and Tamp "Nutating Motion"
By Dave Stephens

«missing video»