[Healeys] Lightened flywheels

[richard mayor]

I should add  one more thing for clarification.  The general rule of thumb
for comparing rotational weight to other weight (sprung or unsprung) is 10
to 1.  So, using that rule, 5 pounds of weight removed from rotational mass
would equal 50 pounds of fuel. As Michael pointed out.
But, it doesn't alway work out that way.  If you removed one pound from the
flywheel in the area where the bolt pattern is then the 10 to 1 rule may
apply.  But if you remove one pound of material out near the ring gear then
it is more like a factor of 30 to 1.  Any rotational weight removed further
away from its axis will have a much greater effect. And when you lighten a
Healey flywheel the place where the meat comes off first is out near the
ring gear.  Removing 3 or 4 pounds has a big effect on acceleration.

On Tue, Sep 7, 2021 at 2:24 PM Michael Salter <michaelsalter at gmail.com>
wrote:

> The total mass of the flywheel is not completely relevant insofar as
> engine moment of inertia is concerned.
> What is important is the mass removed times the square of the radius, so
> just how much weight has been removed per se is not important.
> Secondly removing rotational inertia is not always the best thing to do,
> if it was you can be assured that manufacturers would be all over it as a
> way to save money.
> The rotational mass is often designed in to protect the drive train, in
> particular the gearbox.
> Read this:
> https://www.netbug.net/blogmichael/2017/01/03/austin-healey-100-crank-failures/
> Thirdly lightening a flywheel in of itself has very little effect on
> acceleration.  An engine with a lightened flywheel may accelerate to 6000
> RPM 1 - 2 seconds more quickly but that doesn't necessarily equate to 1-2
> seconds faster to 60 MPH. You may be able to shift marginally faster if the
> gearbox can stand the extra loads and the 4 to 5 pounds off vehicle weight
> is really only the equivalent of half a tank of fuel. (Who ever notices
> that their car accelerates more quickly with a half full gas tank).
>
> Just sayin'
>
> M
>
> On Tue., Sep. 7, 2021, 4:17 p.m. Earl Kagna via Healeys, <
> healeys at autox.team.net> wrote:
>
>> I have Bill Bolton lightened flywheels in both my Healeys.  According to
>> Kent Lambert, who took over Bills Healey business awhile back, the stock
>> weight (6 cyl) is 28.5 pounds, and Bills machining program reduced them to
>> 24.
>>
>>
>>
>> Both of my cars run just fine, no problems at all in the 20 + or so years
>> that I’ve had them installed.
>>
>>
>>
>> Earl Kagna
>>
>> Victoria BC
>>
>> BJ8, BT7 tri-carb
>>
>>
>>
>>
>>
>>
>>
>> *From:* Healeys <healeys-bounces at autox.team.net> *On Behalf Of *richard
>> mayor
>> *Sent:* Tuesday, September 7, 2021 10:23 AM
>> *To:* healeys <healeys at autox.team.net>
>> *Subject:* [Healeys] Lightened flywheels
>>
>>
>>
>> 6 cylinder flywheels vary slightly but are all generally in the 29 pound
>> range. Very aggressive machine work can get the weight down to the 22-23
>> pound range.
>>
>> How much weight you take off will affect your driving style. To maintain
>> the feel of a stock Healey while still improving the engines response, I
>> suggest removing no more than 3 pounds.
>>
>>
>>
>> Richard
>>
>>
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