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  #611  
Old 10-28-2020, 12:01 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by charosenz View Post

I still would be curious about the (fixed) pitch of the props that "regular" RV's typically use.......
I can't imagine that a typical FP RV prop, designed to run at 2500-2700 would do very well on an engine that will max out at 1900 RPM.
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  #612  
Old 10-28-2020, 02:07 PM
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Piper J3 Piper J3 is offline
 
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Quote:
Originally Posted by charosenz View Post
Jim,

I have heard similar comments. I think RPM is an equally important here. What is the max RPM that you use, including max cruise? Does Rotax publish a max temp for operations?

I still will respect my gearbox manufacturer recommendations. They want to update my gearbox so I will send it to them real soon. If I see similar temps after it is updated, then I will work with them on the numbers and potentially add an oil cooler. Until then I am really limited on taking advantage of the actual performance of this set up.
So, the 912 runs at 5500 RPM cruise which is engine redline. It is designed to operate at this speed and produces near 100HP. Gear ratio is 2.43:1 which is a "hunting" ratio to spread wear evenly. Rotax doesn't measure temp on the gearbox.
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Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 633

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  #613  
Old 10-28-2020, 05:13 PM
dmn056 dmn056 is offline
 
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Quote:
Originally Posted by charosenz View Post
UPDATE:

QUESTION: What pitch are folks typicall using for a prop pitch? Google says that 22degrees is about 80-82 inches. Does anyone know if this is valid?

Thanks.
Most propeller pitch measurements are taken at about 3/4 radius. So, for your prop at 22 deg

circumference = pi * 3/4 * 72 = 146.8 inches
pitch = 146.8 * tan( 22) = 59 inches

If you're measuring your pitch angle somewhere else, adjust the numbers accordingly
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  #614  
Old 10-28-2020, 05:15 PM
gasman gasman is offline
 
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Originally Posted by charosenz View Post
UPDATE:

I increased pitch on the 3 bladed 72" warp drive prop from 20 degrees to 21.2 degrees. (not 22.1 as previously posted).

QUESTION: What pitch are folks typically using for a prop pitch? Google says that 22degrees is about 80-82 inches. Does anyone know if this is valid?

Thanks.
Van's recommended FP pitch for 160hp lyc. is 80 inches and 2600 rpm.
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  #615  
Old 10-28-2020, 06:07 PM
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My gear ratio is 2.2 and I run a 76 IVO in-flight adjustable from 115 to 145 inches pitch and similar engine rpms to you. I run about 125 inches pitch for TO and climb at about 2050 prop rpm and 135-145 in cruise at same rpm, depending on power setting and altitude.

I run out of pitch above 10,000 feet and 30 inches MAP in cruise- If I want to go faster, engine/prop rpm will be higher.

As an extreme at 15,500 ft./ 35 inches, prop rpm full coarse was 2500, 182 KTAS.
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  #616  
Old 10-28-2020, 10:38 PM
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charosenz charosenz is offline
 
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Guys,,,,,,

Thank you!!!. This definitely confirms what my research is telling me. Which is that my speed is very closely matched to my ptich and prop RPM.

It gives me something to consider in the future, which is that my set up needs more prop to take advantage of what is available.

There are options.

1) More pitch. I will be increase pitch incrementally under the advisement of the manufacturer. ....
2) Another prop.....(I am currenly utilizing a SAE1 bolt circle so options are limited.
3)Possibly try to get a lower ratio for gearbox to increase prop speed.

On a side note, I am struggling with a pesky oil leak. Driving me nuts.

Oh well. Life is good.
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  #617  
Old 10-29-2020, 12:07 AM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by lr172 View Post
I can't imagine that a typical FP RV prop, designed to run at 2500-2700 would do very well on an engine that will max out at 1900 RPM.
I agree, and would never consider it for my current set up. The information just helps as I consider several options for the future.
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  #618  
Old 10-29-2020, 06:55 AM
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rv6ejguy rv6ejguy is offline
 
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Charlie, when the gearbox is sent back, any chance to get an SAE 2 flange installed or a dual pattern 1 and 2 installed? This would open up some other prop possibilities in the future for you.
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #619  
Old 10-30-2020, 10:54 PM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
Charlie, when the gearbox is sent back, any chance to get an SAE 2 flange installed or a dual pattern 1 and 2 installed? This would open up some other prop possibilities in the future for you.
I am using a saber extension, and yes, Sam can make one for me with an SAE2 pattern. But if I can get the gearbox to keep the temps down at higher (4800-5000rpm) and add one more degree of pitch (22*) I think I can get the full potential of this set up (albeit fixed pitch) and Ill be fine.

I have a 1.25" blast tube of air on the box too, but a larger one would be helpful.

Ill be down until I get the gearbox back. That will give me time add ducting to the intercooler and replace the aluminum brake lines with coppernickel.
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Last edited by charosenz : 10-31-2020 at 12:23 AM.
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  #620  
Old 11-03-2020, 12:20 AM
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charosenz charosenz is offline
 
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Good news. I got an all clear from Viking Aircraft Engines. They said the gearbox is fine. It just gets a bit warmer in my set up than in others.

I have a 1.5" airblast tube on the gearbox but they suggest something larger. I will be enlarging or adding a second airblast tube, and may be a old fashion oil cooler too if needed.

I hate having missed 7-8 beautiful weather days but I felt it was best to be cautions and have the gearbox looked at.

After that oil leak in the valve cover I have oil all over the firewall and down in the belly scoop to clean out. How fun!

I have been studying a lot on prop pitch. Comparing degrees of pitch vs inches of pitch.
l
I have a propeller calculator that is very helpful. You can find it at www.godolloairport.hu

I have been running 21.2 degrees pitch as measured at the tip of my 72" 3 bladed warp drive prop. I can run it at 33"map and 4500 rpm during climb out but due to the gearbox temp getting up past 180F I have to slow it down to 4100rpm so my "top end" speed is really an unknown for now. I am going to push it harder while the gearbox oil is under 180 as soon as I get back to flying. I am also going to increase pitch to 22.0 degrees pitch to see how that will work out. The "book" says that 22.0 degrees should give me 145mph at 2050 Prop RPM. The MAP will vary at altitude. About 32" at MSL and probably 25" at 6000ft. Just raw guesses at this point.

If I can keep the box cool under 185F I would love to run it at 6000ft at 3" to see if I could cruse at say 155mph. That would be pretty good considering I have unfaired gear legs and large tires and a radiator under the belly.....
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