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  #21  
Old 10-09-2018, 07:43 PM
AirHound AirHound is offline
 
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Originally Posted by mdoyle View Post
I weighed all 4 of the floats with an electronic postal scale so the weights could be off some. The external appearance of the new floats appears identical to the Bing floats, but the material is different, a hard epoxy exterior. Perhaps the weight will not double in less than a year like one of the Bing floats did. To me it was worth a try considering Marvel Schebler is a known manufacturer of aviation carburetors.
Marvel Schebler must know the ROTAX standards. Maybe they too have production weight issues.
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  #22  
Old 10-09-2018, 08:49 PM
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Quote:
Originally Posted by mdoyle View Post
I weighed all 4 of the floats with an electronic postal scale so the weights could be off some. The external appearance of the new floats appears identical to the Bing floats, but the material is different, a hard epoxy exterior. Perhaps the weight will not double in less than a year like one of the Bing floats did. To me it was worth a try considering Marvel Schebler is a known manufacturer of aviation carburetors.
I ran across an alternate way of checking the floats some time back. It was from a British Rotax distributor who had gotten authorization from Rotax for the procedure. Simply put, if the pin in the float is not below the surface of the fuel in the bowl the float is OK.

Regardless of the weight, how do the Marvel Schebler floats do with that test?
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  #23  
Old 10-09-2018, 10:21 PM
mdoyle mdoyle is offline
 
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I have not looked at the new floats in gasoline, but on one of the old floats, the pin was definitely below the surface of the fuel in the float bowl, when it was removed from the carburetor.
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  #24  
Old 10-10-2018, 11:54 AM
AirHound AirHound is offline
 
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Originally Posted by tomkk View Post
I ran across an alternate way of checking the floats some time back. It was from a British Rotax distributor who had gotten authorization from Rotax for the procedure. Simply put, if the pin in the float is not below the surface of the fuel in the bowl the float is OK.

Regardless of the weight, how do the Marvel Schebler floats do with that test?
Spoke with MS...the SB doesn't address weighing other than OEM floats. That's to say MS has been using this material for years in other designs and there has been no significant weight gain with their other like products.
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  #25  
Old 10-10-2018, 12:07 PM
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Originally Posted by AirHound View Post
Spoke with MS...the SB doesn't address weighing other than OEM floats. That's to say MS has been using this material for years in other designs and there has been no significant weight gain with their other like products.
Agreed but the purpose of checking the pin position, and the weight, is to figure out whether the floats are floating at an appropriate level inside the bowl. Just wondering whether that's been checked with the new MS floats.
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  #26  
Old 10-10-2018, 02:21 PM
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Quote:
Originally Posted by tomkk View Post
Agreed but the purpose of checking the pin position, and the weight, is to figure out whether the floats are floating at an appropriate level inside the bowl. Just wondering whether that's been checked with the new MS floats.
MS makes lots of floats for carbureted engines running Avgas. I'm wondering how they will hold up to 93E10 Mogas? Also, Trump is tossing the farms in Iowa a bone and changing national fuel standards to E15 year-around. We'll see how Rotax likes extra alcohol. If nothing else, more alcohol -> less power. I guess we need to ask Rotax a few questions before the big day...
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  #27  
Old 10-10-2018, 03:44 PM
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Originally Posted by Piper J3 View Post
MS makes lots of floats for carbureted engines running Avgas. I'm wondering how they will hold up to 93E10 Mogas? Also, Trump is tossing the farms in Iowa a bone and changing national fuel standards to E15 year-around. We'll see how Rotax likes extra alcohol. If nothing else, more alcohol -> less power. I guess we need to ask Rotax a few questions before the big day...
I seem to remember reading somewhere that a lot of the Rotax testing was done in Brazil where they have something like E25 and the engines had no problem. No first hand knowledge of that tho ...
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Last edited by tomkk : 10-15-2018 at 02:05 PM.
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  #28  
Old 10-20-2018, 10:11 PM
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Default Photos of various weight floats in mo-gas

Attached are several photos of bing floats. The first is a Bing 1, 2, or 3 dot float that weighs 2.6 g. In mo-gas, the pin rides just above the surface.


The second shows the newest Bing float that weighs 3.2 g. The pin sits even with the surface.


The third shows the new Marvel Schebler float that weighs 3.8 g. The pin is submerged.


And finally, the super duper 3.2 g Bing float after several months setting in mo-gas. It now weighs 4.0 g and only deserves a poor quality photo.


Some observations:

Each float would be pushed further into the fluid due to the fuel pressure at the float needle, the weight of the float needle, weight of the float arm, and as shown, the weight of the float itself.

Each float height is 0.828 inches, or pin height is 0.414 inches, possibly coincident with the 10.5 mm float arm set up measurement.

The 3.2 g float sits about pin high in the fluid. That means that fully submerged, it could displace 6.4 g of fluid. For each 0.6 g increase in float weight, the float will sink another 0.08 in or 2.0 mm (0.818 in x 0.6 g/ 6.4 g).

If the float sits lower in the fluid, the fluid has to rise higher in the bowl to shut off the float needle. To return to the typical operating fluid level in the bowl, should the float arms be adjusted for the heavier floats? From the typical 10.5 mm to 12.5 mm for the super duper (soon to sink) Bing floats or 14.5 mm for the new MS floats?
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  #29  
Old 10-21-2018, 02:44 AM
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Good sleuthing John...

So, if I‘m following, the first Bing “floats” highest in the fuel (most buoyant) and would therefore control fuel in the bowl at a lower level. So perhaps the original Bing floats are best as long as they don’t absorb fuel over time.

My original floats still weigh less than 7.0g/pair with 400TT using 93E10.
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Jim Stricker
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PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 406

LSRM-A Certificate 2016
Special Thanks to EJ Trucks

Last edited by Piper J3 : 10-21-2018 at 03:32 AM.
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  #30  
Old 10-21-2018, 09:23 AM
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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.
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