Re: [Titanaircraft] Re: Prop failures, Prop Noise

Rob, with the 62 inch prop you are turning, the tip speeds are much higher than a shorter prop produces hence, more noise.  I don't think that messing with your exhaust ports are going to produce much, if any noise reduction. I've been looking for a longer prop extension without any success as my prop is only about 3.5 inches from the exhaust as well. I'm not sure of any down sides to installing a longer extension.  Kimberly has reported significant noise reduction with moving the prop further aft and I'm sure she will be provide her usual fine expertise on this question.
 
Tim Hansen

--- On Tue, 11/10/09, sunzalito <jrceacampo@yahoo.com> wrote:

From: sunzalito <jrceacampo@yahoo.com>
Subject: [Titanaircraft] Re: Prop failures, Prop Noise
To: Titanaircraft@yahoogroups.com
Date: Tuesday, November 10, 2009, 12:31 PM

 

Tim/Kimberly:

I have complaints from the airpark people I fly from about the loud noise the plane makes; I have a Jab 2200, Warp drive tappered tip prop 62", 12.5 degrees pitch. At the muffler, the exhaust tips are one on each side as typically installed. I don't have the exact separation from these tips to the prop but roughly may be around 3-3.5" (I'll double check this). The prop extension is the one supplied by Jabiru.

Any ideas how to reduce this prop noise? I have heard about re-shaping the exhaust tips so that they're open up more at the bottom. Or, extending these pipes (changing them for longer ones) heading towards the bottom, but I don't like the appearance looking at some I've seen,

Your input is well appreciated!
Thanks,
Rob

--- In Titanaircraft@ yahoogroups. com, Tim Hansen <togoforth@. ..> wrote:
>
> Kimberly, thanks for the in-depth discussion of the exhaust gasses & pulses.  Nevertheless, while I had exhaust residue on the blades before I made the change, an obvious improvement occured after the change... I no longer have ANY residue on them, even after a 4 hour cross-country flight. My exhaust ports are about as far out on either side of the muffler as you can get them so my blades are enjoying the maximum cooling available between cycles. The prop still looks brand new after over 150 hours of use. I agree about the FOD problems with pushers which is why I always use wheel pants and lots of safety wire wherever I think something can come loose.
>  
> Tim
>
> --- On Mon, 11/9/09, Kimberly Panos <kimberly@.. .> wrote:
>
>
> From: Kimberly Panos <kimberly@.. .>
> Subject: Re: [Titanaircraft] Prop failures
> To: Titanaircraft@ yahoogroups. com
> Date: Monday, November 9, 2009, 11:29 PM
>
>
>  
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> Tim,
>
> The exhaust is being driven out in long pulses due to the delay caused by the expansion volume inside the muffler, and the baffles in both the exhaust tips. This means the right and left engine pulses share the same muffler volume and distribute the pulse somewhat evenly between the two tips. I can't imagine being able to position the prop just right to miss all of that. The exhaust valve on 4-stroke engines open before BDC, and is not yet completely closed at TDC when the intake is opening(called 'valve overlap'). That means that for just over 180-degrees of crankshaft rotation, one cylinder it breathing fire out the exhuast port in its flaring pulsations. Now, talk all 4-cyinders (or 6 or more) at full throttle, and you've got that going on 360-degrees of cranshaft rotation with the hottest peaks when the crankshaft rod journal is passing 90-degrees perpendicular its cylinder, not counting the slowdown in the muffler or long header pipe. You're bound
> to have hot exhaust gas flowing directly into the blades no matter how you slice it. The Warp props don't complain a bit. The best thing to do is to position the exhaust tips a little more to the side if you are worried about it.
>
> The exhaust tips are angled, but cut parallel to the prop swept area on our 3300. Until we added a 3" spacer to reduce prop noise, the prop clearance was barely 2" after removing the Ivo in-flight and installing the Warp Drive prop we are still using after 5 years.
>
> The Tornado I just delivered to Montana some weeks ago has a P-tip on a 2200, and it still looks brand new. You just clean the exhuast residue off it once in a while. Keep in mind, the muffler may pass in front of a hot pipe for two or three degrees at the most between the two tips, but it has a 357 degree cooling cycle.
>
> Props on pushers take a lot more beating than tractor installations due to FOD kicked up by the tires, (or a spring, clip, bolt, nut, tool, etc coming off a neglected engine). Especially when there are no wheelpants installed. That is another reason we won't run wood props, particularly on pushers.
>
> I hope this helps to ease the concerns.
>
> --Kimberly
>
> ----- Original Message -----
> From: togoforth
> To: Titanaircraft@ yahoogroups. com
> Sent: Sunday, November 08, 2009 9:10 AM
> Subject: [Titanaircraft] Prop failures
>
> The other day, Vivian posted a request for help for a friend grounded with a busted Sensenich. Several others have made comments about prop failures on Sensenichs and I thought I pass on something that I learned from Lonny Prince when I replaced my Sensenich with one of his props. The instructions for mounting the P-tip said that the prop must be at least 6 inches from the engine exhaust ports in a pusher configuration or damage to the prop can occur. My exhausts are only about 3 1/2 inches from the prop disc and I was getting discoloration on the prop from this. I had the same thing going on with the Sensenich. The fix is the remove the prop and rotate it a bolt hole or two (or as needed) until the prop is only passing the exhaust ports when the engine is in compression. This I did, and no more exhaust discoloration. I suspect the failures that have been reported are most likely due to prop damage caused by improper mounting in relation to the high
> exhaust temperatures to which it is being subjected. Sensenich makes a fine product and they have been in the business since dirt was invented. I'm not inclined to think the prop is the problem.
>
> Tim Hansen
>
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