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  #1  
Old 01-26-2020, 01:23 PM
breister breister is offline
 
Join Date: Dec 2006
Location: Atlanta, GA
Posts: 1,231
Default HP capacity of Vaccuum Pump pad

I seem to remember a long time ago reading that the gears for the vaccuum pump are not really strong enough for anything taxing. Is that true?

Reason I'm asking - I am considering (living in the south) installation of a midget car sized air conditioning system in my plane. Yeah, crazy right? The components really don't look to be all that heavy, biggest issue would be finding a place to mount the compressor. And, the compressor sucks about 2-3hp for a small one, according to my research. Changing to a serpentine belt in the front would require cowling changes, and would also put the weight further forward.
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  #2  
Old 01-26-2020, 01:34 PM
RVDan RVDan is offline
 
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I don?t have it, but there is a published spec for the overhang moment, RPM and torque. From that you calculate HP.
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  #3  
Old 01-26-2020, 03:45 PM
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hgerhardt hgerhardt is online now
 
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Location: torrance, ca
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The TCDS shows max torque of 70 in-lb continuous and 450 in-lb static with an overhang moment of 25 in-lb.

At 2700 rpm, the vacuum pump pad is turning 3510 rpm, so 70/12*3510/5252=3.9 HP.
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  #4  
Old 01-27-2020, 12:02 PM
breister breister is offline
 
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Thanks guys.

The draw is probably a good deal higher momentarily whenever the clutch kicks in, and the compressor probably draws close to the same hp irrespective of rpm which might leave idle torque too high. Given how close it is to the tolerances, I think I'll give that idea a pass.
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  #5  
Old 01-27-2020, 12:37 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by breister View Post
Thanks guys.

The draw is probably a good deal higher momentarily whenever the clutch kicks in, and the compressor probably draws close to the same hp irrespective of rpm which might leave idle torque too high. Given how close it is to the tolerances, I think I'll give that idea a pass.
+1

Most cases have a pad for a hydraulic pump on the lower right, though I have never seen the gear setup as most are not fitted with them. I suspect they can handle a higher load than the vac pump. Worth investigating. The pad is often used for governor, but remember reading about options for hydraulic pump. At least on the 540, which has a front mount governor.

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Last edited by lr172 : 01-27-2020 at 12:45 PM.
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  #6  
Old 01-27-2020, 12:57 PM
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hgerhardt hgerhardt is online now
 
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Quote:
Originally Posted by lr172 View Post
+1

Most cases have a pad for a hydraulic pump on the lower right, though I have never seen the gear setup as most are not fitted with them. I suspect they can handle a higher load than the vac pump. Worth investigating. The pad is often used for governor, but remember reading about options for hydraulic pump. At least on the 540, which has a front mount governor.

Larry
IF you do have a front-mount governor, the rear hydraulic pump pad (which is about where the governor would go if rear-mounted) can handle 100/800 in-lb (again per my previously-referenced TCDS) and is in fact where Robinson drives the compressor for R-44's. You can buy a nice bracket from them already made. Might cost you your firstborn, but it's available nonetheless.

Also, Cirruses drive their compressor off the Continental vacuum pump pad. You could check out the TCDS for that engine and see what the capacity is relative to the Lyc one.

Last edited by hgerhardt : 01-27-2020 at 01:00 PM.
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  #7  
Old 01-28-2020, 10:25 AM
breister breister is offline
 
Join Date: Dec 2006
Location: Atlanta, GA
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Quote:
Originally Posted by lr172 View Post
+1

Most cases have a pad for a hydraulic pump on the lower right, though I have never seen the gear setup as most are not fitted with them. I suspect they can handle a higher load than the vac pump. Worth investigating. The pad is often used for governor, but remember reading about options for hydraulic pump. At least on the 540, which has a front mount governor.

Larry
I have an O-290, not likely to sport a governor mount pad but I can look!
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  #8  
Old 01-28-2020, 10:30 AM
breister breister is offline
 
Join Date: Dec 2006
Location: Atlanta, GA
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Quote:
Originally Posted by hgerhardt View Post
IF you do have a front-mount governor, the rear hydraulic pump pad (which is about where the governor would go if rear-mounted) can handle 100/800 in-lb (again per my previously-referenced TCDS) and is in fact where Robinson drives the compressor for R-44's. You can buy a nice bracket from them already made. Might cost you your firstborn, but it's available nonetheless.
Now, THAT is promising if my O-290 has that pad. Looks like they install a pulley, then drive the compressor conventionally.

https://robinsonparts.com/index.php/...-installation/
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