Hi Vance:
I understand what you're saying. Angular momentum/inertia and all that
will definitely suck power when accelerating. However, I'm less
convinced on how much help lightening the flywheel will give in
accelerating the vehicle. Ignoring all calculations of any complexity
let's go for a simple common sense analysis and see what we get:
Neglecting all issues related to friction etc, when the car is at any
velocity, its kinetic energy is primarily stored in two areas, the
linear movement of the entire machine and the angular momentum of the
rotating machinery.
The total car weighs about 2800 lbs with driver, gas and essential
toolkit in the boot. The 10 lbs represents about 0.3% of that mass to
accelerate.
If one adds up the crankshaft and its extensions, transmission/diff
gearing, drive shafts, hubs and wheels, the weight must be 500 pounds of
rotating machinery. The transmission changes how much each part has to
accelerate, but not as much as one might think, considering the mass of
the other parts. The 10 lbs removed from the flywheel would represent 2%
of that mass.
So, after lightening the flywheel, in a smooth one-gear acceleration
from zero to 30mph in first gear you would still have the entire car
(-10lbs) and all the rotating mass (-10 lbs) to accelerate. As above,
the savings would be a reduction of about 0.3% of weight to accelerate
linearly and about 2% mass to acceleration angularly. That's just not a
lot of change. Of course, I understand that the gearing between wheels
and motor in first gear would increase the effect, but not all that
much, I would have thought.
Since 10 hp represents about 10% of the power that is actually moving
the car, I find it difficult to believe that lightening the machinery by
so little will have that much of a difference.
So, while I will absolutely buy into the idea that, with the clutch
disengaged, the rotating mass of the engine will be lighter making
revving and matching gears quicker, I'd like to see an actual
acceleration test to be convinced that the overall vehicle acceleration
effect was significant.
Cheers,
Mark
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Navarrette, Vance
Sent: April 25, 2006 11:38 AM
To: Mark J. Bradakis; 6pack@autox.team.net
Subject: RE: Are stock TR6 engines balance externally?
Mark:
Recall your physics; It requires power to accelerate the
flywheel. It is another mass that requires work to set in motion.
In first gear, lightening the flywheel by 10 lbs can be worth as
much as 10HP to the rear wheels. It is very significant. The benefits
diminish in the higher gears, but are still there.
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Mark J. Bradakis
Sent: April 24, 2006 10:24 PM
To: 6pack@autox.team.net
Subject: Re: Are stock TR6 engines balance externally?
> This engine will rarely see 4,000 rpm.
I'm curious. Why are you installing a lighter flywheel if you won't
be revving the engine?
--
mjb.
http://fatchancegarage.com
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