Not pulling your leg.

Perhaps I could phrase the question another way.

Consider cylinders A and B.



The diameter of cylinder A is much smaller than that of cylinder B.
The cylinders are the same height.
Above each cylinder, a box of lead deep-sea sinkers weighing 130 pounds is pressing down on a piston rod.

Is the pressure in these two cylinders the same or different?

Regards
Timo

hbuchtel wrote:image: http://i25.photobucket.com/albums/c99/hbuchtel/SSL21336.jpg
(apologies for the noise...)

Is the force required to compress a spring equal to the strength with which it presses back?

Henry

I am woefully backwards in these cultural displays- HENRY- Where did you find that sketch?? It is priceless,

timo888 wrote:Not pulling your leg.

Perhaps I could phrase the question another way.

Consider cylinders A and B.

image: http://www.home-barista.com/forums/userpix/915_PressureDiagram_1.jpg

The diameter of cylinder A is much smaller than that of cylinder B.
The cylinders are the same height.
Above each cylinder, a box of lead deep-sea sinkers weighing 130 pounds is pressing down on a piston rod.

Is the pressure in these two cylinders the same or different?

Regards
Timo

The presure in each cylinder would be the weight divided by the area. If the two cylinders were connected by a pipe, the pressure would equalize and the large cylinder would push the weight up.

In any case, the spring presses against the diameter of water in the cylinder, not on the puck, so that is the area to divide into the spring's force to find the pressure. Finding the spring's force at various compressions in an easy way is beyond my abilites -- I would attempt using a bathroom scale and mirror, pressing down on the spring until it is at the right compression, then reading the weight in the mirror. However, I'm doubtful this can be done without any looney tunes style accidents.

mogogear wrote:HENRY- Where did you find that sketch??

Thanks Greg! I 'found' it on my desk, not having anything useful to contribute re: measuring pressure

I still do have a question, on my spring lever machine, can I measure how much weight I'm using to push down the lever (at various points) and calculate the bars of pressure it can produce?

Henry

hbuchtel wrote:Thanks Greg! I 'found' it on my desk, not having anything useful to contribute re: measuring pressure

I still do have a question, on my spring lever machine, can I measure how much weight I'm using to push down the lever (at various points) and calculate the bars of pressure it can produce?

Henry

Hi,
Do you have a fisherman in the area? They use linear spring gauges. Fish weighing scales. You may need someone beside you to do the logging at vsrious points of the pull.
Sincerely
Espressme

hbuchtel wrote:I still do have a question, on my spring lever machine, can I measure how much weight I'm using to push down the lever (at various points) and calculate the bars of pressure it can produce?

Henry,
There was a calculation posted a little while ago by Brooklynshot.

http://www.home-barista.com/levers/calculate-how-much-pressure-is-needed-to-pull-shot-on-lever-machine-t1859.html

You calculate the force applied to the piston rod by the lever.

Then you calculate the pressure exerted upon the puck by that force (Pressure = Force / Surface Area).

The question that had arisen in my mind was, Which Surface? In order to calculate the Surface Area, a radius is required. Which radius was it to be, the basket's or the piston cylinder's, when they differ?

Regards
Timo

timo888 wrote:
The question that had arisen in my mind was, Which Surface? In order to calculate the Surface Area, a radius is required. Which radius was it to be, the basket's or the piston cylinder's, when they differ?

OK, I give up.

another_jim wrote:OK, I give up.

From grade school grammar, Jim. I wrote to Henry, "The question that had arisen in my mind was, Which Surface?" That is, in using the past participle instead of present participle "has arisen" I was acknowledging our earlier exchange and your explanation of Pascal's law.

Regards
Timo

timo888 wrote:From grade school grammar, Jim. I wrote to Henry, "The question that had arisen in my mind was, Which Surface?" That is, in using the past participle instead of present participle "has arisen" I was acknowledging our earlier exchange and your explanation of Pascal's law.

Forget remedial physics, I need remedial English.

Actually, despite the best efforts of Phillip Holt, my old HS physics teacher, I also thought the reason we didn't have 58mm group home levers was too much pressure required; turns out it's just too much brass required, a subject nearer and dearer to my chemistry teacher's heart, since he was a retired industrial chemist

another_jim wrote:Actually, despite the best efforts of Phillip Holt, my old HS physics teacher, I also thought the reason we didn't have 58mm group home levers was too much pressure required; turns out it's just too much brass required, a subject nearer and dearer to my chemistry teacher's heart, since he was a retired industrial chemist

Well, if open-boiler Beast becomes a reality, we won't need a lot of brass for the group to accommodate our 58mm basket. The water will be at temperature and the group will be made of something that takes little heat from the water. The outer bell is mainly a bracket for the portafilter and won't come into contact with the water because it will be separated from the inner cylinder by an insulating gasket.

Regards
Timo