Lightest N/A flywheel?
Rotorhead
Joined: Feb 2001
Posts: 9,136
Likes: 39
From: Charlottesville, Virginia, USA
The metals are just an example because some flywheels are made that way, and most people realize that steel has a higher weight and inertia than aluminum. My point is that INERTIA is the main factor, in which both WEIGHT and DISTRIBUTION are factors. It is totally flawed to think that weight is the only factor. Unfortunately, the vendors think the general public is too stupid to understand the concept of Moment of Inertia (MOI), so they usually advertise their flywheels by weight.
talking head
Joined: Apr 2008
Posts: 2,775
Likes: 15
From: Perth, WA, OZ
Actually, a high-inertia flywheel will tend to keep the wheels spinning at the same speed. A low-inertia flywheel will encourage a change in the spinning speed.
No HP gain, no Torque gain. I don't drift, but I would guess that a low-inertia flywheel would hurt more than it would help. With a low-inertia flywheel, you would need to rev the engine higher to break the wheels loose, and as you go around the track it will make it difficult to maintain the engine rpms because the engine rpm will be more twitchy. A higher-inertia flywheel will not spool up as fast, but it will tend to maintain its speed once it gets there.
Apples and oranges. It depends what you want. If you want to retain inertia, then you use a higher-inertia flywheel. If you want very little inertia, then you use a lower-inertia flywheel.
Idle. In fact, a low-inertia flywheel will usually cause the idle to bounce around.
For those of you who don't understand why weight doesn't matter as much as the moment of inertia, see the picture below. Both flywheels are the same static weight, but the one on the left will have a lower inertia because the weight is centered, while the one on the right will have a higher inertia because the weight is concentrated at the perimeter. The one on the left will therefore spool faster, while the one on the right will better retain its speed, even though they are both the same weight. Make sense?
No HP gain, no Torque gain. I don't drift, but I would guess that a low-inertia flywheel would hurt more than it would help. With a low-inertia flywheel, you would need to rev the engine higher to break the wheels loose, and as you go around the track it will make it difficult to maintain the engine rpms because the engine rpm will be more twitchy. A higher-inertia flywheel will not spool up as fast, but it will tend to maintain its speed once it gets there.
Apples and oranges. It depends what you want. If you want to retain inertia, then you use a higher-inertia flywheel. If you want very little inertia, then you use a lower-inertia flywheel.
Idle. In fact, a low-inertia flywheel will usually cause the idle to bounce around.
For those of you who don't understand why weight doesn't matter as much as the moment of inertia, see the picture below. Both flywheels are the same static weight, but the one on the left will have a lower inertia because the weight is centered, while the one on the right will have a higher inertia because the weight is concentrated at the perimeter. The one on the left will therefore spool faster, while the one on the right will better retain its speed, even though they are both the same weight. Make sense?
-- while the diagram describes the alum faced flywheels,,, its also speaking wonders for the steel one piece ones with integral cut ring gear
moment of inertia,,, learn it !
IMHO its also about the safety factor
cast flywheels of indiscriminate wear and age being applied with sometimes double the stock intended HP and at higher rpms
is asking to have your legs cut off,, or worse,, someone else's
if you have a stock flywheel ,, and 350 RHP,, you are an idiot waiting to kill at the next burn out
i ALWAYS advocate a change to light billet metal flywheels if the motor is asking for more than stock outputs
- the trade off for the much more responsive and faster revving engine with a much higher safety factor built into it
is one that is harder to drive off the line ( especially up hill )
BIG DEAL !!!!
Rotorhead
Joined: Feb 2001
Posts: 9,136
Likes: 39
From: Charlottesville, Virginia, USA
talking head
Joined: Apr 2008
Posts: 2,775
Likes: 15
From: Perth, WA, OZ
-- and how many of these old cast flywheels retain that original skin strength after years of use and shop machine work?
if there is anybody here that does non destructive crack testing and has a bit of free time
i would like to see how most cast s/h flywheels measure up in xray or die check
i think it will get scary !!!
Been here since dirt...
Joined: Jan 2009
Posts: 327
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From: AZ
One of my customers uses a Tilton 5" dual disc clutch and an aluminum flywheel at 3.5 lbs. Works well on a PP N/A engine with no ill effects. Driver will be the mitigating factor. RPM's are instant and controllable. If you are building an engine, pick what ever counter weight you have and have it balanced by a good , experienced shop. No regard s to year is needed. The new balance will correct the differences.
GD
GD
Rotary Freak
Joined: Jan 2005
Posts: 1,534
Likes: 28
From: Good Ol' Ky
I didn't take into consideration how twitchy it would cause the car to be. Nor did I consider the inertia allowing for actual better control of the rpms.
Rotorhead
Joined: Feb 2001
Posts: 9,136
Likes: 39
From: Charlottesville, Virginia, USA
Thanks for the correction, I was thinking along the lines of the better throttle response, and quicker revs would allow more control of the car in a slide.
I didn't take into consideration how twitchy it would cause the car to be. Nor did I consider the inertia allowing for actual better control of the rpms.
I didn't take into consideration how twitchy it would cause the car to be. Nor did I consider the inertia allowing for actual better control of the rpms.
A similar aviation example is the stabilizer bar on the Huey rotor system. It helps keep the aircraft flying smoothly because it acts as a damper. This is great for a transport aircraft. The Cobra attack aircraft doesn't have this stabilizer bar so it can maneuver better, but that also makes the Cobra more twitchy.
http://www.aircav.com/huey/stabiliz.html
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