Today's Message Index:
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1. 05:00 AM - Re: Re: Ford Crankshaft Choice (skipgadd@earthlink.net)
2. 07:44 AM - Re: Ford Crankshaft Choice (braywood)
3. 08:14 AM - Re: Ford Crankshaft Choice (taildrags)
Message 1
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| Subject: | Re: Ford Crankshaft Choice |
John, Just back from Brodhead, so the late reply.
The thing about Piets is they will almost always be tail heavy. My personal building
philosophy is not to worry about weight ahead of cg, but I will have an
A65 that is lighter than your Ford A.
The other thing is your personal weight, the bigger you are the more weight you
will need up front.
Skip
-----Original Message-----
>From: John C Black <john@jcblack.com>
>Sent: Jul 18, 2018 5:42 PM
>To: pietenpol-list@matronics.com
>Subject: Re: Pietenpol-List: Re: Ford Crankshaft Choice
>
>I have heard from 2 guys off list.
>
>I learned that using a 76x44 prop or a 78x42 prop. Model A engine turns 2100
RPM on takeoff, cruises at 1700-1800 RPM, probably never exceeds 2200 RPM.
>
>I took my model A Ford car (pic Below) out and ran the engine at 1700-2200 RPM
and drove at those RPMs. The Model A engine in the car has no counterweights
on the crank. The engine has been balanced. I did not experience any harmonic
vibration. My rearview mirror amplifies the vibration and serves as a great
observable indicator.
>
>Based on this test, I am leaning toward using the 1932 Model B crank without
counterweights. I figure saving 12-14 pounds is a big deal.
>
>John
>
>
>On Jul 18, 2018, at 1:29 PM, taildrags <taildrags@hotmail.com> wrote:
>
>
>John; I'm really surprised that no one has replied to your query about the crank,
since there are quite a number of those engines out there and plenty of hands-on
engine rebuilders too. I know Ernie Moreno up here in Independence is
building up a Ford to put on his Piet to replace the Franklin that he's got on
it now. The extra weight up front will help Ernie's airplane with tail-heaviness.
>
>--------
>Oscar Zuniga
>Medford, OR
>Air Camper NX41CC "Scout"
>A75 power, 72x36 Culver prop
>
>
>Read this topic online here:
>
>http://forums.matronics.com/viewtopic.php?p=481734#481734
>
>
Message 2
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| Subject: | Re: Ford Crankshaft Choice |
Hello Oscar - I am still struggling with the theoretical weight and balance for
my aircraft; so I am not pretending to be an expert or suggest others are incorrect.
For me, the issue of CofG is a question of where you locate the wing - if the aircraft
is tail heavy (or like me, the pilot is tail heavy....), the wing needs
to go back.
If you are changing the engine in an aircraft, then does not the W&B needs to be
a clean sheet? I would think that every pound or Kg we add, is detrimental
to performance. Opting for a heavier solution for a part of the aircraft seems
counterproductive. Is it not better to relocate the wing to provide the correct
CofG location for the lowest aircraft weight? I can understand wanting to
have the cabane struts vertical, but not at the expense of the safety or performance
of the aircraft.
What am I missing??
Mark Bowler
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=481815#481815
Message 3
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| Subject: | Re: Ford Crankshaft Choice |
Mark; you are not missing anything. Your comments are correct, and the wing can
be repositioned to adjust the CG. One negative to shifting the wing aft is
that it makes getting into the cockpit just a bit more challenging, but a hinged
flop or a cutout takes care of that.
It's the builder's choice, like so many things about experimental aviation. "Ya
pays yer money, ya takes yer choice".
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power, 72x36 Culver prop
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=481816#481816
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