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Clocking the prop. Real world data

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kahuna

Joined: 02 Feb 2007
Posts: 93

Posted: Tue Apr 17, 2007 5:52 am Post subject: Clocking the prop. Real world data

After weeks of trial and error, I have finally reached a point where I can safely say that clocking the prop doesn’t just make a difference, it makes ALL the difference.  

   

Several weeks ago I set out on a mission to run to ground a vibration in my RV-8. An IO-540 C4B5 with a Hartzell 2 blade prop. There has been a vibration that I would characterize as objectionable. Common on big engine Rockets and RV’s. The lower the RPM, the more objectionable it was.   

   

I was able to instrument the plane and do some real tests and get real results with real data. The net of it is that by changing the prop clocking, I was able to improve my vibration by 83%. And no Im not kidding. You can read all the details here. http://www2.mstewart.net:8080/super8/index.htm  

   

I captured a lot of data. I sure hope others find it useful. I have a new plane as a result.   

   

Best,  

Mike  

   

      [quote][b]

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khorton01(at)rogers.com
Guest

Posted: Tue Apr 17, 2007 1:15 pm Post subject: Clocking the prop. Real world data

On 17 Apr 2007, at 09:51, Stewart, Michael (ISS Atlanta) wrote:



 	  Quote: 	
		   I was able to instrument the plane and do some real tests and get  

 real results with real data. The net of it is that by changing the  

 prop clocking, I was able to improve my vibration by 83%. And no Im  

 not kidding. You can read all the details here. http:// 

 www2.mstewart.net:8080/super8/index.htm

Mike,
	




Thanks for sharing this very interesting, and useful info.   Comments/ 

questions:



1. Did Les make any mention of whether prop clocking could have any  

effect on engine/prop harmonic vibration compatibility?  I'm no  

expert in this area, but it seems logical that there could be an  

effect in this area.



2. Something is screwy with that web page, at least with some  

browsers.  The two snapshots of the both overwrite some of the text  

from the following paragraphs.  I see this on Safari, Camino on OS X,  

and Firefox with X11.



Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

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ronlee(at)pcisys.net
Guest

Posted: Tue Apr 17, 2007 2:24 pm Post subject: Clocking the prop. Real world data

Ok Mike or anyone else.  Help educate me.  I was under the impression 

that the prop needed to be set in a specific orientation relative to 

something.  Perhaps it is almost horizontal right before the impulse mag 

fires.  I don't know.



Am I wrong about this or can the prop be moved anywhere it will fit and 

in Mikes case, modifed to fit in any orientation.



Ron

Lee



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kahuna

Joined: 02 Feb 2007
Posts: 93

Posted: Tue Apr 17, 2007 2:24 pm Post subject: Clocking the prop. Real world data

Yes I asked this question Kevin. Here is Les' response.

"Regarding the torsional vibration concerns, I don't think that is an

issue.

We're not concerned from a propeller standpoint.  We've done testing to

confirm propeller stresses are not significantly impacted with different

clockings.   We also have hubs that have different clocking positions

(HC-,PHC-, EHC-, DHC-, etc) and Lycoming doesn't care which one we use.

The

DHC-configuration is the one we are trying to duplicate."



Also I fixed the page load. You will have to refresh/reload to get the

changes.



Mike

--

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gcomfo(at)tc3net.com
Guest

Posted: Tue Apr 17, 2007 4:02 pm Post subject: Clocking the prop. Real world data

Subject: Re: Clocking the prop. Real world data




Ok Mike or anyone else.  Help educate me.  I was under the impression 

that the prop needed to be set in a specific orientation relative to 

something.  Perhaps it is almost horizontal right before the impulse mag 

fires.  I don't know.



Am I wrong about this or can the prop be moved anywhere it will fit and 

in Mikes case, modifed to fit in any orientation.



Ron

Lee



Ron:  I believe the customary clocking arose from the desire to enable hand

propping.  Mooney requested the clocking that created the A3B6 but I don't

remember why.  LoPresti clocked a Lyc 200 prop to time the blade passage at

the induction air inlet to coincide with some intake valve event in an

effort to increase manifold pressure. Don't know if it worked.



Gordon Comfort

N363GC

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dasduck(at)comcast.net
Guest

Posted: Sat Apr 28, 2007 8:32 am Post subject: Clocking the prop. Real world data

Randy,

 I have a wood prop that can clock in any position on the  studs.

 i also have the newer extension that Van's sells, that  offsets the studs halfway between the crank bosses, and access to a std  extension in-line with the crank bosses.

 Since I'll need to balance my new prop/spinner anyway, and  the wood prop is easy to take on/off, we could play with  that.

 Might even be able to borrow an aluminum Sensenich to get  the feel of a heavier prop.

 O-360 with FI and one Emag.

 note that Mike's testing was done 'in flight', versus ours  which would be 'static' on the ground.

 don



   From: owner-rv-list-server(at)matronics.com  [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Randy  Lervold

Sent: Tuesday, April 17, 2007 8:06 AM

To:  rv-list(at)matronics.com; rocket-list(at)matronics.com

Subject: Re: RV-List:  Clocking the prop. Real world data

 

 Wow Mike, great info!!!  I've long been curious about  prop clocking but there are some obstacles to just trying it as you ran into  with the crank flange bosses. Of course you're working on a  6-cylinder where most of us are flying 4-cylinders. Anyone out there want to do  some prop clocking experimentation with an O-360?

  

 If anyone in the Northwest wants to try some clocking  experimentation I can assist with the measurement. Our EAA chapter has a DSS  Micro MicroVibe II balancer.... http://www.eaa105.org/Programs/programs.htm#PropBalancing

  

 Best,

 Randy Lervold

  

 [quote]   ---

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