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Discussion Starter #1
1. What is the purpose of the square ridge in the bottom of the air-tube section, just upstream from the main jet/needle? Scott B's latest video discusses this and he correctly decides not to round this off as he does to the air piston. Why would that be a bad idea?

2. What is the purpose of the shallow groove in the bottom of the air piston, parallel to the airstream? This is the groove that you need to straddle with a straight edge for setting the needle shoulder position.

Bonus question. Who is the great engineer/scientist who's name should be associated with the answer to the above questions?

Later all!
Al
:-D
 

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OK, I'll bite....

Just guessing at the ridge you are talking about, but
(1) if you are talking about the square edge on the bridge, I would say you don't want to round it off or is would slow down the speed of the air across the bridge due to a shorter travel distance reducing the VENTURI action across the bridge and lessen the ability to draw fuel from the nozzle. (?)
(2) Wild guess on the slot in the bottom of the piston, but guess it again is part of the VENTURI, except that early carbs and a lot of the British SU's don't have it. I believe it is there to either accomodate 'minimum airflow' required at idle or closed throttle, or possibly to allow that airflow under certain throttle positions to improve emissions characteristics. Or possibly to increase the VENTURI action at idle to allow a slightly leaner nozzle setting again to improve idle emissions.
(3) Would that be Senor' VENTURI?

Am I right, close, out of the ballpark? Any prizes? Even for SWAG's? ;-)
 

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Discussion Starter #3
You get....

a nod for bravery, but no stars yet. :-(

No, not Mr. Venturi or Mr. Bernoulli, either. See prior Pop Quiz:
http://ZCAR.COM/forums/read.php?f=1&i=232375&t=232375

What other giant of engineering should we associate with flow of fluids, and what principle of fluid flow did he describe?

Sorry, but I gotta keep you guys scratching your heads for at least a bit longer.

Later,
Al
 

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ok, my cubicle colleague says...

he says that Archemedies, or Pascal. Some earlier, yet still, great minds. other thatn that I have no Idea.
 

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I gotta tell you guys everything....

The guy's name was Cubik Featper Minnut. From which we derive the modern unit of airflow CFM. He was a medieval scientist who came of note by developing a high flow bellows for the blacksmiths-enabeling them to have higher heat and therefore stronger steel. Really, it's true....
 

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Discussion Starter #6
Did anyone ever hear of...

Mr. Reynolds? Famous Brit.

What was it he talked about?

Later... :)

Al
 

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I'll guess that the ridge has to do with the transition from laminar to turbulent flow. What we want in terms of the fluid flow to the engine is well-mixed flow so the fuel/air mixture is constant.

What Osborne Reynolds did was figure out a dimensionless number related to velocity, density, diameter of pipe (for closed ducts), and viscosity of fluid. The number can generally tell us whether the flow will be laminar (not mixed) or turbulent (well mixed).

I'd imagine that the ridge acts to "whack" the flow into turbulence faster than if the section were smooth.

For the shallow groove, I don't know -- perhaps the relationship of the pressure under the piston to the flow? The groove would increase the surface area along the bottom of the piston, increasing shear stress, and perhaps the "ability" for flow to move the piston up and down.

Anywhere close?

Cheers,
Steve
 
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