Today's Message Index:
----------------------
1. 09:36 AM - evaluating an old engine (flyseaplane)
2. 11:23 AM - Re: What engine are you flying (Tracy Crook)
3. 04:02 PM - Re: What engine are you flying (Tedd McHenry)
4. 06:37 PM - Re: Using dial indicator to check cam lobe wear (CardinalNSB@aol.com)
Message 1
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| Subject: | evaluating an old engine |
--> Engines-List message posted by: "flyseaplane" <flyseaplane@netzero.net>
Steve - -
It really doesn't matter. You are looking for noticeable differences
between lobes. If you find a bad one you'll be able to tell, no problem.
You can do this quickly enough that the oil doesn't have a lot of time to
bleed out of the lifters. Also, do it when the engine is cold. The oil is
thicker, and you won't burn your hands on anything hot.
Unfortunately, this method only detects changes in camshaft lobe lift. It
doesn't do anything for checking if lifters are getting pitted. It only
helps you to find out when the cam is starting to wear down.
Take care,
Linc
========================================
posted by: "steve korney" <s_korney@hotmail.com>
Question...
How long, in seconds, does it take for a lycoming O-320 lifter hydraulic
Message 2
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| Subject: | Re: What engine are you flying |
--> Engines-List message posted by: "Tracy Crook" <lors01@msn.com>
Subject: Re: Engines-List: What engine are you flying
> --> Engines-List message posted by: Tedd McHenry <tedd@vansairforce.org>
>
> On Mon, 16 Jun 2003, Tracy Crook wrote:
>
> > Just curious. Why is a wide torque band seen as a desireable thing in
an
> > aircraft engine?
>
> Tracy:
>
> Depending on the engine, an auto conversion may have a greater difference
> between full power RPM and cruise RPM than a conventional aircraft engine.
> Lycomings cruise at 8/9 of full RPM (i.e. 2400 vice 2700). The
Eggenfellner
> Subaru, by comparison, cruises at 3/4 of full RPM (4200 vice 5600), or
less
> (economy cruise is 3800 RPM). A fairly flat torque curve allows the
Subaru to
> still produce adequate power for cruise at that RPM.
>
> Interestingly, piston speed for the Subaru is about the same at that RPM
as it
> is for a Lycoming at 2400.
>
> > The torque required to turn a propeller varies as a CUBE function of
RPM.
>
> The torque required to turn a propeller varies with the SQUARE of RPM.
The
> power required to turn the prop varies with the CUBE of RPM. Refer to
Stinton,
> eq. 7-13.
>
> Tedd McHenry
> Surrey, BC
You are correct about the torque being a square function of prop speed
(still a *very* steep curve). But the only reason why the Sube is slowed
down more (in terms of percentage) than the Lyc is that they are specifying
a lower percentage of power for cruise, A wise decision on their part.
The prop doesn't care what brand of engine is turning it.
Tracy Crook
Message 3
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| Subject: | Re: What engine are you flying |
--> Engines-List message posted by: Tedd McHenry <tedd@vansairforce.org>
On Tue, 17 Jun 2003, Tracy Crook wrote:
> But the only reason why the Sube is slowed down more (in terms of percentage)
> than the Lyc is that they are specifying a lower percentage of power for
> cruise,
Yes, the Eggenfellner engine is cruising at less than 75 percent power. At
8,000 feet and 4200 RPM it's putting out about 110 HP, according to the power
chart, which is 67 percent of rated power. But the point is that if their
torque curve were narrower they'd have to either run a higher RPM even to get
67 percent power in cruise, giving a higher piston speed and thus more wear, or
they'd have to run the same piston speed and even less than 67 percent power.
That's why the torque curve matters when converting an auto engine for airplane
use.
Naturally, all that assumes a CS prop. With a FP prop, the torque also matters
because a flatter torque curve will give you higher static RPM and therefore
better take-off performance.
Tedd McHenry
Surrey, BC
Message 4
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| Subject: | Re: Using dial indicator to check cam lobe wear |
--> Engines-List message posted by: CardinalNSB@aol.com
Linc, I asked my ap about using a dial indicator to check lobe wear, he said
it wasn't accuract since there is too much "slop" in the valve train. I let
it go but it left me wondering and your post now brings it back up to me. How
would you physically position the dial indicator, I had thought to collapse
the lifter and measure the movement in the end of the pushrod with the rocker
off. Do you simply measure the movement of the rockerarm? Is this a good
"absolute" measurement, or only useful in a relative way. That is, if I do not
have any previous recorded measurements, is it accurate enough to detect a
flattened lobe on a "new used" engine. Thanks, SKip
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