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  #1  
Old 03-01-2017, 11:05 AM
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FlyFastJP FlyFastJP is offline
 
Join Date: Dec 2013
Location: Magnolia, TX
Posts: 69
Default Prop size question

Mine is a 2 blade 70x76 BW wood. I had to replace the carb last weekend and I have a suspicion that the linkage wasn't set up properly to get full throttle. I bought the plane...didn't build it. Original owner couldn't remember anything but having to put smaller jets in to fix a rich issue.... which would align with my current thinking. Even so, it would run 2750 wot at 3000'. Now that I have the linkage correct, I'm thinking it wont have enough prop at now true full throttle.

Also, I can't figure out how to get full travel on the mixture arm. My quadrant gives 1-1/2" of travel, but the mixture arm on the carb needs about 2-1/8". It was an easy fix on the throttle...just drilled another hole higher up on the arm. As you know, the mixture arm is curved and bent.

Any thoughts?
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  #2  
Old 03-01-2017, 12:38 PM
Christopher Murphy Christopher Murphy is offline
 
Join Date: Feb 2007
Location: colorado
Posts: 731
Default Prop size

Unless you are comparing your bw to another bw prop, the pitch number means very little.

I kept my mixture control away from the throttle quadrant . I used a simple push pull control like you see in a cessna 150.. its mounted on the bulkhead forward of the throttle quadrant. It has plenty of travel.

Cm
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  #3  
Old 03-01-2017, 12:46 PM
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FlyFastJP FlyFastJP is offline
 
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Are the BW props different somehow? Vans site recommends a 72x85 sensi for a 180 -4.
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  #4  
Old 03-01-2017, 04:58 PM
Christopher Murphy Christopher Murphy is offline
 
Join Date: Feb 2007
Location: colorado
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Default Props

If you buy a sensenich..
Buy the one that is recommended.

Search this site for more info....each manufacturer measures pitch differently...you should be able to find enough data to select a propellor.

Cm
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  #5  
Old 03-01-2017, 05:48 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
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Before buying anything, retest.

Fixed pitch (cruise) props are typically pitched for roughly full power rpm (~2700-2750) when at 75% power altitude (~7500-8000 feet) at wide open throttle and leaned for best power.

If Bernie (or even his daughter) carved that prop, it's almost certainly going to perform exactly as the purchaser ordered.

As the others mentioned, the pitch numbers can't be compared, brand to brand. The best way to order a prop is to pick a reputable prop maker & tell them the airframe, HP, preferred diameter (get the largest diameter you trust yourself to take off & land with), & expected cruise numbers. If you give him/her valid input data, the prop maker will pitch it correctly; regardless of the number stamped on it.

Charlie

Oh, almost forgot. If you do decide to get rid of that lousy old Warnke, I'll be glad to send you my shipping address. I'll even cover shipping costs....
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  #6  
Old 03-01-2017, 05:56 PM
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FlyFastJP FlyFastJP is offline
 
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Location: Magnolia, TX
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Yes, testing will be done once I get the mixture figured out and everything back together. I may have to go veneer as suggested above, but would really like to keep it on the quadrant.

Being my first owned plane, I was under the impression that a 76 pitch meant 76 for all manufacturers.

As far as my lousy ole Warnke, I'll hold on to it for now. Lol
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  #7  
Old 03-01-2017, 07:21 PM
judoka5051 judoka5051 is offline
 
Join Date: Aug 2010
Location: Stuart, FL
Posts: 186
Default Mixture Fix

I understand the problem of modding the mixture arm. What you might be able to do instead is drilling a hole further from the focal point on the mixture control lever. You can measure the throw on the arm until it's high enough to get the travel you want.
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  #8  
Old 03-01-2017, 09:08 PM
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FlyFastJP FlyFastJP is offline
 
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The problem with that is the arm is angled in such a way that the linkage would bind up after about 1/2". It's not a straight arm like the throttle.
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Warnke Prop
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  #9  
Old 03-01-2017, 09:26 PM
rv7charlie rv7charlie is offline
 
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Do you have room in the quadrant to use the same trick (in reverse)?
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  #10  
Old 03-01-2017, 09:32 PM
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FlyFastJP FlyFastJP is offline
 
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I could drill a hole in the quadrant mixture handle, but then the control cable would be on the top side of the quadrant. That would look terrible, and I'd probably be snagging my fingers on it while manipulating the throttle.
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