REFLECTOR: Running without prop

[Alex Balic]

The engines need the mass of either a flywheel in the case of an automotive
or a prop in the case of an aircraft engine to operate- the crankshaft does
not have enough inertia to allow the engine to continue rotating and
overcome the internal friction of the pistons- to put the pistons
over-center both from sliding friction, and compression friction. The
compression comes from the flywheel moving the pistons around, and the
flywheel gets it's energy from the power of the pistons- and thankfully
there is plenty of extra power to do useful work. sounds redundant, but it
is a matter of timing otherwise you would need a piston on power stroke at
the exact same moment that a piston is on compression stroke- the flywheel
banks the power for a short time to allow the engine to turn smoothly.
Flywheels on even small diesel engines are very heavy because of the
required forces involved. Some mowers might still run (poorly) without the
blade, because it still has the flywheel on the top, but the small ring gear
that engages the starter on the aircraft engine does not have enough mass to
allow the engine to run properly- and you will risk having the pistons
detonate at TDC if you try to run like that. 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Darrell & Nora Kufalk
Sent: Sunday, April 26, 2009 8:17 PM
To: 'Velocity Aircraft Owners and Builders list'
Subject: Re: REFLECTOR: Running without prop

This will convince you.
Take the blade off your lawnmower and see if you can get it to run.




-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Sunday, April 26, 2009 6:08 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Running without prop

I've heard the flywheel reason before.  I thought the flywheel on my
io360 was fairly beefy but that didn't seem to make any difference.

I'm still unconvinced.

Scott

Keith Hallsten wrote:
> Or, to be more precise, the prop is a significant portion of the flywheel
> system that the engine needs to run properly.  The ring gear provides only
a
> portion of the flywheel effect necessary (and it's often held onto the
> crankshaft by the same bolts that would also hold the prop on).  Thus,
some
> additional flywheel needs to bolted on.
>
> If you don't have a prop, you may be able to substitute a stand-in like a
> piece of lumber.  However, you need to be absolutely sure that it's sound,
> balanced, and properly attached.  A piece of lumber coming off a running
> engine would be a lethal missile!
>
> Keith Hallsten
>
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Laurence Coen
> Sent: Sunday, April 26, 2009 10:05 AM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Running without prop
>
> Scott,
>
> I think the difference is that auto engines come with a flywheel and an 
> aircraft engine prop is the flywheel.
>
> Larry Coen
> N136LC
>
> --------------------------------------------------
> From: "Scott Derrick" <scott at tnstaafl.net>
> Sent: Sunday, April 26, 2009 8:45 AM
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Subject: REFLECTOR: Running without prop
>
>   
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