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Old 10-21-2018, 08:38 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 1,427

I suspect engine vibration and airframe turbulence also causes upsets in fuel level in the float bowl. These instances might be transient and get smoothed-out quickly with high fuel flow at cruising speed. The dynamics within the float bowl during flight would be interesting to see...
Jim Stricker
Hinckley, Ohio (1OA2)
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Old 10-30-2018, 08:21 PM
AirHound AirHound is offline
Join Date: Oct 2006
Location: OFallon IL now, everywhere before
Posts: 301

Originally Posted by mdoyle View Post
I purchased and installed a pair of the Marvel Schebler floats. Weight out of the box was: 3.7 and 3.8 grams. They replaced a pair of Rotax floats that weighed 8.4 and 4.7 grams on removal. Needless to say I had a severe leak out of the overflow tube on my right carburetor.
Works great now.
Mike, are they still performing without issue?
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Old 10-30-2018, 10:43 PM
mdoyle mdoyle is offline
Join Date: Jun 2005
Location: Xenia, OH
Posts: 138

No problems so far. Maybe 5 hours flight time.
I have another pair for the left side that I have not installed. I am going to compare the pin size, and hole size with the Bing floats I removed, before installing them.
Mike Doyle
RV-9A, Under Construction
Xenia, OH 45385

Last edited by mdoyle : 10-31-2018 at 12:49 PM.
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Old 11-05-2018, 08:01 AM
EXflyer EXflyer is offline
Join Date: Jan 2016
Location: Chiloquin OR
Posts: 93
Default Just a Note

Originally Posted by John C View Post
Jim, that is what I think. Setting the float arm at 10.5 mm (0.414 in) height sets the float height to close the float needle. It also sets the top of the float near the top of the bowl. With the heavier floats, the fuel has to rise higher to raise the float pin to the 10.5 mm setting.

With the forces/weights: fuel pressure, float needle wt, float arm weight and float weight, I get:

2.6 g float - fluid height on the float is 0.583 in or 0.244 in to top of bowl
3.2 g - 0.661 in or 0.167 in to top of bowl
3.8 g - 0.738 in or 0.089 in to top of bowl

The real question is: how critical is the fuel height in the bowl? Various sources have indicated that the 10.5 mm set up is critical. However, Lockwood said not to mess with the 10.5 when going to the new super duper 3.2 g floats.

I'll be glad to send the spreadsheet and drawings/notes to whomever wants to review. Any review would be welcome. Send a PM.
The fuel height inside the bowl if higher than specs richer it runs or slobbers, lower the leaner it will run. That spec is pretty much a fixed measurement by the manufacture of the carb.
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