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New Marvel Schebler MS80-430 Floats

Praying for the Pair

I sent a note to MS asking if this price was for a "pair". We'll see.

Their website shows two floats, but then I realized it may have been intended to be ?front and back? images of the product. (Murphy?s Law is doubly applicable to first assumptions)
 
Has anyone bought these floats? If so, what was the weight of a new pair. Tragically, I am actually thinking of buying two pairs and paying the outrageous shipping charges. I have been through at least 8 floats so far.
 
I've got a good digital scale. Just hedging my bets on past performance of Bing Floats. The last set I put in are at about 80 hrs. Time will tell. So far so good.
 
Refresh my memory. What are the symptoms of heavy floats? Is there an overflow of the carb bowls onto the drip pans?
 
In my experience: Slight smell of fuel in the cockpit during climb, drip or two of fuel from carb vent tube onto pan, and perhaps a slightly rough idle.
 
Has anyone bought these floats? If so, what was the weight of a new pair. Tragically, I am actually thinking of buying two pairs and paying the outrageous shipping charges. I have been through at least 8 floats so far.

What causes heavy floats? Type gas or inferior material? Ethanol is pretty caustic with plastic such as fuel filters. Are there any original OEM floats in the fleet since day one?
 
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I think it's a materials defect. The SI listed a range of serial numbers newer than mine. We've got 415 hours over 7 years on these carbs and the floats still weigh just over 6g per pair, knock on wood. I'm glad that we've been so lucky.
 
Marvel Schebler MS80-430?FS Float Conversion Kit

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.
 
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.

Rotax Service Bulletin says a pair of floats should weigh less than 7.0g. Your new MS floats weigh 7.5g. Just say'n...
 
FYI -- data points (all weights are new / dry / fresh out of the box):

-- Old-Style ROTAX #861-184 floats = 2.8 grams each
-- New-Style ROTAX #861-188 floats = 3.2 grams each
-- MS 80-430 floats = Reported @ 3.7-3.8 grams each

ROTAX says max 3.5 grams each (7.0 grams per pair). I'm not sure if this ROTAX weight limit applies to another manufacturer's (i.e., non-Bing) replacement float. Maybe the MS has "superior floatation" characteristics? Any hydrodynamicists out there??
 
Float weights

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 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.
 
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?
 
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.
 
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.
 
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.
 
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...
 
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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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.
2.6-L.jpg


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


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


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.
4.0-L.jpg


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?
 
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, 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.
 
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...
 
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?
 
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.
 
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Just a Note

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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