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  #1  
Old 01-09-2022, 03:06 PM
claycookiemonster's Avatar
claycookiemonster claycookiemonster is online now
 
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Location: Midway, UT
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Default Primary/Only Alternator on the Vacuum Pad?

Why not? No belt to worry about.
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  #2  
Old 01-09-2022, 03:23 PM
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RV6_flyer RV6_flyer is offline
 
Join Date: Jan 2005
Location: NC25
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Default

Quote:
Originally Posted by claycookiemonster View Post
Why not? No belt to worry about.
I like the idea and am considering it for the RV-8 project.

The CON that I am concerned with has to do with low engine RPM ground operation not reaching rated output of the alternator. It is possible that I may have enough power from the alternator to run the aircraft on the ground at idle while I taxi but have no current flow back into the battery.
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  #3  
Old 01-09-2022, 04:43 PM
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Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
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Default

Sure, but consider:
- Longer recharge time after engine start. Should not be a problem if you have a healthily battery to start with.
- I have never seen a belt driven alternator with a broken belt (I assume they happen). I have seen a vacuum pad alternator with a broken shear drive.
- Iíd take a close look at the standard 60amp alternator weight to compare. Iíd guess the difference will be in the grass.
- Cost is about the same.

Carl
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  #4  
Old 01-09-2022, 04:48 PM
Avanza Avanza is offline
 
Join Date: Jul 2020
Location: Vastervik Sweden
Posts: 137
Smile Alternator on Vacuum Pad

If the alternator is rated for 40 Amp it should give about 10 Amp on 800 rpm.
This supports a standard equipped plane with EFIS /radios etc.
On 2100 it should carry close to full load.

If you add more load (A) than the alternator can carry at 800 rpm the battery
will supply the difference. A 20 Ah battery in god condition can supply at least
10 A for 15 min without any voltage drop.

However departing with electronic ignition/ fuel injection, I would
like to have a full battery before take off.
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  #5  
Old 01-09-2022, 05:15 PM
Northernliving Northernliving is offline
 
Join Date: May 2005
Location: Boston, MA
Posts: 662
Default This is what I did

Quote:
Originally Posted by claycookiemonster View Post
Why not? No belt to worry about.
I recently installed a new engine/prop and ditched my belt driven alternator in my RV8. I opted for the b&c BC410-H. It doesnít charge at very low RPMs. Thatís the only negative that Iíve experienced. Iím VFR only and donít have high power loads. I only have around 10 hours on the engine, but so for I have no regrets and like the peace of mind with no belt up front to break. The thought of pulling the prop to change a belt wasnít appealing. Here are a few pics.
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  #6  
Old 01-09-2022, 06:13 PM
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rocketbob rocketbob is offline
 
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Quote:
Originally Posted by Northernliving View Post
I have no regrets and like the peace of mind with no belt up front to break.
I don't know if you're reading much of the alternator posts on VAF but I've never seen/heard of anyone breaking a belt and its generally once a week someone posts about issues with a pad-driven alternator.
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N678X F1 Rocket, under const.
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N8155F C150 flying
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  #7  
Old 01-09-2022, 06:45 PM
scsmith scsmith is offline
 
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Quote:
Originally Posted by rocketbob View Post
I don't know if you're reading much of the alternator posts on VAF but I've never seen/heard of anyone breaking a belt and its generally once a week someone posts about issues with a pad-driven alternator.
I had a broken belt on a C-152 early in my ASEL flying experience, on a night flight too.
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  #8  
Old 01-09-2022, 06:48 PM
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rocketbob rocketbob is offline
 
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Quote:
Originally Posted by scsmith View Post
I had a broken belt on a C-152 early in my ASEL flying experience, on a night flight too.
What was the cause?
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Bob Japundza CFII A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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  #9  
Old 01-09-2022, 06:53 PM
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rocketbob rocketbob is offline
 
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And I should clarify: never heard of a RV breaking a belt that a result of age or natural wear.
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Bob Japundza CFII A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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  #10  
Old 01-09-2022, 08:55 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
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Quote:
Originally Posted by rocketbob View Post
What was the cause?
Unknown. It was fine on the afternoon flight - was a pre-flight item to check tension. (could barely get a finger on it through the cooling inlet IIRC. It was fine for the evening return flight departure, failed in flight about half way home.

I assume it was age. This was a Navy Flying Club airplane, and as a rule, the club planes were maintained very well. But the four C-152s did get a lot of hours on them. It was the only squawk/failure I ever had on a Navy Flying Club plane.
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RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet" Flying since Sept. 2009
Hobbs 700
also
1/4 share in 1959 C-182B (tow plane)
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
VAF donation Dec 2021
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