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Tandy quoted his A&P as saying:

Ø     a knowledgeable A&P commented that there were only

Ø     three holes in the mixture control - a full rich, a somewhat

Ø     smaller one and the smallest one.  No continuous

Ø     moderation of the mixture control.

 

Tandy,

 

Sad to say, this is NOT a “knowledgeable A&P.

 

The slide assembly for the Stromberg mixture contains several holes of various sizes, with very special placement.  It seems they employed a good mathematician to design the holes.  As the plate moves, when one hole starts to be covered, the next hole starts to be uncovered.

 

As John Cooper wrote, the design is such that as you pull the mixture, you get a continuous and smooth increment in the mixture.  I never noticed any jerkiness or “stepping” in the mixture.

 

What it does not do is respond instantly.  When you move the control, it allows different airflow through the small tubes inside the carb and this, in turn, soon results in a different air pressure inside the float chamber.  By varying the air pressure inside the float chamber, you change how much fuel is sucked by the venture and mixed into a fuel/air mixture.

 

By moving the control slowly, and monitoring it with a high accuracy EGT gauge, I had really excellent control of my mixture.  I could easily find peak EGT.  I could choose the richness I wanted in 10° increments from peak to 50° rich of peak to 100° rich of peak or whatever I wanted.  I had 10° accurate CONTROL!

 

Your A&P needs to actually look at a Stromberg carb sometime.  My mechanic pulled the carb from the plane, disassembled it, cleaned the inner tubing, cleaned and stropped the mixture control assembly and the plates, reassembled it, installed it and we did a test run on the engine in less than an hour and a half.  It IS worth the cost – if you have a competent mechanic.

 

Ed Burkhead

http://edburkhead.com

ed -at- edburkhead???.com          (change -at- to @ and remove "???")

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